PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EDT FRI APR 30 2010 30-DAY OUTLOOK DISCUSSION FOR MAY 2010 EL NINO CONDITIONS CONTINUE ACROSS THE EQUATORIAL PACIFIC OCEAN WITH SEA SURFACE TEMPERATURE (SST) DEPARTURES OF +1.0 DEGREE C OR GREATER ACROSS PORTIONS OF THE CENTRAL PACIFIC. OCEAN SUB-SURFACE TEMPERATURE ANOMALIES ALSO REMAIN POSITIVE FROM THE SURFACE TO A DEPTH OF 75 METERS FROM NEAR 160 E EASTWARD ALONG THE EQUATOR TO NEAR THE SOUTH AMERICAN COAST. THEREFORE EL NINO OCEANIC CONDITIONS ARE EXPECTED TO CONTINUE AT LEAST INTO MAY 2010. CURRENT ATMOSPHERIC CONDITIONS CONSISTENT WITH EL NINO IN THE TROPICS HAVE BECOME LESS PRONOUNCED. ENHANCED TROPICAL CONVECTION DURING THE PAST FEW WEEKS HAS BEEN OBSERVED ACROSS THE CENTRAL AND EASTERN TROPICAL PACIFIC, FROM ABOUT 140 E EASTWARD TO NEAR 115 W, BUT THIS EXTENSIVE AREA IS 5 DEGREES NORTH OF THE EQUATOR. ANOMALOUS LOW-LEVEL (850-HPA) WINDS HAVE BEEN WEAK AND SOMEWHAT EASTERLY DURING THE PAST 30 DAYS. BASED ON THE PREVIOUSLY MENTIONED OCEANIC AND ATMOSPHERIC CONDITIONS, EL NINO REMAINS A FACTOR, ALBEIT A WEAKENING ONE, IN THE UPDATED MAY 2010 MONTHLY OUTLOOK FOR THE U.S. BOTH STATISTICAL AND DYNAMICAL FORECAST TOOLS WERE CONSIDERED FOR THE MAY 2010 OUTLOOK. THE ZERO-LEAD UPDATED MONTHLY FORECAST HAS THE ADVANTAGE OF INCORPORATING THE LATEST NWP MODEL GUIDANCE, WHICH EXTENDS THROUGHOUT THE FIRST HALF OF MAY. ENSO COMPOSITES FOR AMJ 2010 (CENTERED ON THE TARGET MONTH OF MAY) WERE ALSO CONSULTED, BUT THEIR APPLICATION IN MAY IS THOUGHT TO BE FAIRLY MINIMAL. THE OFFICIAL UPDATED CPC 30-DAY TEMPERATURE OUTLOOK CALLS FOR ENHANCED CHANCES OF ABOVE-NORMAL MEAN TEMPERATURES FOR THE NORTHWEST, MUCH OF THE DESERT SOUTHWEST, AND ALMOST ALL OF ALASKA. THE OUTLOOK ALSO CALLS FOR ENHANCED CHANCES OF BELOW-NORMAL MEAN TEMPERATURES ACROSS FAR NORTHERN CALIFORNIA AND NORTHWESTERN NEVADA, AS WELL AS OVER MUCH OF THE NORTHERN AND CENTRAL GREAT PLAINS. ELSEWHERE, WHICH INCLUDES A SIZABLE PORTION OF THE CONUS, EQUAL CHANCES (EC) OF BELOW-, NEAR-, AND ABOVE-NORMAL MEAN TEMPERATURES ARE ANTICIPATED. GREATER THAN CLIMATOLOGICAL ODDS FOR ABOVE-NORMAL TEMPERATURES EXPECTED OVER THE PACIFIC NORTHWEST AND NORTHERN ROCKIES ARE BASED ON MOST OF THE AVAILABLE TOOLS, INCLUDING THE CAS AND ENSO COMPOSITES, BUT NOT THE CFS, WHICH IS PREDICTING NEAR TO BELOW-NORMAL TEMPERATURES. FOR THE SOUTHWEST, MOST