First: Ernesto. Over the past 18 hours, this system's overall structure has improved markedly, though it continues to suffer from environmental dry air. The intensity as of 15Z today (11am EDT) is 45kts and 1008mb, which is based on an aircraft recon flight into the system. It is now located about 600 miles ESE of Jamaica, and a tropical storm warning has been issued for Jamaica -- with a closest approach to the island expected early Monday, perhaps as a hurricane.
A microwave image of the storm from 1230Z today shows a defined center and a large rainband. The blue-green shades indicate warm/liquid water, while the reds indicate ice... which is only found in deep convective clouds. However, the dark colors within the satellite swath indicate dry air, and TPW (total precipitable water) images confirm that Ernesto is surrounded by dry air, and it extends into the Caribbean as far west as western Cuba. That will almost certainly keep the storm from becoming a monster hurricane in the next few days... particularly good news for Jamaica.
As far as the forecast goes, it will continue to trek through the Caribbean, and reach western Cuba or the Yucatan by Wednesday. The intensity is unfortunately a big unknown; conservatively it could be a tropical storm... but has the potential to be much much stronger. Jamaica, Cuba, Belize, and the Yucatan peninsula should be treating this storm very seriously... although it isn't much now, the potential along this track is big. The plot below shows model guidance from this morning's runs. There is fairly good agreement out to 3 days, but beyond that, the spread increases quite a bit. If I were in the north-central Gulf coast and looking at this, I wouldn't be too concerned about those tracks heading your direction just yet. But stay tuned.
The easterly wave that left the African coast on August 1 was upgraded to TD6 at 03Z today (11pm EDT on Friday). Then just 12 hours later was upgraded again to TS Florence, the sixth named storm of the season. Climatologically, we only see the sixth named storm on September 8, so we continue to be well ahead of pace this season. Florence is a 40kt storm with a 1002mb central pressure, and is located about 340 miles west of the Cape Verde Islands. Although it may intensify a bit more in the next day, it is heading into a very hostile environment and will most likely not have a chance to develop within the next week. On its forecast trajectory, it should be near the northern Lesser Antilles in about 6 days.
Elsewhere, the wave that was near the Bahamas and southern Florida weakened substantially overnight, and is located off the east coast of Florida, north of the Bahamas.
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