Weather Archive

Friday, November 30, 2007

HURRICANE SEASON IS OVER

This season will not be remembered as an active season in the United States but certainly it will leave scars for Caribbean inhabitants. It was a bad season in Jacksonville because of the beach erosion. Northeaster's lashed the coast undermining structure to homes in South Ponte Vedra Beach. Nor'easter's most often result in higher erosion than hurricanes because they last longer.

Only one hurricane made landfall in the US along the upper Texas coast. Humberto was noteworthy because it was the fastest growing storm on record from first advisory to category 1 strength at just 18 hours. Two tropical storms hit the states with little effect. The lack of systems prolonged the drought across the southeast and Florida continues to see a deficit. Actual named storms were 14, with 6 hurricanes, and 2 major. A normal season has 11 named storms, 6 hurricanes, with 2 majors.

Hurricane Dean And Felix were amazingly strong category 5 storms that hit Central America. This was the first year ever to have back to back category five storm make landfall in one season. 27 people died from Dean after it passed through the Lesser Antilles Islands, moving just south of Jamaica, and into Mexico. Felix killed 235 people in Nicaragua.
September was noteworthy for tying the 2002 record of the most named systems during September at 8. But most storms this year barely lasted a day and some almost didn't reach the maximum strength for a named storm. Besides Dean and Felix, the other hurricanes were all within 5 mph above the minimum wind speed for becoming a hurricane. New technology is helping to classify storms which may not have been identified years ago.

Since the season was producing fewer systems than the preseason long range forecasts, there is room to imagine cyclones are getting upgraded to match the predictions. Most storms reached 40 mph in some quadrant of the circulation but internal pressures never dropped below 1000 mb based on aircraft resonance. Lower pressure increases wind. But many of these systems were disorganized as winds were higher than what a typical barometric pressure would support.

The past two years long range seasonal hurricane forecast have been off the mark. Many climate signals pointed to an active 2007 and it was an La Nina year which drives down shear typically increasing storm numbers. So what happened. The CSU team feels an active dust season over the Atlantic may of hampered the numbers. Certainly more research is needed for this type of forecast while near term storm track forecasts improve considerably.

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