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Forecast models vary on tropical wave's strength potential

National Hurricane Center

The wave is southwest of the Cape Verde Islands off the coast of Africa. It's about 3,500 miles east of Miami.

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By NEIL JOHNSON | The Tampa Tribune

Published: August 10, 2009

Updated: 08/10/2009 03:02 pm

TAMPA - A tropical wave making its way west in the Atlantic Ocean continued to lose some of its punch today but still has the potential to become the season's first tropical storm, forecasters say.

Meanwhile, forecasters today started watching another tropical wave much closer but give it less than a 30 percent chance of developing.

The National Hurricane Center has watched the more distant wave southwest of the Cape Verde Islands off the coast of Africa since the weekend. Forecasters say it has a 30 percent to 50 percent chance of turning into a tropical cyclone by Wednesday.

Conditions remain favorable for the wave to develop into a depression or topical storm, forecasters say, even though some of the thunderstorm activity diminished today.

It would be named Ana if it becomes a tropical storm and would also be the season's first named storm.

But intensity models have backed off from Sunday's model runs on predicting just how strong the system may become.

Sunday's model runs almost universally predicted the wave would reach tropical storm strength and hit peak intensity by the end of the workweek just shy of hurricane strength.

Most of the latest model runs keep the wave below tropical storm strength, though some push it barely above the 39-mph threshold to become a named storm.

All have the wave dropping dramatically in strength by the weekend.

The wave is far too distant to cause any concern about landfall. It is about 3,500 miles east of Miami.
The projected path of the wave is generally west at 10 to 15 mph and may take it into some slightly cooler waters and near a mass of drier Saharan air to its north. That could account for the models' lowered expectations of strengthening.

Also, there is some wind shear in the area where the wave is expected to be in a few days.

The track models project the storm will curve to the north before reaching the Caribbean Sea.
The second tropical wave is near the Windward Islands, just east of the Caribbean Sea and also heading west at 10 to 15 mph.

If it does develop into a depression or storm, it will be slowly, the hurricane center said.

So far, the season has produced only one tropical depression. It formed May 28 about 175 miles northeast of Cape Hatteras but only lasted two days.

About 60 tropical waves – masses of thunderstorms – emerge from the African coast each hurricane season but only one in six grow into a named storm.

The peak of hurricane season typically begins about this time, and most of the storms begin as tropical waves in the Atlantic Ocean. The peak usually runs through mid-October.

An El Niño is believed to be responsible for the hurricane season's slow start. The El Niño changes upper atmosphere wind patterns, increasing the strength of winds blowing from the west that disrupt developing storms.

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