HISTORICAL CLIMATOLOGY SERIES 6-5

TROPICAL CYCLONES OF THE EASTERN NORTH PACIFIC BASIN, 1949-2006

Eric S. Blake, Ethan J. Gibney1, Daniel P. Brown, Michelle Mainelli, James L. Franklin and Todd B. Kimberlain

National Hurricane Center

Gregory R. Hammer

National Climatic Data Center

 Asheville, NC

 June, 2009

Prepared by the National Climatic Data Center, Asheville, NC, in cooperation

with the National Hurricane Center, Miami, FL

 

1 I.M. Systems Group at the National Hurricane Center
 Contents

1. Introduction........................................................................ 

2. Motivation.......................................................................... 

3. Classifications of Eastern Pacific Tropical Cyclones......... 

 3.1 Tropical Cyclones........................................................ 

 3.2 Subtropical Cyclones...................................................

 3.3 Extratropical Cyclones................................................

4. Data Sources.......................................................................

5. Accuracy of Tracks and Intensity Classifications...............

6. Eastern North Pacific Tropical Cyclone Tracks.................

7. Frequency of Eastern North Pacific Tropical Cyclones.....

 7.1 Monthly and Annual Frequencies................................

 7.2 Daily Frequencies........................................................

 7.3 Areas of Formation......................................................

 7.4 Mainland Tropical Cyclone Landfalls.........................

 7.5 Coastal Variation of Hurricane Threat.........................

 7.6 Hurricane Damage Potential........................................

8. Acknowledgments and other Comments............................

9. List of Acronyms and Abbreviations..................................

10. References........................................................................

 Appendix A (Chart Series A).............................................

 Appendix B (Chart Series B).............................................

 

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1

This book is a compilation of facts, figures and tracks for tropical cyclones of the eastern North Pacific basin between 1949 and 2006. The eastern 

North Pacific basin is defined as the Pacific Ocean area north of the equator 

bounded by 140°W and the west coast of the Americas. Over the 58-year period 

of record, a total of 769 tropical cyclones of tropical storm strength or greater 

have been documented; an average of about 13 systems per year. The formation 

of these storms, and possible intensification into mature hurricanes, takes place 

over warm tropical waters. Eventual dissipation, averaging less than a week 

later, typically occurs over the colder waters of the eastern North Pacific, or 

when the storms move over land and away from the sustaining marine environment.

Figure 1 shows the areal extent of the eastern North Pacific tropical 

cyclone basin along with the tracks of the 769 tropical cyclones. The eastern 

North Pacific tropical cyclone basin produces the most tropical cyclones per 

square mile of any basin worldwide. It is one of seven in the world; others in the 

Northern Hemisphere are the Atlantic basin, the western North Pacific and the 

northern Indian Ocean. The Southern Hemisphere basins are the southwestern Indian Ocean, the Australia/southeastern Indian Ocean and the Australia/

southwest Pacific Ocean. Two large tropical oceanic areas are virtually devoid 

of tropical cyclone occurrence--the South Atlantic and the eastern portion of 

the South Pacific. On rare occasions, tropical cyclones cross from the Atlantic 

basin to the Pacific basin. An example is Hurricane Cesar (1996) which moved 

westward across Central America as a tropical storm and then became Hurricane Douglas over the eastern North Pacific.

Tropical cyclones have always been a concern to shipping, and are occasionally documented over remote oceanic areas, even in the 19th century and 

earlier. Hurd (1929), for example, presents a twenty-year summary of eastern 

Pacific tropical cyclone activity, with a figure that displays some cyclone tracks 

before 1900. Mariner reports form the basis of the early part of the record before 1956.

A compilation of tracks and data for the Atlantic tropical cyclones 

has long been available (McAdie et al. 2009), but a similar book has never 

been prepared for the eastern Pacific, perhaps because of the offshore nature of 

most of the tropical cyclone tracks. Numerous publications, technical and nontechnical, do describe global and regional tropical cyclone climate on various 

scales, including the eastern Pacific. One useful study on global tropical cyclone activity is a comprehensive World Meteorological Organization (WMO) 

text (Elsberry 1995). The technical document contains charts describing tropical cyclone frequency and motion characteristics over the various global basins. In addition, the document presents an instructive and more theoretical 

treatment of global tropical cyclone climatology, including a discussion of the 

conditions associated with tropical cyclone development. Many studies on individual basins (or even portions of basins such as for Mexico alone [Servicio 

Meteorologico Nacional 1981]) can be found in meteorological libraries. 

Collection and dissemination of global tropical cyclone data is the 

responsibility of the National Climatic Data Center (NCDC), Asheville, NC. 

Data are obtained in an agreed-upon format from WMO-designated Regional 

Specialized Meteorological Centers (RSMCs), and other global meteorological services. In the United States, the National Hurricane Center (NHC), in 

Miami, Florida, serves as an RSMC, with responsibility for both the North 

Atlantic and eastern North Pacific basins. 

For the eastern North Pacific, tropical cyclone tracks have generally been published within annual summaries. From 1953 to 1956, yearly 

Tropical Cyclones of the Eastern North Pacific Basin, 1949-2006

1. INTRODUCTION
2

Figure 1. The tracks of the 769 known eastern North Pacific tropical cyclones reaching at least tropical storm intensity, 1949-2006.

Figure 1. The tracks of the 769 known eastern North Pacific tropical cyclones reaching at least tropical storm intensity, 1949-2006.
3

summaries and occasional tracks of the basin were reported in the annual summary of Climatological Data. Since 1957, yearly summaries have been included in Mariner’s Weather Log articles along with a small figure of the tracks. In 

1968, storm tracks and summaries were included in Monthly Weather Review, 

and have continued to present day. Leftwich and Brown (1981) compiled tracks 

from 1949-1979, and in many ways this book updates and adds to their work. 

This book is also a compilation of data from various sources and presents the tracks and data of eastern Pacific tropical cyclones in an easy-to-understand format that is useful for the general public. It is notable that the eastern 

North Pacific basin is sometimes shortened to the term eastern Pacific in this 

book. In addition, the Atlantic best track book served as a guide to the structure of this book, but there are some differences between the two publications, 

which will discussed in the text.

Section 2 discusses the motivation for the book and other important 

works regarding eastern Pacific tropical cyclones. Section 3 introduces readers 

to relevant definitions related to a tropical cyclone and the typical lifecycle of a 

cyclone. Data sources are discussed in Section 4 and the accuracy and precision of these data are covered in Section 5. Section 6 considers the details on 

how the tracks were produced, and Section 7 covers statistics related to the 

tracks, in addition to hurricane landfalls in Mexico.

2. MOTIVATION

Together with related statistical summaries, this study presents annual 

tropical cyclone tracks for the period 1949-2006 for the eastern Pacific basin. 

For more detailed data on individual cyclones, readers are referred to publications that deal specifically with analysis of eastern Pacific tropical cyclones. 

These include the official summaries published in Climatological Data, Monthly Weather Review and Mariner’s Weather Log, along with works by Smith 

(1986), Warner (1992) and Court (1980) that specifically deal with tropical cyclone effects across the southwestern United States.

Other important works in eastern Pacific climatology include Allard 

(1984), and Renard and Bowman (1976). Finally, the NHC Internet web site: 

http://www.nhc.noaa.gov also contains a large amount of information on current and historical tropical cyclones. Information at that site can be used to 

update this text until additional editions are issued. Also available on the NHC 

web site are the digitized tracks of all eastern Pacific tropical cyclones since 

1949 in a standard format. Charts presented in Chart Series A and B are based 

on these data. 

The motivation of this book was to prepare a track book, similar to 

the Atlantic track compilation, to be a comprehensive source of eastern Pacific 

track and statistical data. There has been a dearth of information published 

since Leftwich and Brown (1981) and, since that time, the dataset has increased 

by 27 years. This document was made more difficult to prepare because three 

different government agencies have had forecast responsibilities for the eastern 

Pacific basin, sometimes with limited references of the procedures of that station. These agencies included the United States Navy before 1970, the Eastern 

Pacific Hurricane Center (National Weather Service office in Redwood City, 

California) from 1970-1987, and the NHC from 1988-present. 

