We are quickly running out of adjectives to describe the destructive potential of Hurricane Irma. As of 2pm ET on Tuesday, the National Hurricane Center upgraded the storm’s sustained winds to 185mph. This is near-record speed for a storm in the Atlantic basin, which includes the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico.
Such high, sustained winds tie Irma for the second-strongest storm on record in the Atlantic, along with Hurricane Wilma (2005), Hurricane Gilbert (1998), and the 1935 Florida Keys hurricane. Only Hurricane Allen, which reached 190 mph in 1980 before striking a relatively unpopulated area of Texas, reached a higher wind speed. Globally, the all-time record for hurricanes is held by Patricia, which reached a staggering 215 mph in the Pacific Ocean in 2015.
Although sustained winds capture the most public attention, meteorologists generally measure the intensity of a storm based upon central pressures, which are considerably lower than sea-level pressure on Earth, 1,103 millibars. Typhoon Tip, in 1979, holds this record at 870 millibars. For now, at least, Irma has a relatively high central pressure of 927 millibars. Why the storm has such an odd wind-speed-pressure relationship isn’t entirely clear.
Unfortunately, the forecast for Irma remains grim. The official forecast
calls for Irma to bring catastrophic winds and potential storm surges to the US Virgin Islands, Puerto Rico, Dominican Republic, and the UK territory of Turks and Caicos this week. Then the forecast brings the storm to the Florida Keys as a major hurricane by late Saturday night or Sunday.
There remains a fair amount of spread in the model forecasts at that point. Irma’s intensity as it approaches Florida will depend considerably on whether the hurricane spends a lot of time over Cuba or if its center remains north of the island as it approaches the Straits of Florida.
What seems clear at this point is that a major wind and storm surge threat exists for Florida and the southeastern United States this weekend. While there is no certainty, clearly Irma has the potential to be a deadly and destructive hurricane. Whereas the majority of damage caused by Hurricane Harvey at the end of September was the result of inland flooding, Irma at this time has a much larger field of hurricane-force winds. Its primary threats will therefore be winds and storm surge