CybrTeddy's tropical weather blog

Tropical Storm Chantal struggling in the eastern Caribbean - 7/9/13

By: CybrTeddy, 4:57 PM GMT on July 09, 2013

Good afternoon everyone and welcome to my tropical weather update for Tuesday, July 9th, 2013. We have several areas of interest to talk about today, but the first is newly designated Tropical Storm Chantal, now trucking along the Caribbean with 60mph sustained winds. Chantal is currently located at 14.4°N 61.5°W, and is moving at a rapid pace of 29mph. The satellite imagery isn't very impressive, you can see the LLC racing ahead of the convection while the convection is beginning to weaken.

The hurricane hunters have been sampling the system and have found that it -- barely -- has a closed circulation. However, Chantal has unusually strong winds at and above the surface, this is because of the high trade wind flow that it is experiencing. The hurricane hunters are only finding minimum pressures of around 1006mb, thanks to the high trade winds. These pressures are very high to be generating these kinds of winds and I am surprised that at the speed it's moving Chantal hasn't opened up into a wave. Chantal isn't a threat to strengthen any further now, but it may become one in the next couple of days.

The forecast for Chantal is tricky, and the environment ahead of Chantal is very unfavorable right now. The spaghetti models all agree that Chantal will continue on a WNW track towards Hispaniola, and may attempt to be like Hurricane Isaac in 2012 and intensify right before landfall into a near-hurricane. Chantal will spend roughly 8-10 hours over Hispaniola, and this will be enough to weaken Chantal into a minimal tropical storm.

This is when the forecast becomes murky. There are two upper-level lows near Chantal, one to the west over the Bahamas that will move west, and another one forming to the east that will be forming behind it. This is a very fickle setup, Chantal needs to move right between the two and be far enough from them to have ventilation occur.

If Chantal ends up being faster than expected, it may end up being sheared by the first ULL. Yesterday's GFS runs showed Chantal being caught between the two and being ventilated into a potent tropical storm. The HWRF and GFDL models are showing this happening as well.

That being said, the 06z GFS has shown Chantal dissipating from the interaction with Hispaniola and not being able to regenerate in the Bahamas. The European model refuses to even acknowledge Chantal's existence and will be discounted from this forecast, while the 00z Canadian run is in line with the GFDL and HWRF with showing a strengthening tropical cyclone.

Now, as Chantal begins to move north under the influence of the weakness it will begin to slow down, and assuming *if* Chantal can position itself between the two upper-level lows, strengthening should begin in earnest, as the CMC, HWRF, and GFDL are all showing. The National Hurricane Center is aligned with the 06z GFS and the SHIPS forecast with showing Chantal weakening in the Bahamas from shear, and this is certainly possible. As it begins to move northward, instead of being turned out to sea it will be forced back westward into the United States under the influence of the very strong ridge we've been seeing this year. This pattern is an extremely dangerous one and Chantal, if given the proper conditions, could become a greater threat as it begins to move westward towards the southeast United States.

Looking beyond Chantal, the GFS and CMC have been very consistent with showing a tropical wave emerging off the coast of Africa in about 30 hours. This wave will need to be watched, as the models are showing this wave rapidly developing by 48 to 72 hours and will, like Chantal, be shoved westward. However this one will likely face less of these problems with trade winds Chantal has been facing. The GFS has been showing a fully developed strong tropical storm reaching the area where Chantal is, and is showing weaker trade winds in that time period. Beyond 144 hours out, it's hard to say but it's likely that this wave will take a similar path to Chantal and will need to watched just as closely.


Invest 95L nearing tropical depression status - July 7th, 2013

By: CybrTeddy, 7:23 PM GMT on July 07, 2013

Finally got a competent mic!


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