Since my last post on Friday, Fiona made landfall in eastern Nova Scotia as an extratropical cyclone of Category 2 hurricane intensity, Tropical Storm Gaston dissipated west of the Azores, Tropical Depression 10 became Tropical Storm Hermine northeast of Cabo Verde and is already gone, and Tropical Depression 9 became Tropical Storm Ian on Friday night then Hurricane Ian on Monday morning. This update will focus solely on Hurricane Ian.
As of Monday morning, Ian is centered just 80 miles west of the Cayman Islands and 250 miles southeast of western of Cuba. There is strong agreement among the model guidance that Ian will quickly reach major hurricane status (the second of the season) perhaps tonight or Tuesday morning as it nears western Cuba. That brief interaction, though extremely high-impact for Cuba, should not disrupt the hurricane too much, so additional strengthening is likely once it's in the eastern Gulf of Mexico by midday Tuesday.
The biggest concern for both Cuba and the west coast of Florida is storm surge. Cuba could be looking 9-14 feet of storm surge east of where the eye crosses the coast, and although preliminary, the 2-3-day storm surge outlook for the southwestern Florida peninsula is shown below. As the storm gets closer, the storm surge guidance will become more accurate and include areas farther north into the Big Bend area. Because of its shape, Tampa Bay is very surge-prone, so the storm's size, intensity, heading, and distance from land will determine if this is a very bad or a catastrophic event there.
The intensity forecast from NHC this morning explicitly includes rapid intensification, a very rare amount of confidence. By design, "rapid intensification" (RI), is the top 5% of intensification rates, and objectively, the common definition is an increase of 35 mph or more in a 24-hour period. Here's the forecast from 5am today:
INIT 26/0900Z 18.2N 82.0W 65 KT 75 MPH 12H 26/1800Z 19.7N 83.0W 90 KT 105 MPH 24H 27/0600Z 21.7N 83.9W 105 KT 120 MPH (+45mph in 24hr) 36H 27/1800Z 23.6N 84.1W 115 KT 130 MPH 48H 28/0600Z 25.3N 84.1W 120 KT 140 MPH
You may recall that the same degree of confidence was shown in the initial forecast for Hurricane Ida last year. Such confidence in an outlier event is a success story of hurricane modeling in the past decade or so.
In the Florida peninsula, tropical storm force winds could reach south Florida Tuesday night into Wednesday morning, central Florida Wednesday morning to Wednesday afternoon, and northern Florida Thursday morning. The western part of the peninsula is more likely to encounter those winds and is on the earlier end of the ranges I mentioned.
In addition to the winds and storm surge associated with a strong hurricane, rainfall is always a significant threat with any tropical cyclone. The map below is the five-day rainfall forecast and there are significant amounts expected in the entire Florida peninsula, then up into eastern Georgia and South Carolina later in the period.
With all of the named storms scattered across the basin, the season's total Accumulated Cyclone Energy has gotten a big boost and is now at 84% of the average value for this date. Hurricane Ian will add to the tally quite a bit in the coming 3-4 days.
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