Tropical Storm Ernesto, Invest 90L, Invest 91L all worth watching - 8/3/12
Good afternoon and welcome to my tropical weather update for Friday, August 3rd, 2012. The tropics are awake that's for sure, with three areas to watch. The first is Tropical Storm Ernesto, located at 13.7°N 62.3°W. Maximum sustained winds remain at a level 50mph . Satellite reveals a decent structure to Ernesto but lacking in convection. This is likely to the fact that Ernesto is entering the ''dead zone'' so to speak where convergence in the area is lackluster. The trade winds though have relaxed over the system and it appears intensification is forth coming in the next few days.
Figure 1. Current satellite image of Tropical Storm Ernesto.
The forecast for Ernesto.
Ernesto is currently trucking west at 20mph, this is a defiant con against real intensification. Such a quick forward motion often tends to not allow storms to use full advantage of the TCHP and SST's currently situated under the system. You have the other fact that Ernesto is entering a deadzone, an area that the Eastern Caribbean is famous for having. Basically the trade winds are causing all the real convergence to be pulled away from Ernesto and pile up in the Western Caribbean. This is a double edged sword, while this will cause Ernesto to only have steady intensification if any at all for the next few days that means that when Ernesto arrives in the very deep TCHP there will be little to stop it from intensifying.
Figure 2. Current TCHP image of the Western Caribbean.
The NHC forecast reflects this fact. They are showing Ernesto maintaining strength until it reaches south of Jamaica. By then it will be entering the Western Caribbean and could become a potent hurricane if the conditions remain so. The models are very so-so on Ernesto. I believe though they are struggling to handle the system thanks to it's small size. A 1002mb 50mph Tropical Storm is going to have a different tug on the steering currents than a 1009mb Tropical wave would as the GFS has been showing and has been burring it into Central America with the European model. I discount these scenarios due to poor initialization. I believe that the system will continue a W-WNW track and continue to be disorganized and then intensify. After that, it appears it is possible that a weakness could develop in the Western Caribbean that will cause to pick up Ernesto or head it WNW-NW, perhaps just scrapping the Yucatan.
Figure 3. Current 'spaghetti' model chart for Tropical Storm Ernesto.
Watching Invest 90L for development
Our second area to watch is off the Cape Verde islands and off the Florida coast. A very healthy looking tropical wave has emerged off the African coast and is being given a 30% chance of development in the next 48 hours, and is now being called 90L. Satellite shows an organizing tropical wave with a fair chance at becoming a named storm. Model support for this is very lackluster, none of the major global models are showing development but it is an area to watch. It is too early to really sniff out a possible track but due to the possibility that I mentioned that a trough might be influencing Ernesto in the future more NW it is possible this system will be pushed away from land.
Figure 4. Current satellite image of Invest 90L.
Invest 91L not a real threat for development
The final area of interest is a disorganized tropical wave just situated to the east of Florida that is producing scattered showers and thunderstorm activity. This wave is encountering heavy shear, but if the shear begins to let up there is a chance that something could happen. Without surprise, the models aren't enthusiastic about developing this either. However, if develop though does begin with this system it is possible that it could influence Ernesto towards land.
Figure 5. Current satellite image of 91L.