PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 
830 AM EDT THU AUG 20 2009 
 
30-DAY OUTLOOK DISCUSSION FOR SEPTEMBER 2009 
 
A WEAK EL NINO WAS PRESENT DURING JULY 2009, AS MONTHLY SEA SURFACE 
TEMPERATURES (SST) DEPARTURES RANGED FROM +0.5C TO +1.5C ACROSS THE EQUATORIAL 
PACIFIC OCEAN, WITH THE LARGEST ANOMALIES IN THE EASTERN HALF OF THE BASIN. 
CONSISTENT WITH THIS WARMTH, ALL OF THE NIñO-REGION SST INDICES WERE 
BETWEEN +0.6C TO +1.0C THROUGHOUT THE MONTH. SUBSURFACE OCEANIC HEAT CONTENT 
ANOMALIES CONTINUED TO REFLECT A DEEP LAYER OF ANOMALOUS WARMTH BETWEEN THE 
OCEAN SURFACE AND THERMOCLINE. ALSO, CONVECTION WAS SUPPRESSED OVER INDONESIA 
AND ENHANCED ACROSS THE WESTERN PACIFIC AND NEAR THE INTERNATIONAL DATE LINE. 
HOWEVER, IMPACTS ACROSS THE UNITED STATES FROM EL NINO ARE TYPICALLY WEAK 
DURING SEPTEMBER, SO ENSO COMPOSITES WERE NOT CONSIDERED FOR THIS FORECAST. 
 
THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR SEPTEMBER HAVE BEEN CONSTRUCTED 
PRIMARILY USING LONG LEAD MONTHLY STATISTICAL TOOLS, INCLUDING THE OCN TREND, 
CCA AND SMLR; LOCAL SSTS ALONG COASTAL AREAS; AND THE CFS COUPLED 
OCEAN-ATMOSPHERE DYNAMICAL MODEL MONTHLY TEMPERATURE AND PRECIPITATION 
PREDICTIONS.  THE ZERO LEAD MONTHLY UPDATE ON AUGUST 31, 2009 WILL INCORPORATE 
INFORMATION FROM THE SHORT RANGE NUMERICAL WEATHER PREDICTION MODELS AND THE 
LATEST CFS MONTHLY PREDICTIONS. 
 
SST ANOMALIES NEAR THE US WEST COAST ARE GENERALLY NORMAL FROM SOUTHERN 
CALIFORNIA NORTH TO WASHINGTON, AND ALONG MOST OF ALASKA'S SOUTH COASTS.  SST 
DEPARTURES ARE ABOVE AVERAGE ALONG THE WESTERN AND NORTHERN ALASKAN COASTS. 
SSTS ARE ABOVE AVERAGE IN THE GULF OF MEXICO AND ALSO ALONG THE EAST COAST FROM 
THE MID-ATLANTIC NORTHWARD. 
 
THE SEPTEMBER MONTHLY TEMPERATURE OUTLOOK FAVORS ABOVE AVERAGE MONTHLY MEAN 
TEMPERATURES IN MUCH OF THE SOUTHWESTERN US FROM SOUTHERN AND WESTERN TEXAS 
EXTENDING NORTHWEST TO SOUTHEASTERN OREGON AND SOUTHERN IDAHO.  SUPPORT FOR 
THIS FORECAST IS DERIVED FROM THE TEMPERATURE TRENDS FROM THE OCN, WITH SUPPORT 
FROM THE SMLR AND CCA FOR PARTS OF THE SOUTHWEST.  CURRENT DROUGHT CONDITIONS 
OVER SOUTHERN TEXAS ALSO INCREASE THE PROBABILITIES FOR ABOVE AVERAGE 
TEMPERATURES IN THIS AREA. INCREASED PROBABILITIES OF ABOVE AVERAGE MONTHLY 
TEMPERATURES ARE ALSO INDICATED FOR THE SOUTHERN HALF OF FLORIDA WITH SUPPORT 
MAINLY COMING FROM THE OCN. THE INCREASED PROBABILITY OF ABOVE NORMAL 
TEMPERATURES FOR NORTHWESTERN REGIONS OF ALASKA IS RELATED TO THE TEMPERATURE 
TREND, INDICATED IN THE OCN AND CCA, AS WELL AS WARMER COASTAL WATERS IN THAT 
REGION. ELSEWHERE, THERE ARE NO CONSISTENT SIGNALS FOR EITHER ABOVE OR BELOW 
AVERAGE MONTHLY MEAN TEMPERATURES. 
 
THE INCREASED VARIABILITY AND LOW PREDICTABILITY OF PRECIPITATION DURING THE 
WARM SEASON RESULTS IN LIMITED COVERAGE IN THE SEPTEMBER PRECIPITATION OUTLOOK. 
 AN INCREASED PROBABILITY OF MONTHLY PRECIPITATION AMOUNTS IN THE BELOW MEDIAN 
TERCILE IS FORECAST FOR A SMALL REGION IN THE PACIFIC NORTHWEST.  THIS FORECAST 
IS SUPPORTED PRIMARILY BY THE OCN PRECIPITATION TREND.  A GREATER LIKELIHOOD OF 
ABOVE MEDIAN PRECIPITATION AMOUNTS FOR SEPTEMBER IS FORECAST FOR THE FLORIDA 
PENINSULA, SUPPORTED BY THE OCN PRECIPITATION TREND.  ELSEWHERE, THERE ARE NO 
CONSISTENT SIGNALS FOR EITHER ABOVE OR BELOW MEDIAN MONTHLY TOTAL 
PRECIPITATION. 
 
FORECASTER: MIKE HALPERT 
 
NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES). 
 
AN UPDATED MONTHLY OUTLOOK... FOR SEP WILL BE ISSUED ON MON AUGUST 31 2009 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD. 
 
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