What began as a blip of news this past weekend — a tropical storm lurking in the Gulf of Mexico, hundreds of miles south of Florida — escalated on Wednesday into the most powerful hurricane to hit the continental United States in decades.
Hurricane Michael took millions of residents by surprise, intensifying from a tropical storm to a major hurricane in just two days and leaving little time for preparations.
“This storm is very special,” said Haiyan Jiang, an associate professor in the department of earth and environment at Florida International University. “It has gone through three rapid intensifications” in its brief lifetime, she added.
Hurricane Michael’s sharp increase in strength as it approached Florida was due in part to its low barometric pressure, said Phil Klotzbach, a research scientist in the atmospheric science department at Colorado State University.
Low barometric pressure increases a storm’s intensity, and the barometric pressure within Hurricane Michael early Wednesday was just 925 millibars. There have only been a half-dozen storms that struck the United States with lower barometric pressure, the most recent being Katrina, Andrew and Camille — and all six “were devastating storms,” Dr. Klotzbach said.
The rapid intensification of the storm, which means growing in wind speed by 35 miles per hour over a 24-hour period, was unexpected. “There’s still stuff we don’t know about hurricanes,” Dr. Klotzbach added.
While prediction of a storm’s path has grown increasingly accurate, the ability to predict rapid intensification has lagged somewhat, said Dr. Jiang.
The strengthening occurred despite pronounced wind shear in the region that might have been expected to weaken the storm, she added.
“The shear was high, so nobody expected it was going to intensify this rapidly,” Dr. Jiang said.
Also part of the explanation for the intensification was warmer-than-average waters in the Gulf of Mexico, which in some places was up by 3.6 degrees Fahrenheit, or two degrees Celsius. “One to two degrees is a big deal,” she said.
Warmer sea surface temperatures, while subject to natural variation, are consistent with the effects of climate change. [Read more about that here.]
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