Florida has had a favorable run of tropical luck over the last few years.
Though climatology says to expect a hurricane landfall in about 40% of seasons, there has not been a direct strike in the state since Michael’s apocalyptic haymaker in the Panhandle, give or take the eastern eyewall of 2020’s Sally in Pensacola.
Consider the three major hurricanes that have brutalized Louisiana in that time, and Florida’s recent punishment has been light indeed.
Unfortunately, that hot streak could well come to an end next week, with Florida facing its most serious threat since Dorian three years ago.
Where is the storm going?: Tropical Depression Nine may hit Florida’s west coast as major hurricane
Be prepared: Here is your one-stop storm preparation guide
And while the state is coming into focus as the likely target of a potential hurricane landfall, there remains significant uncertainty as to which part of Florida will take the brunt of it.
What we know about Tropical Depression Nine: Hermine or Ian in the offing?
Tropical Depression Nine developed early Friday morning in the east-central Caribbean, and as of the 11 a.m. NHC advisory has sustained winds of around 35 mph. The depression is moving a little north of west at around 15 mph, and a general westward track is likely through Saturday.
Wind shear is displacing the depression’s deep convection west of the circulation center, which should keep strengthening gradual for the next two days. Still, TD 9 may become a tropical storm at any time.
(Side note: with the development of TD 10 in the far eastern Atlantic, it remains unknown if TD 9 will be named Hermine or Ian. It would be downright bizarre if it is Hermine, as North Florida faced down a Category 1 landfall by that name just six years ago. We’ll see if the ludicrous 2 Hermines, 2 furious scenario plays out.)
Now, Sunday is when things start to get serious — to a possible Category 3 level
TD 9 will be entering an environment in the western Caribbean in which upper-level outflow is excellent, mid-level moisture is abundant, and vertical wind shear is low. On top of that, the heat content of the northwestern Caribbean waters is the highest anywhere in the Atlantic basin.
These factors are a perfect recipe for rapid intensification, which is defined as sustained winds jumping 30 knots or more in 24 hours.
The NHC intensity forecast is explicitly calling for rapid intensification Sunday into Monday, and TD 9 will likely be in favorable conditions for continued strengthening through Tuesday.
The official forecast is for the storm to reach Category 3 strength by early Wednesday. That is a realistic base case, and I would caution that even faster strengthening is certainly possible between Sunday and Tuesday.
It is exceptionally hard to predict how much strengthening will occur when a rapid intensification cycle occurs. History shows that major hurricanes can come together dizzyingly fast when the necessary ingredients are in place in the western Caribbean and southern Gulf.
All forecast guidance suggests that TD 9’s track will gradually bend more northwestward on Sunday and Monday in response to a deep trough over the Eastern Seaboard, setting the storm on a path in the general direction of western Cuba by late Monday. Subtle differences in steering wind patterns will determine how far west TD 9 makes it before a more northward motion ensues on Tuesday. The most probable path will carry the storm into the eastern Gulf of Mexico, though a track further east into the Straits of Florida remains a possibility.
Hurricane track and model mixer: Bookmark this page for the latest path and computer model runs
Uncertainty abounds: But South Florida residents should prepare now for possible Hurricane Charley scenario
The forecast is uncertain beyond Tuesday.
As of mid-day Friday, the official NHC track takes the storm close to Fort Myers on Wednesday morning as a major hurricane. This track is very similar to the one traced by Category 4 Hurricane Charley in August 2004, a sentence that will no doubt set everyone in Southwest and Central Florida on edge.
This scenario, or one in which the turn north and northeast takes place even faster and puts the Keys and South Florida in the crosshairs on Tuesday, is probably the most dangerous scenario on the table.
The combination of a short timeline for preparation, high population density, and the probable continuation of favorable conditions for strengthening through early Wednesday means that residents of the southern half of the Florida peninsula should begin preparing for a possible major hurricane now.
Panhandle is far from in the clear at this point
TD 9 could also swing farther west towards the Yucatan Channel before angling north and then north-northeast over the eastern Gulf. This scenario would increase the eventual risks for the Panhandle, Big Bend, and west Central Florida, and today’s model runs are edging back west after a sizeable jump east yesterday.
While spending more time over the Gulf sounds like a bad deal, this could be offset by increasing shear and dry air intrusion into the storm beyond Wednesday.
An additional complication is that the eastern U.S. trough will begin to depart in the middle of next week, causing steering currents in the eastern Gulf to weaken in 5-6 days and a period of slower or erratic motion to possibly ensue.
The bottom line is if TD 9 doesn’t sprint across South Florida or east-central Florida on Tuesday or Wednesday, which is very possible, what might happen after that is unclear.
Projecting a landfall point with this type of forecast track is impossible, as the narrow angle of approach between the storm’s motion and the orientation of the Florida Gulf coastline means small track deviations can have huge implications.
During Hurricane Charley, a subtle shift in heading just prior to landfall brought the ferocious core of the storm into the Fort Myers area, rather than Tampa Bay. Don’t focus on a forecast point: as of now, no one is off the hook in Florida.
Storm preparation is essential
There are many new Florida residents since the last serious hurricane threat, which I can tell because some of you are still using your turn signals.
At this stage, know that this threat merits active preparation. In South Florida, you need to be putting your hurricane plans into action, including preparing to evacuate if an order is issued by your local authorities.
In North Florida, get your hurricane plan and kit in order, and continue to monitor the situation. Hopefully Florida’s luck isn’t up this week, but if it is, preparation is essential.
Keep watching the skies.
Dr. Ryan Truchelut is chief meteorologist at WeatherTiger, a Tallahassee start-up providing forensic meteorology and expert witness consulting services, and agricultural and hurricane forecasting subscriptions. Get in touch at email@example.com, and visit weathertiger.com for an enhanced, real-time version of our seasonal outlook.
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This article originally appeared on Tallahassee Democrat: Florida hurricane forecast may be state’s biggest threat in years