Friday, October 13, 2006

Rainy Season Comes To An Early End

By Gene McAvoy, Agricultural Extension Director, LaBelle

LABELLE, FLORIDA -- According to the National Weather Service the 2006 rainy season in South Florida, which began on May 25, came to an end last week on October 6. This is 10 days earlier than the median ending date of October 16. This year`s rainy season lasted a total of 135 days, 18 days less than the average duration of 153 days.

This year`s rainy season was characterized by large variability in area precipitation totals. Miami international airport received 47.21 inches of rain during the wet season period, which is over five inches above the normal wet season value of 42.16 inches. On the other hand, Palm Beach International Airport only received 27.88 Inches of rain, well below the normal amount. Fort Lauderdale/ Hollywood International Airport was in the middle with 36.83 inches.

Overall, south Florida received below normal rainfall during the wet season. Besides Miami International Airport, the exception to this was over western sections of Collier County, which received quite a bit of rain throughout the summer. Naples regional airport received 43.20 inches for the entire rainy season.

With the exception of tropical storm Ernesto that brought large amounts of rain to the western and interior portions of south Florida at the end of august, few significant weather systems affected the area this summer. Therefore, the area’s rainfall this wet season depended largely on small-scale effects such as sea breezes, which can increase the variability of rainfall even over short distances.

The end of the rainy season is determined primarily by the first time the dew point drops below 70 degrees for about three consecutive days. This typically coincides with the first minimum temperature reading below 70 degrees since spring, and a corresponding sharp decrease in the frequency of the daily rainfall patterns, which characterize the rainy season. This year’s end to the rainy season was not accompanied by a significant drop in temperature. However, stronger fronts typically begin arriving in South Florida during the middle to latter part of October.

 It should be noted that it is not uncommon to have periods of rain lasting a day or so during the dry season as cold fronts approach South Florida.  However, these wet episodes are typically transient and only serve to provide occasional relief to the dry weather pattern normally observed between the months of November and April.

 With the return of el Niño this coming winter, precipitation this dry season may end up being above normal. This will depend on the strength of the upcoming el Niño, which is still somewhat uncertain.  During a moderate to strong el Niño, South Florida typically receives more winter rain than normal due to an increase in the frequency of low-pressure areas over the Gulf of Mexico and Florida, which can even produce severe weather outbreaks.

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