WeatherTiger's Idalia Florida Impacts Forecast for August 28th (PM)

Idalia will make landfall on Wednesday. These are the surge, wind, rain, and tornado impacts Florida can expect.

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Florida tropical threat synopsis: A major hurricane landfall in North Florida is more likely than not on on Wednesday. Preparations for destructive surge and wind should be completed by Tuesday evening.

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Why is it always Wednesday?

There’s no answer beyond coincidence for why Florida’s four most recent hurricanes— Michael, Sally, Ian, and Nicole— have all struck on the same cursed day of the week. But we now know that Idalia will join that miserable list, bringing major surge, wind, and rain impacts across the state this Wednesday.

Idalia remains on a collision course with the Florida Gulf Coast. Track expectations have changed only modestly since Sunday, and landfall is most likely in Apalachee Bay or the northern Nature Coast by mid-day Wednesday. Idalia will bring catastrophic surge to a broad swath of the west-central Florida and Big Bend coastline, and a core of destructive winds to an unlucky but still unknown portion of North Florida.

NHC 2 p.m. track map. Click here for the latest NHC graphic.

As of mid-day Monday, the center of Idalia has begun its trek north towards the Gulf of Mexico, and is located about 500 miles south of Tampa, moving due north at about 8 mph. Idalia’s movement per Hurricane Hunter aircraft and Cuban and Mexican radar has closely followed the NHC forecast and most model guidance over the past 12-24 hours, and the official track forecast is little changed since Sunday afternoon. Hurricane and Storm Surge Warnings are now in effect along Florida’s Gulf Coast.

Infrared satellite imagery with 12z GEFS tracks overlaid.

Maximum sustained winds are 70 mph per the 2 p.m. Monday advisory, with Idalia remaining somewhat lopsided for the moment due to drier air and limited outflow in the northern half of the storm. Reconnaissance observations and guidance suggest these factors will keep Idalia’s rate of strengthening in check through early Tuesday.

Unfortunately, conditions remain prime for rapid intensification starting Tuesday morning. Dry air is expected to have mixed out of Idalia’s core by that time, and the incredible heat energy of the eastern Gulf at the surface teamed with twin outflow jets aloft are likely to trigger a dizzying increase in intensity into early Wednesday. It’s impossible to peg how high this potential rapid intensification cycle will loft sustained winds. As of early Monday afternoon, the NHC is predicting a Category 3 hurricane in the eastern Gulf, and a peak at Category 4 is certainly a possibility.

Latest 12z model map via Tropical Tidbits. Click here for latest.

The track forecast continues to be tightly focused on a path towards the eastern Panhandle and northern Nature Coast. With Idalia now embedded in a narrow channel of steering winds between high pressure to the west and a dip in the jet stream to its north, we’re unlikely to see huge leaps in the projected track. Accounting for a mid-day nudge westward with 12z track guidance, the most probable landfall range is between Alligator Point and Crystal River, likely Wednesday morning or early afternoon. As always, adjustments in the forecast track are likely over the next 36 hours, but don’t bank on an 11th-hour reprieve if you’re in the projected path of Idalia.

The anticipated landfall on Wednesday is a dangerous and extremely rare scenario for north-central and west-central Florida. While the Big Bend and Nature Coast are no stranger to hurricanes, should Idalia make landfall there as a major hurricane, it would be just the second Category 3 or higher to do so in the last 170 years.

As the only other major hurricane in that section of coast struck in 1896, there are many communities that are going to be tested by all four hurricane hazards—surge, wind, rain, and tornadoes—with no modern reference point for such an event. Let’s go one-by-one through each of those hazards to get a full picture of the threat Idalia poses to Florida.

NHC surge forecast from 11 a.m. advisory package. Click here for latest graphic.

Storm Surge

Water is the true killer in a hurricane, and there is no hazard more deadly or destructive than storm surge. No matter the precise track, Idalia will be a surge event unlike any hurricane in the modern era for west-central Florida. The powerful windfield of Idalia’s eastern half will push a wall of water north onto the shallow continental shelf that last-minute changes in maximum winds or track can’t alter. Additionally, an ill-timed supermoon on Wednesday will further enhance tides and flood potential.

As such, Storm Surge Warnings are in place for much of Florida’s Gulf Coast extending from central Apalachee Bay to just north of Charlotte Harbor, including Tampa Bay. NHC modeling is currently calling for peak surge of 7-11’ for eastern Apalachee Bay and along the Nature Coast.

