Hurricane Arthur may be typical of what we see this season with tropical systems. Given cooler than normal water in the Tropical Atlantic, dry air over the central Tropical Atlantic, high wind shear levels and a very slowly developing El Niño, many forecasters are saying that the greatest threat from tropical cyclones this year will be from what is colloquially called “home grown storms.”
Given the current and projected weather pattern, we are unlikely to see many “Cape Verde” hurricanes. That is hurricanes that develop in the Tropical Atlantic and roll west into the United States, often as monster storms (such as the 1900 Hurricane and Hurricane Ike). By contrast, the home-grown storms often develop near shore along the Atlantic, or in the Gulf of Mexico or northwest Caribbean Sea. This is not to say they are harmless. Hurricanes Carla and Alicia should rid us of that notion.
Typically, these systems either develop from tropical waves that move undeveloped across the Atlantic, but blossom when they reach the super-warm waters of the Caribbean or Gulf of Mexico; or they develop from frontal boundaries that dip into the Atlantic or Gulf of Mexico, fostering an area of disturbed weather that slowly develops tropical characteristics. Both Arthur and Alicia were examples of this type of storm.
As for rain, given the type of pattern we have over the U.S. right now, it appears that most of our chances for rain over the next month or two will come from tropical waves and other tropical systems, rather than cold fronts and other mid-latitude disturbances. The scattered rains we have been seeing across southeast Texas the past few days are a result of a surge of moisture that track across the Atlantic into the Gulf of Mexico.
Despite the recent spate of thundershowers, most forecasts call for dry conditions through the next two weeks or so. Or best chance for rain will be from tropical waves and their associated surges of moisture. That is what we will watch during the next couple of weeks. Of course, the danger with these “rain opportunities” is that they can develop into a “home-grown” storm, given the right conditions.
At least that is my chief concern as we move into the second month of the Hurricane Season.
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