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TD 9 about to become "Ida". Potentially serious Gulf hurricane threat and possible local impacts.


What is currently Tropical Depression 9, but is about to become Tropical Storm Ida, is getting a lot of attention now... and rightfully so. Environmental conditions appear to be already improving, and TD9/Ida looks to already be organizing near Jamaica this afternoon. Convection is developing near the center of circulation, in the least favorable time of day for convection to strengthen out over the water. There is less instability over the water during the day than at night because there's less of a temperature contrast between the water surface and the air above it. Despite that, thunderstorms are still intensifying and organizing near the center of circulation. Aside from that, outflow is improving on all sides, especially the west side of the system, telling us that shear is starting to relax now. A hurricane hunter recon plane is almost to the system soon and will be reporting back details. We think the National Hurricane Center may officially upgrade this to Tropical Storm Ida at 4:00 pm CT today, based on all available information we have right now.


The 10 am CT track from the National Hurricane Center has the system moving northwest across the far west tip of Cuba and into the southern Gulf by later in the day Friday. By then, the official forecast is for it to already be a strong tropical storm, but don't be surprised if it is already stronger by then given what we are seeing so far. From there, the storm is expected to track northwestward, roughly, toward the Louisiana coastline over the weekend. The official forecast explicitly at face value calls for rapid intensification over the Gulf, and it's very possible that Ida may be a major hurricane (Category 3 or higher) prior to and at landfall.


Shear is now starting to relax in proximity to the system over the northwest Caribbean, but wind shear will go practically non-existent as the system moves out of the Caribbean and into the Gulf. In addition, in the upper-levels of the atmosphere, a big anticyclone (clockwise spinning area of high pressure) will develop over the Gulf, and this will help to set up maximum ventilation for the storm over the weekend. That is a critical piece of the puzzle for a rapidly strengthening system, and it looks like it will be in place.


In addition to the very favorable upper-level environment, the waters in the Gulf of Mexico are VERY warm, with widespread mid 80 and warmer sea surface temperatures. There are several areas of the Gulf with their latest observations actually coming in within the 86 to 90 degree range. In addition, that warm water is deep. That is important because that means the storm is less likely to upwell cooler water as it moves through. Of significant importance is that we notice the track of soon-to-be Ida takes it up the entire length of the Gulf Loop Current through the Gulf of Mexico, including that warm eddy off the coast of Louisiana that was infamously known for helping the 2005 storms rapidly intensify. So, along the entire trip in the Gulf, the system will be over the warmest, and deepest warm waters available out of the entire Gulf. All environmental clues we have give us significant concern that Ida may become a powerful hurricane this weekend in the Gulf.


Here's the bottom line to summarize. Tropical Depression 9 is soon to become Tropical Storm Ida in the northwest Caribbean. Ida then moves into the Gulf of Mexico by Friday night and is likely to rapidly intensify into a significant hurricane over the weekend. On the currently projected track, coastal impacts would start as early as Saturday night and Sunday, with landfall along the Louisiana coast late Sunday into early Monday... but the Gulf Coast from the upper Texas coast to the western Florida panhandle all need to be alert for possible forecast changes (although I don't expect big ones going forward). If this track or something similar to it holds, there WILL be impacts here locally in the Tennessee Valley. Those would include the risks of heavy rain and flooding, gusty winds, and a tornado risk. The exact placement and magnitude of those risks are completely dependent on the eventual track of Ida, and that's something we just don't have a good handle on just yet.


Whether you are here locally in the Tennessee Valley or you are along the coast, the big message is to stay in tune with updated forecast information, and begin preparing for this system now so that you aren't caught off guard and you aren't having to scramble at the last minute. We will provide updated information over the coming days as all of this unfolds.

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