The NHC annually receives hundreds of requests for tropical cyclonerelated information from both official and non-official sources. One of the 

goals of this publication is to provide readily available, correct, and consistent 

answers to some of these queries. Knowledge of climatology is important in 

the forecast process and this publication also provides Hurricane Specialists at 

the NHC with a reliable source of reference material on eastern Pacific tropical 

cyclones.
4

3. CLASSIFICATIONS OF EASTERN PACIFIC TROPICAL CYCLONES

It is beyond the scope of this book to discuss the fine details of tropical 

cyclone characteristics and structure. A few comments and definitions are necessary, however, for proper interpretation of the material presented. The reader 

is referred to Miller (1967) or Anthes (1982) for further detailed information on 

tropical cyclones. Texts by Dunn and Miller (1964), Simpson and Riehl (1981), 

Pielke and Pielke (1997) and Emanuel (2005) are devoted entirely to that topic. 

Certain specialized topics, such as the operational forecasting of tropical cyclone motion and intensity are discussed by Rappaport et al. (2009) and Sheets 

(1990). 

In the course of their lifecycle, tropical cyclones, like other atmospheric weather systems, pass through stages of genesis, intensification, maturity, 

and decay or modification. Avila (1991) and Avila and Pasch (1992) specifically 

address the issue of eastern Pacific cyclogenesis, finding that the majority of 

tropical cyclones come from tropical waves crossing Central America from the 

Atlantic basin. The relationship between these waves and eastern Pacific and 

Atlantic tropical cyclones has been studied by a number of researchers, one of 

the earliest published by Simpson et al. (1968). Molinari et al. (1997) present 

theoretical aspects on the issue of eastern Pacific cyclogenesis. 

However, not all tropical cyclones come from waves in the eastern 

Pacific. Other initiation mechanisms have been theorized, including the Intertropical Convergence Zone (ITCZ) breaking down (Ferreira and Schubert 

1997) and genesis due to terrain influences of the Sierra Madre mountains of 

Mexico (Mozer and Zehnder 1996). These mechanisms are not thought to be 

important in Atlantic basin cyclogenesis. In other basins, however, atmospheric 

conditions which initiate tropical cyclones may be quite different.

One important difference between the Atlantic and eastern Pacific basins is that subtropical cyclones have not been observed to form in the eastern 

Pacific. This may be due to the limited poleward area of formation in the eastern Pacific as compared to the Atlantic basin because of the Mexican mainland. 

The relatively cool water at low latitudes compared to the Atlantic basin also 

probably inhibits the formation of subtropical systems in the eastern Pacific.

“Remnant low” is a relatively new term (introduced in 2002) that describes a former tropical cyclone that has lost central convection but is still 

a well-defined low pressure system. Before 2002, these systems were usually 

characterized as weak tropical depressions in the best track database (McAdie, 

personal communication). The remnant low phase is rather common for many 

eastern Pacific tropical cyclones to enter immediately after their demise as tropical cyclones but before the dissipation of the low pressure area. The remnant 

low stage typically occurs due to the cold waters present north of 20°N west of 

115°W. 

Some tropical cyclones, after moving out of the tropical environment, 

may lose their tropical characteristics and become extratropical. While the 

primary purpose of this publication is to discuss tropical systems, it is necessary, for completeness, to discuss extratropical cyclones as well. It is worth 

noting that extratropical transition happens much less frequently in the eastern 

Pacific than the Atlantic basin, probably because low-latitude Pacific tropical 

cyclones less frequently interact with the middle-latitude westerlies, reducing 

any chance of extratropical or hybrid storm formation. 

3.1 Tropical Cyclones

Any closed circulation, in which the winds rotate counterclockwise in 

the Northern Hemisphere or clockwise in the Southern Hemisphere, is called 

a cyclone. Tropical cyclones are technically defined as warm-core, non-frontal, synoptic-scale2

 cyclones, originating over tropical or subtropical waters, 

with organized deep convection and a closed surface wind circulation about 

2 Synoptic-scale refers to large-scale weather systems as distinguished from local systems such 

as thunderstorms.
5

a well-defined center (OFCM 2009). Further classification depends upon the 

maximum wind speed near the center of the system. The terms “tropical depression,” “tropical storm,” or “hurricane” are assigned depending whether the 

sustained winds are, respectively, less than 34 knots, 34 to 63 knots or greater 

than 63 knots. Tropical cyclones are not named unless they reach at least tropical storm strength.

The term, “sustained wind,” as used in the United States hurricane 

program, refers to the highest near-surface (10-meter) wind averaged over 

1-minute associated with the cyclone circulation. Shorter period gusts or lulls 

in the wind, perhaps only a few seconds duration, can be much higher or lower 

than the sustained wind. In some other countries, the averaging period defining 

a sustained wind can be longer than 1-minute, and is usually near a 10-minute 

average in accordance to WMO standards. The wind criteria separating the 

various stages of tropical cyclones are rigidly defined, but the ability to measure the winds with the precision implied by the definitions seldom exists. In 

practice, a maximum sustained wind is assigned by the hurricane analyst after 

considering all available evidence. 

Tropical cyclones, with their energy derived from the latent heat of 

condensation of water vapor, are generally smaller in extent than extratropical cyclones and typically range from 100 to 600 nautical miles in diameter at 

maturity. Winds normally increase radially inward near the center of tropical 

cyclones with sustained speeds sometimes exceeding 100 knots. Occasionally, 

sustained winds exceeding 140 knots may occur in well-developed systems. 

Apart from the wind, other destructive features of tropical cyclones include 

torrential rains over a large area, and coastal storm tides of 15 to 30 feet above 

normal in extreme cases. Coastal inundation from the storm surge and extreme 

rainfall has been primarily responsible for deaths and damages from storms 

across the world. Landsberg (1960) and Emanuel (2005) pointed out that these 

storms may be a major factor in maintaining the atmospheric heat and moisture 

balance between the Tropics and the higher latitudes; they may be thought of as 

providing a kind of “safety valve” that limits the continued buildup of heat and 

energy in tropical regions.

A unique feature of more intense tropical cyclones is the central “eye”, 

which commonly has a diameter of 10 to 50 miles across. This central region 

area of the storm is typically associated with light winds, minimal cloud cover 

and lowest sea-level pressure. The eye (note the distinct eye of Hurricane Linda 

on the book’s cover) provides a convenient visual and physical entity that can be 

tracked with the aid of aircraft, satellite or radar.

3.2 Subtropical Cyclones

A subtropical cyclone is defined as a non-frontal low pressure system 

that has characteristics of both tropical and extratropical cyclones. In comparison to tropical cyclones, such systems have a relatively broad zone of maximum winds that is located farther from the center, and typically have a less 

symmetric wind field and distribution of convection (OFCM 2009). Although 

no subtropical cyclones have been noted in the eastern Pacific basin, a subtropical formation was noted in the central Pacific basin in 1975 (Burtt and Haller 

1976). For more information on subtropical cyclones, see McAdie et al. (2009), 

Hebert (1973) or Hebert and Poteat (1975).

3.3 Extratropical Cyclones

During the final stages of their life cycle, eastern Pacific tropical cyclones are infrequently classified as extratropical. These cyclones which typically form outside of the Tropics have structures, energetics, and appearances 

(when viewed from weather satellites or radar) that are different from tropical 

cyclones. They derive their energy primarily from large-scale horizontal contrasts of temperature and are typically associated with cold and warm fronts. 

The transformation from a tropical cyclone to an extratropical cyclone is a 

gradual process: the size of the circulation usually expands, the speed of the 

maximum wind typically decreases, and the distribution of winds, rainfall, and 

temperatures around the center becomes increasingly asymmetric. 

