In the jargon of meteorologists, Gilbert has been a stunningly powerful but ``well behaved'' hurricane. It has followed a predictable course at a steady speed - 15 miles an hour. This has offered ample warning to those in its path. The warning has served well. The record-breaking winds that removed four of every five roofs in Jamaica long before Gilbert even reached full strength has resulted in comparatively few deaths.
The National Hurricane Center here, full of mapping screens and computers, has been cluttered with camera crews and wandering reporters all week. Hurricane specialists, particularly center director Bob Sheets, are giving 85 to 100 separate broadcast interviews a day to warn of Gilbert's progress.
Even when it appeared by mid-week that Gilbert would most likely hit the mainland in northern Mexico or the southern tip of Texas, the hurricane center extended the watch to the Louisiana coast. A broad warning for such a potent storm was, as one meteorologist put it, the ``course of least regret.''
Hurricanes, like spinning tops, tend to follow steering currents of wind. In the tropics, subtle changes in atmospheric pressure as far away as Japan can derail the storm's course within 24 hours.
Gilbert, however, is so massive that to some extent it is producing its own steering current, says William Gray of Colorado State University, a leading hurricane expert.
The destructive power of hurricanes is determined more by human preparedness than wind speed and storm surges.
The storm that inundated Galveston, Texas, in 1900 and killed 6,000 people blew gusts of an estimated 120 miles an hour - little over half the speed of Gilbert's gusts over Canc'un, Mexico, Wednesday. At the time of writing, no casualties had been reported from Mexico.
The most dangerous aspect of hurricanes is not wind but water, the storm tide that rises 15 feet or more above normal tide level and carries wind-driven waves on its back. The best defense is to evacuate the coastline.
Wind and water equally destroy property, however. The kinds of coastal zoning and hurricane engineering that are gaining ground in the United States can cut losses tremendously.
Gilbert, for example, has left nearly a fifth of Jamaica homeless in what Prime Minister Edward Seaga calls the worst natural disaster in the nation's history. But the US has been hit by some 50 hurricanes of Gilbert's still-forming strength when it hit Jamaica, says Paul Hebert of the National Hurricane Center, without such pervasive property damage.
Conditions have been ripe for hurricane formation. The eastern Caribbean is warm, ready to feed energy to storms. The eastern, equatorial Pacific is running cold, allowing upper-level winds over the Caribbean to blow from the east, helping tropical storms form.
Scientists still know little, however, about what causes these conditions to coalesce into a hurricane, notes Richard Pasch, a University of Miami meteorologist.
Barometric pressure is the best indicator of hurricane strength. The pressure measured in Gilbert's eye is the lowest ever recorded in a hurricane - 26.13 inches. Moreover, this uncommonly large storm tightened to form an unusually small eye. Before hitting Mexico's Yucat'an Peninsula, the eye measured about eight miles across, less than half that of the average hurricane center. Tighter eyes mean greater intensities and wind speeds surrounding the eye.
Gilbert became a full-fledged hurricane at 10:30 p.m. Sunday. The next day it crossed Jamaica. Tuesday the tempest brushed over the Cayman Islands, although the highest-velocity winds immediately surrounding the eye skirted the islands. By the time Gilbert crossed the tip of the Yucat'an Peninsula, tens of thousands of people had evacuated the major coastal island and beachfront resort cities in its path.
On the Texas and Louisiana coasts, residents were mobilizing by midweek. ``Those people don't wait for anybody to tell them to get out,'' Mr. Hebert says.