PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EST THU MAR 31 2005 30-DAY UPDATED OUTLOOK DISCUSSION FOR APRIL 2005 . SST ANOMALIES ALONG THE EQUATOR IN THE PACIFIC HAVE DECREASED SINCE THE BEGINNING OF THE YEAR... WITH DEPARTURES MORE THAN 1 DEGREE C ABOVE NORMAL OBSERVED MAINLY BETWEEN 165E AND 170W BY THE END OF MARCH. ANOMALIES MORE THAN 0.5 DEGREE C ABOVE NORMAL WERE OBSERVED FROM 140E TO 120W. EQUATORIAL SSTS WERE GENERALLY BELOW NORMAL FROM 120W TO THE SOUTH AMERICAN COAST. SINCE THE BEGINNING OF THE YEAR THE ENSO INDICES HAVE DECREASED ACROSS THE PACIFIC... BECOMING NEGATIVE IN NINO 3 BY THE MIDDLE OF FEBRUARY. THE INDEX VALUE IN NINO 3.4 DECREASED TO ITS SMALLEST VALUE SINCE LAST JULY BY EARLY MARCH BEFORE INCREASING TO 0.5 BY THE MIDDLE AND END OF MARCH. THE NINO 4 INDEX VALUE HAS REMAINED MORE THAN 0.5 DEGREES ABOVE NORMAL THROUGH THE END OF MARCH. CONVECTIVE ACTIVITY INCREASED OVER THE WEST CENTRAL PACIFIC AND PERSISTED DURING FEBRUARY AND EARLY MARCH. THIS ENHANCED CONVECTION CONTRIBUTED TO AN EASTWARD EXTENSTION OF THE PACIFIC JET STREAM DURING THE MIDDLE AND LATTER PART OF FEBRUARY. HOWEVER CONVECTION SHIFTED WEST AND WEAKENED DURING EARLY MARCH AND THE JET STREAM ACROSS THE PACFIC BECAME MORE VARIABLE. SINCE EXPECTATIONS ARE THAT THIS ENSO EPISODE WILL CONTINUE TO WEAKEN... ENSO IS NOT EXPECTED TO INFLUENCE THE CLIMATE DURING APRIL OVER NORTH AMERICA. THE TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON A SUBJECTIVE BLEND OF THE MONTHLY STATISTICAL TOOLS AND MODEL FORECASTS COMBINED WITH SHORT TERM GUIDANCE FROM DYNAMICAL MODELS COVERING THE FIRST TWO WEEKS OF THE MONTH. THE UPDATED TEMPERATURE OUTLOOK SHOWS A LARGER AREAL COVERAGE OF ABOVE NORMAL TEMPERATURES ACROSS THE NORTHERN PLAINS AND A SHIFT TO EQUAL CHANCES IN THE EXTREME PACIFIC NORTHWEST. INDICATIONS FOR THE FIRST COUPLE OF WEEKS OF APRIL SHOW TROUGHING IN THE PACIFIC NORTHWEST AND RIDGING EXTENDING FROM CANADA ACROSS THE NORTHERN PLAINS. THE REMAINDER OF THE FORECAST OVER THE CONUS IS SIMILAR TO THE 0.5 MONTH LEAD... WITH THE STATISTICAL TOOLS FAVORING ABOVE NORMAL TEMPERATURES IN THE WEST AND THE DYNAMICAL MODELS ALSO FORECASTING ABOVE NORMAL TEMPERATURES ACROSS THE NORTHERN PLAINS AND BELOW NORMAL TEMPERATURES IN TEXAS AND FLORIDA. BELOW NORMAL SSTS CONTINUE TO SURROUND FLORIDA... WHICH ALSO FAVORS BELOW NORMAL TEMPERATURES IN THIS STATE. THE LARGEST CHANGES IN THE UPDATED FORECAST ARE OVER ALASKA... WHERE THE FORECAST OF ABOVE NORMAL TEMPERATURES IN THE PANHANDLE AND SOUTHEASTERN ALASKA HAS BEEN REPLACED BY EC... AS THE GUIDANCE FOR THE FIRST TWO WEEKS OF THE MONTH INDICATES BELOW NORMAL TEMPERATURES ACROSS THE ENTIRE STATE. WITH STRONG TRENDS AFFECTING MUCH OF THE STATE... THIS FORECAST HAS BEEN CHANGED TO EQUAL CHANCES FOR MUCH OF STATE... WITH BELOW NORMAL TEMPERATURES FORECAST IN WESTERN ALASKA. THE UPDATED PRECIPITATION OUTLOOK FOR APRIL HAS FORECASTS OF ABOVE NORMAL PRECIPTATION IN THE PACIFIC NORTHWEST... ALONG THE EAST COAST... AND OVER THE NORTHERN PLAINS. THE NORTHERN PLAINS REGION IS A HOLDOVER FROM THE 0.5 MONTH LEAD OUTLOOK AND ALSO HAS SUPPORT IN THE WEEK-1 AND 6-10 DAY PERIODS. THE EXPECTED CIRCULATION PATTERN OVER NORTH AMERICA DURING THE FIRST HALF OF THE MONTH FAVORS ABOVE NORMAL PRECIPITATION IN THE PACIFIC NORTHWEST. A VERY WET SYSTEM IN THE FIRST FEW DAYS OF THE MONTH ALONG THE EAST COAST COMBINED WITH A CONTINUED OUTLOOK FOR ABOVE NORMAL RAINFALL IN THE 6-10 AND 8-14 DAY RANGES IN THE MID-ATLANTIC AND NORTHEAST RESULTED IN THE INCLUSION OF THE ABOVE NORMAL AREA ALONG THE EAST COAST... WITH THE HIGHEST PROBABILITIES OVER THE NORTHEAST. FORECASTER: M. HALPERT NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILTIES) ARE NOW LABELED EC (EQUAL CHANCES). NOTE - THE NEXT 0.5 MONTH LEAD-TIME MONTHLY OUTLOOK WILL BE ISSUED THU APR 21 2005. THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD. $$