While these characteristic features develop, some tropical features, 

such as a small area of strong winds near the center, the remnants of an eye, and 

extremely heavy rainfall may be retained for a considerable time. Extratropical 
6

cyclones are relatively rare in the eastern Pacific, with only three noted in the 

database (Kevin 1991, Guillermo and Ignacio, 1997). Cold waters west of Baja 

California, as well as the limited poleward extent of the basin, are thought to 

limit extratropical transitions to only rare cases. 

during that six year period, and the works of Hansen (1972), Baum and Rausch 

(1975) and Renard and Bowman (1976) provided more data for inclusion or 

modification of the best tracks. 

The lack of specific intensity documentation before 1970 should not be 

interpreted as a complete lack of knowledge about these early storms. Indeed, 

portions of many of these tracks were well documented if they were associated 

with disasters either ashore or at sea. For example, the category five hurricane of October 1959 (number 12), which brought devastation to southwestern 

Mexico, is described in Crooks (1959). Persons seeking specific information on 

this, and on other hurricane events occurring in later years, should consult the 

references given in Section 10.

The best track database from 1976-1987 was based on advisories issued by the Eastern Pacific Hurricane Center in Redwood City, California. 

Some in-house modification of tracks and intensities was performed by Arthur 

Pike after the NHC assembled the best track database in 1976 (Neumann, personal communication). Other best track files were modified and extended based 

on a study by Court (1980). Operational responsibility for the eastern Pacific 

was assumed by the NHC in 1988, and the NHC has maintained the best tracks 

database to present day. Annual summaries of storms issued by the NHC and 

published in Monthly Weather Review are the definitive source of information 

since 1988. However, there have been few recent official summary publications 

on tropical cyclone tracks over the eastern Pacific. Baum and Rausch (1975) 

digitized tropical cyclone track data from 1961-1974. Brown and Leftwich 

(1982) provided a short summary of eastern Pacific data, along with a composite of all tropical cyclones observed in the basin. 

4. DATA SOURCES

For the early part of the NHC best track record, 1949-1975, the best 

tracks were obtained from the U.S. Navy at 12 hour intervals (Leftwich and 

Brown 1981) and interpolated to 6 hour intervals based on Akima (1970). These 

early period tracks appear to be closely based on advisories issued by the United States Navy Fleet Weather Center in Alameda, California up to 1970. During that era, Rosendal (1962) provided data and discussion on hurricanes from 

1947-1961, some of which were included in the final best track.

Intensity values in the early part of the record have been assigned in 

multiple ways. Before 1954, only the maximum intensity of a storm is used for 

the entire track of the storm, similar to the 1886-1898 years of an older version 

of the Atlantic track book (Neumann et al. 1999). Between 1954 and 1964, 

some wind information was found in Mariner’s Weather Log, Monthly Weather 

Review, and Climatological Data and was incorporated into the best-track file, 

along with advisory information from the U.S. Navy. These wind data increased 

in 1965 with more detailed summary information and more observational capability in 1966 with the launch of geostationary satellites. However, for most of 

the systems prior to 1970, cyclones were categorized as a tropical depression, 

tropical storm or hurricane, and given average intensities of 25, 45, or 75 kt 

respectively. 

From 1970-1975, advisories were issued by the Eastern Pacific Hurricane Center, part of the National Weather Service (NWS) office in San Francisco, California. Advisories/warnings were issued in coordination with the 

United States Navy Fleet Weather Center in Alameda and the Air Force Hurricane Liaison Officer at McClellan Air Force Base in California (D. Roberts, 

personal communication). The NWS advisories formed the basis of best tracks 

There are no wind speed criteria associated with the term extratropical and such systems may indeed have hurricane-force winds. Usually, when 

storms move out of the Tropics, wind speeds near the center of a storm gradually subside. In some cases, however, re-intensification of the system may occur 

when mechanisms conducive to extratropical development predominate.
7

The tropical cyclone tracks presented here are technically referred 

to as “best-tracks.” They represent the best estimate of the smoothed path 

of the circulation center as it moves across the earth’s surface (Jarvinen et al. 

1984). Smoothing is necessary to remove small-scale oscillatory motions of the 

storm center, which can deviate some 5 to 30 nautical miles from a mean path 

Agencies responsible for determining earlier storm tracks and intensities did not have the benefit of regular satellite data before 1966. In addition, the 

observations of a tropical cyclone simply did not exist or were very uncertain in 

the early years. Consequently, these earlier tracks are subject to considerable 

uncertainties. Today, a widespread network of land stations, ships, aircraft, 

radar, satellites, drifting buoys, etc., along with sophisticated instrumentation 

and communication, is available for the detection, tracking and understanding 

of tropical cyclones. The reader is referenced to McAdie et al. (2009) that further details the changing technology involved in tropical cyclone observation.

One specific problem with the eastern Pacific dataset before 1971 is 

the lack of major hurricanes (greater than or equal to Category 3 intensity on 

the Saffir-Simpson Hurricane Scale, see Table 3), compared to the modern era. 

It is thought that a few factors contribute to this issue, in addition to the lack 

of any satellite data before 1961. The first is the small amount of ship traffic 

and other oceanic data compared to other basins such as the Atlantic and the 

western Pacific. This would reduce the likelihood of a chance encounter with 

a strong hurricane. The second factor is that regular visible satellite pictures 

were not available until the early 1970s over the eastern Pacific, with improved 

picture quality. This upgraded quality and quantity allowed the forecaster, using techniques developed for Atlantic tropical cyclones (Velden et al. 2006), to 

accurately diagnose higher intensities. Another possible reason for the data disparity is that the official agency that prepared the best tracks changed in 1970. 

Thus, the intensity data are quite suspect for the early years (see also 

Section 4) and little attention should be paid to the exact intensities in the best 

track in the early part of the record, especially before 1966. Although there are 

5. ACCURACY OF TRACKS AND INTENSITY CLASSIFICATIONS

Tropical cyclones often traverse thousands of miles but spend most 

of their lives over the ocean. Before the era of aircraft reconnaissance and 

weather satellites, the detection of these storms depended on chance encounters 

with shipping or populated land areas. Over the eastern Pacific, the intersection 

of mean tropical cyclone tracks with shipping lanes is somewhat limited and 

major storms could have gone completely undetected before the satellite era. 

Even with the knowledge of a storm’s presence, however, it is difficult, without 

additional observational platforms, to specify the exact location and/or the exact intensity. 

 

The first aircraft reconnaissance flights into eastern Pacific tropical 

storms were made in 1956. Before the operational availability of satellite data 

in 1961, these flights proved to be important in the early detection of storms. It 

is worth noting that these flights were more sporadic in the eastern Pacific than 

the Atlantic basin and were only dispatched after a disturbance was noted. It is 

probable that many storms and hurricanes went undetected in the early years 

of the dataset since most eastern Pacific tropical cyclones remain out to sea and 

away from significant shipping lanes. 

After the introduction of continuous weather satellite surveillance in 

the late 1960s, there was a high probability that the location of a storm was 

determined with a reasonable degree of accuracy. Since the storm tracks for 

the 1966 through 2006 eastern Pacific hurricane seasons were prepared with 

the benefit of geostationary satellite imagery (as well as some aircraft reconnaissance typically near land and other conventional data), the track accuracy 

should be good, considering the scale of the maps and the large-scale of the 

motion depicted. 

(Lawrence and Mayfield 1977). These smaller scale motions are transitory and 

are not representative of the more conservative motion of the entire storm envelope. Storm tracks in Chart Series A and B should therefore be considered as 

the average path of the larger-scale storm circulation center rather than a precise 

location of the eye at any given time.
8

still some questions about the accuracy of data in the 1970s, the year 1971 is 

considered a good starting point for more reliable records. Around that year, 

consistent, quality satellite imagery was also available for analysis and better 

satellite intensity estimation techniques were in use by forecasters by that time, 

e.g. Dvorak (1973). 

