Isaac Update…Hurricane Warnings Posted for Haiti/DR
Busy afternoon for the NOAA and AF hurricane hunters. Both are out in the Caribbean right now at the surface and aloft trying to figure out what exactly is going on Isaac’s insides and how the Bermuda High is behaving. Both of these flights will ingest their data into the global and tropical models later tonight so that we’ll have a better idea of where and when Isaac is going. In addition to recon, many southeastern US (and all FL) NWS offices will be doing intermediate weather balloon launches every 6 hours in order to get a better idea of the upper level conditions.
Although they have found relatively light winds at the surface near the center, winds up to 45 mph were found to the east of Isaac’s center with a minimum central pressure of 1004 millibars during the first pass. The graphic below shows Isaac’s current location as determined by recon and the current watches and warnings. Remember that a hurricane warning means that winds greater than 75 mph are expected in that area, in particular for Haiti. If you can get shelter there, please do so in an area that does not flood. Rainfall alone (not including water from surge or tide) could reach 20 inches across the mountainous areas of Hispaniola in the hurricane/tropical storm warned areas and inland. Tropical storm watches may be issued at any time for parts of Cuba or the Bahamas, and they should be expected by the mid weekend for parts of Florida if the current track continues.
The forecast has gotten a tad bit cloudier, for the lack of a better pun, over the last day or so. I’ll start with the medium term since that’s what everyone wants to know. There is a stepping stone that is land interaction with Hispaniola and Cuba, which will come Friday night in Saturday. Storms are known for looking a lot different on the other side of those two islands, and models don’t always handle it all too well. The track models are still in very good agreement for landfalls in Haiti and in Florida by next Tuesday as seen below. Track will be effected by how much Isaac weakens due to land interaction, but not by much I don’t think. The models did shift a bit to the westward at 18Z, and I think that may be the beginning of a trend. Isaac has redeveloped to the south a couple of times, which will make for less land interaction with Haiti and a farther western landfall in the eastern Gulf.
In the short term, recon and satellite indicate a lop-sided, multivortex system with weak winds near the center. The strongest winds so far have been located on the right side, which is generally where they are supposed to be. Recon is finding rather confusing obs that at one point did indicate winds rotating in the wrong direction. This should correct itself during the course of the afternoon and evening today, and I suspect winds should begin to increase overnight. We’ll know early tomorrow morning exactly where impacts will be on Haiti, but as of right now I am thinking somewhere around or to the west of Coquille, Haiti. Strong tropical storm force winds with gusts to hurricane strength anywhere on the Haitian peninsula are possible on Friday afternoon into Saturday mid-day. I do think Isaac will make landfall as a strong tropical storm.
One more caution for Isaac that I want to throw out there is that if Isaac can sustain a distinct inner core for longer than 12-18 hours, conditions are favorable for rapid intensification.
I’ll look at Florida impacts when Isaac is reaching or just passing Cuba in a couple days
I do want to mention Joyce for a half a second here, but as I mentioned the other day Joyce will remain from most land. Impacts could be felt in Bermuda as Joyce recurves east of the US, and those impacts would likely be felt on Monday night on that island.