U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2005–5085

Spatial and Temporal Variations in Oceanographic 

and Meteorologic Forcing Along the Central 

California Coast, 1980–2002
Spatial and Temporal Variations in Oceanographic 

and Meteorologic Forcing Along the Central 

California Coast, 1980–2002

By Curt D. Storlazzi and Dana K. Wingfield

Scientific Investigations Report 2005–5085

U.S. Department of the Interior

U.S. Geological Survey 
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2005

For sale by U.S. Geological Survey Information Services

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Denver, CO 80225-0046

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Produced in the Western Region, Menlo Park, California

Manuscript approved for publication, April 26, 2005

Text edited by George A. Havach

Layout and design by Stephen L. Scott 
Contents

Abstract	 ----------------------------------------------------------------------------------------------------- 1

Introduction---------------------------------------------------------------------------------------------------1

Study Area ----------------------------------------------------------------------------------------------------1

Methods -----------------------------------------------------------------------------------------------------3

Results	 	 ------------------------------------------------------------------------------------------------------5

	 Significant Wave Height -----------------------------------------------------------------------------5

	 Dominant Wave Period-------------------------------------------------------------------------------8

	 Sea-Level Barometric Pressure---------------------------------------------------------------------9

	 Sea-Surface Water Temperature ----------------------------------------------------------------- 12

	 Windspeed------------------------------------------------------------------------------------------- 14

	 Frequency of Winds from the Southwest -------------------------------------------------------- 17

	 Directional Variations in Significant Wave Height, Dominant Wave Period, and

	 	 Windspeed-------------------------------------------------------------------------------------- 17

	 Recurrence Intervals ------------------------------------------------------------------------------- 20

Discussion -------------------------------------------------------------------------------------------------- 22

Conclusions------------------------------------------------------------------------------------------------- 22

Acknowledgments------------------------------------------------------------------------------------------ 23

References Cited------------------------------------------------------------------------------------------- 23

Appendixes

	 	 1.	 Raw and calculated datasets from eight buoys deployed off the central California

	 	 	 	 		 	 the National Oceanic and Atmospheric Administration’s National Data Buoy

	 	 	 	 		 	 Center over the study period (1980–2002)--------------------------------------------------- 25

2–7.	 Schematic plots of mean monthly data coverage at eight buoys deployed by

	 	 	 	 		 	 the National Oceanic and Atmospheric Administration’s National Data Buoy

	 	 	 	 		 	 Center buoys over the study period (1980–2002) for:

	 	 	 	 	 2.	 Significant wave height ----------------------------------------------------------------------- 26

	 	 	 	 	 3.	 Dominant wave period ------------------------------------------------------------------------ 27

	 	 	 	 	 4.	 Sea-level barometric pressure --------------------------------------------------------------- 28

	 	 	 	 	 5.	 Sea-surface water temperature ------------------------------------------------------------- 29

	 	 	 	 	 6.	 Windspeed-------------------------------------------------------------------------------------- 30

	 	 	 	 	 7.	 Frequency of winds from the southwest ---------------------------------------------------- 31

8–15.	 Mean monthly statistics of oceanographic and meteorologic parameters for

	 	 	 	 		 	 all months and for El Niño and La Niña months at:

	 	 	 	 	 8.	 Eel River buoy----------------------------------------------------------------------------------- 32

	 	 	 	 	 9.	 Point Arena buoy------------------------------------------------------------------------------- 33

	 	 	 	 10.	 Bodega buoy------------------------------------------------------------------------------------ 34

	 	 	 	 11.	 San Francisco buoy---------------------------------------------------------------------------- 35

	 	 	 	 12.	 Half Moon Bay buoy --------------------------------------------------------------------------- 36

	 	 	 	 13.	 Monterey Bay buoy ---------------------------------------------------------------------------- 37

	 	 	 	 14.	 Cape San Martin buoy------------------------------------------------------------------------- 38

	 	 	 	 15.	 Point Arguello buoy ---------------------------------------------------------------------------- 39

III
Figures

	 1.	 California, showing the locations of offshore study area and eight buoys

	 	 	 	 	 deployed off the central coastline by the National Oceanic and Atmospheric

	 	 	 	 	 Administration’s National Data Buoy Center over the study period ------------------------2

	 2. 	Bar chart showing data coverage at eight buoys deployed off central California

	 	 	 	 	 by the National Oceanic and Atmospheric Administration’s National Data Buoy

	 	 	 	 	 Center over the study period --------------------------------------------------------------------3

3–21. 	Plots of:

	 	 	 3.	Multivariate El Niño-Southern Oscillation index over the study period--------------------5

	 	 	 4. 	Monthly variation in mean significant wave height during all months, El Niño

	 	 	 	 	 	 months, and La Niña months throughout study area over the study period------------6

	 	 	 5.	Monthly variation in significant wave heights larger than 4 m during all months,

	 	 	 	 	 	 El Niño months, and La Niña months throughout the study area over the study

	 	 	 	 	 	 period -------------------------------------------------------------------------------------------6

	 	 	 6.	Monthly variation in significant wave heights larger than 6 m during all months,

	 	 	 	 	 	 El Niño months, and La Niña months throughout the study area over the study

	 	 	 	 	 	 period -------------------------------------------------------------------------------------------7

	 	 	 7. Long-term trends of mean significant wave height throughout the study area

	 	 	 	 	 	 over the study period--------------------------------------------------------------------------8

	 	 	 8.	Long-term trends of exceedances of significant wave heights larger than 4 m

	 	 	 	 	 	 and larger than 6 m throughout the study area over the study period ------------------9

	 	 	 9. 	Monthly variation in mean dominant wave period during all months, El Niño

	 	 	 	 	 	 months, and La Niña months throughout the study area over the study period -------9

	 	 10. 	Long-term trends of mean dominant wave period throughout the study area

	 	 	 	 	 	 over the study period------------------------------------------------------------------------ 10

	 	 11. 	Monthly variation in mean sea-level barometric pressure during all months,

	 	 	 	 	 	 El Niño months, and La Niña months throughout the study area over the study

		 	 	 	 period ----------------------------------------------------------------------------------------- 11

	 	 12. 	Monthly variation in sea-level barometric pressures lower than 1000 mbars

	 	 	 	 	 	 during all months, El Niño months, and La Niña months throughout the study

	 	 	 	 	 	 area over the study period------------------------------------------------------------------ 11

	 	 13. 	Monthly variation in sea-level barometric pressures lower than 990 mbars

	 	 	 	 	 	 during all months, El Niño months, and La Niña months throughout the study

	 	 	 	 	 	 area over the study period------------------------------------------------------------------ 12

	 	 14. 	Long-term trends of mean sea-level barometric pressure throughout the

	 	 	 	 	 	 study area over the study period ---------------------------------------------------------- 13

	 	 15. 	Long-term trends of sea-level barometric pressures lower than 1000 mbars

	 	 	 	 	 	 throughout the study area over the study period ---------------------------------------- 14

	 	 16. 	Monthly variation in mean sea-surface water temperature during all months,

	 	 	 	 	 	 El Niño months, and La Niña months throughout the study area over the study

	 	 	 	 	 	 period ----------------------------------------------------------------------------------------- 14

	 	 17. 	Long-term trends of mean sea-surface water temperature throughout the

	 	 	 	 	 	 study area over the study period ---------------------------------------------------------- 15

	 	 18. 	Monthly variation in mean windspeed during all months, El Niño months,

	 	 	 	 	 	 and La Niña months throughout the study area over the study period---------------- 16

IV
	 	 	 	 19. Long-term trends of mean windspeed throughout the study area over

	 	 	 	 	 	 the study period ---------------------------------------------------------------------------- 16

	 	 	 	 20. Monthly variation in the frequency of winds from the southwest during all

	 	 	 	 	 	 months, El Niño months, and La Niña months throughout the study area

	 	 	 	 	 	 over the study period----------------------------------------------------------------------- 16

	 	 	 	 21. Long-term trends in the frequency of winds from the southwest throughout

	 	 	 	 	 the study area over the study period----------------------------------------------------- 17

22–24. 	Compass plots of:

	 	 	 	 22. Variation in hourly significant wave height as a function of hourly dominant

	 	 	 		 	 wave direction at the Monterey Bay buoy during years when concurrent

	 	 	 		 	 directional wave and wind data were available ---------------------------------------- 18

	 	 	 	 23. Variation in hourly dominant wave period as a function of hourly dominant

	 	 	 	 	 	 wave direction at the Monterey Bay buoy during years when concurrent

	 	 	 	 	 	 directional wave and wind data were available---------------------------------------- 18

	 	 	 	 24. Variation in hourly windspeed as a function of hourly wind direction at the

	 	 	 	 	 	 Monterey Bay buoy during years when concurrent directional wave and

	 	 	 	 	 	 wind data were available------------------------------------------------------------------ 19

	 	 	 	 25. Bar charts showing frequency distribution of the highest 10 percent of

	 	 	 	 	 largest hourly significant wave heights as a function of hourly dominant

	 	 	 	 	 	 wave direction during El Niño events, La Niña events, and changes in

	 	 	 	 	 	 dominant wave direction between two end members, from observations

	 	 	 	 	 	 at the Monterey Bay buoy during years when concurrent directional wave

	 	 	 	 	 	 and wind data were available------------------------------------------------------------- 20

	 	 	 	 26. Diagram illustrating general wave patterns along the central California

	 	 	 	 	 	 coast, synthesized from more than 2,800,000 hourly observations of

	 	 	 	 	 	 significant wave height, dominant wave period, dominant wave

	 	 	 	 	 	 direction, windspeed, and wind direction at Monterey Bay buoy during

	 	 	 	 	 	 years when concurrent directional wave and wind data were available ----------- 21

Tables

1. 	Station data for eight deep-water buoys deployed by the National Oceanic and

	 	 Atmospheric Administration’s National Data Buoy Center along the central

	 	 California coast since the early 1980s----------------------------------------------------------------3

2. 	Recurrence-interval projections of maximums of oceanographic and meteorologic

	 	 parameters -------------------------------------------------------------------------------------------- 20

3. 	Long-term trends of oceanographic and meteorologic parameters throughout

	 	 the study area over the study period (1980–2002) ------------------------------------------------ 23

V


Abstract

Since the 1980s, our understanding of such important 

large-scale phenomena as El Niño events and the California 

Current System that drive physical, chemical, and biologic 

processes along the U.S. west coast has greatly improved. 

However, our ability to predict the influence of annual and 

interannual events on a regional scale still remains limited. We have analyzed high-resolution hourly data from 

eight National Oceanic and Atmospheric Administration 

buoys deployed since the early 1980s off central California 

to study spatial and temporal variations in oceanographic 

and meteorologic forcing along the coast. We identified 

seasonal to interannual trends in significant wave height, 

dominant wave period, sea-level barometric pressure, seasurface water temperature, windspeed, and wind direction 

were identified, as well as significant departures in these 

trends during El Niño and La Niña periods. The results suggest increasing wave heights and wave periods, decreasing 

sea-level barometric pressures and variations in sea-surface 

water temperatures, and increasing variations in windspeed 

and wind direction off central California between 1980 and 

2002.

Introduction

The El Niño events between 1980 and 2002 (most notably in 1982–83 and 1997–98) adversely affected the entire 

North American Pacific coast (Komar, 1998). Studies by 

Seymour (1983) and Inman (1991) suggest that winter-storm 

intensity and the resulting wave heights off southern California are increasing. Allan and Komar (2000) and Bromirski 

and others (in press) also noted considerable interannual 

variation in storm-generated wave heights, as well as a general trend of increasing wave heights in the eastern North 

Pacific, while the area off central California is a “transition 

zone” from high-energy wave action in the Pacific Northwest to milder wave conditions off southern California. 

This increase in storminess, as well as in the frequency of 

storms propagating at lower latitudes across the northeastern 

Pacific (Brewer and Jackson, 2000), leads to greater coastal 

erosion, with especially severe shoreline damage during El 

Niño years (Seymour and others, 1984; Storlazzi and Griggs, 

2000). Schwing and others (2002) observed the evolution 

of oceanic and atmospheric anomalies (that is, sea-surface 

water temperature, sea-level barometric pressure, windspeed, 

and wave height) associated with El Niño/La Niña events 

in both the Northeast Pacific and the California Current 

System (CCS). Some studies have focused on the large-scale 

biologic-physical coupling in the CCS during El Niño years 

(Chelton and others, 1982; Lynn and others, 1998), and 

others on smaller, more localized impacts, such as El Niño’s 

effects on processes in Monterey Bay (Griggs and Johnson, 

1983; Kudela and Chavez, 2000).

Although our understanding of these important physical 

phenomena that drive physical, chemical, and biologic processes along the U.S. west coast has improved since 1990, 

our ability to predict the oceanographic and meteorologic 

forcing that drives these processes over large spatial and 

temporal scales in the “transition zone” off central California 

remains limited. The deployment and continued maintenance 

of robust operational oceanographic deep-water buoys by the 

National Oceanic and Atmospheric Administration (NOAA) 

since the early 1980s provides numerous high-resolution 

hourly data, such as significant wave height, dominant wave 

period, windspeed, wind direction, sea-level barometric pressure, air temperature, and sea-surface water temperature. The 

datasets generated by these systems are now long enough in 

duration to clearly identify long-term trends and calculate 

statistically significant probability estimates of the behavior 

of the measured parameters. In this report, we discuss the 

spatial and temporal variations in these parameters for eight 

stations along the central California coast between the Eel 

River and Point Conception over seasonal to interannual 

(that is, El Niño and La Niña) climatic cycles.

Study Area

This study focuses on the 640-km-long central California coast from the Eel River in the north to Point Conception 

in the south (fig. 1). Central California has a rugged coastline characterized by a narrow continental shelf and coastal 

mountains cut with high seacliffs and narrow river valleys. 

The distribution of sediment varies across the shelf. The 

Spatial and Temporal Variations in Oceanographic 

and Meteorologic Forcing Along the Central 

California Coast, 1980–2002

By Curt D. Storlazzi and Dana K. Wingfield
Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

coarsest sediment accumulates in shallow depressions, in the 

surf zone, and at the shelf break (Anima and others, 2002; 

Edwards, 2002), and fine to medium sediment offshore to 

depths of about 20 m, where large volumes of sand generally 

do not move in response to surface waves during most of the 

year (Dingler and Reiss, 2002).

The general offshore wave climate of California is 

characterized by three regimes: Northern Hemisphere swell, 

Southern swell, and locally wind driven waves (Storlazzi and 

Griggs, 2000). Northern Hemisphere swell is generated by 

extratropical cyclones in the North Pacific, generally during 

the winter months of November through March, when deepwater waves can exceed 8 m in height (National Marine Consultants, 1960). Southern swell is generated by winter storms 

in the South Pacific during the Northern Hemisphere’s 

summer or by hurricanes and tropical depressions off Central America during the Northern Hemisphere’s summer and 

early fall. Although Southern swell produces long periods 

(>20 s) waves, these waves generally are much smaller in 

height than those produced by Northern Hemisphere swell. 

Locally wind-driven waves develop rapidly in the winter 

when low-pressure systems track near central California, or 

CALIFORNIA 

Point Arguello 

46023 

Half Moon Bay 46012 

San Francisco 

46026 

Bodega 

46013 

Eel River 

46022 

PACIFIC

0 100 200 

KILOMETERS

124°

120° 

42° 

39° 

37° 

35° 

33° 

115° 

117° 

120° W 

OCEAN 

Los 

Angeles 

San

Diego

Point Arena 

46014 

Cape San Martin 46028 

Monterey Bay 46042 

San 

Francisco 

Cape 

Mendocino

Point 

Conception 

NORTHERN 

CENTRAL

SOUTHERN 

Figure 1. California, showing locations of offshore study area and eight buoys (colored circles) deployed off central coastline by the National Oceanic and Atmospheric Administration’s National Data Buoy Center over study period (1980–2002). 