In Apalachee Bay, 7-11’ of surge is a potential value; if Idalia’s center tracks south and east of the Bay, actual surge will be lower than it would in the very possible outcome of Idalia tracking through the Bay. We won’t know what will happen until closer to landfall, so hope for the best but absolutely prepare for the worst here, especially with 12z model guidance ticking a bit farther west.

A realistic depiction of surge distribution assuming the NHC 11 a.m. forecast track is exactly correct.

For the Nature Coast, this surge is life-threatening, without living precedent, and likely to happen. Whether Idalia makes landfall in the Nature Coast or passes just north and west, strong, onshore winds out of the southeast driving catastrophic coastal flooding are virtually certain to a greater or lesser extent. If you are told to evacuate, leave. You can hide from the wind, but you need to run from water.

This applies to Tampa Bay as well, where the current NHC projection is 4-7’ of surge. While Idalia will not make landfall in Tampa, a track west of the metro area means south and southeast winds will push water into the bay, rather than out of it as in Irma and Ian. Know your evacuation zone, have a way of receiving emergency information, and react if you get an evacuation order. Even moving just a few miles inland can keep you out of harm’s way.

Southwest Florida, though well away from the storm itself, is also likely to see 2-4’ of surge above normal high tides. This area is under a Storm Surge Watch as of mid-day Monday.

NWS Hurricane Threats and Impacts graphic issued noon Monday. Click here for latest graphic from NWS Tallahassee.

Wind

Wind is the hardest hurricane threat to pin down. While damaging, tropical-storm-force gusts capable of knocking out power and damaging trees will occur over a wide region extending from the Central Panhandle to Central Florida to coastal Southwest Florida starting late Tuesday, Idalia’s truly destructive winds, are likely to occur over a much more limited area near the center of circulation on Wednesday.

For this reason, it’s too soon to put a fine point on local wind expectations, not for the least of reasons that maximum winds can ramp up or down quickly. In the eastern Panhandle, including Tallahassee, we simply don’t know at this point whether Idalia will pass far enough south and east of us such that hurricane-force winds will miss us, or whether we will get a portion of Idalia’s core. Both are possible. What can be said at this point is the highest chances of wind gusts exceeding 100 mph are focused on the west-central Florida and eastern Apalachee Bay coastlines. The greatest odds of hurricane-force wind gusts inland lies roughly between Gainesville, Tallahassee, and coastal Georgia. This could change. Stay tuned.

NHC rain forecast from 11 a.m. Monday advisory. Click here for latest graphic.

Rainfall

When people think of hurricane threats, excessive rainfall and flooding isn’t necessarily the first thing that comes to mind. But it should be—nearly one-third of tropical cyclone-related casualties are caused by freshwater flooding.

With Idalia likely accelerating by landfall to a forward speed of a brisk 15-20 mph, heavy rainfall will be a secondary impact of the storm. Periodic rain bands will overspread the southern half of Florida through mid-day Tuesday, and the remainder of the state by Tuesday night.

Look for rains to be heaviest and most persistent through mid-day Wednesday in the eastern Panhandle, northeast Florida, and west-central Florida, where storm totals of 4-8” are likely and localized flash flooding is possible. Otherwise, accumulations across the state will be 1-4”, with a sharp cutoff in Idalia’s rains to the storm’s west, and much lower totals in the western Panhandle.

SPC Tornado outlook for Tuesday. Click here for latest graphic.

Tornadoes

Tornadic activity is common in landfalling hurricanes, mostly in bands north and east of the circulation center. Occasional tornadic cells within outer bands are most likely on Tuesday in west-central Florida, with some chance of short-lived tornadoes across the rest of the peninsula as well. Tornado risks will spread north and focus on northeast Florida on Wednesday.

It’s hard to find much of a cause for optimism as yet another Wednesday’s child, full of woe, bears down on Florida. Idalia is four-quadrant threat that will combine widespread, life-threatening, and damaging surge with more locally destructive wind impacts. These projected impacts may shift prior to landfall, and everyone in Southwest Florida, Central Florida, North Florida, and the eastern Panhandle should be closely monitoring the latest information from the National Hurricane Center, your National Weather Service office, and local emergency management. You have until Tuesday evening to make preparations, so use your time wisely. I will be back tomorrow with a region-by-region threat breakdown ahead of the worst of the storm.

Good luck, Florida. Once again, we will need it. Keep watching the skies.  

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Updated at 9:30 p.m. with the video forecast below: