TD 7 Forms & Will Become Gaston. Invest 99L Is One To Watch Closely

Update: We will have a new detailed post by 9AM EDT on Invest 99L.

Invest 90L in the eastern Atlantic was just upgraded to Tropical Depression Seven and is forecasted to become Tropical Storm Gaston tonight or tomorrow morning. The NHC is forecasting this system to become The 3rd hurricane of the season. As of the latest outlook, this storm should stay safely away from land. Although, Bermuda may want to keep an eye on it in case it tracks further west just as Fiona did.

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 First forecast from the NHC for TD 7.

First forecast from the NHC for TD 7.

The focus of today's discussion is going to be in Invest 99L which is located approximately 700 miles east of the Lesser Antilles. At this time, we are not expecting anything more than squally weather throughout portions of the NE Caribbean Sea mid-week as this system passes just to the north of the islands (see our Alert Level Map below). Chances of this system developing into a depression or tropical storm within the next 2 to 3 days is low at around 20%. However, As of this post there is about a 50 to 60% chance of development over the next five days. Development of this wave is expected to be slow due to its large size and also due to its interaction with dry air. Environmental conditions will likely become more conducive for this system to organize and strengthen late this week when the system is expected to move towards the southeastern and central Bahamas. A Hurricane Hunter mission is scheduled for tomorrow to investigate the system.

 Invest 99L has a medium chance of development over the next 5-7 days. Chances are rising.

Invest 99L has a medium chance of development over the next 5-7 days. Chances are rising.

 Invest 99L has more convection and thunderstorms than it did over the last few days. It has a broad surface low and an ever-improving structure. Dry air intrusions should keep it in check for the next few days.

Invest 99L has more convection and thunderstorms than it did over the last few days. It has a broad surface low and an ever-improving structure. Dry air intrusions should keep it in check for the next few days.

 Low 5 day alert levels for the NE Caribbean, but guarded in the Bahamas where there's a greater chance of impacts from a classified system.

Low 5 day alert levels for the NE Caribbean, but guarded in the Bahamas where there's a greater chance of impacts from a classified system.

Track: Confidence is high that Invest 99L will track generally off towards the west northwest over the next five days and should be in the central Bahamas in about one week. Beyond seven days, the track forecast gets complicated due to several features that will determine where the system tracks. Models have been trending towards a stronger ridge of high pressure setting up over the southeastern portions of the United States and the clockwise flow around the high pressure may be enough to shove the storm west towards Florida or even into the eastern Gulf of Mexico. However, Tropical Depression Fiona (or its remnants) could create a weakness on the eastern side of the ridge which could open up a path for the the system to track further north or out to sea (sea images below). To further complicate matters, future Tropical Storm Gaston will be marching west north west across the Atlantic and could influence the strength of this ridge in the long term. So, at this time all options are on the table if this system does develop. It could turn west and impact Florida and possibly portions of the Gulf of Mexico, it could go north and impact portions of the southeastern United States or finally could turn and go out to sea harmlessly. If you have been following along, you know that the computer models have not been very helpful as they have been flip-flopping all over the place making this a very tricky forecast in the long term (we wouldn’t expect anything less from them!). Hopefully, within the next 2 to 3 days we will have a better idea as to how the atmosphere is going to set up and which direction the storm could possibly track. Please review our outlook cone below and long-range impact chances to see what the current chances of this storm impacting your area. These will be updated as new data comes in, so please check back in the app.

 Many options on where this system may track beyond 5-7 days. This is not a forecast, just an outlook based on the latest data.

Many options on where this system may track beyond 5-7 days. This is not a forecast, just an outlook based on the latest data.

 Will this system threaten you? Check out out our long range impact chances. These are subject to change as new data comes in. 

Will this system threaten you? Check out out our long range impact chances. These are subject to change as new data comes in. 

 Today's models may be trying to trend towards S FL impacts and an entry into the E Gulf. Again, not a forecast.

Today's models may be trying to trend towards S FL impacts and an entry into the E Gulf. Again, not a forecast.

Intensity: The intensity of a tropical system is always one of the most difficult challenges in weather forecasting. It’s way too early to know whether this system will be a depression, tropical storm, or even a hurricane seven days from now. What we can say is that the computer models are showing a favorable environment for possible intensification. The sea surface temperatures are running higher than they have in the last several years (mid-upper 80’s) and that could definitely provide enough “fuel” for this system to strengthen if it were to form. The European model did show a possible hurricane striking South Florida in about a week, and while that is not the forecast, it is a possibility. The UKMET & Canadian models lend it some support as well. See the image below.

 Shear is super low along the expected path of Invest 99L

Shear is super low along the expected path of Invest 99L

For now, all interests in the Bahamas, Gulf of Mexico, Florida, and the southeast United States coast should check in often on the progress of this system as the models and data will change several times over the few several days. Please be mindful, there is no imminent threat from the system and at this time, it is not forecasted to impact the United States, but it is a possibility based on the overall pattern that is setting up.

Please stay tuned here at the Hurricane Tracker App for frequent updates on Invest 99L throughout the rest of this week and into next. We will be tracking this one for at least the next week.

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A NEW POST WILL BE ISSUED IF THERE ANY CHANGES IN THE CURRENT OUTLOOK.

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