Colors correspond to individual buoys’ data plots in figures 4–6, 9, 11–13, 16, and 18.


in spring and summer when strong sea breezes are generated 

(Griggs and Johnson, 1979).

Methods

Since the early 1980s, NOAA’s National Data Buoy 

Center (NDBC) has deployed several buoys off the U.S. 

coast to monitor various oceanographic and atmospheric 

parameters. This study is based on data from eight offshore 

buoys along the central California coast (fig. 1; table 1). 

Each buoy is designated with a five-digit, location-specific 

station number of the style “460XX”. Datasets are available 

online at the National Data Buoy Center’s (2004) Web site. 

These buoys record hourly data for various oceanographic 

and meteorologic parameters, including significant wave 

height (Hsig), dominant wave period (Tdom), dominant wave 

direction (WVdir), sea-level barometric pressure (SLBpres), seasurface water temperature (Wtemp), windspeed (WNDspd), and 

wind direction (WNDdir). The only buoy equipped to measure 

WVdir is the Monterey Bay buoy (sta. 46042), which acquired 

that capability in the early 1990s, and so the WVdir dataset is 

only 10 years long (1993–2002). Other recorded parameters 

not discussed here include air temperature (in degrees Celsius), dewpoint temperature, wind-gust speed, average wave 

period, station visibility, and pressure tendency (in pascals).

After 2 decades of data acquisition, these datasets are 

now long enough in duration to determine significant patterns and long-term (decadal) trends in these parameters in 

the study area (fig. 1). To desample and increase the statistical significance of the data, monthly means, minimums, 

maximums, and standard deviations were calculated for 

Hsig, Tdom, SLBpres, Wtemp, and WNDspd during each month of 

the entire study period. Owing to varying buoy-deployment 

dates, buoy failure, and maintenance operations, however, 

some gaps exist in the datasets throughout the study period 

(fig. 2). Initial deployment dates range from 1980 (Half 

Moon Bay buoy, sta. 46012, fig. 1) to 1987 (Monterey Bay 

buoy, sta. 46042). Gaps in the datasets due to buoy failure 

and (or) maintenance range in duration from several weeks 

to entire seasons. When calculating monthly statistics, sufficient data were required by which to compare various buoys. 

To obtain equally weighted calculations, months with less 

Methods

Table 1. Station data for eight deep-water buoys deployed by the 

National Oceanic and Atmospheric Administration’s National Data Buoy 

Center along the central California coast since the early 1980s

[See figure 1 for locations. All stations recorded hourly data on significant wave height, 

dominant wave period, sea-level barometric pressure, sea-surface water temperature, 

windspeed, and wind direction, except the Monterey Bay buoy, which also recorded 

dominant wave direction]

Buoy Station Latitude

N.

Longitude

W.

Water depth

(m)

Eel River --------------- 46022 40°43’12” 124°31’12” 329

Point Arena ------------ 46014 39°13’00” 123°57’57” 265

Bodega ----------------- 46013 38°13’30” 123°19’00” 123

San Francisco---------- 46026 37°45’32” 122°50’00” 52

Half Moon Bay-------- 46012 37°21’28” 122°52’53” 88

Monterey Bay --------- 46042 36°45’11” 122°25’21” 1,920

Cape San Martin ------ 46028 35°44’08” 121°53’24” 1,112

Point Arguello --------- 46023 34°42’50” 120°58’00” 384

YEAR

NORTH

SOUTH

1980 1990 2000

46022

46014

46013

46026

46012

46042

46028

46023

STATION

Point Arena

Eel River

Bodega

San Francisco

Half Moon Bay

Monterey

Cape San Martin

Point Arguello

Figure 2. Bar chart showing data coverage at eight buoys deployed off central California (see fig. 1 for locations) by the National Oceanic and 

Atmospheric Administration’s National Data Buoy Center over study period (1980–2002). Gaps are due to variations in deployment dates, maintenance periods, and instrument failure.
 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

than 480 hours (20 days) worth of data were excluded from 

the analysis.

Monthly exceedances, in terms of the percentage of 

time over which a parameter was observed to exceed a given 

value, were determined to identify periods of sustained 

extreme conditions whose cumulative effects are important 

for certain physical processes but might not be adequately 

described by the mean and standard deviation. Monthly 

exceedances were calculated for Hsig values greater than 4, 

6, and 8 m and for SLBpres values lower than 1000, 990, and 

980 mbars for each buoy. In this way, the frequency and 

magnitude of monthly Hsig and SLBpres values throughout El 

Niño events, La Niña events, and months of neither event 

could be calculated by dividing the number of hours over 

which the chosen value of Hsig and (or) SLBpres was exceeded 

during a given month by the total number of recorded hours 

of observation during that month.

Wind directions along the central California coast are 

typically from the west-northwest at azimuths 270–359°

(Inman and Jenkins, 1997), driven by a region of high pressure, termed the “California High” that generally resides 

off northern California during the spring and summer. 

Observations of wind directions at (blowing from) azimuths 

070–250° were of particular interest because these directions would be counter to the normal wind direction. The 

frequency of winds from the southwest (WNDwsw), in combination with Ekman steering, drives warm surface water 

onshore and downward, causing “downwelling” at the coastline. This parameter has been shown by numerous workers 

to be significant to many physical processes along the U.S. 

west coast (Inman and Jenkins, 1997; Storlazzi and Griggs, 

2000; Storlazzi and others, 2003, 2004). Monthly means, 

minimums, maximums, and standard deviations of WNDwsw

were also calculated.

Once calculated, monthly statistics were separated into 

three parts of the study area (fig. 1): northern (Eel River 

buoy, sta. 46022, and Point Arena buoy, sta. 46014), central (San Francisco buoy, sta. 46026, and Half Moon Bay 

buoy, sta. 46012), and southern (Cape San Martin buoy, 

sta. 46028, and Point Arguello buoy, sta. 46023). Data from 

the Bodega buoy (sta. 46013) and the Monterey Bay buoy 

(sta. 46042) were omitted so that the calculations for part 

of the study area were based on the same number of buoys. 

The data from each buoy were equally weighted and averaged together to give values for each oceanographic and 

atmospheric parameter in each part of the study area. The 

minimum, maximum, mean, standard deviation, observed 

exceedances, and long-term trends of each parameter were 

then determined for each part of the study area.

From recurrence-interval projections and calculated 

extreme values, the average time between events of a given 

magnitude can be estimated (Carter and others, 1986). For 

example, a 2-year recurrence interval for Hsig suggests that 

the probability of an occurrence of a given extreme value 

is once every 2 years. The inverse, or reciprocal, of the 

recurrence interval is the probability of such an occurrence 

equaling or exceeding the given extreme value. Return 

magnitudes were based on Fisher-Tippet type I distributions 

(Carter and others, 1986) of monthly maximums, and 2-, 

10-, 50-, and 100-year return-magnitude projections were 

calculated for Hsig, Tdom, SLBpres, Wtemp, and WNDspd.

The El Niño-Southern Oscillation (ENSO) cycle is an 

interannual phenomenon composed of episodic El Niño 

and La Niña climatic events. The Southern Oscillation 

index (SOI), which is a proxy measure used to determine 

the presence and strength of an ENSO event, is the quantitative difference in the pressure centers of Tahiti, French 

Polynesia (generally a region of low sea-level barometric 

pressure), and Darwin, Australia (typically a region of high 

sea-level barometric pressure). These two opposite ends of 

the Southern Oscillation create a pressure gradient that is 

used to characterize warm and cold ENSO phases (Glantz, 

2001). A negative SOI phase represents an El Niño event, in 

which below-average barometric pressures occur at Tahiti 

and above-average barometric pressures at Darwin, whereas 

a positive SOI phase represents a La Niña event and reverse 

barometric pressure gradients, respectively (Glantz, 2001).

Although the SOI is derived specifically from 

barometric-pressure anomalies, the multivariate ENSO 

index (MEI), devised by Wolter and Timlin (1998), 

incorporates multiple factors to give a weighted average 

of the main oceanic-atmospheric ENSO-related features. 

In addition to sea-level barometric pressure, other 

variables include sea-surface water temperature, surface 

air temperature, total cloudiness, and zonal (north-south) 

and meridional (east-west) components of surface winds. 

The MEI (fig. 3) is read opposite to the SOI, with negative 

values representing cold ENSO phases (La Niña) and 

positive values representing warm ENSO phases (El Niño).

To understand how these oceanographic and 

meteorologic parameters are influenced by ENSO events, 

we broke down the monthly statistics into three categories 

based on the corresponding MEIs for each specific month: 

all months of the study period, El Niño months, and La 

Niña months. Monthly MEIs before 1993 were normalized 

to an average MEI of 0.0 and a standard deviation of 

1.0 (National Oceanic and Atmospheric Administration, 

Climate Diagnostics Center, 2004). Cutoff MEIs were 

used to separate index values of El Niño, La Niña, and 

“normal” months, that is, months when neither El Niño nor 

La Niña conditions were observed. Any month when the 

MEI was greater than 1.0 was defined as an El Niño month, 

any month when the MEI was less than −0.5 as a La Niña 

month, and any month when the MEI was less than 1.0 but 

greater than −0.5 as a normal month. The monthly mean, 

standard deviation of the mean, and mean of the standard 

deviation of Hsig, Tdom, SLBpres, Wtemp, WNDspd, and WNDwsw

were matched with their corresponding monthly MEIs. 

In this way, monthly numeric MEI intensities could be 

assigned with concurrent buoy data to categorize the oceanic 

and atmospheric parameters into El Niño months, La Niña 

months, or normal months.


Results

Significant Wave Height

In general, mean Hsig values are larger in the northern 

part of the study area (fig. 1) and smaller in the southern 

part. A significant deviation from this trend is visible on the 

San Francisco buoy’s (sta. 46026) wave record, which on 

average is much lower than those of the surrounding buoys. 

These smaller-than-average Hsig values are due to this 

buoy’s location on the inner part (50-m depth) of the broadest section of the Continental Shelf in the study area. By the 

time these waves reach the San Francisco buoy, they have 

lost much of their energy and, thus, Hsig value, owing to dissipation of wave energy as they interact with the sea floor 

in the shallower parts of the Continental Shelf. Seasonally, 

mean Hsig values are largest during the winter (November–February), ranging from 2.74 to 3.09 m in the northern 

part of the study area and from 2.31 to 2.50 m in the southern part (fig. 4A; see apps. 2, 8–15). Spatial trends show 

an increasing wave-climate variation during the winter, 

with mean Hsig values 0.35 to 0.59 m larger in the northern 

part of the study area than in the southern part. During the 

summer (June–August), mean Hsig values are generally 

smaller, ranging from 1.62 to 1.96 m in the northern part of 

the study area and from 1.72 to 2.02 m in the southern part.

Mean Hsig values range from 0.26 to 1.16 m larger 

during El Niño winter months than during normal winter 

months (fig. 4B). During the El Niño month of February, 

mean Hsig are largest in all parts of the study area (fig. 1): 

almost 0.5 m larger (1.16 m larger than average) in the 

northern part of the study area than in the southern part 

(0.70 m larger than average). Mean Hsig values during El 

Niño summer months vary less than during the winter. 

Mean Hsig values are lowest in May (0.44 m smaller than 

average).

Although mean Hsig values are larger than normal 

during La Niña winter months, they are only 0.04 to 0.36 m 

larger than average (fig. 4C). Mean Hsig values are largest 

during the La Niña month of November, when they are 0.18 

m larger than average in the southern part of the study area 

0.15 m larger than average in the northern part. Mean Hsig

Results

-2

-1

0

1

2

3

4

YEAR

MULTIVARIATE ENSO INDEX (MEI)

La Nina

El Nino~

~

1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

Figure 3. Multivariate El Niño-Southern Oscillation (ENSO) index (MEI) over study period (1980–2002). MEI is opposite of the 

Southern Oscillation index, with negative (blue) values representing cold ENSO phases (La Niña conditions) and positive 

(red) values representing warm ENSO phases (El Niño conditions).
 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

Figure 5. Monthly variation in significant wave heights (Hsig) larger 

than 4 m during all months (A), during El Niño months (B), and during 

La Niña months (C) throughout study area (fig. 1) over study period 

(1980–2002). Colored curves in figure 5A correspond to individual 

buoys located in figure 1. Note that Hsig values larger than 4 m are 

most frequent during El Niño late winter months.

1 2 3 4 5 6 7 8 9 10 11 12 

1 2 3 4 5 6 7 8 9 10 11 12 

FREQUENCY OF SIGNIFICANT WAVE HEIGHTS LARGER

THAN 4 m, IN PERCENT

1 2 3 4 5 6 7 8 9 10 11 12 

North 

Central 

South 

North 

Central 

South 

MONTH 

A 

B 

C 

0 

5 

10 

15 

20 

25 

-40 

-30 

-20 

-10 

0 

10 

20 

30 

40 

-40 

-30 

-20 

-10 

0 

10 

20 

30 

40 

Figure 4. Monthly variation in mean significant wave height (Hsig) 

during all months (A), during El Niño months (B), and during La Niña 

months (C) throughout study area (fig. 1) over study period (1980–

2002). Colored curves in figure 4A correspond to individual buoys 

located in figure 1. Note that mean Hsig values are typically largest 

during El Niño winter months.

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

MONTH

1.0

1.5

2.0

2.5

3.0

3.5

-1.0

-0.5

0

0.5

1.0

1.5

-1.0

-0.5

0

0.5

1.0

MEAN SIGNIFICANT WAVE HEIGHT, IN METERS

North 

Central 

South

North 

Central 

South

A

B

C

values during La Niña summer months are typically smaller 

than during normal summer months, ranging from 0.25 m 

smaller than average to only 0.19 m larger than average.

Monthly Hsig values larger than 4 m are most frequent 

in the northern part of the study area (figs. 1, 5A) in December, when they make up as much as 21.64 percent of total 

monthly Hsig values observations. In contrast, monthly Hsig

values larger than 4 m are most frequent in the southern 

part of the study area in March, when they make up as 

much as 11.41 percent of total monthly Hsig observations. 

So few monthly Hsig values larger than 4 m occur during the 

summer that they are not statistically significant.

Throughout the study period, monthly Hsig values larger 

than 4 m are most frequent during El Niño winter months 

(November–February, fig. 5B): as much as 32.08 percent 

more frequent than average in the northern part of the study 

area (fig. 1) and as much as 14.59 percent more frequent 

than average in the southern part. Monthly Hsig values larger 

than 4 m are less frequent and vary less during La Niña 

winters than during El Niño winters (fig. 5C). As during El 

Niño winter months, monthly Hsig values larger than 4 m are 

most frequent in February, ranging from 4.45 percent more 

frequent in the southern part of the study area to as much as 

9.70 percent more frequent in the northern part.

Monthly Hsig values larger than 6 m during normal, 

non-ENSO periods are most frequent in the early winter 

(December), when they make up 2.63 percent of total 

monthly Hsig values in the northern part of the study area 

(figs. 1, 6A). During El Niño winter months, monthly Hsig

values larger than 6 m are most frequent in February, ranging from 1.20 percent more frequent than average in the 

southern part of the study area to 3.98 percent more frequent than average in the northern part (fig. 6B). Whereas 

El Niño monthly Hsig values larger than 6 m are most frequent during the late winter, La Niña monthly Hsig values 

larger than 6 m are most frequent in the early winter. For 

example, during the La Niña month of December they are 

as much as 1.31 percent more frequent than average in the 


Figure 6. Monthly variation in significant wave heights (Hsig) larger 

than 6 m during all months (A), during El Niño months (B), and during 

La Niña months (C) throughout study area (fig. 1) over study period 

(1980–2002). Colored curves in figure 6A correspond to individual 

buoys located in figure 1. Note that Hsig values larger than 6 m are 

consistently most frequent in northern part of study area (fig. 1).

