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Official 90-day Outlooks are issued once each month near mid-month
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PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EDT SAT OCT 31 2009 30-DAY OUTLOOK DISCUSSION FOR NOVEMBER 2009 THE ZERO LEAD TEMPERATURE AND PRECIPITATION OUTLOOKS FOR NOVEMBER ARE BASED PRIMARILY ON HIGH-RESOLUTION NUMERICAL WEATHER PREDICTION MODEL FORECASTS OUT TO DAY 7 AND ENSEMBLE MODEL FORECASTS FOR WEEK 2, INCLUDING THE GFS AND ECMWF MODELS. THE CFS ZERO-LEAD FORECAST FOR NOVEMBER WAS ALSO CONSIDERED, AS WELL AS STATISTICAL SIGNALS RELATED TO ENSO AND DECADAL TRENDS. SEA SURFACE TEMPERATURES IN THE EQUATORIAL PACIFIC HAVE INCREASED IN THE LAST MONTH AND EXCEED 1 DEGREE C FOR THE NINO 3.4 REGION. EL NINO CONDITIONS ARE EXPECTED TO STRENGTHEN AS WINTER APPROACHES. WHILE THE CLIMATE SIGNALS OF THE CURRENT EL NINO ARE EXPECTED TO HAVE SOME IMPACT ON US TEMPERATURES AND PRECIPITATION DURING NOVEMBER, DYNAMICAL GUIDANCE FOR THE FIRST 15 DAYS OF NOVEMBER ARE THE MOST IMPORTANT SOURCE OF INFORMATION FOR THE ZERO LEAD UPDATE. THE EXPECTED NEAR ZONAL FLOW PATTERN OVER THE CONUS FOR THE BEGINNING OF NOVEMBER SHOULD PRODUCE RELATIVELY DRY AND WARM CONDITIONS FOR MOST AREAS OF THE LOWER 48 STATES, WITH THE EXCEPTION OF NORTHERN CALIFORNIA AND THE PACIFIC NORTHWEST AHEAD OF A PREDICTED TROUGH. CHANGES TO THE HALF MONTH LEAD TEMPERATURE FORECAST INCLUDE REMOVAL OF THE AREA OF ENHANCED LIKELIHOOD FOR BELOW NORMAL TEMPERATURES FROM TEXAS AND LOUISIANA DUE TO A FORECAST OF NEAR TO ABOVE NORMAL TEMPERATURES EARLY IN THE MONTH. THE AREA OF INCREASED CHANCES FOR ABOVE NORMAL TEMPERATURES WAS EXTENDED INTO THE GREAT LAKES REGION WITH ABOVE NORMAL HEIGHTS PREDICTED OVER THE CONUS DURING AT LEAST THE FIRST 2 WEEKS OF NOVEMBER. THE PROBABILITY OF ABOVE NORMAL TEMPERATURES IS GREATEST OVER THE NORTHERN CENTRAL US WHERE THE FORECAST IS FOR POSITIVE TEMPERATURE ANOMALIES DURING THE FIRST 2 WEEKS OF NOVEMBER. AN INCREASED CHANCE OF ABOVE NORMAL IN THIS AREA IS ALSO CONSISTENT WITH SIGNALS RELATED TO EL NINO AND DECADAL TRENDS. A SIGNIFICANT CHANGE TO THE PRECIPITATION OUTLOOK FOR NOVEMBER ISSUED EARLIER THIS MONTH IS THE REMOVAL OF THE AREA OF INCREASED LIKELIHOOD OF BELOW NORMAL PRECIPITATION FROM THE PACIFIC NORTHWEST, WHICH IS LIKELY TO RECEIVE SIGNIFICANT PRECIPITATION DURING THE FIRST HALF OF THE MONTH. ABOVE NORMAL PRECIPITATION IS PREDICTED FOR NORTHERN CALIFORNIA AND WESTERN OREGON AND WASHINGTON IN THE EXTENDED RANGE, LEADING TO AN ENHANCED PROBABILITY OF ABOVE NORMAL PRECIPITATION AMOUNTS IN NORTHERN CALIFORNIA FOR NOVEMBER, WHERE PREDICTED PRECIPITATION AMOUNTS ARE A GREATER FRACTION OF NORMAL MONTHLY TOTALS THAN AREAS OF THE PACIFIC NORTHWEST TO THE NORTH. AN AREA OF ENHANCED PROBABILITY FOR BELOW NORMAL PRECIPITATION IN THE SOUTHEAST RESULTS FROM DYNAMICAL MODEL FORECASTS FOR RELATIVELY DRY CONDITIONS DURING THE FIRST HALF OF THE MONTH. THE UPDATED MONTHLY PRECIPITATION FORECAST IS CONSISTENT WITH THE TYPICAL IMPACTS OF EL NINO AND DECADAL TRENDS FOR ABOVE NORMAL PRECIPITATION IN NORTHERN CALIFORNIA, SOUTHERN TEXAS AND SOUTHERN FLORIDA AND BELOW NORMAL PRECIPITATION IN PARTS OF THE SOUTHEAST. THIS FORECAST SUPERSEDES THE ORIGINAL HALF-MONTH LEAD FORECAST FOR NOVEMBER ISSUED OCTOBER 15. FORECASTER: DAN COLLINS NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES). THE NEXT MONTHLY OUTLOOK...FOR DECEMBER 2009...WILL BE ISSUED ON THU NOV 19 2009 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD. $$
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