In addition to observational deficiencies, it is known that large-scale 

atmospheric conditions such as El Niño or variations in sea-surface temperatures, in general, can influence tropical cyclone frequency and intensity. La 

Niña generally diminishes tropical activity in the eastern Pacific Ocean, and 

El Niño typically enhances tropical cyclone activity. Some of these factors are 

discussed by Gray (1984).

6. EASTERN NORTH PACIFIC TROPICAL CYCLONE TRACKS

The tracks of all recorded eastern Pacific tropical cyclones for each 

year from 1949 through 2008 are presented in Chart Series A (Appendix A). 

Extremely active years are separated into two or three charts for legibility. 

These tracks come exclusively from the best track database (HURDAT), as 

currently maintained by the NHC in November 2007. To be included on these 

charts, a tropical cyclone had to reach tropical storm status within the eastern 

Pacific, or be initially classified as a depression in the eastern Pacific and become a tropical storm or hurricane in the Central Pacific waters east of 150°W. 

An example of the latter case is Hurricane Iniki of 1992. 

The objective of the charts was to depict accurately, throughout their 

existence, the position and intensity of each tropical cyclone that formed in the 

eastern Pacific basin, and attained storm strength east of 150°W. Unfortunately, 

the quality of some of the data prevented full realization of this goal; many positions and intensities, particularly for the earlier years, are estimates, reflecting 

consideration of various data sources.

For the years 1949-1964, the data are rather fragmented, and for most 

cases, the assigned track intensity is assumed to be the maximum attained by 

the system at some point along the track. Intensity and classification criteria 

were given in Section 3. 

One specific problem with the tracks in the eastern Pacific prior to 

1988 is the premature termination of some tracks at landfall. One example of 

this problem is Hurricane Paul of 1982 (page 78). This hurricane made landfall 

in mainland Mexico and the track of the cyclone ends at hurricane strength just 

inland. A full reanalysis needs to be done to correct this problem in the eastern 

Pacific database.

Before 1960, there was no formal nomenclature for the identification 

of cyclones. Noteworthy storms were informally designated by such descriptive terms as “Great Hurricanes”. Female names were first given to storms in 

the eastern Pacific in the 1960 season. Unlike today, the names in the early 

1960s were used sequentially, such that if the last storm of a year was the “H” 

storm, then the first storm of the next year would be the “I” storm. This process 

was continued until the 1966 season, when four lists of names were created. 

These names were rotated every year until 1978, when six new annual lists of 

names replaced the previous four lists, and incorporated both male and female 

names.

In Chart Series A, certain storms lack names, even after the formal 

naming of tropical cyclones began. Some of these storms were found after 

the season due to late-arriving ship reports that confirmed their presence (e.g. 

Storm 1 of 1956 [Quinn 1956] or Storms 4 and 8 of 1962 [Benkman 1962]). 

In a few cases, the storms were thought to have developed west of 140°W and 

were given names from the Central Pacific, but the start of the tracks were later 

extended eastward into the eastern Pacific (e.g. Kanoa of 1957). 

Chart Series B provides storm tracks according to selected intraseasonal periods. This series is similar to work presented by Leftwich and Brown 
9

7. FREQUENCY OF EASTERN NORTH PACIFIC TROPICAL CYCLONES

(1981) and the Atlantic track book (McAdie et al. 2009). These charts are presented for months May through December and for 10- (or 11-) day periods, May 

through November. Figure 1, illustrating the entire storm sample, can also be 

considered as part of Series B. This rendition of the entire 769 storm sample 

shows the bounds of the eastern North Pacific tropical cyclone basin. The relative frequency of storms in any given area can be roughly identified by the track 

density. 

The tracks in Chart Series B are presented without regard to identification other than they are assigned to the period in which they first became 

a tropical cyclone. Additional labels would clutter the chart and detract from 

their main purpose: the identification of spatial and temporal shifts in tropical 

cyclone occurrence. 

All tracks were drawn by means of a computer interpolation routine 

using GIS technology and the 6-hourly storm positions in the best track file. 

With these positions as anchor points, a reasonably faithful rendition of a handdrawn track can be expected. In a few cases, however, the 6-hourly points are 

insufficient to define tight loops or sudden changes in direction.

 7.1 Monthly and Annual Frequencies

Tables 1, 2 and 3 present monthly and annual frequencies of recorded 

eastern Pacific tropical cyclones, excluding the tropical depression stage (if 

any). Storm counts are determined by the date a particular status was first 

attained: for example, a storm reaching tropical storm strength on August 31, 

reaching hurricane strength on September 5 and dissipating on September 10, 

would be counted as an August tropical storm but as a September hurricane.

Based on all eastern Pacific tropical cyclone tracks east of 140°W from 

1949 through 2006, the average duration of a tropical cyclone was 4 days, but 

as shown in Figure 2, may vary from less than 1 to as many as 18 full days (i.e., 

a storm which begins at 0600 UTC on one day and ends 0600 UTC on the next 

would be assigned a duration of 1 day rather than 2). The ability to detect tropical cyclones has improved in recent years such that the distribution shown in 

Figure 2 may be somewhat biased toward higher values.

Long duration tropical cyclones include Tina of 1992, Trudy of 1990, 

and Kevin of 1991, all of which lasted longer than two weeks. These systems 

formed at low-latitude east of 100°W, and travelled slowly westward due to 

weakening steering currents late in the year. The maximum duration noted in 

the eastern Pacific is far below the Atlantic basin, which has had tropical cyclones almost lasting a month (e.g. Ginger of 1971). Many tropical storms have 

been observed to last less than a day in the eastern Pacific, most recently Rosa 

of 2006.

The number of storms occurring in any given year varies widely. Frequency distributions of tropical storms and hurricanes are presented in Figure 

3 and 4, with a year-by-year summary in Figure 5. Only four tropical storms 

were documented in 1953, while 24 storms occurred in 1992. Only one storm 

reached hurricane strength in 1964 and 1965 while 16 hurricanes occurred in 

1990. A number of hurricane seasons has never observed a major hurricane 

(last noted in 2003), while 8 major hurricanes occurred in 1983, 1992 and 1993. 

Note that the minimum activity records are in question before the age of continuous satellite imagery. Since 1971, the minimum number of tropical storms 

and hurricanes observed in a year is 8 and 4, respectively, in 1977. Only twice, 

in 1977 and 2003, have no major hurricanes been noted in the geostationary 

satellite era. 
10

Table 1. Number of recorded eastern Pacific tropical cyclones that reached tropical storm intensity in specified month and year, 

1949-2006. Refer to Table 4 for summaries of these data. Data are probably incomplete before 1966.

Year May Jun Jul Aug Sep Oct Nov Dec All Year May Jun Jul Aug Sep Oct Nov Dec All

