ABSTRACT

Since 1965, measurements have been made of deep water wave heights and winds generated by severe hurricanes in the Gulf of Mexico. Platforms have provided additional data on maximum wave heights from damage sustained during hurricanes. These measurements and inferred wave heights have been used to calibrate a hind cast model and characterize its reliability.

The calibrated model has been applied in a hind cast of deep water maximum sea states generated by major hurricanes which affected the Texas-Louisiana Mississippi Continental Shelf from 1900 through 1969. The history of expected maximum wave heights at nine fictitious platform sites spaced 60 miles apart in 300 feet of water is detailed. Wave height measurements and observations used to calibrate and define hind cast reliability are given.

INTRODUCTION

The primary objective of the effort reported in this paper was to provide background information required to select design criteria for bottom supported drilling and production platforms (3). The methods, focus, and statistical characterizations are shaped by this objective.

The area studied is shown in Figure 1. Nine fictitious platform sites in 300 feet of water (designated "a" through "j") were set up at 60 nautical mile intervals along the edge of the Continental Shelf. These sites were the monitoring points for effects generated by maj or hurricanes which attacked this area from 1900 through 1969.

The wave hind cast model allseed was that developed by Wilson (39, 40, 41). The wind field model used was that developed by Goodyear (20, 42). The winds hind cast by, this model have been calibrated by Patterson (32) using wind measurements obtained in several hurricanes. The reader should consult the references cited for details on the models.

Basically, the hurricane's differential pressure (P) and radius to maximum winds (R) are used to describe a circulating wind field. This wind field is then moved along the path of the hurricane at the forward speed of the storm (VF)' The components of the wind along given vectors to a site are used to generate wave heights at the site in a time-wise manner. In this way, each location builds a time history of sea states, expressed as height of the significant waves (Hs), from many different directions. The maximum sea state (Hs max) and its duration are obtained from such a site history.

Note that a history can be developed on the maximum winds and their direction. Also, if a wind and surge driven current hind cast model are brought into the picture, a history can be developed on the magnitude and direction of the currents. With a basic goal of deriving an environmental total force characterization, a "model" platform can be placed at a site, and the history of combined forces due to winds, waves, and currents detailed. The focus is on total force (3). In this manner, the sticky problems of dealing with separate probabilities of wind, wave, and current and their joint probabilities are avoided. Maj or emphasis in this paper will be given to the expected maximum wave heights (He max) at the nine sites shown in Figure 1.

This content is only available via PDF.
You can access this article if you purchase or spend a download.