1 2 3 4 5 6 7 8 9 10 11 12 

1 2 3 4 5 6 7 8 9 10 11 12 

1 2 3 4 5 6 7 8 9 10 11 12 

North 

Central 

South 

North 

Central 

South 

0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

-4.0 

-3.0 

-2.0 

-1.0 

0 

1.0 

2.0 

3.0 

4.0 

-4.0 

-3.0 

-2.0 

-1.0 

0 

1.0 

2.0 

3.0 

4.0 

MONTH 

A 

B 

C 

FREQUENCY OF SIGNIFICANT WAVE HEIGHTS LARGER

THAN 6 m, IN PERCENT

northern part of the study area but only 0.59 percent more 

frequent than average in the southern part.

Long-term trends of mean, maximum, and minimum 

Hsig values, as well as monthly Hsig exceedances (>4 m and 

>6 m), all increased over the study period. Monthly mean 

Hsig values on average increased by 0.020 m/yr in all parts 

of the study area (figs. 1, 7A). Long-term trends of Hsig

variation increased the most (by 0.010 m/yr) in the southern 

part of the study area and the least (by 0.006 m/yr) in the 

northern part (fig. 7B). In addition, long-term trends of 

maximum Hsig values on average also increased over the 

study period, specifically in a north-to-south trend: from 

0.057 m/yr in the northern part of the study area, through 

0.068 m/yr in the central part, to 0.077 m/yr in the southern 

part (fig. 7C). In contrast, long-term trends of minimum 

Hsig, values on average increased much less: by 0.009 m/yr 

in the northern part of the study area and by only 0.002 

m/yr in the southern part (fig. 7D). Long-term trends of 

monthly Hsig values larger than 4 m on average increased 

by 0.004 m/yr at the north end of the study area and by 

0.002 m/yr at the south end (fig. 8A). Long-term trends 

of monthly Hsig values larger than 6 m trends were not 

statistically significant (fig. 8B).

Dominant Wave Period

Mean Tdom values range from 8.78 to 10.09 s during the 

summer and from 12.08 to 13.71 s during the winter (fig. 

9A; see apps. 3, 8–15). Mean Tdom values typically peak in 

February: at 12.94 s in the northern part of the study area 

(fig. 1) and at 13.71 s in the southern part. Generally, mean 

Tdom values are shorter in the summer and shortest in July 

and August: 8.78 s in the northern part of the study area 

and 9.44 s in the southern part. Annual mean Tdom values on 

average are 0.60 s longer in the southern part of the study 

area than in the northern part.

Mean Tdom values are typically 0.24 to 1.81 s longer 

during El Niño winter months than during normal winter 

months (fig. 9B). El Niño Tdom values generally peak in 

January, 1 month earlier than during normal months, ranging from 0.96 s longer in the northern part of the study area 

(fig. 1) to 1.81 s longer in the southern part. Only in the 

central part of the study area are mean Tdom values shorter 

than normal (by 0.15 s) in February, possibly owing to the 

passage of storms through this part of the study area. Mean 

Tdom values are longer than normal in the northern and 

southern parts of the study area during February (by 0.86 

s and 0.07 s, respectively). Mean Tdom variation is greater 

during El Niño summer months than during El Niño winter 

months, ranging from 0.46 s shorter than average to 0.41 s 

longer than average. Mean Tdom values in the southern part 

of the study area remain slightly longer than in the central 

or northern parts until September, when they are 0.30 s 

shorter than average in the northern part of the study area 

and 0.74 s shorter than average in the southern part.

During La Niña winter months, mean Tdom values peak 

in November, ranging from 1.13 s longer in the northern 

part of the study area to 1.28 s longer than normal in the 

southern part (figs. 1, 9C). During La Niña months, mean 

Tdom values are shortest in February, ranging from 0.41 

to 0.60 s shorter than average throughout the study area. 

During La Niña summer months, mean Tdom values are 

generally at or above average in the southern and central 

portions of the study area, and generally slightly below 

average in the northern part. During La Niña summer 

months, mean Tdom values range from 0.30 s shorter than 

average in the northern part of the study area to 0.79 s 

longer than average in the southern part. In general, mean 

Tdom variation is greatest in the southern part of the study 

area throughout the year during both El Niño and La Niña 

months.

Long-term trends of mean Tdom variation on average 

increased over the study period (fig. 10A): from 0.035 s/yr 

in the northern part of the study area to 0.045 s/yr in the 

Results
Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

1

1.5

2

2.5

3

3.5

4

4.5

5

1980 1985 1990 1995 2000 2005

South = + 0.0191, R= 0.2627

Central = + 0.0214, R= 0.2795 

North = + 0.0209, R= 0.1905

0.2

0.4

0.6

0.8

1

1.2

1.4

1980 1985 1990 1995 2000 2005

YEAR

South = + 0.0096, R= 0.2556

Central = + 0.0077, R= 0.2193

North = + 0.0062, R= 0.1530 

0

0.5

1

1.5

2

MINIMUM SIGNIFICANT WAVE HEIGHT,

1980 1985 1990 1995 2000 2005

IN METERS

YEAR

North = + 0.0087, R= 0.1722 

Central = + 0.0110, R= 0.3212 

South = + 0.0017, R= 0.0494

2

4

6

8

10

12

1980 1985 1990 1995 2000 2005

MAXIMUM SIGNIFICANT WAVE HEIGHT,

IN METERS

North = + 0.0570, R= 0.1958

Central = + 0.0681, R= 0.3114

South = + 0.0765, R= 0.3470

A

B

C

D

MEAN SIGNIFICANT WAVE HEIGHT,

IN METERS

STANDARD DEVIATION OF MEAN SIGNIFICANT

WAVE HEIGHT, IN METERS

Figure 7. Long-term trends of mean significant wave height (Hsig) throughout study area (fig. 1) over study period (1980–2002). A, Mean Hsig

value. B, Standard deviation of mean Hsig value. C, Maximum Hsig value. D, Minimum Hsig value. Note that trendlines show increases in all 

parameters.
Results

Figure 8. Long-term trends of exceedances of significant wave heights (Hsig) larger than 4 m (A) and larger than 6 m (B) 

throughout study area (fig. 1) over study period (1980–2002). Note that trendlines show increases in both parameters.

1980 1985 1990 1995 2000 2005

North = + 0.41, R= 0.1893 

Central = + 0.10, R= 0.1468 

South = + 0.19, R= 0.1502

1980 1985 1990 1995 2000 2005

North = + 0.07, R= 0.2065 

Central = + 0.01, R= 0.1977 

South = + 0.02, R= 0.1630 

YEAR 

FREQUENCY OF MEAN SIGNIFICANT WAVE HEIGHT

S

LARGER THAN 6 m, IN PERCENT

YEAR 

A B 

FREQUENCY OF MEAN SIGNIFICANT WAVE HEIGHT

S

LARGER THAN 4 m, IN PERCENT

0 

10

20

30

40

50

60

70

80

0 

2 

4 

6 

8 

10

12

Figure 9. Monthly variation in mean dominant wave period (Tdom) during 

all months (A), during El Niño months (B), and during La Niña months 

(C) throughout study area (fig. 1) over study period (1980–2002). Colored 

curves in figure 9A correspond to individual buoys located in figure 1. 

Note that monthly mean Tdom variation is greatest during El Niño late 

winter months and La Niña early winter months.

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

MONTH

MEAN DOMINANT WAVE PERIOD, IN SECONDS

A

B

C

8.0

9.0

10.0

11.0

12.0

13.0

14.0

-2.0

-1.5

-1.0

-0.5

0

0.5

1.0

1.5

2.0

-2.0

-1.5

-1.0

-0.5

0

0.5

1.0

1.5

2.0

North 

Central 

South

North 

Central 

South

southern part (figs. 1, 10A). In addition, the mean Tdom

standard deviation increased in all parts of the study area. 

Long-term trends of maximum Tdom values increased in 

all parts of the study area: from 0.035 s/yr in the southern 

part of the study area to 0.061 s/yr in the northern part (fig. 

10C). Long-term trends of minimum Tdom values increased 

in both the northern and southern parts of the study area 

(by 0.001 and 0.028 s/yr, respectively), whereas the variation in minimum Tdom values for the central part was not 

statistically significant (fig. 10D).

Sea-Level Barometric Pressure

Mean SLBpres values range from 1017.52 to 1019.55 

mbars during normal winter months and from 1014.26 to 

1017.31 mbars during normal summer months (fig. 11A; 

see apps. 4, 8–15). Mean SLBpres north-to-south spatial 

variation is less in winter than in summer. For example, 

during normal winter months, mean SLBpres values on average 

are only 0.60 mbar higher in the northern part of the study 

area (fig. 1) than in the southern part. In contrast, during the 

summer months, mean SLBpres values on average are 2.64 

mbars higher in the northern part of the study area than in the 

southern part. Mean SLBpres values generally peak in the winter 

and reach their lowest point in the late summer. During the 

winter months of December and January, mean SLBpres values 

are highest in the north-central part of the study area (Bodega 

buoy, sta. 46013, fig. 1), reaching 1019.95 mbars. Conversely, 

mean SLBpres values are lowest from June to August, dropping 

to 1014.44 mbars in the southern part of the study area.

Mean SLBpres values are generally 0.34 to 7.44 mbars 

lower during El Niño winter months than during normal winter 

months (fig. 11B). Mean SLBpres variation is greatest during 
10 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

Figure 10. Long-term trends of mean dominant wave period (Tdom) throughout study area (fig. 1) over study period (1980–2002). A, Mean Tdom

value. B, Standard deviation of mean Tdom value. C, Maximum Tdom value. D, Minimum Tdom value. Note that trendlines show increasing spatial 

variation in mean, standard deviation of mean, and minimum Tdom values.

3

4

5

6

7

8

9

1980 1985 1990 1995 2000 2005

14

16

18

20

22

24

26

1980 1985 1990 1995 2000 2005

North = + 0.0611, R= 0.1215

Central = + 0.0371, R= 0.0868

South = + 0.0347, R= 0.0763

North = + 0.0014, R= 0.0111 

Central = - 0.0042, R= 0.0253

South = + 0.0275, R= 0.2006

8

9

10

11

12

13

14

15

1980 1985 1990 1995 2000 2005

1.5

2

2.5

3

3.5

4

1980 1985 1990 1995 2000 2005

North = + 0.0387, R= 0.1199 

Central = + 0.0249, R= 0.0928

South = + 0.0445, R= 0.1534

North = + 0.0056, R= 0.0747

Central = + 0.0004, R= 0.0061

South = + 0.0051, R= 0.0651

YEAR

MINIMUM DOMINANT WAVE PERIOD,

IN SECOND

S

YEAR

MAXIMUM DOMINANT WAVE PERIOD,

IN SECONDS

A

B

C

D

MEAN DOMINANT WAVE PERIOD,

IN SECONDS

STANDARD DEVIATION OF DOMINANT

WAVE PERIOD, IN SECONDS
Results 11

Figure 11. Monthly variation in mean sea-level barometric pressure 

(SLBpres) during all months (A), during El Niño months (B), and during 

La Niña months (C) throughout study area (fig. 1) over study period 

(1980–2002). Colored curves in figure 11A correspond to individual 

buoys located in figure 1. Note that monthly mean SLBpres values are 

lower during El Niño late winter months than during La Niña winter 

months.

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

North 

Central 

South

North 

Central 

South

1012

1013

1014

1015

1016

1017

1018

1019

1020

1021

-8.0

-6.0

-4.0

-2.0

0

2.0

4.0

6.0

8.0

-8.0

-6.0

-4.0

-2.0

0

2.0

4.0

6.0

8.0

MONTH

MEAN SEA-LEVEL BAROMETRIC PRESSURE, IN MILLIBARS

A

B

C

Figure 12. Monthly variation in sea-level barometric pressures 

(SLBpres) lower than 1000 mbars during all months (A), during El Niño 

months (B), and during La Niña months (C) throughout study area 

(fig. 1) over study period (1980–2002). Colored curves in figure 12A

correspond to individual buoys located in figure 1. Note that although 

SLBpres values lower than 1000 mbars are frequent during normal 

winter months, they are most frequent during El Niño winter months, 

particularly January through March, when storms are most common.

1 2 3 4 5 6 7 8 9 10 11 12 

1 2 3 4 5 6 7 8 9 10 11 12 

1 2 3 4 5 6 7 8 9 10 11 12 

0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

4.0 

-8.0 

-6.0 

-4.0 

-2.0 

0 

2.0 

4.0 

6.0 

8.0 

-8.0 

-6.0 

-4.0 

-2.0 

0 

2.0 

4.0 

6.0 

8.0 

North 

Central 

South 

North 

Central 

FREQUENCY

South 

 OF SEA-LEVEL BAROMETRIC PRESSURES

LOWER THAN 1000 MILLIBARS, IN PERCENT

MONTH 

A 

B 

C 

the El Niño month of February, ranging from 1.81 mbars 

lower than average in the southern part of the study area 

(fig. 1) to 7.44 mbars lower than average in the northern 

part. Mean SLBpres values are consistently lower than average during El Niño winter months but typically slightly 

higher than average during La Niña winter months, when 

mean SLBpres values peak in December (fig. 11C). During 

La Niña winter months, mean SLBpres values range from 

1.45 mbars higher than average in the southern part of the 

study area to 2.48 mbars greater than average in the northern part.

Mean SLBpres variation is generally less during the 

summer than during the winter for both El Niño and La 

Niña events. During El Niño summer months from May to 

July, mean SLBpres values are 0.15 to 0.87 mbar below average in the northern part of the study area and 0.32 to 0.66 

mbar below average in the southern part (figs. 1, 11B). In 

the central part of the study area, mean SLBpres variation is 

greatest during El Niño summer months, ranging from 1.27 

mbars below average in June to 4.06 mbars above average in August. In contrast, mean SLBpres values during La 

Niña summer months range downward from 1.27 mbars 

above normal in May to only 0.27 mbar above normal 

in July (fig. 11C). During the La Niña month of August, 

mean SLBpres values in the southern part of the study area 

decrease the most—to 0.93 mbar below average.

Over the study period, monthly SLBpres values lower 

than 1000 mbars are typically more frequent from November to March (fig. 12A). Conversely, almost no monthly 

SLBpres values less than 1000 mbars occur during the rest 

of the year. In December, as many as 3.27 percent of total 

monthly SLBpres observations are lower than 1000 mbars at 

the north end of the study area (fig. 1) but almost none in 

the southern part, where they are more frequent in the late 
12 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

winter (February), when as many as 1.17 percent of total 

monthly SLBpres observations are lower than 1000 mbars.

Monthly SLBpres values lower than 1000 mbars are 

0.30 to 7.42 percent more frequent during El Niño winter 

months than during normal winter months (fig. 12B). In 

the northern part of the study area (fig. 1), they are most 

frequent in February, when they are 7.42 percent more frequent than average. In the central and southern parts of the 

study area, they are most frequent in March, when they are 

3.91 percent more frequent than average in the central part 

and 0.94 percent more frequent than average in the southern part. Conversely, they are even less frequent during La 

Niña winter months than during normal winter months. In 

the northern part of the study area, they are least frequent 

in December, when they are as much as 2.42 percent less 

frequent than average (fig. 12C).