1949 0 2 0 0 4 0 0 0 6 1978 1 3 4 6 2 2 0 0 18

1950 0 1 2 2 0 1 0 0 6 1979 0 2 2 2 1 2 1 0 10

1951 1 2 1 2 2 0 1 0 9 1980 0 3 5 2 2 2 0 0 14

1952 1 1 2 0 2 1 0 0 7 1981 1 1 3 4 2 4 0 0 15

1953 0 0 0 1 2 1 0 0 4 1982 1 1 6 5 3 3 0 0 19

1954 0 1 3 0 5 2 0 0 11 1983 1 1 6 3 4 4 1 1 21

1955 0 2 1 0 1 2 0 0 6 1984 2 3 3 4 4 1 1 0 18

1956 2 2 2 1 3 1 0 0 11 1985 0 5 7 4 4 2 0 0 22

1957 0 0 1 2 4 3 0 0 10 1986 1 2 3 5 5 1 0 0 17

1958 0 2 4 1 3 2 0 0 12 1987 0 1 6 5 3 3 0 0 18

1959 0 2 3 3 2 2 0 0 12 1988 0 2 6 3 1 1 0 0 13

1960 0 2 1 2 1 1 0 0 7 1989 0 3 4 6 4 0 0 0 17

1961 0 1 3 1 1 2 2 0 10 1990 1 4 4 3 5 3 0 0 20

1962 0 1 1 3 3 1 0 0 9 1991 1 3 2 2 3 2 1 0 14

1963 0 1 2 0 3 1 0 0 7 1992 0 3 6 5 5 5 0 0 24

1964 0 0 3 1 1 0 0 0 5 1993 0 2 3 5 3 1 0 0 14

1965 0 4 0 3 3 0 0 0 10 1994 0 3 4 4 5 1 0 0 17

1966 0 1 0 4 6 2 0 0 13 1995 0 1 3 3 3 0 0 0 10

1967 0 3 4 3 3 3 0 0 16 1996 1 2 2 0 4 0 0 0 9

1968 0 1 4 8 3 3 0 0 19 1997 0 3 4 3 5 1 1 0 17

1969 0 0 3 2 4 1 0 0 10 1998 0 2 3 3 2 3 0 0 13

1970 1 3 6 4 1 2 1 0 18 1999 0 1 2 3 2 1 0 0 9

1971 1 1 6 5 2 2 1 0 18 2000 1 2 2 5 4 2 1 0 17

1972 0 1 1 6 2 1 1 0 12 2001 1 1 3 1 5 4 0 0 15

1973 0 3 4 1 3 1 0 0 12 2002 1 1 3 3 2 2 0 0 12

1974 1 3 3 6 2 2 0 0 17 2003 1 2 3 4 3 3 0 0 16

1975 0 2 4 5 3 1 1 0 16 2004 1 0 3 4 2 2 0 0 12

1976 0 2 4 3 4 1 0 0 14 2005 1 2 2 4 6 0 0 0 15

1977 1 1 1 1 3 1 0 0 8 2006 1 0 4 6 2 3 2 0 18
11

Table 2. Number of recorded eastern Pacific tropical cyclones that reached at least hurricane intensity in specified month and year, 

1949-2006. Refer to Table 4 for summaries of these data. Data before 1971 are probably incomplete.

Year May Jun Jul Aug Sep Oct Nov Dec All Year May Jun Jul Aug Sep Oct Nov Dec All

1949 0 0 0 0 2 0 0 0 2 1978 1 2 3 3 2 1 0 0 12

1950 0 1 2 1 0 1 0 0 5 1979 0 1 1 2 1 1 0 0 6

1951 0 1 0 0 1 0 0 0 2 1980 0 2 1 3 1 0 0 0 7

1952 0 0 1 0 1 1 0 0 3 1981 0 1 1 3 1 2 0 0 8

1953 0 0 0 0 1 1 0 0 2 1982 0 0 4 3 3 1 0 0 11

1954 0 0 2 0 1 1 0 0 4 1983 1 1 2 1 3 3 0 1 12

1955 0 1 0 0 0 1 0 0 2 1984 1 3 2 2 4 0 0 0 12

1956 1 2 1 1 2 0 0 0 7 1985 0 2 1 2 4 2 0 0 11

1957 0 0 1 1 1 3 0 0 6 1986 1 1 2 1 2 2 0 0 9

1958 0 1 2 0 2 0 0 0 5 1987 0 0 2 2 4 1 0 0 9

1959 0 0 0 0 2 1 0 0 3 1988 0 0 2 3 1 0 0 0 6

1960 0 0 1 2 1 1 0 0 5 1989 0 2 2 2 3 0 0 0 9

1961 0 1 0 0 0 0 1 0 2 1990 1 2 4 3 4 2 0 0 16

1962 0 1 0 0 0 1 0 0 2 1991 0 2 2 1 2 2 1 0 10

1963 0 1 2 0 0 1 0 0 4 1992 0 1 4 2 5 2 0 0 14

1964 0 0 1 0 0 0 0 0 1 1993 0 1 3 4 2 0 0 0 10

1965 0 0 0 1 0 0 0 0 1 1994 0 1 2 2 2 1 0 0 8

1966 0 1 0 3 2 0 0 0 6 1995 0 1 2 1 3 0 0 0 7

1967 0 1 0 2 1 2 0 0 6 1996 0 2 1 0 1 1 0 0 5

1968 0 0 0 3 2 1 0 0 6 1997 0 0 3 2 2 1 1 0 9

1969 0 0 1 1 1 1 0 0 4 1998 0 1 2 2 1 3 0 0 9

1970 0 1 1 1 0 1 0 0 4 1999 0 1 1 2 2 0 0 0 6

1971 1 1 4 3 2 1 0 0 12 2000 1 1 1 2 1 0 0 0 6

1972 0 1 0 6 0 1 0 0 8 2001 1 0 1 1 3 1 1 0 8

1973 0 1 3 0 1 2 0 0 7 2002 1 0 2 2 0 1 0 0 6

1974 0 2 2 4 2 1 0 0 11 2003 0 0 0 2 2 3 0 0 7

1975 0 1 2 3 1 1 0 0 8 2004 0 0 2 1 3 0 0 0 6

1976 0 2 1 2 2 1 0 0 8 2005 1 0 0 2 4 0 0 0 7

1977 0 0 1 1 1 1 0 0 4 2006 0 0 3 4 1 1 1 0 10
12

Table 3. Number of recorded eastern Pacific tropical cyclones that reached major hurricane intensity (≥ category 3) in specified 

month and year, 1949-2006. Refer to Table 4 for summaries of these data. Data before 1971 are considered suspect.

Year May Jun Jul Aug Sep Oct Nov Dec All Year May Jun Jul Aug Sep Oct Nov Dec All

1949 0 0 0 0 0 0 0 0 0 1978 0 2 3 0 1 0 0 0 6

1950 0 0 0 0 0 0 0 0 0 1979 0 0 1 2 0 1 0 0 4

1951 0 0 0 0 0 0 0 0 0 1980 0 1 0 1 1 0 0 0 3

1952 0 0 0 0 0 0 0 0 0 1981 0 0 0 0 0 1 0 0 1

1953 0 0 0 0 0 0 0 0 0 1982 0 0 2 0 1 1 0 0 4

1954 0 0 0 0 0 0 0 0 0 1983 0 1 1 0 3 3 0 0 8

1955 0 0 0 0 0 0 0 0 0 1984 0 1 2 1 1 1 0 0 6

1956 0 0 0 0 0 0 0 0 0 1985 0 1 2 0 3 1 0 0 7

1957 0 0 0 0 0 1 0 0 1 1986 0 0 1 1 0 1 0 0 3

1958 0 0 0 0 0 0 0 0 0 1987 0 0 0 1 2 1 0 0 4

1959 0 0 0 0 0 1 0 0 1 1988 0 0 0 1 0 0 0 0 1

1960 0 0 0 0 0 0 0 0 0 1989 0 0 0 2 2 0 0 0 4

1961 0 0 0 0 0 0 0 0 0 1990 0 0 2 1 2 1 0 0 6

1962 0 0 0 0 0 0 0 0 0 1991 0 1 0 1 2 1 0 0 5

1963 0 0 0 0 0 0 0 0 0 1992 0 1 3 0 2 2 0 0 8

1964 0 0 0 0 0 0 0 0 0 1993 0 0 2 3 3 0 0 0 8

1965 0 0 0 0 0 0 0 0 0 1994 0 0 1 1 2 0 0 0 4

1966 0 0 0 0 0 0 0 0 0 1995 0 1 1 0 1 0 0 0 3

1967 0 0 0 0 0 1 0 0 1 1996 0 0 1 0 1 0 0 0 2

1968 0 0 0 0 0 0 0 0 0 1997 0 0 2 2 2 1 0 0 7

1969 0 0 0 0 0 0 0 0 0 1998 0 1 1 3 0 1 0 0 6

1970 0 0 0 0 0 0 0 0 0 1999 0 0 1 1 0 0 0 0 2

1971 0 0 2 1 2 1 0 0 6 2000 0 1 1 0 0 0 0 0 2

1972 0 0 0 3 0 0 0 0 3 2001 1 0 0 0 1 0 0 0 2

1973 0 1 2 0 0 0 0 0 3 2002 1 0 1 2 0 1 0 0 5

1974 0 1 0 1 0 0 0 0 2 2003 0 0 0 0 0 0 0 0 0

1975 0 0 2 0 1 1 0 0 4 2004 0 0 1 0 2 0 0 0 3

1976 0 1 0 2 1 1 0 0 5 2005 0 0 0 0 1 0 0 0 1

1977 0 0 0 0 0 0 0 0 0 2006 0 0 2 2 1 0 0 0 5
13

Another record of interest is the maximum number of hurricanes in 

consecutive years. The data are found in the annual totals given in Table 2:

26 hurricanes were observed in 1990-1991 (2 consecutive years);

40 hurricanes were observed in 1990-1992 (3 consecutive years);

50 hurricanes were observed in 1990-1993 (4 consecutive years);

59 hurricanes were observed in 1989-1993 (5 consecutive years).

