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STUDY TITLE: Meteorology of the Northeastern Gulf of Mexico

REPORT TITLE: Meteorology of the Northeastern Gulf of Mexico: Data from 1995 to 

1997, Final Report

CONTRACT NUMBER: 435-01-97-CT-30826

SPONSORING OCS REGION: Gulf of Mexico

APPLICABLE PLANNING AREAS: Eastern Gulf of Mexico 

FISCAL YEARS OF PROJECT FUNDING: 1995-2000

COMPLETION DATE OF REPORT: November 2000

COSTS: FY 1997: $51,513.01; FY 1998: $177,938.73; FY 1999: $79,316.40; FY 2000: 

$10,595.76, CUMULATIVE PROJECT COST: $319,363.90 

PROJECT MANAGER: Dr. Mark A. Yocke

AFFILIATION: ENVIRON International Corporation

ADDRESS: 101 Rowland Way, Suite 220, Novato, CA 94945

PRINCIPAL INVESTIGATORS*: Dr. Mark Yocke and Dr. Paul Roberts

KEY WORDS: meteorology, meteorological data, Gulf of Mexico, meteorological 

modeling, weather patterns, meteorological data base, software 

BACKGROUND: There is renewed interest in oil and gas extraction activities in the 

Northeastern Gulf of Mexico (NEGOM). Further, the National Environmental Policy Act 

(NEPA) mandates multidisciplinary environmental assessments of major Federal 

actions, such as oil and gas leases and related activities in the NEGOM. Such 

assessments could benefit from a meteorological database. The research conducted 

for this study resulted in a database useable for ongoing and future MMS studies in the 

NEGOM. In addition, the meteorological and oceanographic science communities 

should benefit from an improved understanding of atmospheric-oceanic interactions in 

this area. The database and software system from this study may be used as a 

“handbook” by planners and analysts in future industrial activities in the area, or as 

initial assessment of conditions associated with non-routine or accidental hazardous 

events. Knowledge acquired in this study will improve understanding of wind field 

patterns and sea breeze structures, atmospheric boundary layer behavior and its 

moisture fluxes across the land-sea interface, wind stress patterns on the sea surface, 

and cold air outbreaks. 
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OBJECTIVES: (1) To collect wind data from available sources (National Weather 

Service, National Data Buoy Center, stations funded by Minerals Management Service, 

and other private sources) spanning the NEGOM, and estimate the temporal/frequency 

contents and spatial scales of variation from these measurements; (2) To collect 

humidity, and air and sea-surface temperature measurements throughout the NEGOM 

from these same institutions, prepare maps of the mean and variance fields, and 

estimate the temporal and spatial scales of variation; (3) To calculate mean and 

variance fields of surface wind stress and heat flux over the NEGOM and prepare maps 

of these quantities, to estimate wind curl and vertical vorticity means and variability with 

and without effects of sea breezes (i.e. with and without filtering techniques), and to use 

these data to the maximum extent possible to study winter cyclogenesis and cold frontal 

passage in the NEGOM; (4) To assess how frontal passage and the modification of air 

masses affect the local fields of temperature, humidity, pressure and other relevant 

meteorological parameters; (5) To estimate the transport of water-vapor and latent heat 

across water-land boundaries or coastlines and the properties of the atmospheric 

boundary layer, and to evaluate the temporal and spatial variation scales analyzed as 

functions of atmospheric and climatological forcing; (6) To collect, archive, and analyze 

the gridded output of a prognostic meteorological model (the Eta model) for the same 

time periods as the observational database. (7) To develop an ACCESS relational 

database containing both observed data, derived parameters, and gridded Eta model 

output for a two-year period (1996-1997); and (8) To develop an expert software system 

to provide the users of the NEGOM meteorological database with a simple way to 

access and display the database and the data analysis products of the study. 

DESCRIPTION: The study area was defined as the region enclosed within the latitudes 

of 28o-32oN and the longitudes 82o-90oW. The data collection period of interest for this 

study was Jan 1,1996 through December 31, 1997. (In addition, 1995 observational 

data were included in the ACCESS database because they were collected at the 

beginning of the study to test archival and analysis methods.) Data were acquired data 

from many agencies and more than 200 gigabytes of meteorological data from more 

than 50 measurement sites were processed. From this raw data, a very large relational 

ACCESS relational database was produced, containing more than 5.2 gigabytes of 

meteorological data. Extensive analyses of these data were conducted, numerous 

derived meteorological parameters were calculated, and graphical products and maps 

created. A software system was developed to access and display raw data, analysis 

results, and graphical products.

SIGNIFICANT CONCLUSIONS: Review of annual and seasonal frequency of 

occurrence of meteorological pattern types for the period 1996-1997 reveals that, the 

NEGOM is dominated by fair weather conditions. 

• Conditions are infrequently punctuated in all seasons by frontal passage. 

• Tropical storms occur infrequently, most often in fall. 

• Winds are strongest in the winter, and lighter and more variable in the summer. 

