965
FXUS07 KWBC 292049
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EST FRI FEB 29 2008
30-DAY OUTLOOK DISCUSSION FOR MARCH 2008
STRONG LA NINA CONDITIONS CONTINUE THROUGHOUT THE TROPICAL PACIFIC AND WILL
CONTINUE TO FORM THE UNDERLYING BASIS FOR THIS UPDATED MONTHLY FORECAST. WELL
BELOW AVERAGE SEA SURFACE TEMPERATURES (SSTS) ARE OBSERVED ACROSS THE CENTRAL
AND EASTERN EQUATORIAL PACIFIC. SSTS MORE THAN 2 DEG CELSIUS BELOW AVERAGE
WERE OBSERVED BETWEEN 175E AND 120W AND THE NINO 3.4 REGION INDEX VALUE HAS
BEEN NEAR -2.0 FOR THE PAST MONTH. IN ADDITION THE LOW LEVEL EQUATORIAL
EASTERLY WINDS HAVE BEEN STRONGER THAN AVERAGE ACROSS THE CENTRAL EQUATORIAL
PACIFIC... STRONGER THAN AVERAGE UPPER LEVEL WESTERLY WINDS HAVE BEEN
OBSERVED... AND CONVECTION HAS BEEN SUPPRESSED OVER THE CENTRAL PACIFIC.
COLLECTIVELY, THESE ATMOSPHERIC AND OCEANIC CONDITIONS ARE CONSISTENT WITH
STRONG LA NINA CONDITIONS. SST FORECASTS FROM THE CFS AND A SUITE OF OTHER
STATISTICAL AND DYNAMICAL MODELS INDICATE THAT LA NINA SHOULD REMAIN STRONG OR
MODERATE THROUGH MARCH AND INTO THE SPRING. THEREFORE, THE MARCH TEMPERATURE
AND PRECIPITATION FORECASTS ARE BASED STRONGLY ON LA NINA COMPOSITES FOR THE
FEBRUARY - APRIL SEASON.
INTRASEASONAL (MJO) ACTIVITY HAS BEEN RATHER PERSISTENT SINCE MID-NOVEMBER, AND
HAS MODULATED LA NINA IMPACTS ACROSS THE CONUS AT VARIOUS TIMES DURING THE
WINTER. DURING MIDDLE TO LATE FEBRUARY THE MJO PROPAGATED THROUGH THE WESTERN
PACIFIC INTO THE WESTERN HEMISPHERE BEFORE STALLING AND WEAKENING. VARIOUS
MODEL FORECASTS ARE GENERALLY INDICATING THAT THE CURRENT MJO WILL STRENGTHEN
AND BEGIN PROPAGATING DURING EARLY MARCH, POTENTIALLY REACHING A LOCATION THAT
WOULD HELP TO REINFORCE THE EXPECTED LA NINA SIGNAL. THEREFORE THE UPDATED
MARCH FORECAST IS LARGELY CONSISTENT WITH THE HALF MONTH LEAD... DESPITE
INDICATIONS OF A DIFFERENT PATTERN IN THE SHORT TERM.
THE TEMPERATURE OUTLOOK FOR MARCH FAVORS ABOVE AVERAGE TEMPERATURES ACROSS MOST
OF THE SOUTH FROM NEW MEXICO EASTWARD... ACROSS THE SOUTHERN AND CENTRAL
PLAINS... AND ALONG THE EASTERN SEABOARD FROM FLORIDA NORTHWARD THROUGH THE
NORTHERN MID-ATLANTIC. BELOW-AVERAGE TEMPERATURES ARE MOST LIKELY IN THE
PACIFIC NORTHWEST AND IN SOUTHERN CALIFORNIA AND ALSO IN SOUTHERN ALASKA AND
THE ALASKAN PANHANDLE. THE OBSERVED BELOW-AVERAGE SSTS ALONG THE CALIFORNIA
COAST FAVOR A CONTINUATION OF BELOW AVERAGE TEMPERATURES IN SOUTHERN
CALIFORNIA. THE TEMPERATURE FORECAST OVER THE REST OF THE CONUS AND ALASKA IS
CONSISTENT WITH OBSERVATIONS FROM PREVIOUS STRONG LA NINA EPISODES. THE
TEMPERATURE FORECAST IN THESE REGIONS IS ALSO SUPPORTED BY THE SMLR AND THE
CCA, AS WELL AS UPDATED FORECASTS FROM THE CFS.
THE PRECIPITATION FORECAST FOR MARCH USED FEBRUARY - APRIL LA NINA COMPOSITES
AS THE STARTING POINT, WHICH INDICATES MEAN DRY CONDITIONS ACROSS THE ENTIRE
SOUTHERN U.S. AND WETTER THAN AVERAGE CONDITIONS IN THE PACIFIC NORTHWEST AND
IN THE OHIO AND TENNESSEE VALLEYS. INDICATIONS IN THE SHORT TERM FAVORED
EXPANDING THE REGION IN THE OHIO AND TENNESSEE VALLEYS INTO PARTS OF THE
NORTHEAST... AND SCALING BACK SOME OF THE DRY IN THE SOUTHEAST. DRIER THAN
AVERAGE CONDITIONS ARE ALSO FAVORED IN SOUTHERN ALASKA... AS INDICATED BY THE
CFS AND THE CCA.
FORECASTER: MIKE HALPERT
NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES).
THE NEXT MONTHLY OUTLOOK...FOR APRIL 2008...WILL BE ISSUED ON THU MAR 20 2008
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD.
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