The area of the eastern Pacific basin experiencing the maximum amount 

of activity is near 17°N, 108°W (approximately 240 nautical miles southwest of 

Manzanillo, Mexico). Tropical cyclones (hurricanes) have passed within 60 

nautical miles of this location 133 (59) times from 1949 through 2006. 

Long-term upward or downward trends in the frequency of tropical 

cyclones, if not accounted for, make the average frequency a function of the 

period of record. To illustrate, Table 4 uses data from Tables 1-3 averaged over 

two periods: 1949-2006 and 1971-2006. The first period contains years with serious observational deficiencies in addition to a lack of regular satellite pictures. 

The final period begins with the introduction of regular, high-quality satellite 

pictures. Note the extreme differences in major hurricanes and hurricanes between the two periods, suggesting that the early part of the best tracks database 

is severely lacking information. The substantial differences in the figures for 

the final two periods appear in Table 4. The period 1971 through 2006 probably 

best represents eastern Pacific tropical cyclone frequencies as they currently 

exist.

7.2 Daily Frequencies

Figure 6 illustrates the daily frequency of tropical cyclones over the 

eastern Pacific basin for the 8-month period that tropical cyclones have been 

observed. This plot has been smoothed using a 9-day moving average, eliminating much of the noise inherent in the raw data, yet preserving the largerscale intraseasonal cycles.

The daily frequencies in Figure 6 help define seasonal fluctuations in 

tropical cyclone frequency over the eastern Pacific. These intraseasonal changes include a slight maximum around mid-June, followed by a slight decline 

until early July. This decline is followed by a steep increase in frequency until 

mid-July, then a substantial drop in activity is noted through mid-August. It is 

interesting that forecasters from the 1960s often said that August brings a lull 

in tropical storm activity (Gustafson 1969). A rapid increase in activity occurs 

by the third week in August, attaining a level a little higher than the July peak. 

The frequency remains relatively steady until the end of September, where it 

trails off rapidly, save a slight increase in activity in the third week of October. 

In general, the season starts a few weeks earlier than the Atlantic basin, but also 

ends a few weeks earlier. It is also of note that the hurricane and major hurricane frequency from early July to late September is rather steady, except for 

the large drop in activity from late July to mid-August. Figure 6 is somewhat Figure 2. Distribution of the duration of tropical cyclones east 

of 140°W, excluding depression stage, 1949-2006. 
14

similar to one presented by Leftwich and Brown (1981) using limited data, and 

still shows the mid-season minimum in activity during late July and early August.

It is noted in Figures 6-8 that the storm frequency on any given day 

is specified in units of estimated number of storms per 100 years. This unit of 

measurement is convenient for comparing eastern Pacific storm frequencies 

with similarly normalized charts for other basins having dissimilar periods of 

record. In preparing these figures, multiple storm occurrences on single days 

were included in the overall totals. Thus, the occurrence of three storms on a 

given date in a single year and none on that day during the next two years, for 

example, would yield the same average as a single storm on the same date for 

each of three successive years.

This counting methodology needs to be considered when making interpretations of these data. It should be noted on Figures 7 and 8 that multiple 

storm and hurricane occurrences on a single day are reasonably common during a large portion of the middle of hurricane season. 

The maximum multiple occurrence event depicted on these figures is 

the “at least three” category for tropical storms and the “at least two” category 

for hurricanes. The maximum number of simultaneous tropical storm occurrences on a single day over the eastern Pacific is four although such an event 

is quite rare; in fact, it has only been observed in one year. This 4-storm event 

occurred in 1974 when four tropical storms or hurricanes were in existence 

during the periods from August 23-24 and August 26-27. Ione, Joyce, Kirsten 

and Lorraine were observed in the first period, and Joyce, Kirsten, Lorraine 

and Maggie were active simultaneously during the second period. The only 

Figures 3 and 4. Distribution of the annual number of tropical storms and hurricanes (left) and hurricanes 

only (right), 1949-2006. Data derived from Tables 1 and 2.
15

other time that the eastern Pacific basin was close to having four storms active 

at once was on September 18, 2005, when Jova, Kenneth, Lidia and Max were 

all active, but Lidia weakened into a tropical depression at the same time that 

Max became a tropical storm.

Insofar as hurricanes alone are concerned, there were only two years 

(1974, 1992) when 3 hurricanes existed simultaneously. Hurricanes Ione, 

Kirsten, Joyce were active on August 23-24 for twelve hours, and 18 years later 

the record was matched by Roslyn, Seymour and Tina.

Figure 5. Eastern North Pacific basin tropical storms, hurricanes and major hurricanes by year, 1949-2006.
16

The official eastern Pacific hurricane season extends from May 15 to 

November 30. Very rarely does the season begin or end outside of those dates, 

unlike the Atlantic basin. Figure 9 presents a cumulative percentage frequency 

distribution (Burlington and May 1957) of the beginning and ending dates of 

the eastern Pacific tropical cyclone season. The figure shows that only about 

3% of activity occurs out of the hurricane season. Figure 9 also shows that the 

median (50% cumulative percentage frequency) starting date is June 2 while 

the median ending date is October 24.

There is a modest negative correlation between the beginning and 

ending dates of a season (r = -0.39). Seasons that begin early tend to end late, 

and vice versa. As might be expected, there is also a moderate correlation 

Table 4. Total and average number of tropical storms, hurricanes and major hurricanes beginning each month 

in two periods.

1949 - 2006

MAY JUN JUL AUG SEP OCT NOV DEC YEAR

TROPICAL STORMS 25 104 177 177 172 98 15 1 769

AVERAGE OVER PERIOD 0.4 1.8 3.1 3.1 3.0 1.7 0.3 * 13.3

HURRICANES 11 48 84 95 96 56 5 1 396

AVERAGE OVER PERIOD 0.2 0.8 1.4 1.6 1.7 1.0 0.1 * 6.8

MAJOR HURRICANES 2 14 37 32 38 23 0 0 146

AVERAGE OVER PERIOD * 0.2 0.6 0.6 0.7 0.4 0.0 0.0 2.5

1971 - 2006

MAY JUN JUL AUG SEP OCT NOV DEC YEAR

TROPICAL STORMS 20 72 131 134 115 67 11 1 551

AVERAGE OVER PERIOD 0.6 2.0 3.6 3.7 3.2 1.9 0.3 * 15.3

HURRICANES 10 36 69 79 76 39 4 1 314

AVERAGE OVER PERIOD 0.3 1.0 1.9 2.2 2.1 1.1 0.1 * 8.7

MAJOR HURRICANES 2 14 37 32 38 20 0 0 143

AVERAGE OVER PERIOD * 0.4 1.0 0.9 1.1 0.6 0.0 0.0 4.0

Note: Data have been summarized from Tables 1-3. Asterisk (*) indicates less than 0.05 storms
17

between starting date and the number of storms. Seasons that begin early tend 

to have more storms than those that begin late. The linear correlation coefficient (-0.47) indicates that the starting date explains about 23% of the variance 

in the number of tropical storms.

7.3 Areas of Formation

Seasonal shifts in the formation areas in the eastern Pacific are generally more subtle than those documented in the Atlantic basin (Neumann et al. 

