Tropics Tranquil for Now, Several Waves to Track

August 8, 2011; 5:00 PM ET
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"The only real area of concern is over the eastern Atlantic by the Cape Verde Islands."


Meteorologists in the AccuWeather.com Hurricane Center are predicting a period of tranquil weather in the tropical Atlantic in the wake of Emily's demise. However, there are a few features to track that may eventually develop into a storm as we approach the typically busiest part of the tropical season during late August and September.

Emily, which became a tropical depression again over the northern Bahamas on Saturday, dissipated again while pushing to the northeast on Sunday. What's left of the storm is passing near Bermuda today and is causing winds to gust to around 50 mph and squalls of rain. It will merge with a front northeast of Bermuda over the next day or two.

Farther south, there are a few tropical waves to watch as they move westward across the Atlantic Basin. One is over the Caribbean Sea, south of Cuba. It is producing very little in the way of thunderstorms and shows no sign of becoming better organized.

A more impressive wave is approaching the Windward and Leeward islands. Although there appears to be a swirl of clouds along this wave on satellite pictures, upper-level winds in this area are unfavorable for further development, especially once it reaches the Caribbean.

The only real area of concern is over the eastern Atlantic by the Cape Verde Islands. A very strong tropical wave is moving over the area from Africa, which is causing thunderstorms, and clouds are swirling around low pressure currently just southwest of the islands. Despite this, computer model forecasts are not calling for this to become a storm in the coming days, likely due to the influence of dry air ahead of an north of the wave.

It looks as though the wave train from Africa will continue over the next several days. Satellite pictures show that two more strong tropical waves crossing the continent will require close watch when they arrive in the Atlantic over the next several days.

One other area to watch starting later this week will be the eastern Gulf of Mexico, the Bahamas and western Caribbean. A cool front now over the Midwest will get unusually far to the south for this time of year, reaching the area around Florida and Cuba by Thursday. There is some chance that low pressure will form along this front and gradually turns into a tropical depression or storm.

The waters in the Atlantic are very warm and ready to fuel any developing tropical system. The warmest waters are found over the central and western Caribbean into the eastern Gulf of Mexico.

One of the problems that these waves likely will run into will be wind shear. Wind shear is a large difference in speed or direction between the winds close to the surface and at the upper levels of the atmosphere. Tropical storms are more likely to form in areas where the winds are nearly the same speed and direction from the surface to the tropopause, the top of the layer of the atmosphere where almost all weather occurs. It was strong wind shear that caused the final demise of Emily last weekend, as the surface wind was southwesterly while the upper winds were from the northeast. This situation literally tore the top off Emily's thunderstorms.

The other problem is the presence of dry, sinking air over parts of the Atlantic. Obviously, this will slow the development of any embryonic tropical storm system that will depend on the presence of warm, moist air. AccuWeather Expert Senior Meteorologist Dan Kottlowski says that this has been a problem for developing storms and looks to remain a problem for the next few days.

"The eastern Atlantic ridge remains farther south than usual for this time of year," said Kottlowski. "This is pushing dry air from the northeastern Atlantic into the tropics at regular intervals, and it's hard for a developing tropical system to fight this off."

When asked if this situation will change in the near future, he replied, "we are heading toward the time of year where the Atlantic ridge typically starts to shift. That could happen in as little as a week but should occur by the end of the month. I'm worried that when this does happen, we see a period of a weeks where everything that comes off Africa develops."

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