Over the study period, monthly SLBpres values lower 

than 990 mbars are rare (fig. 13A). During normal months, 

they are most frequent in the northern part of the study area 

(fig. 1) but so infrequent as not to be statistically significant 

in the southern part. They are most frequent March, when 

they are typically 0.50 percent more frequent than average, 

and in December, when they are 0.35 percent more frequent 

than average. During El Niño winter months, monthly SLBpres values lower than 990 mbars are also most frequent in 

the northern part of the study area from February to March 

(fig. 13B), when they are as much as 1.54 percent more frequent than in normal winter months. Conversely, during La 

Niña winter months, monthly SLBpres values lower than 990 

mbars are 0.17 and 0.31 percent less frequent than average 

in February and March, respectively, in the northern part of 

the study area (fig. 13C).

Although interannual events have varying effects 

on mean SLBpres values, long-term trends of mean SLBpres

values decreased over the study period, mainly in the northern and central parts of the study area (0.044 and 0.046 

mbar/yr, respectively), while the long-term trend in the 

southern part was not statistically significant (figs. 1, 14A). 

Long-term trends of SLBpres variation in the southern part of 

the study area were not statistically significant (figs. 14B, 

14C). Long-term trends of minimum mean SLBpres values 

decreased in the northern and southern parts of the study 

area—almost twice as fast in the northern part as in the 

southern part (0.142 and 0.055 mbar/yr, respectively, fig. 

14D).

Long-term trends of the frequency of monthly SLBpres

values lower than 1000 mbars increased by 0.03 percent/

yr in the northern part of the study area; the long-term 

trend in the central and southern parts was not statistically 

significant (figs. 1, 15).

Sea-Surface Water Temperature

The distribution of monthly mean Wtemp values in the 

study area (fig. 1) is plotted in figure 16A (see apps. 5, 

8–15). The coolest seasonal mean Wtemp values are generally during the spring and early summer months, ranging 

from 10.78 to 11.17°C in the northern part of the study 

area and from 12.04 to 13.45°C in the southern part. The 

coolest mean Wtemp values for all parts of the study area are 

at Bodega Bay, one of the north-central buoy locations. 

Between the spring and early summer, mean Wtemp values at 

Bodega Bay drop from 11.82°C (March) to 9.95°C (June), 

likely owing to southward advection of the water upwelled 

just south of Point Arena by typical winds out of the northwest. Monthly mean Wtemp values are warmest in August 

and September, ranging from 12.74°C in the northern part 

of the study area to 15.95°C in the southern part. Winter 

mean Wtemp values from November to February are typically 

the coolest of the year, averaging 11.45°C in the northern 

part of the study area and 14.18°C in the southern part, 

resulting in a spatial variation of approximately 2.73°C 

Figure 13. Monthly variation in sea-level barometric pressures (SLBpres) lower than 990 mbars during all months (A), during El Niño months 

(B), and during La Niña months (C) throughout study area (fig. 1) over 

study period (1980–2002). Colored curves in figure 13A correspond to 

individual buoys located in figure 1. Note that although SLBpres values 

lower than 990 mbars are frequent during normal winter months, they 

are most frequent during El Niño winter months, particularly January 

through March, when storms are most common.

1 2 3 4 5 6 7 8 9 10 11 12 

1 2 3 4 5 6 7 8 9 10 11 12 

1 2 3 4 5 6 7 8 9 10 11 12 

North 

Central 

South 

North 

Central 

South 

0 

0.1 

0.2 

0.3 

0.4 

0.5 

-2.0 

1.5 

-1.0 

-0.5 

0 

0.5 

1.0 

1.5 

2.0 

-2.0 

-1.5 

-1.0 

-0.5 

0 

0.5 

1.0 

1.5 

2.0 

MONTH 

A 

B 

C 

FREQUENCY OF SEA-LEVEL BAROMETRIC PRESSURES

LOWER THAN 990 MILLIBARS, IN PERCENT
Results 13

Figure 14. Long-term trends of mean sea-level barometric pressure (SLBpres) throughout study area (fig. 1) over study period (1980–2002). A, 

Mean SLBpres value. B, Standard deviation of mean SLBpres value. C, Maximum SLBpres value. D, Minimum SLBpres value. Note that trendlines show 

decreases in mean, maximum, and minimum SLBpres values and increasing SLBpres variation.

1015

1020

1025

1030

1035

1980 1985 1990 1995 2000 2005

980 

985 

990 

995 

1000

1005

1010

1015

1980 1985 1990 1995 2000 2005

North = - 0.0116, R= 0.0166 

Central = - 0.0441, R= 0.0574 

South = - 0.0233, R= 0.0396 

North = - 0.1417, R= 0.1207 

Central = - 0.0208, R= 0.0244 

South = - 0.0554, R= 0.1259 

1010

1015

1020

1025

1980 1985 1990 1995 2000 2005

2 

4 

6 

8 

10

1980 1985 1990 1995 2000 2005

North = - 0.0439, R= 0.0999 

Central = - 0.0461, R= 0.0926 

South = - 0.0139, R= 0.0360

North = + 0.0204, R= 0.0643 

Central = + 0.0005, R= 0.0021 

South = + 0.0038, R= 0.0236 

YEAR 

MINIMUM SEA-LEVEL BAROMETRIC PRESSURE,

YEAR 

IN MILLIBARS 

MAXIMUM SEA-LEVEL BAROMETRIC PRESSURE,

IN MILLIBARS

A 

B 

C 

D 

MEAN SEA-LEVEL BAROMETRIC PRESSURE,

IN MILLIBARS 

STANDARD DEVIATION OF MEAN SEA-LEVEL BAROMETRIC

PRESSURE, IN MILLIBARS
14 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

tion in the northern part was not statistically significant 

(fig. 17B). Long-term trends of maximum Wtemp values 

also were not statistically significant (fig. 17C). In addition, long-term trends of minimum Wtemp values on average 

increased by 0.03°C/yr in the northern part of the study 

area and on average decreased by 0.02°C/yr in the southern 

part; the long-term trend in the central part was not statistically significant (fig. 17D).

Windspeed

Unlike most of the other parameters, the WNDspd

value does not show any well-defined north-to-south 

trend, although the two most southerly stations generally 

recorded the highest WNDspd values (fig. 18A; see app. 6). 

Throughout the year, monthly mean WNDspd values are 

generally highest during the late spring and early summer 

(March–June) and lowest during the fall and early winter 

Figure 15. Long-term trends of sea-level barometric pressures 

(SLBpres) lower than 1000 mbars throughout study area (fig. 1) over 

study period (1980–2002). Trends are not statistically significant.

1980 1985 1990 1995 2000 2005

North = + 0.030, R= 0.0645

Central = - 0.003, R= 0.0248

South = + 0.001, R= 0.0022

0

5

10

15

20

25

MEAN SEA-LEVEL BAROMETRIC PRESSURE,

YEAR

IN MILLIBARS

Figure 16. Monthly variation in mean sea-surface water temperature 

(Wtemp) during all months (A), during El Niño months (B), and during 

La Niña months (C) throughout study area (fig. 1) over study period 

(1980–2002). Colored curves in figure 16A correspond to individual 

buoys located in figure 1. Note mean Wtemp values are warmer than 

normal year round during El Niño months and cooler than normal 

during La Niña winter months.

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

9.0

10.0

11.0

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North 

Central 

South

North 

Central 

South

MONTH

MEAN SEA-SURFACE WATER TEMPERATURE, IN DEGREES CELSIUS

A

B

C

between the northern (cooler) and southern (warmer) parts 

of the study area.

During El Niño months, monthly mean Wtemp values 

are warmer than normal year round (fig. 16B). In winter, 

monthly mean Wtemp values are 0.17–1.46°C warmer than 

average, and in spring and early summer 0.37–1.46°C 

warmer than average. Mean Wtemp variation in the southern part of the study area (fig. 1) is greatest in September, 

when mean Wtemp values are 1.19°C warmer than average, 

but in the northern and central parts is greatest from February to May, when mean Wtemp values are 1.72°C warmer 

than average in the northern part and 1.75°C warmer than 

average the central part.

In contrast to the warmer-than-average mean Wtemp

values during El Niño winter months, mean Wtemp values 

during La Niña winter months are cooler than average. 

Mean Wtemp values are 0.21–0.64°C cooler than average in 

the northern part of the study area (fig. 1) and 0.49–1.20°C 

cooler than average in the southern part (fig. 16C). In 

addition, mean Wtemp values are coolest during the La Niña 

month of March, when they are 0.97–1.29°C cooler than 

average.

Long-term trends of mean Wtemp values on average 

increased 0.03°C/yr in the northern part of the study area 

(fig. 1) but on average decreased 0.03°C/yr in the southern 

part (fig. 17A). Long-term trends of the standard deviation 

of mean Wtemp, values indicate a decrease in the mean Wtemp

variation in the central and southern parts of the study 

area over the study period; the change in mean Wtemp varia-
Results 15

10

12

14

16

18

20

1980 1985 1990 1995 2000 2005

North = + 0.0236, R= 0.0835 

Central = - 0.0137, R= 0.0481 

South = - 0.0418, R= 0.1546 

8 

9 

10

11 

12

13

14

15

1980 1985 1990 1995 2000 2005

North = + 0.0299, R= 0.1705 

Central = + 0.0107, R= 0.0529 

South = - 0.0183, R= 0.0981 

10

12

14

16

18

1980 1985 1990 1995 2000 2005

North = + 0.0310, R= 0.1556

Central = - 0.0117, R= 0.0531

South = - 0.0312, R= 0.1401 

0.5 

1 

1.5 

2 

1980 1985 1990 1995 2000 2005

North = - 0.0001, R= 0.0155 

Central = - 0.0051, R= 0.1049 

South = - 0.0087, R= 0.1709 

YEAR 

MINIMUM SEA-SURFACE WATER TEMPERATURE,

IN DEGREES CELSIUS 

YEAR 

MAXIMUM SEA-SURFACE WATER TEMPERATURE,

IN DEGREES CELSIUS 

A 

B 

C 

D 

MEAN SEA-SURFACE WATER TEMPERATURE, 

IN DEGREES CELSIUS 

STANDARD DEVIATION OF MEAN SEA-SURFACE WATE

R

TEMPERATURE, IN DEGREES CELSIUS

Figure 17. Long-term trends of mean sea-surface water temperature (Wtemp) throughout study area (fig. 1) over study period (1980–2002). A, 

Mean Wtemp value. B, Standard deviation of mean Wtemp value. C, Maximum Wtemp value. D, Minimum Wtemp value. Note that although trendlines 

vary between parts of study area, overall north-to-south spatial variation decreases.
16 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

(September–December). The greatest longshore variation in 

mean monthly WNDspd values (3.83 m/s) occurs during August, 

and the least (0.77 m/s) during February.

During El Niño events, monthly mean WNDspd values on 

average are higher in the northern part of the study area and 

lower in the central and southern parts (fig. 1); during La Niña 

events, no overall general north-to-south trends in monthly 

mean WNDspd values are evident (figs. 18B, 18C). The month 

in which monthly mean WNDspd values increase the most 

varies throughout the study area. In the northern part, they 

increase the most (1.92 m/s) during El Niño events in February; however, in the central and southern parts they increase 

the most during La Niña events, specifically during March 

(1.09 m/s) and May (1.11 m/s), respectively.

Long-term trends of mean WNDspd values increased over 

the north half of the study area (fig. 1): by 0.034 m/s/yr in the 

northern part and by 0.027 m/s/yr in the central part (fig. 19); 

the long-term trend in the southern part was not statistically 

Figure 18. Monthly variation in mean windspeed (WNDspd) during all 

months (A), during El Niño months (B), and during La Niña months (C) 

throughout study area (fig. 1) over study period (1980–2002). Colored 

curves in figure 18A correspond to individual buoys located in figure 

1. Note that mean WNDspd values are greater than normal during 

El Niño winter months and less than normal during La Niña winter 

months.

1 2 3 4 5 6 7 8 9 10 11 12 

1 2 3 4 5 6 7 8 9 10 11 12 

1 2 3 4 5 6 7 8 9 10 11 12 

North 

Central 

South 

North 

Central 

South 

2.0 

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0 

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0 

0.5 

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1.5 

2.0 

MONTH 

MEAN WINDSPEED, IN METERS PER SECOND

A 

B 

C 

Figure 19. Long-term trends of mean wind speed 

(WNDspd) throughout study area (fig. 1) over study 

period (1980–2002). Note that trendlines show increases 

in northern and central parts of study area, suggesting 

increasing storm tracks through northern California.

3 

4 

5 

6 

7 

8 

9 

10 

1980 1985 1990 1995 2000 2005 

North = + 0.0338, R= 0.1712 

Central = + 0.0267, R= 0.1125 

South = + 0.0056, R= 0.0303 

YEAR 

MEAN WINDSPEED, IN METERS PER SECOND

Figure 20. Monthly variation in frequency of winds from the 

southwest (WNDwsw) during all months (A), during El Niño months 

(B), and during La Niña months (C) throughout study area (fig. 1) 

over study period (1980–2002). Colored curves in figure 20A correspond to individual buoys located in figure 1. Note that WNDwsw

values are higher than normal during El Niño months and lower 

than normal during La Niña months.

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

North 

Central 

South

MONTH

FREQUENCY OF WINDS FROM THE SOUTHWEST, IN PERCENT

A

B

C

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Results 17

significant. As these long-term trends continued over the 

study period, the north-to-south spatial gradient of mean 

WNDspd values increased.

Frequency of Winds from the Southwest

Throughout the year, monthly WNDwsw values are highest in the winter and lowest in the summer months (fig. 

20A; see apps. 7–15). Monthly WNDwsw values are highest 

between November and February, ranging from 61.26 to 

75.80 percent in the northern part of the study area (fig. 

1) and from 38.17 to 55.76 percent in the southern part. 

During these winter months, the north-to-south spatial 

gradient of monthly WNDwsw values is greatest in December—33.99 percent greater in the northern part of the study 

area than in the southern part—but least in February—only 

5.50 percent greater in the northern part. Monthly WNDwsw

values are much lower in the spring and summer months 

than in the winter: 38.71 to 61.36 percent of monthly 

WNDwsw values in the northern part of the study area and 

21.30 to 45.14 percent of monthly WNDwsw values in the 

southern part.

Monthly WNDwsw values are highest during El Niño 

winter months (fig. 20B). The month in which they are 

highest varies throughout the study area (fig. 1): in the 

southern part in early winter (December), when they are as 

much as 21.08 percent higher than average; in the central 

part during late El Niño winters (February), when they are 

as much as 20.25 percent higher than average; and in the 

northern part in April, when they are 26.50 percent higher 

than average.

In contrast, monthly WNDwsw values are typically, but 

not always, lower than average during La Niña winter 

months (fig. 20C). For example, in November, they are 

only 3.78 percent lower than average in the southern part 

of the study area (fig. 1) but 17.55 percent lower than average in the northern part. In January to March, they are 4.79 

to 15.93 percent lower than average in the northern and 

southern parts of the study area and as much as 12.84 percent higher than average in the central part.

Long-term trends of monthly WNDwsw values on average increased over the study period: by 0.34 percent/yr in 

the northern part of the study area (fig. 1) and by 0.23 percent/yr in the southern part; the long-term trend in the central part was not statistically significant (fig. 21). As these 

trends continued over the study period, the north-to-south 

spatial gradient of monthly WNDwsw values increased.

Directional Variations in Significant Wave 

Height, Dominant Wave Period, and Windspeed

As stated above, only the Monterey Bay buoy (sta. 