1999). Chart Series B shows the monthly tracks of all of the tropical cyclones. 

Figure 6. Intraseasonal variations in the 100-year expectancy of tropical cyclone occurrence, based on data 

from 1949-2006. The blue bar is for tropical storms, the red bar is for hurricanes and the black bar is for 

major hurricanes. The data has been smoothed by a 9-day running mean.
18

Some distinguishing characteristics can be noted. Tropical cyclone development in May and June generally occurs in the eastern part of the basin, south 

of Mexico. June cyclones form at a slightly higher latitude than May, probably 

due to the northward seasonal migration of the Intertropical Convergence Zone 

(ITCZ). 

The area of tropical cyclone formation expands greatly westward in 

July, with a large area of formations noted from July through September, reaching the highest latitude in September. The genesis area retreats eastward somewhat in September, with both the latitude of formation and number of cyclones 

significantly diminishing in October. May and November formation areas are 

similar to one another. Many additional features relating to temporal and spatial variations in storm frequency can be identified by careful analysis of Chart 

Series B. It is often helpful to consider these charts in conjunction with Figures 

6 and 7, depicting the daily frequencies. 

7.4 Mainland Tropical Cyclone Landfalls

Of the 769 tropical cyclones of at least storm strength that have been 

recorded over the eastern Pacific tropical cyclone basin, 1949-2006, a total of 

151 or about 20% are estimated to have caused at least tropical storm force 

winds along the Mexican coastline. For marginal cases, or those systems that 

brushed the coast, a review of the data along with the tropical cyclone reports or 

published seasonal summaries in Monthly Weather Review was used to make a 

determination of the maximum wind speeds that likely occurred on the coast.

Tropical storms affecting land areas other than Mexico in the eastern 

Pacific basin are quite rare. In fact, there are only four tropical storms that have 

affected areas of the Pacific coast of Central America (Simone 1968, Olivia 

1971, Miriam 1988, Adrian 2005). Two of these systems, Olivia and Miriam, 

Figure 7. Intraseasonal variation in the expected 100-year frequency of 

tropical storms.

Figure 8. Same as Figure 7 except for hurricanes.
19

were former Atlantic hurricanes that quickly redeveloped after entering the 

eastern Pacific. 

Seventy-one hurricane strikes (a hurricane strike is defined as a hurricane that is estimated to have caused sustained hurricane-force winds on the 

coastline, but does not necessarily make landfall in the area of hurricane-force 

winds) have been noted along with ten landfalling major hurricanes. All of 

these hurricanes struck Mexico. Figure 10 shows the year-to-year distribution 

of these systems, including all tropical storms. The long-term record for hurricane strikes seems to be more reliable than the basin-wide records, with little 

trend in numbers indicated. 

It is also of note that most of the hurricanes and major hurricanes occur 

late in the season, with a sharp maximum in September and October (Figure 

11). These two months account for about 60% of the seasonal strikes. June has 

a secondary maximum in hurricane impacts, but the maximum is smaller than 

either September or October. In terms of major hurricanes, October is by far 

the most dangerous month for Pacific coastal residents of Mexico, with 8 out 

of 10 recorded systems observed in that month. These systems have tended to 

approach Mexico from the south or southwest as the mid-latitude westerlies dip 

far enough to the south to allow recurvature of the major hurricanes.

7.5 Coastal Variation of Hurricane Threat

Many factors relate to the geographical variation of coastal tropical 

cyclone frequency and intensity. Since the intensity of a hurricane depends 

on a continuous supply of warm and very moist air near the surface, a marine 

environment with warm sea-surface temperatures is an important factor. Thus, 

in general, storms hitting the northern Baja California coast are likely to be less 

frequent and less intense than those hitting the other areas of Mexico. Another 

factor is the location and orientation of the coastline in relation to mean storm 

tracks. There is a significant clustering of hurricane landfall points (Figure 12) 

Figure 9. Cumulative percentage frequency distribution of beginning and ending dates of eastern 

Pacific tropical cyclone season, 1949-2006. (Dates are of first and last recorded position with at least 

tropical storm strength.)
20

Figure 10. Central American and Mexican landfalls and strikes, 1949-2006.
21

in southern Mexico near Manzanillo and in the Mexican state of Sinaloa. Note 

that eleven major hurricane landfall points are shown on Figure 12 because one 

storm impacted both Baja California and Sinaloa as a major hurricane. The figure does not specifically address tropical cyclones that do not cross the coast but 

still cause coastal hurricane-force winds, although there is a reasonably good 

correlation between hurricane strikes and the frequencies shown on the figure.

Locations of the tropical cyclones referred to in Figure 10 can be found 

on the appropriate yearly map in Chart Series A. In regard to impacts, the 

weather is usually very asymmetrical about the point of landfall. Looking in 

the direction of storm motion, the worst weather is normally to the storm’s 

right side where rotational winds and translational (forward) motion are complementary; thus, for a hurricane moving into southern Mexico from the south, 

Figure 11. Monthly distribution of hurricane and major hurricane landfalls and strikes for 

Mexico, 1949-2006. 
22

strongest winds and storm surge would normally be on the right (east) side; for 

a storm moving into the Mexican west coast from the west, maximum wind and 

storm surge would be expected south of the landfall point. 

Other meteorological conditions and terrain features also contribute to 

wind, wind gusts, weather and storm surge asymmetries such that it is difficult 

to speculate on the extent and nature of storm damage at a particular site given 

Figure 12. Distribution of hurricane (red) and major hurricane (black) landfall points in Mexico.
23

only the storm track and storm classification. In addition, building standards 

vary from location to location. Accordingly, persons desiring to know the specific effect or potential effect of past or future storms on a given site should seek 

further meteorological or engineering advice. 

7.6 Hurricane Damage Potential

A previous section (7.4) dealt with all tropical cyclones greater than 

storm strength. This section concerns only hurricanes. The amount of damage caused by hurricanes is highly variable and depends on a number of factors. Obviously, more intense storms can be expected to cause more damage. 

However, there are numerous other factors which need be considered such as 

wind gusts, storm size, the speed of translational motion (affecting rainfall and 

fresh-water flooding), storm surge (affected by offshore water depth and coastal 

configuration), astronomical tide, terrain features, local building codes, etc. 

In 1972, the U.S. National Weather Service accepted a hurricane damage scale devised by Herbert Saffir, and later expanded upon by Robert Simpson. The Saffir-Simpson hurricane scale (Simpson 1974), as it has come to 

be known, relates the strength of hurricane-force winds and associated storm 

surge with potential damage. The scale is now widely used in public awareness 

programs and by the news media. It gives the public and disaster preparedness 

officials a good estimate of what can be expected from various levels of intensity (Table 5).

Operationally, the assignment of category is solely based on the sustained wind speed. For this publication, the Saffir-Simpson hurricane scale 

value shown in Table 6 is taken from the maximum sustained winds at landfall 

in the eastern Pacific tropical cyclone best track database. For marginal cases, 

or those systems that brushed the coast, a review of the data along with the 

tropical cyclone reports or published seasonal summaries in Monthly Weather 

Review was used to make a determination of the maximum wind speeds that 

likely occurred on the coast.

The data presented in Table 6 are summarized by region in Table 7. 

Entries in Table 7 may be made for the same hurricane more than once if it 

affected more than one section; thus, sectional totals cannot be summed to get 

national totals. The initial line of Table 7 is an actual count of the number of 

hurricanes that have affected Mexico from 1949-2006, where only the highest 

Saffir-Simpson category in any individual state is used. 

Thus, over the 58-year period 1949 through 2006, a total of 71 hurricanes have struck the Mexican coastline. This is an average of a little more than 

one hurricane per year. The maximum number of strikes was 4 in 1996, and the 

minimum observed is zero in numerous years, mostly recently in 2005.
24

Scale No. 1--Winds of 74 to 95 miles per hour. Likely effects include: Damage primarily to shrubbery, trees, foliage, and unanchored mobile homes. No real 

damage to other structures. Some damage to poorly constructed signs. Storm surge 4 to 5 feet above normal. Low-lying coastal roads inundated, minor pier 

damage, some small craft in exposed anchorage torn from moorings. 

