September 12, 2020
TD 19 is now over land in South Florida and will enter the eastern Gulf later today or tonight. It was very close to tropical storm strength at landfall but has since weakened. It currently has a lopsided structure with most of the convection (storminess) to the southeast over the Florida Straits. It'll be interesting to see if the low level center tries to reform down in this direction. If it does that could change the forecast a bit.
The official forecast from the NHC isn't much different than it was yesterday. They're still forecasting a strong tropical storm to make landfall near the MS/LA border Tuesday or early Wednesday. This is weaker than the intensity model consensus and the NHC has again stated that a hurricane or stronger is possible at landfall. There is some wind shear that could inhibit development so the NHC is keeping their forecast conservative as there's some uncertainty regarding how much this may limit the intensity. The track forecast is still a bit uncertain after two days. One worrisome trend is that the storm is expected for move slowly which could allow more time for strengthening and drop a lot of rain as it nears the coast. Isolated tornadoes are also possible Sunday into Monday across north Florida.
Model guidance is a little more concerning this morning. The HWRF shows a category 3 storm making landfall along the Mississippi coast Tuesday morning. This model can overdo intensity at times so keep that in mind, but sometimes it is right. It forecast Laura's intensity pretty well. I'm not skilled enough yet to know when it is acting up but what it shows is concerning. The GFS brings a category 1 storm into almost the same location but it has the storm grazing extreme southeast Louisiana before hooking north and hitting Mississippi. The Euro brings the storm in a little faster and a hair more to the west as a tropical storm. Yesterday I said the Euro had this as a hurricane, that was a mistake, it had a tropical storm similar to what we see this morning. Either way, I now think the Euro is probably too low on its intensity forecast. There are various other model solution but I think you get the idea. I think it's more likely than not that TD 19 will become a hurricane by late Sunday or early Monday in the northeastern Gulf. I don't have much to say about the track guidance as I think the NHC's cone captures that fairly well. I made a statement yesterday that implied that a stronger storm would be more likely to go west, that is incorrect the way I stated it. In a general sense the longer the storm is over water, the more west it will go. However, a stronger storm will feel a different steering influence than a weaker storm and will turn to the north earlier. So given a certain steering influence, a stronger storm is likely to go more the east and a weaker storm more to the west. Levi Cowan covered this well in his video last night.
Taking a brief look at the rest of the tropics, there remains quite a bit of other activity. Paulette looks to threaten Bermuda as a hurricane in a few days. The red 'x' is still out there moving west, now Invest 95L. Models have cooled somewhat on developing this and a track to sea now looks more likely but not certain. The Lesser Antilles could still see some impacts but I think the US might be out of danger. Another wave that will come off of Africa Monday (not shown) may be the next one to watch.
I'll send out another update on TD 19 later today or tomorrow morning. It's a good time to think about your hurricane plans and get some supplies if you need some. No need to get too excited, but it's good to be prepared. Have a good Saturday.
Chris
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