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Tropic Watch 7/26/11

By: SouthDadeFish , 4:21 PM GMT on July 26, 2011

Yet again, the only significant feature in the tropics is reactivated invest 90L located at 20.0N 83.0W as of 12Z. 90L has continued to grow better organized, and I think these two images are very telling of how far 90L has come.

Figure 1.1: Visible shot of 90L at 1945Z yesterday.

Figure 1.2: Visible shot of 90L at 1445Z today.

The main factor 90L is lacking for continued development is a surface circulation. Morning visible images reveal increased SW inflow, but a circulation is still not established at the surface. 850mb vorticity has continued to increase through the past 24 hours and it appears more and more likely that 90L will develop into our next tropical cyclone. If 90L reaches tropical storm strength it will be named Don.

Wind shear is fairly conducive for intensification over the system, at about 10 knots. The atmosphere is moist and 90L is sitting over the notoriously warm waters of the NW Caribbean. Although the NHC is currently giving 90L a 20% chance at becoming a tropical cyclone over the next 48 hours, I am putting these odds around 50-60%. Look for the NHC to raise the chances as the day goes on.

There is a recon mission scheduled to fly into 90L tomorrow at 18Z, if necessary as always.

I would like to discuss the future of 90L assuming it does develop, but this is difficult to do at this time without a definite center. Assuming it does develop in the next 24-36 hours, SHIPS is showing relatively favorable conditions for intensification beyond 24 hours. It is unclear how 90L will interact with a possible landfall in the Yucatan peninsula. This may disrupt a developing low-level center, or it may act to help solidify one due to increased convergence. After this, conditions should allow 90L to intensify into Tropical Storm Don with the possibility of a minimal hurricane at landfall.

Figure 2.1: 12Z GFS 60 hour 200mb forecast. The GFS is depicting relatively favorable upper-level conditions for a possible tropical cyclone in the Gulf of Mexico.

As far as track goes it appears 90L will continue to move WNW for the next 24-36 hours. In about 36 hours, a trough is expected move through the Great Plains area eroding the ridge over the SE US. This may allow 90L to gain more latitude as it scrapes around the western periphery of the ridge. This would yield a landfall in the South/Central Texas area. With that being said, there is very low confidence to this forecast at this time due to lack of a definite center. Furthermore, the model guidance is still very hesitant to develop 90L at all, but this may be due the small size of the system. However, anyone living on the Western Gulf Coast should closely monitor the progress of 90L as it still has the potential to become Tropical Storm or even Hurricane Don.

Thanks for reading,

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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1. TropicalAnalystwx13
4:31 PM GMT on July 26, 2011
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About SouthDadeFish

I have my B.S. in atmospheric science from Florida International University and am currently in graduate school conducting hurricane research.

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