Aug 17, 2011

DAY 78

Invest 93L is still cruising along at 15 to 20 mph. It is now located south of Jamaica, and is slowly organizing. The broad cyclonic turning is quite obvious with it now, and it does also appear to be consolidating its size. That circulation is apparently not so nice at the surface though. The Hurricane Hunters did run a recon mission out to 93L today but did not find a closed surface circulation. The overall surface pressures were actually not that impressive either at 1010 to 1011 mb.

(Invest 93L)
Based on 93L's progress today, the Hurricane Center is giving it a 60% chance of become a tropical cyclone in the next 48 hours. It is forecast to continue moving west and possibly scrape the tip of the Mosquito Coast near the Nicaragua/Honduras border. Computer intensity models have come way down, because it is running out of time before land interference. If it misses the coast to the north it will have a little more time to gain strength before hitting Belize or the Mexican Yucatan.

93L will have a good chance at becoming Tropical Storm Harvery over the next 3 days. It looks from the satellite pictures that the models may have initiated 93L a little to far south. But analysis of the low level steering layer with surface vorticity shows why the models are pushing 93L down into Nicaragua. The map below shows the infrared image of 93L with the dark orange circle highlighting the surface vorticty. The white lines with arrows show the mean surface steering layer with a slight southward bend guiding 93L into the Nicaragua/Honduras border. This works better if you know exactly where the surface circulation is, so if it is north of that orange circle, it could miss Nicaragua and take an extra day or so in open water.

The National Hurricane Center has also recognized that tropical wave that is now about 800 miles west of the Cape Verde Islands. It was circled in the 8pm Tropical Weather Outlook with a 10% chance of becoming a tropical cyclone in the next 48 hours. Conditions are not great out in the open Atlantic however, and 93L will likely remain a low threat for development. The long range computer forecast models like the GFS, CMC, UKMET and the NOGAPS are all on board with some type of development out of this system next week.

Out in the Pacific where they're trying to stay perfect, Tropical Storm Fernanda has not yet become a hurricane. She is not forecast to do so, although there is still time for her and she has a nice spin to her. Greg has become a hurricane already, so the Pacific is 6 out of 7 right now. It's all up to Fernanda to keep up the perfect record.

(Left to Right: TS Fernanda, Hurricane Greg)

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