document: With the winds of Hurricane Gilbert clocked at 175 miles per hour , U.S. weather officials called Gilbert the most intense hurricane ever recorded in the Western Hemisphere . Mark Zimmer , a meterologist at the National Hurricane Center , reported an Air Force reconnaissance plane measured the barometric pressure at Gilbert 's center at 26.13 inches at 5:52 p.m. EDT on Tuesday . Gilbert was barreling toward Mexico 's Yucatan Peninsula . `` That 's the lowest pressure ever measured in the Western Hemisphere , '' Zimmer said . The previous record low pressure of 26.35 inches was set by the 1935 Labor Day hurricane that struck the Florida Keys with winds above 150 mph , killing 408 people , he said . With tropical storm force winds extending 250 miles north and 200 miles south of the hurricane 's center , Gilbert also was one of the largest . But because the circumference of a hurricane changes so often during its course , no records are kept on their overall size , said center meterologist Jesse Moore . Hurricane Debby , which barely crossed the 74 mph threshold to hurricane strength before striking Mexico last month , was probably about half that size , Moore said . Gilbert is one of only three Category 5 storms in the hemisphere since weather officials began keeping detailed records . The others were the 1935 Labor Day hurricane and Hurricane Camille , which bulldozed the Mississippi Coast with 172 mph winds and a 28-foot wave in 1969 , leaving $ 1.4 billion in damage and 256 dead . A 1900 hurricane is responsible for the worst natural disaster in U.S. history , however . That storm hit Galveston , Texas , Sept. 8 and killed more than 6,000 people . Category 5 storms have winds greater than 155 mph , barometric pressure of less than 27.17 inches and a storm surge higher than 18 feet . The storm surge _ a great dome of water that follows the eye of the hurricane across coastlines , bulldozing everything in its path _ accounts for nine out of 10 hurricane fatalities . Camille 's storm surge was 25 feet high , but the hurricane center was forecasting a surge of only 8-12 feet for Gilbert , Zimmer said . The damage from these worst-case hurricanes is catastrophic _ shrubs and trees blown down , all street signs gone , roofs and windows blown away and shattered , and mobile homes destroyed . `` Moisture and heat are what drives the hurricane , '' Zimmer said . `` The engine itself is this tall chimney of warm , moist air in the center . If the atmospheric conditions in general allow this warm chimney to build to very high levels , 10-12 miles high , then you can have a severe hurricane . '' Category 4 storms cause extreme damage with winds from 131 to 155 mph , surge of 13-18 feet and pressure of 27.17 to 27.90 . The weakest hurricanes , Category 1 , cause minimal damage with winds of 74 to 95 mph , 4-5 foot surge and pressure at 28.94 or more .
extractive_keyphrases: hurricane gilbert intense hurricane western hemisphere national hurricane center barometric pressure storm surge hurricane fatalities tropical storm force winds