Scale No. 2--Winds of 96 to 110 miles per hour. Likely effects include: Considerable damage to shrubbery and tree foliage; some trees blown down. Major 

damage to exposed mobile homes. Extensive damage to poorly constructed signs. Some damage to roofing materials and buildings; some window and door 

damage. Storm surge 6 to 8 feet above normal. Coastal roads and low-lying escape routes inland cut by rising water 2 to 4 hours before arrival of hurricane 

center. Considerable damage to piers. Marinas flooded. Small craft in unprotected anchorages torn from moorings. Evacuation of some shoreline residences 

and low-lying island areas required.

Scale No. 3--Winds of 111 to 130 miles per hour. Likely effects include: Foliage torn from trees; large trees blown down. Practically all poorly constructed 

signs blown down. Some structural damage to roofing materials of buildings; some window and door damage. Some structural damage to small buildings. 

Mobile homes destroyed. Storm surge 9 to 12 feet above normal. Serious flooding at coast and many smaller structures near coast destroyed; larger structures near coast damaged by battering waves and floating debris. Low-lying escape routes inland cut by rising water 3 to 5 hours before hurricane center 

arrives. Flat terrain 5 feet or less above sea level flooded 8 miles or more. Evacuation of low-lying residences within several blocks of shoreline possibly 

required.

Scale No. 4--Winds of 131 to 155 miles per hour. Likely effects include: Shrubs and trees blown down; all signs down. Extensive damage to roofing materials, windows and doors. Complete failure of roofs on many small residences. Complete destruction of mobile homes. Storm surge 13 to 18 feet above 

normal. Flat terrain 10 feet or less above sea level flooded inland as far as 6 miles. Major damage to lower floors of structures near shore due to flooding 

and battering by waves and floating debris. Low-lying escape routes inland cut by rising water 3 to 5 hours before hurricane center arrives. Major erosion 

of beaches. Massive evacuation of all residences within 500 yards of shore possibly required, and of single-story residences on low ground within 2 miles of 

shore.

Scale No. 5--Winds greater than 155 miles per hour. Likely effects include: Shrubs and trees blown down; considerable damage to roofs of buildings; all 

signs down. Very severe and extensive damage to windows and doors. Complete failure of roofs on many residences and industrial buildings. Extensive 

shattering of glass in windows and doors. Some complete building failures. Small buildings overturned or blown away. Complete destruction of mobile 

homes. Storm surge greater than 18 feet above normal. Major damage to lower floors of all structures less than 15 feet above sea level within 500 yards of 

shore. Low-lying escape routes inland cut by rising waters 3 to 5 hours before hurricane center arrives. Massive evacuation of residential areas on low ground 

within 5 to 10 miles of shore possibly required.

Table 5. The Saffir-Simpson Hurricane Scale.
25

Table 6. Chronological listing of hurricane landfalls and strikes and coastal states affected, 1949-2006. Geographical areas are defined as 

southern mainland Mexico (states of Chiapas, Oaxaca, Guerrero, Michoacan, Colima, and Jalisco), northern mainland Mexico (states of 

Nayarit, Sinaloa, and Sonora), southern Baja Peninsula (state of Baja California Sur), and northern Baja Peninsula (state of Baja California 

Norte). The asterisk means that the center stayed offshore.
26

Table 6 (continued). Chronological listing of hurricane landfalls and 

strikes and coastal states affected, 1949-2006.
27

Table 7. Number of hurricanes striking Mexico, 1949-2006, categorized according to the Saffir-Simpson 

hurricane scale. Regional definitions are found in Table 6.

8. ACKNOWLEDGMENTS AND OTHER COMMENTS

In any document of this type, it is impossible to acknowledge all persons and agencies who have contributed their time, effort and expertise. Documentation of tropical cyclone tracks and the transfer of these data from analog 

to digital form has been underway at the NHC for many years. Some of this 

work was accomplished by part-time students assigned to the NHC on various 

work/study, cooperative education or international exchange programs. Colin McAdie, Chris Landsea, and Charlie Neumann, recent authors of a similar 

Atlantic best track book, provided invaluable suggestions. Valuable computer 

assistance was given by Chris Sisko. Hurricane specialists at the NHC provided 

thorough reviews and significantly improved the text. Many thanks also go to 

the graphics team at NCDC for outstanding work on this project.

The work of George Cry, lead- or co-author of the earliest editions of 

the Atlantic track book text, is acknowledged. Indeed, he structured much of 

the framework about which later editions were patterned (Cry 1959). The late 

Dr. Arthur Pike of TPC/NHC is acknowledged for his work on the best track 

database in the eastern North Pacific.
28

9. LIST OF ACRONYMS AND ABBREVIATIONS

HURDAT Hurricane Data from the best tracks database at the National 

 Hurricane Center.

ITCZ Intertropical Convergence Zone.

kt knots (nautical miles per hour). Multiply knots by 1.152 to 

 obtain miles per hour.

m/s meters per second - Multiply m/s by 1.94 to obtain knots.

mph miles per hour - Multiply mph by 0.868 to obtain knots.

NCDC National Climatic Data Center, Asheville, NC 

(a branch of NOAA).

NHC National Hurricane Center.

NOAA National Oceanographic and Atmospheric Administration 

(parent agency of NHC).

NWS National Weather Service.

RSMC Regional Specialized Meteorological Center (an agency 

designated by WMO as a major forecasting Center).

UTC Universal Time Coordinated Global time system 

(formerly Greenwich Mean Time or Z time).

WMO World Meteorological Organization (an agency of the 

 United Nations).
29

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APPENDIX A

TRACKS OF EASTERN NORTH PACIFIC TROPICAL CYCLONES BY YEARS, 1949-2008 

(CHART SERIES A)

 INFORMATION INCLUDED ON CHART

(See Section 3 for definition of various stages)

1949-1964 Track type shown usually indicates maximum intensity believed to have been attained at some point along with a reasonable dissipation for

 systems that impact land. A few storms have a full lifecycle but they are the minority. Major hurricanes are rarely indicated.

1965-2008 Tropical depression, tropical storm, hurricane, major hurricane, extratropical, and low stages are commonly indicated. Major hurricanes are rarely

indicated before 1971. The low stage is used much more often after 2001.

Notes: In the storm description box, under the TYPE column, occasionally two storm classes are listed. The first one is the maximum intensity attained

while the system was in the eastern Pacific, and the second one in parenthesis is the maximum intensity attained during the storm’s entire life

cycle outside of the eastern Pacific.

Before 1988, storms were often tracked to the coast of Mexico and then no longer tracked (e.g. Paul 1982). The reader should be aware of this 

problem, and there is ongoing work to fix this systematic error in the best tracks.

Following the 2008 season, a set of blank pages has been provided for displaying later charts. These are normally published in Monthly Weather Review

or available at http://www.nhc.noaa.gov

YEARS
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129

ATTACH 2009 TRACK CHART
130

ATTACH 2010 TRACK CHART
131

ATTACH 2011 TRACK CHART
132

ATTACH 2012 TRACK CHART
133

ATTACH 2013 TRACK CHART
134

Tracks of eastern North Pacific tropical cyclones reaching at least storm strength, including depression stage if known, by months, May through 

December and by 10- (or 11-) day periods, May 10 through November 30. Red dots indicate the genesis point of each tropical cyclone that eventually reached 

at least tropical storm strength. The monthly numbers of tropical cyclones given in Appendix B do not necessarily match the totals of just tropical storms and 

hurricane formations given in Table 4 because Appendix B includes the tropical depression stage.

APPENDIX B

TRACKS OF EASTERN NORTH PACIFIC TROPICAL CYCLONES BY 

INTRASEASONAL PERIODS, 1949-2006

(CHART SERIES B)
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162