46042, fig. 1) has the capability to measure WVdir, which 

it gained only in 1993. Thus, to investigate the relations 

between directional variations in Hsig, Tdom, and WNDspd, 

these analyses are limited to the 10 years of concurrent 

hourly (not monthly mean) Hsig, Tdom, and WNDspd data from 

1993 to 2002. The hourly variation in Hsig as a function of 

WVdir throughout the year is plotted in figure 22. Hourly 

Hsig values are higher, and their variation is greater, in the 

winter months than in the summer, when Hsig values are 

smaller and WVdir is primarily out of the northwest or south 

and the southwest. The hourly variation in Tdom as a function of WVdir throughout the year is plotted in figure 23. In 

the winter, Tdom values are longer out of the northwest and 

shorter out of the south and southwest; and in the summer, 

Tdom values are more consistently shorter out of the northwest and longer out of the south and southwest. The hourly 

variation in WNDspd as a function of WNDdir throughout the 

year is plotted in figure 24. In the winter, the variation in 

WNDdir is much greater, including a substantial number of 

high offshore WNDspd values that are not observed during 

the rest of the year; in the summer, WNDspd are commonly 

higher, and WNDdir are much more consistently out of the 

northwest.

Numerous observations during previous El Niño 

winters (Griggs and Johnson, 1983; Seymour, 1983; Storlazzi and Griggs, 2000) suggest that during intense winter 

storms, high waves approaching the coast of California are 

more out of the west and southwest than during normal 

(non-El Niño) winters. Although statistical analyses looking for mean hourly variations in WVdir for all hourly 

Figure 21. Long-term trends in frequency of winds from the southwest (WNDwsw) throughout study area (fig. 1) over study period 

(1980–2002). Note that trendlines show greatest increase in northern 

part of study area, suggesting increasing storm tracks through northern California.

1980 1985 1990 1995 2000 2005

North = + 0.34, R= 0.0974 

Central = + 0.11, R= 0.0439 

South = + 0.23, R= 0.1122 

YEAR

0

20

40

60

80

100

FREQUENCY OF WINDS FROM THE SOUTHWEST,

IN PERCENT
18 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

Figure 22. Compass plots of variation in hourly significant wave height (Hsig) as a function of hourly 

dominant wave direction (WVdir) at Monterey Bay buoy (sta. 46042, fig. 1) during years when concurrent 

directional wave and wind data were available (1993–2002). Radial axis, Hsig values (in meters) increase 

outward (0–10 m) from center of compass plot; circumferential axis, azimuth of WVdir values (in degrees). 

Note greater Hsig and WVdir variations in winter than in summer.

Figure 23. Compass plots of variation in hourly dominant wave period (Tdom) as a function of hourly 

dominant wave direction (WVdir) at Monterey Bay buoy (sta. 46042, fig. 1) during years when concurrent 

directional wave and wind data were available (1993–2002). Radial axis, Tdom values (in seconds) increase 

outward (0–20 s) from center of compass plot; circumferential axis, azimuth of WVdir value (in degrees). 

Note greater Tdom and WVdir variation in winter, and shorter Tdom values more consistently out of northwest 

and longer Tdom values more consistently out of southwest in summer.

 5

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JANUARY FEBRUARY

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MARCH APRIL

MAY JUNE

SEPTEMBER OCTOBER

JULY AUGUST

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JANUARY FEBRUARY

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MARCH APRIL

MAY JUNE

SEPTEMBER OCTOBER

JULY AUGUST
Results 19

Figure 24. Compass plots of variation in hourly windspeed (WNDspd) as a function of hourly wind 

direction (WNDdir) at Monterey Bay buoy (sta. 46042, fig. 1) during years when concurrent directional 

wave and wind data were available (1993–2002). Radial axis, WNDspd values (in meters per second) 

increase outward (0–20 m/s) from center of compass plot; circumferential axis, azimuth of WVdir value (in 

degrees). Note greater WNDspd and WNDdir variations in winter and WNDdir values more consistently out 

of northwest in summer.

30

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JANUARY FEBRUARY

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SEPTEMBER OCTOBER

JULY AUGUST

Hsig values between El Niño and La Niña periods were 

inconclusive, similar analyses for the highest 10 percent 

of hourly Hsig values during El Niño and La Niña periods 

reveal a significant departure in hourly WVdir values (fig. 

25). During El Niño periods, the highest 10 percent of 

hourly Hsig values show a distinct shift to more southerly 

and southwesterly directions relative to La Niña periods, 

likely resulting in a more direct impact of waves on California’s generally southwest facing coastline, increasing 

wave-induced setup, and a change in the general southerly 

direction of longshore sediment transport, as suggested by 

the USGS/UCSC/NASA/NOAA Collaborative Research 

Group (1998) and Storlazzi and Griggs (2000).

In an attempt to generalize wave patterns along 

the central California coast, we synthesized more than 

2,800,000 hourly observations of Hsig, Tdom, WVdir, WNDspd, 

and WNDdir from the Monterey Bay buoy (sta. 46042, fig. 

1) collected over the years 1993–2002, when concurrent 

directional wave and wind data were available (fig. 26). 

Extratropical lows and cold fronts in the North Pacific 

generate long-Tdom swell that impacts the study area (fig. 1) 

from the west and northwest, with a general WVdir of azimuth 290° and a WVdir range of azimuths 210–330°, which 

we refer to as North Pacific Swell. These waves have Hsig

values of 2 to 10 m and Tdom values of 10 to 25 s, with 

the largest Hsig and longest Tdom values during the winter 

(October–May). Northwest winds generated by the California High blowing over the open ocean and insolationdriven sea breezes generate short-Tdom waves that impact 

the study area from the northwest, with a general WVdir

of azimuth 310° and a WVdir range of azimuths 280–350°, 

which we refer to as Northwest Wind Waves. These waves 

have Hsig values of 1 to 4 m and Tdom values of 3 to 10 s. 

Although they occur throughout the year, they occur most 

consistently (90–95 percent of the time) from April to 

October and less frequently (55–65 percent of the time) 

in the winter. Storms in the South Pacific and off Central 

America generate long-Tdom waves that impact the study 

area from the south and southwest, with a general WVdir

of azimuth 290° and a WVdir range of azimuths 150–260°, 

which we refer to as Southern Swell. These waves have Hsig

values of 0.3 to 3 m and Tdom values of 10 to 25 s. Although 

they occur throughout the year, they occur most consistently and with the largest Hsig values from April to October, when large storms occur in the South Pacific during 

the Southern Hemisphere’s winter and tropical cyclones 

develop off Central America. Storms passing through central California generate short-Tdom waves that can impact 
20 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

Significant wave height (m) 

Dominant wave period (s) 

Sea-level barometric pressure (mbars) 

Sea-surface water temperature (oC) 

Windspeed (m/s) 

Table 2. Recurrence-interval projections of maximums of oceangraphic and meteorologic parameters.

[See figure 1 for locations]

Figure 25. Bar charts showing frequency distribution of highest 10 

percent of hourly significant wave heights (Hsig) as a function of hourly 

dominant wave direction (WVdir) during El Niño events (A), La Niña 

events (B), and the change in WVdir distribution between El Niño and 

La Niña events (C), from observations at Monterey Bay buoy (sta. 

46042, fig. 1) during years when directional wave data were available 

(1993–2002). Fewer of the largest Hsig values are out of the northwest, 

and more of the largest Hsig values are out of the west and southwest, 

during El Niño events than during La Niña events.

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STATISTICAL FREQUENCY OF HIGHEST 10 PERCENT OF SIGNIFICANT WAVE HEIGHTS

DOMINANT WAVE DIRECTION, IN DEGREES 

A 

B 

C 

the study area from all orientations, depending on the latitude of the storm’s track; we refer to these waves as Local

Wind Waves. These waves have Hsig values of 1 to 4 m and 

Tdom values of 3 to 10 s and are most frequent in the winter 

months (October–May).

Recurrence Intervals

Recurrence-interval projections of maximum Hsig

values are greatest in the northern part of the study area 

(fig. 1), where calculated extreme values range from 9.01 

m (on a 2-year recurrence interval) to 14.20 m (on a 100-

year recurrence interval), as listed in table 2. Recurrence 

interval projections of maximum Tdom values are greatest in 

the central part of the study area, where calculated extreme 

values range from 26.84 s (on a 2-year recurrence interval) 

to 36.45 s (on a 100-year recurrence interval). Recurrence 

interval projections of maximum SLBpres values are higher 

in the southern part of the study area, where calculated 

extreme values are 1000.35 mbars (on a 2-year recurrence 

interval) and 988.79 mbars (on a 100-year recurrence 

interval), and lower in the northern part, where calculated 

extreme values are 989.74 mbars (on a 2-year recurrence 

interval) and 967.17 mbars (on a 100-year recurrence interval). Recurrence-interval projections of maximum Wtemp
21

Figure 26. General wave patterns (in degrees of azimuth) along the central California coast, synthesized from more than 2,800,000 

hourly observations of significant wave height, dominant wave period, dominant wave direction, windspeed, and wind direction 

at Monterey Bay buoy (sta. 46042, fig. 1) during years when concurrent directional wave and wind data were available (1993–

2002). Concentric bands delineate typical range of direction, and arrows denote mean direction, for a given wave pattern.

Santa

Cruz

Monterey

San

Jose

Salinas

CALIFORNIA

M a p

A r e a

150o

Local Wind Waves

GENERATION:

Storms passing through central California

OCCURRENCE:

Generally in October-April;

typical year: 50 percent of the time

HEIGHT: 1-4 m

PERIOD: 3-10 s

210o

330o

North Pacific Swell

GENERATION:

Storms in the North Pacific, mid-latitude lows,

and cold fronts

OCCURRENCE:

Throughout the year; largest in October-May;

largest waves to impact the region

HEIGHT: 2-10 m

PERIOD: 10-25 s

290o

280o

350o

Northwest Wind Waves

GENERATION:

Northwest winds generated by the California

High blowing over the open ocean; sea breezes

OCCURRENCE:

Throughout the year; dominant in April-October;

summer: 90-95 percent, winter: 55-65 percent of the time 

HEIGHT: 1-4 m

PERIOD: 3-10 s

310o

260o

200o

Southern Swell

GENERATION:

Storms in the South Pacific and off Central America

OCCURRENCE:

Throughout the year; generally in April - October;

typical year: 50 percent of the time

HEIGHT: 0.3-3 m

PERIOD: 10-25 s

Results
22 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

values are greater in the southern part of the study area 

than in the northern part, where calculated extreme values 

are 21.98°C and 18.42°C, respectively (on a 2-year recurrence interval), but greatest in the central part, where the 

calculated extreme value is 29.44°C (on a 100-year recurrence interval). Finally, recurrence-interval projections of 

maximum WNDspd values are greatest in the northern part of 

the study area, where calculated extreme values range from 

25.31 m/s (on a 2-year recurrence interval) to 40.94 m/s (on 

a 100-year recurrence interval).

Discussion

Although many studies have documented the impacts of El 

Niño and La Niña events with respect to the California coastline, none has documented how these events specifically affect 

the “transition zone” off central California and their implications for physical and biologic processes. The results of this 

study indicate significant statistical trends over the study period 

for almost all oceanographic and meteorologic parameters. 

Storms during normal winter months typically track across 

the Northeast Pacific, resulting in larger mean Hsig values and 

shorter mean Tdom values in the northern part of the study area 

(fig. 1), and smaller mean Hsig values and longer mean Tdom

values in the southern part. In addition, WNDdir variation is 

generally greater (increased WNDwsw values) in the northern 

part of the study area, as westerly and southwesterly winds 

are associated with winter-storm activity (Bixby, 1962) and 

the relative latitude of the California High during the summer. 

During normal winter months, storminess tends to be greatest in 

December and January. The development of the California High 

during normal summer months results in lower mean Hsig and 

Tdom values throughout the study area, as wave conditions are 

milder in the summer. Spatial variation in mean SLBpres values is 

greater, as barometric pressures are higher in the northern part 

of the study area because of the position of the California High. 

The lower mean SLBpres values in the southern part of the study 

area are due not only to tropical-cyclone activity off Mexico and 

Central America during normal summer months but also to the 

Mexican monsoon, a seasonal reversal of atmospheric circulation that transports moisture from the Gulf of California to the 

Southwestern United States. As expected, the spatial variation 

in mean Wtemp values shows cooler temperatures in the northern 

part of the study area and warmer temperatures in the southern 

part year round.

During El Niño events, wind and wave behavior changes 

significantly throughout the “transition zone” off central 

California. Winter El Niño storms generally track farther 

to the south, striking the California coastline more directly 

and resulting in larger mean Hsig values and longer mean 

Tdom values throughout central California, including a higher 

percentage of WVdir values from the south and southwest. In 

addition, lower mean SLBpres values, larger mean SLBpres variations, and higher WNDwsw values also suggest more frequent 

and bigger storms tracking throughout the study area during 

El Niño events. In contrast, La Niña events generally impact 

the “transition zone” less directly, as storm tracks are farther 

north, resulting in smaller mean Hsig values and more frequent 

northwesterly WVdir values than during El Niño winter months 

(but sometimes still larger than during normal winter months) 

and smaller SLBpres and WNDwsw variations. Thus, La Niña 

winter months bring less frequent and earlier storminess than 

either El Niño or normal months, generally resulting in less 

coastal erosion (Storlazzi and Griggs, 2000).

Long-term trends of mean Hsig values on average 

increased by 2.0 cm/yr throughout central California (fig. 

1) over the study period. These results contradict previous 

observations of no significant long-term increase in Hsig values 

off central California (Allan and Komar, 2000). Lower mean 

SLBpres values, longer mean Tdom values, and increasing mean 

WNDspd and WNDwsw values suggest increasing storminess and 

storm intensity over the study period, as noted by Graham 

and Diaz (2001). Long-term trends suggest a decreasing Wtemp

variation over the study period, resulting in a smaller north-tosouth longshore temperature gradient and a more nearly homogeneous Wtemp distribution along the central California coast.

These long-term trends of increased storminess, lower 

mean SLBpres values, and cooler mean Wtemp values in the 

Northeast Pacific concur with the suggestions by Hare and 

Mantua (2002) that the Pacific Decadal Oscillation (PDO), 

an interdecadal change in climate, has begun to shift from 

a warm phase to a cool phase. Because its phases generally 

last 20–30 years, with the latest warm phase starting in 1977, 

some workers believe that a PDO phase shift occurred with 

the demise of the 1997/98 El Niño and the subsequent inception of the 1998/99 La Niña event, as discussed by Hare and 

Mantua (2002). A warm PDO phase is marked by unusually 

warm mean Wtemp values along the U.S. west coast and high 

mean SLBpres values over western North America, whereas a 

cold PDO phase exhibits cooler mean Wtemp values along the 

Northeast and tropical Pacific. A shift to a cool PDO phase 

would result in more La Niña-like conditions and thus stronger 

and longer La Niña events and shorter, weaker El Niño events 

(Hare and Mantua, 2002).

Conclusions

We have analyzed more than 20 years of hourly deepwater buoy data from off central California to investigate 

long-term trends and compute statistically significant probability estimates of the behavior of measured oceanographic 

and meteorologic parameters during different climatic regimes 

(table 3). Significantly different trends were observed in the 

datasets during El Niño and La Niña months, reinforcing longheld but relatively unsupported theories on the spatial and 

temporal variations in oceanographic and meteorologic forcing along the central California coast during different ENSO 

phases. Because storms generally track directly across California during El Niño months, mean Hsig values are higher, with 

Hsig values greater than 4 m as much as 30 percent more frequent than average. In addition, mean Tdom values are shorter, 
References Cited 23

mean SLBpres values are lower, and mean WNDwsw values are 

higher, suggesting greater storminess and storm proximity.

These intense wave conditions impact the “transition 

zone” off central California most significantly during El Niño 

winter months, when mean Hsig values are greater than average, mean WNDwsw values are higher than average, and mean 

Wtemp values are warmer than average. In contrast, their impact 

is less direct during La Niña winter months, when mean Hsig

values are lower than during El Niño months and the largest 

storms generally strike earlier in the winter. Mean Wtemp values 

are cooler than average during the spring and summer as 

northwesterly winds predominate (decreased WNDwsw values).

