New storm invest 90L in eastern Atlantic- Here we go....

[n2doc]

90L forms in far eastern Atlantic
NHC has designated an area of thunderstorms in the tropical Atlantic as Invest 90L (8.5 N, 30.0 W). Microwave remote sensing suggests there are some decent thunderstorms in 90L, as peak rain rates were around 1 - 2 inches per hour. According to CIMMS wind-shear analyses, 90L is under a moderate 10 - 15 knots of wind shear, and upper level winds over the disturbance are diverging, which creates a vacuum effect that will enhance updrafts and thunderstorm growth. The disturbance is tracking into a broad area of weak shear to the west and northwest. The steering currents for 90L are to the west-northwest, which will move it into this area of weaker shear. The disturbance is at 8°N latitude, which is too close to the Equator to leverage the Earth's spin very well to spin up. As 90L's west-northwest motion carries it farther from the Equator, the additional spin the disturbance gains from the Earth's rotation will aid development, particularly once 90L gets north of 10°N latitude.The Saharan Air Layer with its dust and dry air lurks just to the north of 90L, but the SHIPS model predicts 90L will remain far enough from the dry air over the next five days so that it will not interfere with development.



Model Forecasts and Climatology
The latest 2pm EDT (18Z) runs of the GFDL and HWRF models show 90L developing into a hurricane 3 - 5 days from now. These models suggest that 90L will pass well northeast of the Lesser Antilles Islands. The 18Z GFS model develops 90L into a tropical storm about 7 days from now, and forecasts a track through the northern Lesser Antilles Islands 7 - 8 days from now. The 18Z NOGAPS and 12Z ECMWF models show little development of 90L. The GFDL and HWRF models are too aggressive developing 90L, and likely show too much of a northward motion due to excessive depth of the system they portray. The GFS solution, showing a more delayed development and possible threat to the Lesser Antilles Islands is probably more reasonable. Looking at climatology based on research done by Dr. Bob Hart at Florida State University,, 90L has a 36% chance of developing into a tropical cyclone by 2pm Saturday. NHC is putting these odds at 20%. Dr. Hart also has an experimental product showing that historically, about 30% of all tropical cyclones at 90L's current position eventually hit land as a hurricane. Of course, 90L is not yet a tropical cyclone, but these odds suggest that 90L has the potential to become a dangerous Cape Verdes-type hurricane that will affect land.

http://www.wunderground.com/tropical/tracking/at201090_model.html