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AL080410 -- Invest 92L – Ex-TS Colin
Definitions (These are my definitions, and are not from the NHC or anywhere else)
o Invest: Area of interest that the National Hurricane Center and others are watching for possible development into a tropical cyclone. Short for investigation; generally of low pressure areas.
o Wind Shear: Directional wind moving in a direction that hinders cyclonic development in the tropics. Shear takes the tops of clouds off the top of a cyclone.
o Ocean Heat Content: Temperature of greater depth than just a few feet below sea level feeds storms much more successfully than a shallow sea surface temperature.
o Cyclogenesis: birth of a cyclone
Invest 92L seems to be drying up while Ex-TS Colin seems to be getting its act together;
...Synopsis... Starting tonight with Invest 92L, which is looking the worst that it has since its genesis. This disturbance is located near 14.6N76.5W and is moving towards the west. The main culprit with this one is that its lower level environment. By this I mean that in the lower parts of the atmosphere, 92L is not bringing in air (convergence) to send it up to the upper atmosphere where 92L is actively diverting air away from the system, therefore it is removing all of the air and moisture from itself. This is mainly due to a anticyclone that would normally set itself up over a tropical system, but 92L is not feeding the anticyclone. Until 92L can get some sort of convergence going to feed the upper atmosphere, 92L will not look any better.
In a completely different case, ex-TS Colin is looking very well organized tonight. This disturbance is located in the vicinity of 20.2N62.1W under a very strong ball of convection. It seems that the shear that was ripping Colin apart yesterday has abated by quite a bit, and dry air does seems to have moved out of the way. The shredder that was seen yesterday on satellite is now gone. The upper air patterns seems to be good for now, but I have some concern with some higher shear to the west where divergence is actually negative. There still is a rather dry area associated with an upper level low to the north. The entire system has begun to slow down, but is now moving at speeds about 15-20kts. Ocean Heat Content will be losing its punch as Ex-Colin gains latitude, but the SST's ahead are well warm enough to provide fuel to the system.
...Prognosis for Track and Intensity... For 92L, I am using the lower level currents to describe track, but there is some uncertainty with quite a few NWS offices along the gulf coast. The low level currents should take 92L W or WNW along the northern coast of Honduras. There is an outside chance that 92L will get further north and could move into the central Yucatan, then we would be forecasting for the Bay of Campeche. I am almost ready to say this should be undeclared as an invest, and in the last hour or so the NHC has shown some signs of the same thoughts. At this time I cannot forecast any growth, and until I see some sign of convergence, I have to say there is nearly dead.
As for Ex-TS Colin, I will start with track. Movement over the next few days will be quite slow. The 00Z BAMS seem to show a slow recurve, while others recurve it rather quickly. The further west Ex-Colin gets, the less steering currents there are. I think that Ex-Colin will recurve well to the west of the island of Bermuda, somewhere between half and one-third of the way from Bermuda to the US coast. This will be a little easier to forecast when we see a curve taking place.
The NHC has noted that Ex-Colin has winds of Tropical Storm force. Many of the models quickly ramp Ex-Colin up to hurricane strength within 3-4 days when shear completely relaxes. Some of this growth may come from an acceleration with latitude commonly found with exiting tropical cyclones. I think that the chances of becoming a strong tropical storm are pretty good over the weekend or on Monday. This would bring a brush of a moderate Tropical Storm to Bermuda, possibly around 50kts. Colin should regain tropical status in the next 24-36 hours.
...Interests...Honduras, Nicaragua, Belize, and the Yucatan peninsula of Mexico should be watching 92L for the threats of heavy rain and moderate to heavy wind.
Bermuda should be watching Colin for the threat of tropical storm force winds, heavy rain, and light surge/high waves on the southern and western facing beaches. Interests in the Bahamas and in the southeastern US should be watching for higher than normal waves with the passing of Colin.
Forecast Likelihoods:
Forecast Confidence: 60%
92L Cyclogenesis: <5%
Colin Cyclogenesis (Re-attainment of Tropical Status): 70%
Meteorology Student Jonathan -- Fact789
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Please bear with me in doing forecasts for each system. I will be moving to Florida State over the next two weeks and my time will become crunched, and I may not be able to make as many forecasts as I would like.
