Isaac's Storm - Erik Larson [78]
Barometers elsewhere in the city got widely varied readings. In Galveston harbor, the first mate of the English steamer Comino, moored at Pier 14, recorded in the ship’s log a pressure of 28.30 inches, and noted: “Wind blowing terrific, and steamer bombarded with large pieces of timber, shells, and all manner of flying debris from the surrounding buildings.” At one point the wind picked up a board measuring four feet by six inches and hurled it with such velocity it pierced the Comino’s hull. The hull was built of iron plates one inch thick. In the train station, the scientist with the barometer—apparently unaware of his fast-eroding popularity—called out a pressure of 27.50 inches, and announced that against such impossibly low pressures “nothing could endure.”
Years later, scientists with NOAA put the lowest pressure of the storm a notch lower, at 27.49.
In 1900, however, even Blagden’s reading of 28.48 stretched credibility. “Assuming that the reading of the barometer reported at Galveston the evening of the 8th was approximately correct,” wrote one of Moore’s professors, carefully hedging for error, “the hurricane at that point was of almost unparalleled severity.”
The highest speed recorded by the Galveston station’s anemometer before it blew away was 100 miles per hour. The bureau later estimated that between 5:15 P.M. and 7 P.M. Galveston time, the wind reached a sustained velocity of “at least” 120 miles per hour.
Most likely the true velocity was far greater, especially within the eyewall itself. Gusts of two hundred miles an hour may have raked Galveston. Each would generate pressure of 152 pounds per square foot, or more than sixty thousand pounds against a house wall. Thirty tons.
As John Blagden sat in his office, powerful bursts of wind tore off the fourth floor of a nearby building, the Moody Bank at the Strand and 22nd, as neatly as if it had been sliced off with a delicatessen meat shaver. Captain Storms of the Roma had practically bolted his ship to its pier, but the wind tore the ship loose and sent it on a wild journey through Galveston’s harbor, during which it destroyed all three railroad causeways over the bay. The wind hurtled grown men across streets and knocked horses onto their sides as if they were targets in a shooting gallery. Slate shingles became whirling scimitars that eviscerated men and horses. Decapitations occurred. Long splinters of wood pierced limbs and eyes. One man tied his shoes to his head as a kind of helmet, then struggled home. The wind threw bricks with such force they traveled parallel to the ground. A survivor identified only as Charlie saw bricks blown from the Tremont Hotel “like they were little feathers.”
All this was nothing, however, compared to what the wind had been doing in the Gulf of Mexico. Ever since leaving Cuba, the storm had piled water along its leading edge, producing a dome of water that twentieth-century meteorologists would call a storm surge.
Early scientists believed that reduced pressure alone accounted for storm tides. By the mid-nineteenth century, however, they came to understand that a one-inch decline in pressure raised the sea only a foot. Thus even a pressure as low as 27.49 inches would cause the sea to rise only two and a half feet. Yet the Galveston storm shoved before it a surge that was over fifteen feet deep.
The single most important force needed to build a storm surge is wind. A strong wind will develop a surge in any body of water. A fan blowing across a water-filled container will cause the water to swell at the downwind side. Strong winds blowing over some of Minnesota’s biggest northern lakes will pile ice to the height of a McDonald’s sign. One of the deadliest storm surges in American history occurred on Lake Okeechobee in Florida, in 1928, when hurricane winds blowing across the long fetch of the lake raised a storm surge that