• Winds are generally from the east, yet progressively turn from southerly in the 

summer to northeasterly in the winter. 
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• Surface air temperatures follow expected season patterns. 

• Annually, sea-surface temperature (SST) is greater than air temperatures (unstable 

regime). In spring and summer, SST is less than the air temperature (stable 

regime), but in the fall and winter, unstable conditions prevail as offshore flow moves 

cooler continental air over the Gulf. 

• Geostrophic vorticity is slightly positive annually, suggesting the dominance of 

cyclonic curvature of surface-level winds; negative vorticity (anti-cyclonic curvature) 

is evident in spring and summer, likely due to the dominance of high pressure 

regimes. 

• Variability in vorticity is larger in the winter, possibly due to the larger frequency of 

transient systems moving through the area, while it is least variable in the summer 

with the establishment of constant and stationary high-pressure systems. 

• Wind stress curl follows the vorticity patterns since the two are directly related. 

• The effects of land-sea breeze recirculation and flow reversals are not felt far 

offshore; certainly less than 80 km and probably no further than about 50 km. This 

finding is consistent with prior analyses of coastal meteorology in the Gulf of Mexico. 

 The land-sea breeze effect is much less pronounce offshore Louisiana; probably 

due to the predominance of swamps and a poorly defined coastline. 

These findings are consistent with expectations based on common-sense 

meteorological reasoning, prior studies, and longer-term historical climatology. 

However, it must be remembered that a strong El Niño event marked the second half of 

1997, and the related eastern movement of the Southern Oscillation in the Pacific was 

signaled in late 1996. El Niño events are known to suppress western Atlantic tropical 

storm development in the summer and fall months following onset. 

STUDY RESULTS: Meteorological data for the 1995-1997 period from all available 

sources (National Weather Service, National Data Buoy Center, stations funded by 

Minerals Management Service, and other private sources) spanning the region of the 

Northeastern Gulf of Mexico (NEGOM) were collected. Estimates of the 

temporal/frequency contents and spatial scales of variation from these wind 

measurements were prepared. Humidity, air and sea-surface temperature 

measurements for the same period throughout the NEGOM were also analyzed and 

maps of the mean and variance fields, and estimate the temporal and spatial scales of 

variation were prepared. Calculations of mean and variance fields of surface wind 

stress and heat flux over the NEGOM were made and maps prepared of the quantities 

to estimate wind curl and vertical vorticity means and variability after effects of sea 

breezes were identified via filtering techniques. These data were used to study winter 

cyclogenesis and cold frontal passage in the NEGOM. Assessments were made of 

frontal passage and the modification of air masses affecting the local fields of 

temperature, humidity, pressure and other relevant meteorological parameters. 

Temporal and spatial variation scales were analyzed as functions of atmospheric and 

climatological types. Prognostic meteorological model output was also archived for the 

same period to supplement the observational database for the NEGOM region. A 

computer-based expert software system was developed that allows rapid, real-time 
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access to the information and products developed in this study and aid in interpretation 

of current and forecast meteorological conditions.

STUDY PRODUCT(S): Yocke, M.A., C.A. Emery, P. Roberts, C. MacDonald, D. 

Ladner, J. Prouty, and A. Barnett. 1999. Meteorology of the Northeastern Gulf of 

Mexico. An Interim Report for U.S. Dept. of the Interior, Minerals Management Service, 

Gulf of Mexico OCS Region, New Orleans, La. 70123-2394. 

Yocke, M.A., C.A. Emery, P. Roberts, C. MacDonald, D. Ladner, J. Prouty, and A. 

Barnett. 2000. Meteorology of the Northeastern Gulf of Mexico. A Final Report for U.S. 

Dept. of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New 

Orleans, La. 70123-2394. 

An ACCESS relational database containing more than 5.2 Gigabytes of meteorological 

data. Users can easily access this data and rapidly sort and prepare reports of the data 

subsets utilizing MS Access97 software. The Access data set is available on magnetic 

tape cartridge from MMS or the National Climatic Data Center (NCDC). The ACCESS 

database contains all observational data and Eta model output for the study period. 

A software system called the North East Gulf of Mexico Expert System (NEGOMES). 

This software allows its users to browse the statistical and analysis products of the 

study. The system’s graphical user interface capabilities allow users to easily access, 

select, sort, view, and navigate data maps and other tabular and graphical data 

products. The expert system also allows the user to quickly forecast and view 

projections of wind trajectories based on the stored wind statistics. The expert software 

system and supporting data are available from the MMS on a 5 CD-ROM set. The 

supporting NEGOMES database consists of nearly 3 Gigabytes of processed 

meteorological data and graphical displays that includes: 

♦ 1996-1997 surface observation statistics; 

♦ 1996-1997 aloft observation statistics; 

♦ 1996-1997 gridded observation statistics; 

♦ 1996-1997 transect data derived from observed surface data; 

♦ 1996-1997 Eta gridded surface data; 

♦ 1996-1997 Eta gridded 3-D data; 

♦ 1996-1997 gridded Eta surface statistics. 

*P.I.’s affiliation may be different than that listed for Project Manager(s). 
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