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Eastern Atlantic waves bear watching

Posted by Andy Johnson under Daily updates

Two tropical waves in the eastern Atlantic appear to be merging into one system. Both of the waves are south of the very strong Saharan Air Layer (SAL) that has caused dry dusty air over much of the eastern Atlantic north of 15°. Convection has increased today, although NHC has stopped running models on this system, at least for now. Once a new center is identified after some contraction, NHC will likely start running new models, perhaps by Sunday afternoon. Shear is relatively low near the combined wave and is forecast to be low for the next few days. Long range models such as the GFS eventually show a threat from the wave to the northern Leeward Islands as a tropical storm. The long range models have great uncertainty but the 18Z GFS run today (July 31) shows a tropical cyclone threat to the east coast of Florida by the end of next weekend. In addition, the large convective cluster that is inland over Africa and will be exiting into the Atlantic over the next day or so poses a threat for development, also. The 18Z GFS run shows a potential tropical cyclone in the mid-Atlantic by next weekend with a potential  threat to the Lesser Antilles.

Another wave in the central Caribbean is interacting with a TUTT low just to its west. The moderate shear over the wave will relax by Monday but by then the wave will be approaching Central America. At that point in time, the wave will likely be too close to land to develop.

I have circled the 3 waves in the enhanced satellite image below.

The enhanced GOES image below shows the position of the  TUTT low to the location of the tropical wave to its west. The upper low is causing moderate shear over the wave at the present time.

The Saharan Air Layer (SAL) shown in the image below in orange and red tints remains strong much of the eastern Atlantic but is just far enough north (of 15°) to not have any major dampening effect on the merged tropical wave centered closer to 8° N.

The graphic below is the 228 hr forecast plot from the 18Z GFS model on July 31, 2010. The models are subject to large errors in intensity and location at this time range. However, the model is currently showing a potential threat to the east coast of Florida by the merged wave currently in the central Atlantic by next weekend. It also shows another potential tropical cyclone developing from the convective cluster currently over the Sahel region of Africa.