421
FXUS07 KWBC 311901
PMD30D
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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