Our study indicates that mean Hsig and WNDwsw values 

increased, mean Tdom and SLBpres values decreased, and mean 

Wtemp variation was smaller throughout the study area (fig. 1) 

over the study period. These results indicate that the “transition zone” off central California (from high-energy wave 

conditions in the Pacific Northwest to milder wave conditions 

off southern California) is actually more energetic than once 

believed. With the advantage of seasonal, interannual, and 

long-term data, our study anticipates a better understanding 

of the influence of spatial and temporal variations in oceanographic and meteorologic forcing on physical, geologic, and 

biologic processes along the central California coast.

Acknowledgments

This research is part of the USGS Central California 

Regional Synthesis Project and Benthic Habitats Project’s 

effort to better understand the impact of geologic and oceanographic processes on central California’s shoreline and 

nearshore ecosystems. We thank Jane Reid (USGS), who overextended herself in helping us with geospatial data analysis 

and numerous small but extremely important tasks. We also 

thank Bruce Richmond (USGS) and Guy Cochrane (USGS), 

who contributed numerous excellent suggestions and timely 

reviews of the manuscript. George Havach of the USGS Western Publication Group deserves special thanks for working 

hard with us to get this report into the correct format.

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Parameter Part of

study area Mean Minimum Maximum Standarddeviation

North +2.0 +0.9 +5.7 +0.6

Central +2.1 +1.1 +6.8 +0.8

Significant wave height

(cm/yr). South +1.9 +0.2 +7.7 +1.0

North +0.039 +0.001 +0.061 +0.006

Central +0.025 N.S. +0.037 N.S.

Dominant wave period

(s/yr). South +0.045 +0.030 +0.035 N.S.

North –0.04 –0.14 N.S. N.S.

Central –0.05 N.S. N.S. N.S.

Sea-level barometric

pressure (mbar/yr).

South N.S. –0.06 N.S. N.S.

North +0.03 +0.01 +0.02 N.S.

Central N.S. N.S. N.S. –0.01

Sea-surface water temperature (oC/yr). South –0.03 +0.02 –0.04 –0.01

North +0.34 – – – – – –

Central N.S. – – – – – –

Frequency of winds from

the southwest

(percent/yr). South +0.23 – – – – – –

Table 3. Long-term trends of oceanographic and meteorologic parameters throughout the study area over the study period (1980–2002).

[N.S., not statistically significant]
24 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

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25–40.
25

Hourly Raw Data

The following data were collected from all eight buoys:

1. Wind direction (in degrees)

2. Windspeed (in meters per second)

3. Significant wave height (in meters)

4. Dominant wave period (in seconds)

5. Dominant wave direction (in degrees of azimuth)

6. Sea-level barometric pressure (in millibars)

7. Sea-level air temperature (in degrees Celsius)

8. Sea-surface water temperature (in degrees Celsius)

Monthly Mean Statistics

 The following parameters were calculatedonly for those 

months with more than 480 hours (20 days) of data. Besides 

calculating the dataset for all months, data subsets were 

created for El Niño months, La Niña months, and non-El 

Niño-La Niña months, on the basis of the MEI:

1. Wind direction (in degrees): minimum, maximum, 

mean, and standard deviation

2. Windspeed (in meters per second): minimum, maximum, mean, and standard deviation

3. Significant wave height (in meters): minimum, maximum, mean, and standard deviation

4. Dominant wave period (in seconds): minimum, maximum, mean, and standard deviation

5. Dominant wave direction (in degrees of azimuth): minimum, maximum, mean, and standard deviation

6. Sea-level barometric pressure (in millibars): minimum, 

maximum, mean, and standard deviation

7. Sea-level air temperature (in degrees Celsius): minimum, maximum, mean, and standard deviation

8. Sea-surface water temperature (in degrees Celsius): 

minimum, maximum, mean, and standard deviation

9. Exceedance (in percent) of significant wave heights 

greater than 4, 8, and 8 m

10. Exceedance (in percent) of sea-level barometric pressures lower than 1000, 990, and 980 mbars

11. Frequency (in percent) of southerly/southwesterly/westerly wave directions between azimuths 080° and 270°

12. Frequency (in percent) of southerly/southwesterly/

westerly wave directions between azimuths 070° and 

250°

Recurrence-Interval Projections and Calculated 

Extreme Values

The following extreme values calculated on 2-, 10-, 25-, 

50-, and 100-year recurrence intervals are based on FisherTippet type I distributions of monthly extreme values (n>150):

1. Maximum windspeed (in meters per second)

2. Maximum significant wave height (in meters)

3. Maximum dominant wave period (in seconds)

4. Maximum sea-level barometric pressure (in millibars)

5. Maximum sea-level air temperature (in degrees Celsius)

6. Maximum sea-surface water temperature (in degrees 

Celsius)

Appendix 1. Raw and Calculated Datasets from Eight Buoys Deployed off the Central 

California Coast by the National Oceanic and Atmospheric Administration’s National 

Data Buoy Center over the Study Period (1980–2002)

Appendixes
26 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

Appendix 2. Mean Monthly Significant Wave Height at Eight 

Buoys Deployed by the National Oceanic and Atmospheric 

Administration’s National Data Buoy Center over the Study 

Period (1980–2002)

0

2

4

0

2

4

0

2

4

0

2

4

MEAN SIGNIFICANT WAVE HEIGHT, IN METERS

0

2

4

0

2

4

0

2

4

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

0

2

4

Eel River

Point Arena

Bodega

San Francisco

Half Moon Bay

Monterey Bay

Cape San Martin

Point Arguello

YEAR
Appendixes 27

Appendix 3. Mean Monthly Dominant Wave Period at Eight 

Buoys Deployed by the National Oceanic and Atmospheric 

Administration’s National Data Buoy Center over the Study 

Period (1980–2002)

5

10

15

20

5

10

15

20

5

10

15

20

5

10

15

20

MEAN DOMINANT WAVE PERIOD, IN SECONDS

5

10

15

20

5

10

15

20

5

10

15

20

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

5

10

15

20

Eel River

Point Arena

Bodega

San Francisco

Half Moon Bay

Monterey Bay

Cape San Martin

Point Arguello

YEAR
28 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

Appendix 4. Mean Monthly Sea-Level Barometric Pressure at 

Eight Buoys Deployed by the National Oceanic and Atmospheric 

Administration’s National Data Buoy Center over the Study 

Period (1980–2002)

1010

1020

1030

1010

1020

1030

1010

1020

1030

1010

1020

1030

MEAN SEA-LEVEL BAROMETRIC PRESSURE, IN MILLIBARS 1010

1020

1030

1010

1020

1030

1010

1020

1030

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

1010

1020

1030

Eel River

Point Arena

Bodega

San Francisco

Half Moon Bay

Monterey Bay

Cape San Martin

Point Arguello

YEAR
Appendixes 29

Appendix 5. Mean Monthly Sea-Surface Water Temperature 

at Eight Buoys Deployed by the National Oceanic and 

Atmospheric Administration’s National Data Buoy Center 

over the Study Period (1980–2002)

5

10

15

20

5

10

15

20

5

10

15

20

5

10

15

20

MEAN SEA-SURFACE WATER TEMPERATURE, IN DEGREES CELSIUS

5

10

15

20

5

10

15

20

5

10

15

20

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

5

10

15

20

Eel River

Point Arena

Bodega

San Francisco

Half Moon Bay

Monterey Bay

Cape San Martin

Point Arguello

YEAR
30 Spatial and Temporal Variations in Oceanographic and Meteorologic Forcing Along the Central California Coast

Appendix 6. Mean Monthly Windspeed at Eight Buoys 

Deployed by the National Oceanic and Atmospheric 

Administration’s National Data Buoy Center over the Study 

Period (1980–2002)

0 

5 

10 

0 

5 

10 

0 

5 

10 

0 

5 

10 

0 

5 

10 

MEAN WINDSPEED, IN METERS PER SECOND

0 

5 

10 

0 

5 

10 

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 

0 

5 

10 

Eel River 

Point Arena 

Bodega 

San Francisco 

Half Moon Bay 

Monterey Bay 

Cape San Martin 

Point Arguello 

YEAR 
Appendixes 31

Appendix 7. Mean Monthly Frequency of Winds from the 

Southwest at Eight Buoys Deployed by the National Oceanic 

and Atmospheric Administration’s National Data Buoy Center 

over the Study Period (1980–2002)

0 

50 

100 

0 

50 

100 

0 

50 

100 

0 

50 

100 

FREQUENCY OF WINDS FROM THE SOUTHWEST, IN PERCENT

0 

50 

100 

0 

50 

100 

0 

50 

100 

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 

0 

50 

100 

Eel River 

Point Arena 

Bodega 

San Francisco 

Half Moon Bay 

Monterey Bay 

Cape San Martin 

Point Arguello 

YEAR 
Appendix 8. Mean ±1 Standard Deviation Monthly Statistics of Oceanographic and MeParameters at the Eel River Buoy (sta. 46022, fig. 1) for All Months and for El Niño and L

Month Significant wave height (m) Dominant wave period (sec) Sea-level barometric pressure (mbars) Sea-surface water temperature (°C) 

All months January (1) 3.06 ± 0.54 12.91 ± 0.96 1018.57 ± 3.52 11.22 ± 0.40 

February (2) 3.09 ± 0.40 12.91 ± 1.12 1017.70 ± 4.06 11.03 ± 0.76 March (3) 2.90 ± 0.21 12.39 ± 0.69 1016.76 ± 3.00 11.03 ± 0.67 April (4) 2.43 ± 0.28 11.19 ± 0.81 1018.83 ± 1.11 10.97 ± 0.71 May (5) 2.09 ± 0.14 9.95 ± 0.79 1018.18 ± 1.25 11.18 ± 1.05 June (6) 1.99 ± 0.25 9.43 ± 0.76 1017.08 ± 1.15 11.69 ± 0.80 July (7) 1.81 ± 0.32 8.75 ± 0.42 1017.20 ± 1.24 12.14 ± 0.86 August (8) 1.66 ± 0.22 8.97 ± 0.45 1016.54 ± 0.86 12.94 ± 0.96 September (9) 1.92 ± 0.16 9.93 ± 0.68 1015.12 ± 0.73 12.75 ± 0.97 October (10) 2.33 ± 0.33 11.30 ± 0.46 1017.42 ± 1.39 12.27 ± 1.22 November (11) 2.84 ± 0.54 12.34 ± 0.76 1018.52 ± 3.06 12.06 ± 1.23 December (12) 3.22 ± 0.59 13.04 ± 0.88 1019.35 ± 2.60 11.63 ± 1.12 

El Niño months January (1) 3.45 ± 0.25 13.34 ± 0.53 1015.19 ± 4.52 11.77 ± 1.17 

February (2) 3.86 ± 1.04 13.76 ± 1.31 1010.52 ± 2.91 12.58 ± 0.65 March (3) 2.82 ± 0.38 12.71 ± 0.59 1013.04 ± 3.07 12.39 ± 0.24 April (4) 2.30 ± 0.21 11.34 ± 1.20 1017.57 ± 2.13 12.01 ± 1.03 May (5) 1.94 ± 0.34 9.70 ± 1.04 1017.33 ± 0.79 12.41 ± 0.87 June (6) 2.04 ± 0.14 9.53 ± 0.72 1016.55 ± 1.26 12.01 ± 1.26 July (7) 1.81 ± 0.23 8.78 ± 0.52 1016.94 ± 0.75 12.53 ± 0.94 August (8) 1.66 ± 0.26 9.01 ± 1.27 1016.59 ± 0.86 13.61 ± 1.07 September (9) 1.84 ± 0.23 9.63 ± 1.01 1015.31 ± 1.24 13.39 ± 2.26 October (10) 2.28 ± 0.36 11.23 ± 0.73 1016.98 ± 0.49 12.28 ± 0.67 November (11) 2.96 ± 0.36 12.38 ± 0.59 1017.83 ± 3.76 12.55 ± 1.76 December (12) 3.40 ± 0.31 13.37 ± 0.59 1018.31 ± 0.78 11.87 ± 1.58 

La Niña months January (1) 2.94 ± 0.36 13.01 ± 1.01 1020.75 ± 2.25 10.83 ± 1.13 

February (2) 3.10 ± 0.65 12.45 ± 1.14 1018.82 ± 3.38 10.40 ± 1.06 March (3) 3.15 ± 0.49 12.73 ± 1.49 1018.06 ± 1.79 9.70 ± 0.48 April (4) 2.31 ± 0.45 10.60 ± 0.31 1018.52 ± 0.82 10.58 ± 1.23 May (5) 2.04 ± 0.28 10.12 ± 0.21 1019.01 ± 1.09 10.54 ± 1.07 June (6) 1.97 ± 0.00 9.56 ± 0.00 1017.98 ± 0.00 12.88 ± 0.00 July (7) 1.77 ± 0.01 8.47 ± 0.71 1017.56 ± 0.44 11.52 ± 0.23 August (8) 1.85 ± 0.14 8.68 ± 0.64 1015.33 ± 0.64 11.97 ± 0.70 September (9) 2.10 ± 0.11 9.74 ± 0.43 1014.41 ± 1.81 11.96 ± 1.25 October (10) 2.36 ± 0.00 11.65 ± 0.00 1017.81 ± 0.55 12.42 ± 0.20 November (11) 2.96 ± 0.76 13.30 ± 0.01 1018.34 ± 2.26 11.67 ± 0.68 December (12) 3.20 ± 0.82 12.73 ± 1.34 1021.43 ± 2.44 11.08 ± 0.47 
Appendix 9. Mean ±1 Standard Deviation Monthly Statistics of Oceanographic and MeParameters at the Point Arena Buoy (sta. 46014, fig. 1) for All Months and for El Niño anMonths

Month Significant wave 

height

(m)

Dominant wave 

period

(sec)

Sea-level barometric 

pressure

(mbars)

Sea-surface water 

temperature

(°C)

F

f

All months 

January (1) 2.86 ± 0.46 13.15 ± 1.01 1018.74 ± 2.79 11.94 ± 0.52 February (2) 2.95 ± 0.44 13.20 ± 1.16 1017.78 ± 2.30 11.77 ± 0.43 March (3) 2.80 ± 0.22 12.71 ± 0.65 1017.39 ± 2.84 11.33 ± 0.70 April (4) 2.35 ± 0.29 11.64 ± 1.01 1017.98 ± 0.96 10.96 ± 0.68 May (5) 2.16 ± 0.16 9.97 ± 0.76 1016.56 ± 1.08 11.06 ± 0.63 June (6) 2.11 ± 0.26 9.23 ± 0.96 1015.46 ± 0.77 11.24 ± 0.72 July (7) 1.96 ± 0.21 8.74 ± 0.84 1015.29 ± 1.30 12.36 ± 3.29 August (8) 1.75 ± 0.13 8.86 ± 0.43 1014.88 ± 0.99 12.85 ± 1.82 September (9) 1.91 ± 0.15 10.23 ± 0.70 1014.07 ± 1.06 13.41 ± 0.96 October (10) 2.22 ± 0.25 11.60 ± 0.68 1016.58 ± 0.96 13.05 ± 1.15 November (11) 2.74 ± 0.41 12.43 ± 0.76 1018.07 ± 2.02 12.85 ± 1.07 December (12) 3.08 ± 0.41 13.33 ± 1.02 1019.47 ± 2.22 12.47 ± 0.85 

