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Rainfall Discussion:
Based on the
expectation of a moderate La Nina and
the possibility of strong La Nina conditions, rainfall is forecast to be well below normal during the upcoming 2007-08
Florida dry season (1 November - 30 April). Statistical
forecasts predict 10 inches of rain averaged over Florida for the
dry season compared to a normal of 14.5", but these forecasts have been overly optimistic in recent
seasons and are given less weight. Also the trend has been for drier dry
seasons in recent years. Logistic regression results show a 43 percent chance of extreme dryness should a
moderate La Nina be sustained into winter and only a 1% chance rainfall
could be well above normal. Interestingly, the record La Nina of 1988-89
was below normal in rainfall at at 12" rather than well below
normal as might be expected, This was also the case for the 1998-99 La
Nina, but the 1999-2000 La Nina had only 9" of rain. The weak La Nina of
2000-01, however, was the driest of all at 7.1". What this all means is
that there is a high probability this dry season will be below normal in
precipitation, but the confidence in it being an extremely dry season is
less. Logistic regression also indicates that it is more likely to be
drier in the late winter and spring than in the fall and early winter.
The probability of rainfall in November, December and January being well
below normal is about 40% while the probability of well below rainfall
in February, March and April is nearly 65%. The official CPC forecast linked
above is also for below normal rainfall over Florida for
the upcoming dry season.
This forecast will
be updated before December 15th.
For a more in depth discussion on ENSO and it's effects on Florida's Rainfall see our "Florida's Dry Season Rainfall and EL NIÑO-Southern Oscillation Educational Material." |
National Weather Service Forecast Office
