Watching the Gulf and East Coast as Post-Trop Ida Struggles West

Update - Monday, 28 September, 11PM
The low level circulation of TD11 has swept in underneath the convection during the past few hours, with improved structure overall. Estimates from estimating agencies are increasing, and the has concurred, making ELEVEN the tenth named storm of the 2015 Atlantic Hurricane Season.

Joaquin is officially forecast to head west, and then turn north-northwest, intensifying into a high-end Tropical Storm as it does. The model spread is rather large, but it is becoming more certain that interests along the east coast from roughly the Carolinas all the way to Maine (yes, quite a spread) would be wise to start following this system closely. For further discussion about these model spreads or to post your own best guesses, there is more over in the Joaquin Lounge .

In the Gulf, two notable lows are affecting both the east and west coasts. Invest 99L in the northeastern GOM is presently producing very heavy rains and has maximum sustained winds of roughly 40 MPH. While the window for 99L to become a tropical cyclone is closing, many of its effects have and will continue to be just the same as a very wet TD or low-end TS. In the extreme northwestern GOM, a well-defined surface circulation with associated convection is an extension of a mid/upper-level low there.
-Ciel

Update - Monday, 28 September, 3PM
Invest 99L is actually kind of close to being classifiable, but it's just not quite there, and the window for further development is closing with it likely coming inland within the next 18-36 hours. Nonetheless, very tropical depression-like rains and blustery winds are odds-on to continue for at least another day or two along the northeastern Gulf Coast. Flash Flooding is already occurring.

TD ELEVEN is now forecast to become a named storm and head in the direction of the Mid Atlantic to New England.

Elsewhere, the remnants of Ida have a slight chance of redevelopment later this week.
-Ciel

Update - Sunday, 27 September, 11PM
Invest 98L has acquired sufficient organization to be classified as a Tropical Depression, and advisories have been started. ELEVEN is not presently forecast to become a named storm, but only a slight increase in winds would do so.

Elsewhere, 99L now has Moderate odds of becoming a tropical cyclone before it moves inland over the northeastern Gulf of Mexico this week. Regardless of classification, 99L will likely continue to produce significant heavy rains over portions of the northeastern Gulf Coast for the next several days.
-Ciel

Update - Saturday, 26 September, 1PM
Ida has weakened to a Tropical Depression but shear is expected to relax soon and Ida could regain Tropical Storm intensity. A ridge building over Ida will change the direction of movement to the southwest over the weekend and to the west early next week.

An area east of the southern Bahamas (Invest 98L) is expected to drift north and eventually weaken as upper air conditions become more hostile early next week.

A low pressure area over the central Yucatan has been tagged as Invest 99L. The convective pattern is fairly decent but atmospheric conditions in the Gulf are less than ideal for development. Its still an area worth watching closely as the system moves north and brings the potential for heavy rainfall to the northern Gulf coast (and the Florida peninsula) late Monday into Tuesday. More info on the Invest is available in the Storm Forum .
ED

5:00 AM 22 September Update
Ida continues to ride the spin cycle of shear in the central Atlantic early this morning.

Meanwhile, closer to home, a large non-tropical Low off the coast of North Carolina is showing a little bit of organization, and conditions are marginally supportive of development, especially so long as it remains over the Gulf Stream. This feature has been tagged 97L. Regardless of subtropical or tropical development, this Low will likely produce blustery weather along the coast of the Carolinas for at least another day or two, and it may actually stick around a while more.
-Ciel

Original Update
TS Ida has slowed to a crawl about 1,000 miles to the east northeast of the northern Leeward Islands and the system is expected to meander in that same general area for most of the week. A large upper level low near 22N 62.5W at 21/20Z is drifting slowly westward and could relax the northwesterly windshear currently affecting Ida, however, the upper level progs tend to downplay this possibility and suggest that the northwesterly shear is likely to increase over the next 36 to 48 hours. Although SSTs are at 29C, slow upwelling over the next couple of days could cool down the sea surface. For Ida this means little opportunity to strengthen until late in the week - and the tropical cyclone could actually weaken somewhat until the shear relaxes. Eventually Ida is expected to start moving north northwestward later in the week and, if the TS survives the struggle with windshear, additional intensification - perhaps to hurricane strength - is possible over the weekend. No matter what intensity is achieved (or not), Ida should remain at sea.
ED

Invest 99L Event Related Links

Flhurricane Satellite Floater Animation of of 99 - New for 2018

Animated Skeetobite Model Plot of 99