STATISTICAL TOOLS SUPPORT ABOVE-NORMAL TEMPERATURES, WHILE THE CAS AND CFS ARE PREDICTING NEAR, AND BELOW NORMAL, TEMPERATURES RESPECTIVELY. GIVEN SUCH A STRONG TREND FOR ANOMALOUS WARMTH ACROSS THE SOUTHWEST DURING THE PAST 10 YEARS, IT IS THOUGHT THAT THE CFS COLD SIGNAL IS SIGNIFICANTLY LESS LIKELY TO VERIFY. THE ENHANCED CHANCES OF BELOW-NORMAL MEAN TEMPERATURES EXPECTED OVER NORTHERN CALIFORNIA AND NORTHWESTERN NEVADA IS ATTRIBUTED TO EXPECTED LINGERING EFFECTS OF AN UPPER-LEVEL TROUGH ANTICIPATED DURING AT LEAST THE FIRST HALF OF MAY, AND TO COOLER-THAN-NORMAL SSTS. THE BELOW-NORMAL TEMPERATURES PREDICTED OVER MUCH OF THE NORTHERN AND CENTRAL GREAT PLAINS IS BASED LARGELY ON THE CFS, THE CAS, AND THE WEEK 1 AND WEEK 2 GFS ENSEMBLE TEMPERATURE FORECASTS. IN ALASKA, GREATER THAN CLIMATOLOGICAL ODDS FOR WARMER-THAN-NORMAL MEAN TEMPERATURES ARE FORECAST OVER MOST OF THE STATE, ESPECIALLY SOUTH-CENTRAL ALASKA. THIS IS PRIMARILY BASED ON THE SMLR, CCA, AND OCN TOOLS, AND THE WARM SIGNAL FOR SOUTH-CENTRAL ALASKA ALSO PASSES THROUGH THE CFS SKILL MASK. THE UPDATED PRECIPITATION OUTLOOK FOR MAY 2010 CALLS FOR ELEVATED CHANCES OF ABOVE-MEDIAN PRECIPITATION OVER THE OHIO AND TENNESSEE VALLEYS, PORTIONS OF THE LOWER MISSISSIPPI VALLEY, THE CENTRAL GULF COAST STATES, AND THE CENTRAL AND SOUTHERN APPALACHIANS. THE HIGHEST PROBABILITIES FOR ABOVE-MEDIAN RAINFALL ARE OVER THE LOWER TENNESSEE VALLEY AND SURROUNDING AREAS, WHERE DYNAMICAL MODEL GUIDANCE SUGGESTS 5 TO 8 INCHES OF RAIN COULD FALL DURING THE FIRST FIVE DAYS OF MAY. THE SKILL-MASKED CFS AND THE CAS BOTH SUPPORT THIS CORE WET AREA. THE THREE TRADITIONAL STATISTICAL TOOLS (SMLR, CCA, AND OCN) GIVE WEAK AND CONFLICTING PRECIPITATION SIGNALS NOT ONLY OVER THIS REGION, BUT OVER MOST OF THE COUNTRY. THERE ARE ELEVATED CHANCES OF DRIER-THAN-MEDIAN RAINFALL OVER MOST OF FLORIDA, EASTERN PORTIONS OF BOTH GEORGIA AND THE CAROLINAS, AND ALSO OVER THE TEXAS PORTION OF THE RIO GRANDE VALLEY. THE SKILL-MASKED CFS TOOL LENDS SUPPORT FOR BOTH AREAS, AS DOES THE LATEST WEEK 2 PRECIPITATION OUTLOOK, WHEREAS THE CAS FAVORS THE DRIER-THAN-MEDIAN AREA ONLY OVER THE SOUTHEAST U.S. FORECASTER: ANTHONY ARTUSA NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES). THE NEXT MONTHLY OUTLOOK...FOR JUNE 2010...WILL BE ISSUED ON THU MAY 20 2010 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD. $$