El Niño months 

January (1) 3.33 ± 0.28 13.72 ± 0.71 1016.65 ± 4.03 12.51 ± 1.17 February (2) 3.80 ± 0.67 14.12 ± 0.94 1013.26 ± 4.15 12.99 ± 0.99 March (3) 2.81 ± 0.05 12.47 ± 0.29 1014.59 ± 2.70 12.37 ± 1.00 April (4) 2.57 ± 0.14 12.77 ± 0.57 1016.88 ± 1.61 11.73 ± 0.72 May (5) 1.86 ± 0.31 10.38 ± 0.85 1016.37 ± 1.24 12.52 ± 0.85 June (6) 2.19 ± 0.08 9.45 ± 0.57 1014.81 ± 0.89 11.75 ± 0.98 July (7) 1.95 ± 0.20 8.43 ± 0.57 1015.26 ± 0.92 12.25 ± 0.81 August (8) 1.61 ± 0.26 9.45 ± 1.51 1015.64 ± 1.15 13.59 ± 1.01 September (9) 1.87 ± 0.22 10.19 ± 1.05 1014.86 ± 1.32 13.77 ± 0.99 October (10) 2.11 ± 0.35 11.82 ± 0.93 1016.80 ± 0.77 13.60 ± 1.06 November (11) 2.77 ± 0.31 12.40 ± 0.62 1017.05 ± 3.19 13.78 ± 1.82 December (12) 3.39 ± 0.33 13.66 ± 0.60 1018.29 ± 1.67 12.88 ± 1.13 

La Niña months 

January (1) 2.80 ± 0.52 13.35 ± 0.89 1019.86 ± 1.36 11.64 ± 0.97 February (2) 2.97 ± 0.54 12.78 ± 1.26 1018.39 ± 3.29 11.20 ± 1.16 March (3) 3.02 ± 0.48 13.20 ± 1.45 1018.29 ± 1.25 10.31 ± 0.39 April (4) 2.27 ± 0.64 11.33 ± 0.80 1017.66 ± 1.20 11.84 ± 0.00 May (5) 2.09 ± 0.57 10.00 ± 0.19 1018.19 ± 0.85 10.65 ± 0.00 June (6) 2.08 ± 0.00 8.98 ± 0.00 1015.36 ± 0.00 11.49 ± 0.00 July (7) 1.85 ± 0.04 8.92 ± 0.54 1016.00 ± 1.33 11.13 ± 0.00 August (8) 1.73 ± 0.17 8.49 ± 1.03 1014.44 ± 1.96 12.17 ± 0.78 September (9) 2.04 ± 0.19 10.07 ± 0.13 1013.66 ± 1.65 12.85 ± 0.43 October (10) 2.29 ± 0.01 12.16 ± 0.04 1017.41 ± 0.96 12.52 ± 0.77 November (11) 2.90 ± 0.35 13.28 ± 0.50 1018.78 ± 1.04 12.33 ± 0.44 December (12) 2.93 ± 0.49 13.42 ± 0.86 1021.65 ± 3.66 11.86 ± 0.35 
Appendix 10. Mean ±1 Standard Deviation Monthly Statistics of Oceanographic and MParameters at the Bodega Buoy (sta. 46013, fig. 1) for All Months and for El Niño and La 

Month Significant wave height (m) Dominant wave period (sec) Sea-level barometric pressure (mbars) Sea-surface water temperature (°C) All months January (1) 2.63 ± 0.34 13.11 ± 1.05 1019.83 ± 2.86 11.81 ± 0.63 February (2) 2.63 ± 0.39 12.74 ± 1.02 1018.73 ± 2.87 11.69 ± 0.76 March (3) 2.68 ± 0.25 12.70 ± 0.76 1017.88 ± 2.11 11.38 ± 0.95 April (4) 2.38 ± 0.30 11.39 ± 0.90 1017.70 ± 1.15 10.78 ± 0.95 May (5) 2.21 ± 0.09 9.82 ± 0.79 1016.05 ± 1.31 10.32 ± 0.58 June (6) 2.10 ± 0.34 9.39 ± 1.22 1014.96 ± 0.56 10.23 ± 0.81 July (7) 1.81 ± 0.21 9.13 ± 0.79 1014.85 ± 0.86 11.20 ± 0.83 August (8) 1.71 ± 0.17 8.76 ± 0.93 1014.79 ± 0.83 12.14 ± 0.81 September (9) 1.77 ± 0.10 10.42 ± 0.87 1014.20 ± 1.34 12.94 ± 1.09 October (10) 1.98 ± 0.24 11.51 ± 0.73 1016.42 ± 1.11 12.91 ± 1.17 November (11) 2.51 ± 0.46 12.40 ± 0.85 1018.88 ± 1.43 12.50 ± 1.16 December (12) 2.72 ± 0.39 13.21 ± 1.08 1020.08 ± 1.87 12.08 ± 0.87 

El Niño months January (1) 3.07 ± 0.33 13.77 ± 0.77 1017.85 ± 3.37 12.46 ± 0.52 

February (2) 2.79 ± 0.20 12.63 ± 0.63 1016.54 ± 2.03 12.53 ± 1.17 March (3) 2.63 ± 0.00 12.67 ± 0.00 1017.60 ± 0.00 11.44 ± 0.00 April (4) 2.58 ± 0.34 12.12 ± 1.49 1017.28 ± 1.72 11.56 ± 0.84 May (5) 2.15 ± 0.14 10.29 ± 1.47 1015.79 ± 1.37 11.71 ± 0.81 June (6) 2.13 ± 0.19 9.54 ± 0.96 1014.73 ± 1.15 10.77 ± 1.02 July (7) 1.89 ± 0.32 8.90 ± 0.55 1014.84 ± 1.18 11.65 ± 1.09 August (8) 1.57 ± 0.17 9.04 ± 1.57 1015.70 ± 1.52 12.94 ± 1.13 September (9) 1.65 ± 0.11 9.76 ± 0.61 1015.24 ± 1.13 12.98 ± 0.61 October (10) 1.79 ± 0.23 11.75 ± 0.92 1016.52 ± 1.27 13.31 ± 0.41 November (11) 2.41 ± 0.43 12.10 ± 0.93 1018.86 ± 2.30 12.57 ± 1.58 December (12) 2.87 ± 0.42 13.56 ± 0.65 1018.80 ± 1.48 12.29 ± 0.94 

La Niña months January (1) 2.61 ± 0.36 13.17 ± 0.78 1020.98 ± 1.56 11.32 ± 0.70 

February (2) 2.80 ± 0.54 12.77 ± 1.11 1019.22 ± 2.95 11.23 ± 1.09 March (3) 2.94 ± 0.47 13.07 ± 1.41 1018.02 ± 0.89 10.58 ± 0.59 April (4) 2.84 ± 0.00 10.56 ± 0.00 1017.24 ± 0.03 10.74 ± 1.42 May (5) 2.14 ± 0.31 9.13 ± 0.87 1016.72 ± 0.74 9.57 ± 1.43 June (6) 2.15 ± 0.00 9.89 ± 0.00 1015.27 ± 0.00 11.14 ± 0.00 July (7) 1.74 ± 0.13 9.47 ± 0.54 1015.19 ± 0.38 10.76 ± 0.06 August (8) 1.63 ± 0.04 8.60 ± 1.27 1014.10 ± 1.24 12.44 ± 0.49 September (9) 1.89 ± 0.18 10.50 ± 0.33 1013.55 ± 1.66 12.92 ± 0.68 October (10) 2.00 ± 0.33 11.92 ± 1.08 1017.17 ± 0.68 12.66 ± 0.18 November (11) 2.79 ± 0.24 13.17 ± 0.14 1019.49 ± 0.56 12.10 ± 0.71 December (12) 2.68 ± 0.35 13.14 ± 1.04 1021.58 ± 3.22 11.53 ± 0.43 

F

f
Appendix 11. Mean ±1 Standard Deviation Monthly Statistics of Oceanographic and MParameters at the San Francisco Buoy (sta. 46026, fig. 1) for All Months and for El Niño Months

Month Significant wave 

height

(m)

Dominant wave 

period

(sec)

Sea-level barometric 

pressure

(mbars)

Sea-surface water 

temperature

(°C)

All months 

January (1) 2.24 ± 0.34 13.41 ± 0.92 1019.45 ± 2.60 11.35 ± 0.59 February (2) 2.28 ± 0.36 13.43 ± 0.68 1018.05 ± 2.46 11.75 ± 0.7. March (3) 2.13 ± 0.20 12.68 ± 0.87 1017.74 ± 2.21 11.91 ± 1.14 April (4) 1.83 ± 0.22 11.60 ± 0.75 1017.58 ± 0.97 11.49 ± 0.66 May (5) 1.70 ± 0.12 10.39 ± 0.53 1016.01 ± 1.04 11.32 ± 0.46 June (6) 1.67 ± 0.26 9.90 ± 1.21 1014.70 ± 0.69 11.72 ± 1.04 July (7) 1.39 ± 0.20 9.64 ± 0.82 1015.13 ± 1.05 13.04 ± 0.84 August (8) 1.29 ± 0.19 9.44 ± 0.55 1014.80 ± 1.23 13.87 ± 0.86 September (9) 1.38 ± 0.13 10.90 ± 1.04 1013.70 ± 0.95 14.39 ± 1.16 October (10) 1.59 ± 0.25 11.72 ± 0.70 1016.24 ± 1.07 14.01 ± 1.00 November (11) 1.96 ± 0.44 12.35 ± 0.73 1018.66 ± 1.34 12.87 ± 1.13 December (12) 2.22 ± 0.47 13.47 ± 0.99 1020.16 ± 2.19 11.63 ± 0.75 

El Niño months 

January (1) 2.58 ± 0.33 13.80 ± 0.94 1017.47 ± 2.84 11.79 ± 0.29 February (2) 2.88 ± 0.87 13.49 ± 1.11 1014.75 ± 2.59 12.65 ± 0.57 March (3) 2.24 ± 0.43 12.76 ± 0.44 1015.01 ± 2.17 13.13 ± 1.13 April (4) 1.84 ± 0.29 11.90 ± 1.91 1017.42 ± 1.56 12.48 ± 0.73 May (5) 1.46 ± 0.17 10.55 ± 1.47 1015.49 ± 1.16 12.82 ± 0.42 June (6) 1.62 ± 0.30 9.89 ± 0.89 1014.06 ± 1.31 12.27 ± 0.88 July (7) 1.36 ± 0.22 9.33 ± 1.52 1015.00 ± 1.08 13.34 ± 1.22 August (8) 1.14 ± 0.12 9.43 ± 1.83 1015.55 ± 1.11 14.54 ± 1.34 September (9) 1.33 ± 0.30 10.61 ± 0.55 1014.04 ± 1.62 14.80 ± 0.90 October (10) 1.51 ± 0.32 11.85 ± 1.32 1016.27 ± 1.41 14.00 ± 0.51 November (11) 2.04 ± 0.41 12.07 ± 1.27 1017.24 ± 2.96 13.32 ± 1.97 December (12) 2.39 ± 0.46 13.50 ± 0.89 1018.87 ± 1.02 11.88 ± 0.94 

La Niña months 

January (1) 2.17 ± 0.50 13.51 ± 0.85 1021.36 ± 1.52 10.62 ± 0.79 February (2) 2.16 ± 0.62 12.96 ± 0.63 1018.99 ± 3.14 11.27 ± 1.17 March (3) 2.30 ± 0.46 12.77 ± 1.34 1018.21 ± 0.92 11.19 ± 0.37 April (4) 1.33 ± 0.00 12.48 ± 0.00 1017.06 ± 0.00 12.60 ± 0.00 May (5) 1.75 ± 0.40 10.35 ± 0.87 1016.81 ± 0.52 10.58 ± 1.10 June (6) N.D. N.D. N.D. N.D. July (7) 1.41 ± 0.20 10.31 ± 0.04 1015.15 ± 0.41 12.69 ± 0.13 August (8) 1.22 ± 0.03 9.66 ± 1.07 1013.97 ± 0.96 13.91 ± 0.80 September (9) 1.48 ± 0.28 11.14 ± 0.35 1013.36 ± 2.13 14.09 ± 0.53 October (10) 1.75 ± 0.22 12.40 ± 0.30 1016.77 ± 0.52 13.72 ± 0.54 November (11) 2.21 ± 0.15 13.07 ± 0.35 1019.43 ± 0.48 12.48 ± 0.51 December (12) 2.20 ± 0.24 13.66 ± 0.57 1022.55 ± 1.73 11.28 ± 0.14 

F

[N.D., no data]
Appendix 12. Mean ±1 Standard Deviation Monthly Statistics of Oceanographic and MParameters at the Half Moon Bay Buoy (sta. 46012, fig. 1) for All Months and for El Niño Months Month Significant wave height (m) Dominant wave period (sec) Sea-level barometric pressure (mbars) Sea-surface water temperature (°C) All months January (1) 2.38 ± 0.31 12.80 ± 1.12 1019.78 ± 2.53 12.27 ± 0.63 

February (2) 2.57 ± 0.37 12.72 ± 0.89 1018.58 ± 2.05 12.17 ± 0.88 March (3) 2.51 ± 0.27 12.46 ± 0.37 1017.36 ± 2.38 12.37 ± 0.87 April (4) 2.14 ± 0.22 11.15 ± 0.83 1017.50 ± 0.66 11.85 ± 0.65 May (5) 2.02 ± 0.49 10.25 ± 0.84 1016.34 ± 1.24 12.25 ± 0.64 June (6) 1.83 ± 0.23 9.58 ± 1.18 1015.04 ± 0.83 12.69 ± 0.71 July (7) 1.63 ± 0.18 9.72 ± 1.07 1015.31 ± 1.40 13.84 ± 0.61 August (8) 1.49 ± 0.14 9.52 ± 0.52 1016.47 ± 1.30 14.56 ± 0.63 September (9) 1.58 ± 0.12 10.77 ± 0.98 1014.73 ± 1.23 14.60 ± 1.12 October (10) 1.87 ± 0.20 11.44 ± 0.75 1016.89 ± 1.19 14.18 ± 1.13 November (11) 2.31 ± 0.42 12.22 ± 0.71 1018.72 ± 1.25 13.17 ± 1.16 December (12) 2.47 ± 0.38 12.85 ± 1.11 1019.91 ± 1.68 12.61 ± 0.73 

El Niño months January (1) 2.59 ± 0.16 13.23 ± 0.68 1019.60 ± 1.57 12.70 ± 1.06 

February (2) 3.13 ± 0.82 12.80 ± 1.30 1015.73 ± 0.39 13.69 ± 0.32 March (3) 2.74 ± 0.64 12.66 ± 0.29 1013.89 ± 0.96 13.88 ± 0.24 April (4) 2.08 ± 0.08 10.51 ± 1.18 1016.45 ± 1.65 13.45 ± 0.89 May (5) 1.67 ± 0.22 10.27 ± 1.56 1015.89 ± 1.37 13.43 ± 0.44 June (6) 1.97 ± 0.33 9.52 ± 0.66 1013.78 ± 1.29 13.30 ± 0.62 July (7) 1.87 ± 0.58 9.36 ± 0.83 1015.67 ± 0.69 14.51 ± 0.61 August (8) 1.52 ± 0.31 9.37 ± 1.84 1022.06 ± 12.25 15.95 ± 1.66 September (9) 1.71 ± 0.54 10.30 ± 0.68 1019.04 ± 6.40 14.72 ± 0.55 October (10) 1.89 ± 0.40 11.67 ± 0.82 1018.51 ± 6.50 14.53 ± 0.79 November (11) 2.36 ± 0.16 12.16 ± 0.67 1018.76 ± 2.06 13.27 ± 1.41 December (12) 2.70 ± 0.31 13.14 ± 0.81 1019.08 ± 0.91 12.98 ± 0.85 

