Masters student in tropical meteorology at FSU. Raised in Alaskan blizzards, but drawn toward tropical cyclones by their superior PGF.
By: Levi32 , 4:10 PM GMT on June 23, 2009
Update 5:30 eastern time:
Andres has been upgraded to a hurricane according to the latest advisory from the NHC. This is based on the 65kt surface winds found by a recon flight earlier this afternoon. This upgrade can be a bit deceiving because Andres is not strengthening. He is in fact, weakening, and has lost almost all of his deep convection, especially over and north of the center, due to dry air entrainment, proximity to land, and unfavorable upper-level conditions. What this tells us is that Andres was likely already a hurricane last night, and may have reached a peak intensity of around 80 knots - a solid Cat 1 hurricane. Since last night the hurricane has been weakening as it lost its convection and inner core structure, and is only barely a hurricane now. Andres has been able to efficiently hold off rapid weakening due to his impressive low-level structure, but he likely won't stay a hurricane for long. Gradual weakening should continue into tonight with more steady and rapid weakening by tomorrow as the system moves into a stable airmass over colder SSTs.
Tropical Tidbit from 12:00pm EDT Tuesday, June 23, 2009:
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Tropical Storm Andres:
Despite advisories from the NHC keeping Andres a 70mph tropical storm, he appears to have weakened overnight. Cloud tops within the CDO have warmed and the core structure is ragged and disorganized. The 3 main factors that have caused this weakening that I outlined yesterday are 1) Lack of poleward outflow 2) Proximity to land 3) Low ocean heat content and dry, stable air associated with low SSTs to the NW. On Satellite Imagery you can see the outflow boundary to Andres' northwest that is trying to expand north but is getting shunted southward by an upper low over central Mexico and the big upper ridge in the NW Gulf of Mexico. I believe this lack of favorable upper-level conditions to be the primary reason for Andres' decline. Proximity to land may also be playing a role here, and on its current track Andres will be passing very close to the Mexican coast in the next 24 hours, and may even make landfall briefly if his track deviates even a little to the NE.
Andres is being steered NW on the SW periphery of the sub-tropical high over the NW Gulf of Mexico, and this high is forecast to build westward over the next few days, eventually curving Andres to the west as he moves over cold SSTs and dissipates. Some of the track models now are indicating that the upper trough over California may be slow in lifting out and allowing the ridge to build west, which may take Andres closer to the Baja Peninsula than originally thought. If this verifies Baja will likely only get some light rain and nothing worse than that.
I do not expect Andres to significantly strengthen again, but he still has a 12-18 hour window to reach my forecasted intensity of a minimal Cat 1 hurricane. He was only 5mph short of it last night according to the NHC. The NHC has also been forecasting a maximum intensity of a border-line hurricane, and continues to do so this morning. A recon plane is en route to the system as I type, and will give a clearer picture of the strength and health of Andres. I do not expect Andres to reach hurricane intensity, and I think this is likely the start of a gradual weakening period that will continue for the rest of Andres' existence. A hurricane warning is still in effect for part of the Mexican coastline. Refer to the National Hurricane Center for official forecasts and information.
The Atlantic basin is still quiet for the most part. The trough split that will be occurring in 2-3 days in the Gulf of Mexico will have to be watched as the old frontal boundary extending from east of Florida into the GOM will have to be watched for little lows forming along it. Right now nothing significant is being forecasted by the models but this type of a situation must always be watched. The GFS and NOGAPS try to form something in the western Caribbean in 4-6 days, likely from the tropical wave currently passing through the windward islands. This area will have to be watched as well as the TUTT lifts out and an upper anticyclone builds over the NW Caribbean during that time. The GFS is forecasting some development of an African wave that will exit the coast in 48 hours. With the eastern Atlantic TUTT also forecasted to lift out there may be some breathing room for development so I will keep an eye on that as well.
The disturbance in the Bay of Campeche has slightly increased thunderstorm activity but remains disorganized and I still don't see it as a threat to develop, as it will run out of time and water soon as it gets steered NW inland over Mexico.
We shall see what happens!
NASA High-Resolution Visible Loop of Andres and BOC disturbance
National Hurricane Center official Andres forecast track:
Andres Visible Satellite: (click image for loop)
Caribbean Visible Satellite: (click image for loop)
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