581
FXUS07 KWBC 171359
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EDT THU APR 17 2008
30-DAY OUTLOOK DISCUSSION FOR MAY 2008
MODERATE LA NINA CONDITIONS CONTINUE THROUGHOUT THE TROPICAL PACIFIC. BELOW
AVERAGE SEA SURFACE TEMPERATURES (SSTS) ARE OBSERVED ACROSS THE CENTRAL AND
EAST-CENTRAL EQUATORIAL PACIFIC. SSTS MORE THAN 1 DEGREE CENTIGRADE BELOW
AVERAGE WERE OBSERVED BETWEEN 160E AND 120W. THE LATEST WEEKLY NINO 3.4 REGION
INDEX VALUE IS NOW -0.9 DEGREES C WHICH REPRESENTS A WEAKENING OF THE NEGATIVE
DEPARTURES FROM TWO WEEKS AGO BY 0.1 DEGREES. THE UPPER-OCEAN HEAT CONTENT
CONTINUED TO RISE AS WELL, THOUGH ANOMALIES ARE STILL NEGATIVE EAST OF THE DATE
LINE. LOW LEVEL EQUATORIAL EASTERLY WINDS CONTINUE TO BE STRONGER THAN AVERAGE
ACROSS THE CENTRAL EQUATORIAL PACIFIC... STRONGER THAN AVERAGE UPPER LEVEL
WESTERLY WINDS ALSO CONTINUE, AND CONVECTION HAS BEEN SUPPRESSED OVER THE
CENTRAL PACIFIC. COLLECTIVELY, THESE ATMOSPHERIC AND OCEANIC CONDITIONS ARE
SIMILAR TO THOSE ACCOMPANYING THE LAST STRONG LA NINA EPISODE IN 1998-2000.
SST FORECASTS FROM THE CFS AND A SUITE OF OTHER STATISTICAL AND DYNAMICAL
MODELS INDICATE THAT LA NINA SHOULD REMAIN MODERATELY STRONG THROUGH BOREAL
SPRING. THEREFORE, THE MAY TEMPERATURE AND PRECIPITATION FORECASTS ARE STILL
BASED TO A SIGNIFICANT DEGREE ON LA NINA COMPOSITES FOR THE APRIL - MAY - JUNE
SEASON.
INTRASEASONAL (MJO) ACTIVITY WAS RATHER PERSISTENT THROUGH MARCH, BUT IS
CURRENTLY AT NEGLIGIBLE LEVELS. VARIOUS MODEL FORECASTS ARE INDICATING
INCREASING UNCERTAINTY REGARDING THIS MJO, ESPECIALLY DURING THE TWO TO THREE
WEEK TIME FRAME. THEREFORE, THE MJO DOES NOT HAVE A SIGNIFICANT INFLUENCE ON
THIS MONTHLY FORECAST.
THE TEMPERATURE OUTLOOK FOR MAY FAVORS ABOVE AVERAGE TEMPERATURES IN SOUTHERN
SECTIONS OF NEVADA AND UTAH, ARIZONA, NEW MEXICO, AND SECTIONS OF WEST TEXAS.
BELOW-AVERAGE TEMPERATURES ARE MOST LIKELY FROM SOUTHERN SECTIONS OF THE ALASKA
PANHANDLE THROUGH THE PACIFIC NORTHWEST. CFS, SMLR, CCA AND LA NINA COMPOSITES
CONTRIBUTE TO THIS FORECAST PATTERN. ELSEWHERE, EQUAL CHANCES OF BELOW-,
NEAR-, AND ABOVE NORMAL TEMPERATURE ARE FORECAST.
THE PRECIPITATION FORECAST FOR MAY CALLS FOR ABOVE-MEDIAN PRECIPITATION IN
NORTHERN ALASKA, BASED ON THE CFS, SMLR, CCA AND OCN. ABOVE-MEDIAN RAINFALL IS
ALSO EXPECTED FOR THE GREAT LAKES, WISCONSIN, MINNESOTA, AND CENTRAL AND
EASTERN SECTIONS OF NORTH DAKOTA, BASED ON THE CFS, AND ON WEAK INDICATIONS
FROM OTHER STATISTICAL TOOLS. SUB-MEDIAN RAINFALL IS EXPECTED FOR THE
SOUTHWEST, CENTRAL AND SOUTHERN SECTIONS OF TEXAS, WESTERN SECTIONS OF
OKLAHOMA, KANSAS, AND NEBRASKA, AND EASTERN SECTIONS OF COLORADO, BASED ON THE
CFS, CCA AND LA NINA COMPOSITES. ELSEWHERE, EQUAL CHANCES OF BELOW-, NEAR-,
AND ABOVE NORMAL PRECIPITATION ARE FORECAST.
FORECASTER: ED O'LENIC
NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES).
AN UPDATED MONTHLY OUTLOOK... FOR MAY WILL BE ISSUED ON WED APRIL 30 2008
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD.
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