La Niña months January (1) 2.38 ± 0.34 13.09 ± 0.91 1020.57 ± 2.00 11.56 ± 0.68 

February (2) 2.54 ± 0.55 12.42 ± 0.98 1018.57 ± 3.21 11.59 ± 0.78 March (3) 2.50 ± 0.38 12.47 ± 1.30 1018.23 ± 1.62 11.29 ± 0.55 April (4) 1.95 ± 0.50 11.60 ± 1.17 1017.37 ± 0.93 11.44 ± 2.07 May (5) 1.79 ± 0.28 10.50 ± 0.74 1017.65 ± 1.37 12.29 ± 0.23 June (6) 1.96 ± 0.00 10.28 ± 0.00 1016.02 ± 0.00 12.43 ± 0.00 July (7) 1.51 ± 0.00 9.64 ± 0.00 1015.69 ± 0.00 13.53 ± 0.00 August (8) 1.42 ± 0.05 9.55 ± 0.44 1014.38 ± 1.08 14.31 ± 0.78 September (9) 1.62 ± 0.20 11.01 ± 0.40 1013.43 ± 1.95 14.49 ± 0.64 October (10) 1.76 ± 0.39 11.80 ± 0.70 1016.79 ± 1.05 13.86 ± 0.31 November (11) 2.44 ± 0.21 12.92 ± 0.16 1019.45 ± 1.04 12.69 ± 0.54 December (12) 2.36 ± 0.26 13.06 ± 0.93 1021.21 ± 2.84 11.95 ± 0.52 

F

f
Appendix 13. Mean ±1 Standard Deviation Monthly Statistics of Oceanographic and MParameters at the Monterey Bay Buoy (sta. 46042, fig. 1) for All Months and for El Niño Months

Month Significant wave 

height

(m)

Dominant wave 

period

(sec)

Sea-level barometric 

pressure

(mbars)

Sea-surface water 

temperature

(°C)

All months 

January (1) 2.66 ± 0.43 13.08 ± 1.02 1019.34 ± 2.80 12.24 ± 0.48 February (2) 2.67 ± 0.37 13.07 ± 0.42 1018.44 ± 2.39 12.00 ± 0.59 March (3) 2.65 ± 0.27 13.04 ± 0.58 1017.95 ± 2.14 11.90 ± 0.94 April (4) 2.24 ± 0.19 11.84 ± 0.56 1018.08 ± 1.12 12.11 ± 0.42 May (5) 2.09 ± 0.10 10.92 ± 0.39 1016.39 ± 0.94 12.06 ± 0.65 June (6) 2.01 ± 0.16 10.02 ± 1.03 1015.21 ± 0.82 12.50 ± 0.89 July (7) 1.70 ± 0.21 9.73 ± 0.85 1015.27 ± 1.13 13.48 ± 0.72 August (8) 1.64 ± 0.14 9.79 ± 0.37 1014.98 ± 1.26 14.34 ± 1.13 September (9) 1.75 ± 0.14 11.02 ± 0.55 1014.11 ± 0.83 14.83 ± 0.85 October (10) 2.09 ± 0.19 11.67 ± 0.50 1016.04 ± 1.18 14.61 ± 0.69 November (11) 2.45 ± 0.31 12.46 ± 0.73 1019.31 ± 0.85 12.96 ± 0.63 December (12) 2.77 ± 0.43 13.22 ± 0.79 1020.16 ± 1.50 12.39 ± 0.82 

El Niño months 

January (1) 3.03 ± 0.35 13.52 ± 0.44 1017.97 ± 3.19 12.26 ± 0.44 February (2) 2.52 ± 0.00 12.23 ± 0.00 1015.57 ± 0.00 N.D. March (3) 2.30 ± 0.00 13.26 ± 0.00 1014.56 ± 0.00 N.D. April (4) 2.42 ± 0.58 12.27 ± 1.30 1018.46 ± 1.46 N.D. May (5) 1.85 ± 0.26 11.30 ± 0.63 1015.50 ± 0.61 13.19 ± 0.00 June (6) 2.07 ± 0.23 9.93 ± 0.33 1014.29 ± 0.83 12.68 ± 1.48 July (7) 1.76 ± 0.26 9.67 ± 0.70 1014.94 ± 0.77 13.62 ± 0.14 August (8) 1.54 ± 0.16 10.40 ± 1.31 1015.43 ± 0.83 15.59 ± 0.71 September (9) 1.80 ± 0.31 10.49 ± 0.68 1014.06 ± 1.91 17.12 ± 0.00 October (10) 2.09 ± 0.44 11.55 ± 0.88 1015.48 ± 0.99 15.36 ± 0.78 November (11) 2.72 ± 0.03 12.44 ± 0.56 1019.56 ± 0.40 12.48 ± 0.00 December (12) 3.09 ± 0.34 13.27 ± 0.27 1018.38 ± 0.79 12.62 ± 0.36 

La Niña months 

January (1) 2.65 ± 0.52 13.00 ± 0.89 1020.21 ± 1.06 11.97 ± 0.61 February (2) 3.04 ± 0.33 13.36 ± 0.64 1018.09 ± 2.77 11.91 ± 0.87 March (3) 3.07 ± 0.26 13.58 ± 0.77 1017.76 ± 0.77 11.56 ± 0.21 April (4) 1.71 ± 0.00 12.18 ± 0.00 1018.09 ± 0.00 12.84 ± 0.00 May (5) 2.18 ± 0.00 11.00 ± 0.00 1018.81 ± 0.00 12.54 ± 0.00 June (6) 2.07 ± 0.00 10.39 ± 0.00 1015.28 ± 0.00 12.59 ± 0.00 July (7) 1.62 ± 0.00 9.84 ± 0.00 1014.95 ± 0.00 13.19 ± 0.00 August (8) 1.54 ± 0.16 9.68 ± 0.22 1014.40 ± 1.35 14.56 ± 0.38 September (9) 1.86 ± 0.06 10.82 ± 0.64 1012.78 ± 1.14 14.57 ± 1.04 October (10) 1.88 ± 0.33 11.86 ± 0.96 1016.52 ± 0.57 14.11 ± 0.42 November (11) 2.67 ± 0.31 13.16 ± 0.33 1019.49 ± 0.51 12.77 ± 0.49 December (12) 2.64 ± 0.29 13.51 ± 0.69 1022.20 ± 1.66 11.84 ± 0.46 

F

[N.D., no data]
Appendix 14. Mean ±1 Standard Deviation Monthly Statistics of Oceanographic and MParameters at the Cape San Martin Buoy (sta. 46028, fig. 1) for All Months and for El NiñMonths Month Significant wave height (m) Dominant wave period (sec) Sea-level barometric pressure (mbars) Sea-surface water temperature (°C) All months January (1) 2.59 ± 0.45 13.27 ± 1.40 1020.28 ± 2.33 12.86 ± 0.65 

February (2) 2.68 ± 0.60 13.46 ± 0.69 1019.27 ± 2.26 12.57 ± 0.67 March (3) 2.67 ± 0.18 12.65 ± 0.49 1018.30 ± 1.20 12.60 ± 0.75 April (4) 2.40 ± 0.32 11.75 ± 0.84 1017.44 ± 1.00 12.10 ± 0.81 May (5) 2.32 ± 0.15 10.24 ± 0.49 1015.98 ± 1.07 12.29 ± 0.74 June (6) 2.23 ± 0.20 9.77 ± 1.18 1014.69 ± 0.80 12.86 ± 0.81 July (7) 1.90 ± 0.22 9.53 ± 0.83 1015.01 ± 0.87 14.05 ± 0.77 August (8) 1.85 ± 0.16 9.32 ± 0.38 1014.71 ± 0.93 15.17 ± 0.92 September (9) 1.84 ± 0.12 10.60 ± 0.91 1014.00 ± 1.22 15.50 ± 1.06 October (10) 2.11 ± 0.19 11.81 ± 0.62 1015.91 ± 1.13 15.10 ± 0.49 November (11) 2.49 ± 0.28 12.69 ± 0.87 1018.81 ± 0.94 14.05 ± 0.62 December (12) 2.88 ± 0.44 13.51 ± 1.09 1019.81 ± 1.11 13.52 ± 0.76 

El Niño months January (1) 2.78 ± 0.48 14.78 ± 0.76 1021.08 ± 0.20 13.13 ± 0.69 

February (2) 3.06 ± 0.00 13.29 ± 0.00 1017.98 ± 0.00 13.32 ± 0.00 March (3) 2.64 ± 0.00 12.87 ± 0.00 1018.30 ± 0.00 12.94 ± 0.00 April (4) 2.46 ± 0.00 13.19 ± 0.00 1018.03 ± 0.40 11.93 ± 0.00 May (5) 2.00 ± 0.30 10.61 ± 0.23 1015.26 ± 0.75 12.70 ± 0.97 June (6) 2.35 ± 0.20 9.89 ± 0.51 1014.67 ± 2.04 12.94 ± 0.74 July (7) 1.99 ± 0.20 9.46 ± 0.71 1014.67 ± 0.78 14.63 ± 1.35 August (8) 1.79 ± 0.12 9.80 ± 1.32 1015.62 ± 1.35 16.20 ± 1.47 September (9) 1.75 ± 0.22 9.94 ± 0.55 1015.57 ± 0.73 16.31 ± 1.53 October (10) 1.88 ± 0.34 12.11 ± 0.95 1016.03 ± 0.89 16.41 ± 1.23 November (11) 2.56 ± 0.32 13.01 ± 0.51 1019.39 ± 0.06 15.04 ± 1.34 December (12) 3.10 ± 0.27 14.18 ± 0.60 1019.53 ± 0.39 14.36 ± 0.61 

La Niña months January (1) 2.65 ± 0.38 13.80 ± 0.80 1020.52 ± 1.45 12.46 ± 0.84 

February (2) 2.77 ± 0.45 13.29 ± 0.91 1019.72 ± 2.67 12.29 ± 1.07 March (3) 2.83 ± 0.61 12.90 ± 1.91 1017.40 ± 1.63 11.99 ± 0.26 April (4) 2.38 ± 0.69 11.70 ± 0.84 1016.66 ± 0.18 12.34 ± 0.92 May (5) 2.36 ± 0.38 9.95 ± 0.46 1016.62 ± 0.75 12.36 ± 1.16 June (6) 2.03 ± 0.00 10.09 ± 0.00 1015.61 ± 0.00 14.25 ± 0.00 July (7) 1.77 ± 0.32 10.00 ± 0.62 1015.25 ± 0.10 13.55 ± 0.21 August (8) 1.55 ± 0.00 9.46 ± 0.00 1013.29 ± 0.00 16.08 ± 0.00 September (9) 1.82 ± 0.15 10.59 ± 0.57 1013.19 ± 1.90 15.71 ± 0.45 October (10) 1.88 ± 0.61 11.34 ± 1.51 1015.85 ± 1.09 14.49 ± 0.07 November (11) 2.81 ± 0.19 13.78 ± 0.01 1018.84 ± 0.88 13.41 ± 0.40 December (12) 3.01 ± 0.51 13.19 ± 1.23 1020.01 ± 2.30 12.87 ± 0.50 

F

f
Appendix 15. Mean ±1 Standard Deviation Monthly Statistics of Oceanographic and MParameters at the Point Arguello Buoy (sta. 46023, fig. 1) for All Months and for El Niño Months

Month Significant wave 

height

(m)

Dominant wave 

period

(sec)

Sea-level barometric 

pressure

(mbars)

Sea-surface water 

temperature

(°C)

All months 

January (1) 2.56 ± 0.32 13.79 ± 1.03 1018.88 ± 2.22 13.62 ± 0.72 February (2) 2.67 ± 0.37 13.61 ± 0.71 1018.00 ± 2.02 13.32 ± 0.63 March (3) 2.65 ± 0.31 13.22 ± 0.69 1016.98 ± 1.47 13.20 ± 0.66 April (4) 2.39 ± 0.42 11.92 ± 1.22 1016.44 ± 0.93 12.59 ± 0.52 May (5) 2.19 ± 0.19 10.43 ± 0.74 1015.34 ± 0.92 12.57 ± 0.91 June (6) 2.05 ± 0.23 10.21 ± 1.03 1014.02 ± 0.73 13.48 ± 0.70 July (7) 1.75 ± 0.20 9.68 ± 0.72 1014.53 ± 1.01 15.04 ± 0.69 August (8) 1.68 ± 0.17 9.50 ± 0.76 1014.28 ± 1.16 15.56 ± 1.33 September (9) 1.75 ± 0.09 10.92 ± 1.08 1013.21 ± 0.86 16.07 ± 1.57 October (10) 2.00 ± 0.21 11.80 ± 0.65 1015.34 ± 1.02 15.99 ± 1.06 November (11) 2.40 ± 0.53 12.68 ± 1.12 1017.64 ± 0.65 15.31 ± 0.64 December (12) 2.61 ± 0.47 13.76 ± 0.88 1019.54 ± 1.20 14.12 ± 0.77 

El Niño months 

January (1) 2.93 ± 0.16 14.40 ± 0.91 1017.26 ± 1.17 14.43 ± 1.07 February (2) 3.26 ± 0.86 14.17 ± 1.04 1015.38 ± 0.93 14.53 ± 0.86 March (3) 2.68 ± 0.41 13.47 ± 0.30 1015.11 ± 1.46 14.18 ± 0.92 April (4) 2.52 ± 0.43 12.25 ± 1.26 1015.85 ± 1.04 13.17 ± 0.77 May (5) 2.02 ± 0.17 10.83 ± 1.34 1014.76 ± 1.06 13.80 ± 0.58 June (6) 2.08 ± 0.30 10.34 ± 1.04 1013.56 ± 1.40 14.06 ± 0.83 July (7) 1.82 ± 0.24 9.51 ± 0.97 1013.99 ± 0.68 15.39 ± 1.05 August (8) 1.67 ± 0.13 9.49 ± 2.05 1014.53 ± 0.57 16.30 ± 1.17 September (9) 1.82 ± 0.26 10.40 ± 1.00 1013.47 ± 1.49 16.49 ± 1.36 October (10) 2.00 ± 0.22 11.98 ± 1.12 1015.05 ± 0.93 16.48 ± 0.81 November (11) 2.53 ± 0.32 12.71 ± 0.86 1015.82 ± 1.37 16.60 ± 2.06 December (12) 2.80 ± 0.15 13.84 ± 0.97 1017.72 ± 0.75 15.37 ± 0.98 

La Niña months 

January (1) 2.50 ± 0.25 13.98 ± 0.67 1019.98 ± 0.75 12.93 ± 0.64 February (2) 2.59 ± 0.39 13.20 ± 1.27 1019.66 ± 2.05 12.57 ± 0.88 March (3) 2.72 ± 0.36 13.50 ± 1.4 1017.92 ± 0.93 12.02 ± 0.36 April (4) 2.16 ± 0.65 12.12 ± 0.69 1016.59 ± 0.96 12.58 ± 1.10 May (5) 2.19 ± 0.26 10.21 ± 0.92 1016.34 ± 0.49 11.91 ± 0.58 June (6) 2.03 ± 0.00 10.74 ± 0.00 1014.62 ± 0.00 12.14 ± 0.00 July (7) 1.64 ± 0.00 10.67 ± 1.25 1015.18 ± 0.77 14.95 ± 0.67 August (8) 1.56 ± 0.06 9.72 ± 0.89 1013.73 ± 1.13 14.75 ± 0.85 September (9) 1.73 ± 0.09 11.31 ± 0.90 1013.25 ± 1.51 15.87 ± 1.03 October (10) 1.94 ± 0.26 11.67 ± 1.05 1015.90 ± 0.70 15.13 ± 0.11 November (11) 2.50 ± 0.35 13.49 ± 0.16 1019.26 ± 0.82 13.81 ± 0.22 December (12) 2.60 ± 0.40 13.83 ± 0.36 1021.94 ± 1.02 12.87 ± 0.33 

F

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