Tropical Depression Forms, Expected to Become Imelda. Tropical Storm Watches Issued for East-Central Florida.
Imelda to form and strengthen into a hurricane but slow or stall near the coasts of South Carolina or southeast Georgia early next week, bringing a threat of prolonged impacts
Author’s note: This is a special Saturday edition of the tropical newsletter to discuss Potential Tropical Cyclone Nine, which is forecast to become Imelda by Sunday and threaten the southeast U.S., possibly as a hurricane, starting early next week.
Tropical Depression Nine formed late Saturday morning over the southeastern Bahamas and is forecast to steadily strengthen into Hurricane Imelda by early next week as it approaches the coast of South Carolina. The verdict is out on whether Imelda’s core will move over land, skirt the coast, or turn before reaching the U.S., but heavy rain and coastal impacts are likely as it makes it closest approach Monday and Tuesday.
Meanwhile, to the east over the open Atlantic Humberto rapidly strengthened 75 mph in only 24 hours – a dizzying rate over twice that of the threshold for rapid intensification – to a now Category 4 hurricane. Although Humberto’s forecast to flirt with Category 5 status, its dangerous core will turn safely between the U.S. and Bermuda, though a brush with Bermuda could bring outer winds and weather to the British Overseas Territory by next Tuesday and Wednesday.
How close will future Imelda get?
Tropical Depression Nine is still in its formative stages, with disorganized storminess and a weak and diffuse wind field as sampled by Hurricane Hunters early Saturday. The next 24-36 hours will be crucial to the forecast as Imelda’s circulation consolidates and the storm organizes and strengthens.
Although Tropical Storm Watches have been issued north of South Florida for parts of east-central Florida (north of Palm Beach to just north of Daytona Beach) for the possibility of gusty winds reaching tropical storm strength (39 mph or higher) tomorrow and Monday, the risk of sustained tropical force winds remains low as Imelda passes to the east.
The outer bands of strengthening Imelda could bring intermittent squally weather to Florida’s immediate east coast tomorrow into early Monday, but the primary hazard along Florida’s eastern peninsula will be dangerous surf, rip currents, and boating conditions.
As Imelda strengthens and nears the southeast U.S. late Monday and on Tuesday, it will begin to affect the coasts from northeast Florida to the Carolinas. This is where forecast models diverge on possible outcomes.
Model runs have been oscillating between a turn west toward South Carolina, a slowdown or stall near or off the coast, or an abrupt turn south and east away from the U.S. Below you can see the dramatic change in the forecast from Google DeepMind’s hurricane model in only 6 hours Saturday morning.
The bottom line is it’s too soon to say if Imelda will move fully inland or stay offshore, but either way it’ll be close enough to bring impacts.
Heavy rain and flooding a concern regardless
Although since yesterday, forecast models have been slower with moving and developing Imelda – which would favor more influence from Humberto’s circulation as it catches up to Imelda by Monday and Tuesday – it’s worth reiterating that even a track offshore could bring the possibility of heavy rains and coastal flooding to parts of the Carolinas next week.
As we discussed in previous newsletters, heavy rainfall is expected from southeastern Georgia through the Carolinas, including inland areas of the southern Appalachians, whether Imelda makes landfall or stays offshore. Officially, the National Weather Service is predicting 5 to 10 inches of rain centered on the coastal Carolinas next week, but we’ll need to watch the trends closely.
A more extreme rainfall scenario could come if Imelda strengthens into a hurricane and stalls near or over the coast, with strong winds on its eastern flank jamming water into the coast and not allowing days of heavy rainfall to drain out into the Atlantic. Although the higher-end rainfall scenario is still in the cards, it’s at least trended in the right direction since Friday.
The bottom line is interests from northeast Florida through the Carolinas especially will want to follow the forecasts closely this weekend for what’s shaping up to be a multi-day threat from Imelda. Even in an offshore-only scenario, Imelda will still likely bring coastal impacts to these areas.
Humberto flirting with Category 5 status
After rapidly strengthening on Friday from a tropical storm to a Category 4 hurricane northeast of the Caribbean Islands, Humberto plateaued overnight.
Unfortunately, we’ve had no Hurricane Hunter airplanes yet to confirm Humberto’s true strength, but satellite estimates suggest it may once again be resuming a strengthening trend and the forecast is for Humberto to be nearing Category 5 strength later today.
For the next few days, Humberto will only be a problem for shipping interests. By next Tuesday and Wednesday, it should pass about 100 to 200 miles west of Bermuda as it rounds the western side of the Bermuda high.
Interests in Bermuda will want to monitor the forecast closely as a closer pass could bring squally weather on Humberto’s stronger east side to the archipelago. Additionally, rough seas and dangerous surf will affect the waters around the British Overseas Territory for the early to middle part of next week.
Although Humberto is forecast to be a major Category 3 hurricane on its closest pass to Bermuda next week, its dangerous and destructive core is not expected to pose a direct threat.
Thanks for the special weekend update. Future Imelda is a concern for all along the Atlantic's southeast coastline.
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