#1422 Postby Houstonia » Fri Aug 03, 2012 8:33 am
Morning observations from Jeff Lindner (HCFCD):
Tropical storm passing through the Windward Island with strong winds.
Discussion:
Ernesto moving through the Windward Islands. Winds gusted to 63mph at St Lucia and sustained winds of 43mph at Barbados in the last few hours. Ernesto is racing westward at 24mph this morning…very fast for a tropical cyclone…and the result in a disorganized system even though some strong winds are being reported on the islands. First few visible images this morning show a sheared system with an exposed low level center to the west of a small and decreasing ball of deep convection. The fast forward motion of the low level center is pushing the center out from under the deep convection and the net result is about 20kts of shear over the system. While the system is well defined on radar, it is not well organized and will have to slow its fast forward motion. It is possible that Ernesto may open up into a tropical wave over the next 24 hours.
Track:
Ernesto remains to the south of a very strong mid Atlantic ridge resulting in the fast forward motion, and this should continue for the next 1-2 days taking the system generally W to WNW through the eastern and central Caribbean Sea. BY the end of day 3 (Sunday) the system will begin to approach the western edge of the sub-tropical high over the SW Atlantic and start to encounter a weakness over the Gulf of Mexico. This weakness which is currently over the SE US will be moving westward this week as the TX high pressure cell builds/moves westward. The GFS and EURO take a weak system into the southern Yucatan and then MX while the CMC, UKMET, GFDL, and HWRF all show Ernesto turning NW into the weakness. The reasoning for the spilt in the guidance at the longer range is the intensity of the system. A weaker system will follow the low level flow and stay southward, while a stronger system feels the weakness in the ridge and begins to bend WNW and then NW. Current NHC track is pretty much down the middle road of the guidance with the GFS and EURO on the left and the GFDL and HWRF on the right. The track forecast for the next 48 hours is fairly high confidence, but the confidence lowers after 48 hours as the guidance spread becomes increasingly large.
Intensity:
The intensity forecast remains a problem as the near term environment is marginally favorable for development and the long term environment favorable. The question is does Ernesto survive the short term to take advantage of the long term. Based on the satellite presentation this morning it is questionable if Ernesto will survive the next 24 hours as the fast westward motion will continue to produce moderate to strong wind shear. Additionally, the eastern Caribbean Sea is typically not a very favorable region for developing tropical systems. Also the GFS and EURO continue to insist that the system will not intensify much, while the latest GFDL, HWRF, and CMC all show Ernesto reaching hurricane intensity in the western Caribbean Sea. Current NHC forecast is leaning toward the stronger guidance and takes Ernesto to a hurricane south of Jamaica and into the NE Yucatan and the SE Gulf of Mexico. It should be noted that conditions will be fairly favorable in the western Caribbean Sea and the LGEM and GFDI guidance makes Ernesto a major hurricane. It is also noted that most of the guidance makes Ernesto a category 2 hurricane about 48 hours prior to the official NHC forecast.
Now would be a good time for residents to review their hurricane preparation plans!
90L:
New tropical wave/surface low south of the Cape Verde Islands has developed some organized thunderstorms and continues to show signs of development this morning. NHC gives this system a 30% chance of tropical cyclone formation as it moves WNW at 10-15mph.
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