PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 
830 AM EDT THU OCT 18 2007 
 
30-DAY OUTLOOK DISCUSSION FOR NOVEMBER 2007 
 
LA NINA CONDITIONS STRENGTHENED DURING SEPTEMBER 2007, AS NEGATIVE SST 
ANOMALIES ALONG THE EQUATOR EXPANDED WESTWARD AND NOW EXTEND FROM 170E TO THE 
SOUTH AMERICAN COAST. THE LATEST WEEKLY ANALYSIS SHOWS THE LARGEST SST 
DEPARTURES (-2C TO -3C) BETWEEN 120W AND THE COAST, WITH DEPARTURES OF -0.5C TO 
-1C CENTERED NEAR THE DATE LINE. THE MAGNITUDE OF THE NEGATIVE SST ANOMALIES 
INCREASED IN ALL OF THE NINO REGIONS, WITH THE NINO-3.4 INDEX DROPPING TO -1.2C 
AND THE NINO-4 INDEX DROPPING TO -0.5C BY THE END OF THE MONTH. THE UPPER-OCEAN 
HEAT CONTENT (AVERAGE TEMPERATURES IN THE UPPER 300 M OF THE OCEAN) IN THE 
CENTRAL AND EAST-CENTRAL EQUATORIAL PACIFIC REMAINED BELOW AVERAGE DURING 
SEPTEMBER, WITH TEMPERATURES RANGING FROM 2C TO 4C BELOW AVERAGE AT THERMOCLINE 
DEPTH. CONSISTENT WITH THESE CONDITIONS, THE LOW-LEVEL EASTERLY WINDS AND 
UPPER-LEVEL WESTERLY WINDS REMAINED STRONGER THAN AVERAGE ACROSS THE CENTRAL 
EQUATORIAL PACIFIC, CONVECTION REMAINED SUPPRESSED THROUGHOUT THE CENTRAL AND 
EASTERN EQUATORIAL PACIFIC, AND ENHANCED CONVECTION AGAIN COVERED PARTS OF 
INDONESIA AND THE FAR WESTERN PACIFIC. COLLECTIVELY, THESE OCEANIC AND 
ATMOSPHERIC CONDITIONS REFLECT A STRENGTHENING LA NINA. 
 
SINCE LA NINA IS EXPECTED DURING NOVEMBER, COMPOSITES FROM PAST LA NINAS HAVE 
BEEN USED EXTENSIVELY IN THIS FORECAST.  U.S. LA NINA IMPACTS OFTEN INCLUDE 
RELATIVE DRYNESS IN THE SOUTH AND HEAVIER THAN MEDIAN RAINFALL IN THE 
NORTHWEST, ALONG WITH WARMER THAN NORMAL CONDITIONS OVER MUCH OF THE CONUS, AND 
COLDER THAN NORMAL TEMPERATURES IN ALASKA.  THE COMPOSITES INDICATE A TENDENCY 
TOWARD SUB-NORMAL TEMPERATURES EAST OF THE MISSISSIPPI AND SOUTH OF THE GREAT 
LAKES AND NEW ENGLAND, DURING NOVEMBER, BUT A WARM TREND MAKES COLD LESS 
LIKELY, AND THE REGION HAS BEEN DESIGNATED AS HAVING EQUAL CHANCES OF BEING IN 
ANY ONE OF THE TERCILES. 
 
ABOVE NORMAL AVERAGE TEMPERATURES ARE EXPECTED FROM TEXAS TO THE NORTHWEST, 
ACROSS THE CENTRAL AND SOUTHERN ROCKIES, THE CENTRAL AND SOUTHERN GREAT PLAINS, 
THE GREAT LAKES AND NEW ENGLAND.  BELOW-NORMAL TEMPERATURES ARE EXPECTED IN 
SECTIONS OF ALASKA. 
 
THERE IS WEAK, BUT CONSISTENT AGREEMENT AMONG THE TRADITIONAL STATISTICAL TOOLS 
ON ABOVE-MEDIAN PRECIPITATION IN THE NORTHWEST AND BELOW-MEDIAN IN THE SOUTH, 
WITH THE EXCEPTION OF THE OCN, WHICH SHOULD NOT BE EXPECTED TO GIVE LA NINA 
INDICATIONS.  THE CFS, INDICATES BELOW-MEDIAN PRECIPITATION IN THE NORTHWEST, 
WHERE IT HAS NO SKILL, BUT BELOW-MEDIAN IN THE SOUTH, WHERE POSITIVE SKILL 
EXISTS.  CCA AND SMLR ARE AT ODDS IN ALASKA.  COMPOSITES INDICATE A SLIGHT 
PREFERENCE FOR BELOW-MEDIAN PRECIPITATION THERE, AND THAT IS WHAT WAS 
PREDICTED.  ABOVE-MEDIAN PRECIPITATION IS PREDICTED IN THE NORTHWEST. 
BELOW-MEDIAN PRECIPITATION IS ALSO PREDICTED FOR EASTERN SECTIONS OF THE 
SOUTHWEST, SOUTHERN TEXAS, LOUISIANA, THE GULF COAST STATES, AND FOR ATLANTIC 
COAST STATES FROM FLORIDA TO SOUTHERN NEW JERSEY. 
 
 
FORECASTER: ED O'LENIC 
 
NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES). 
 
AN UPDATED MONTHLY OUTLOOK... FOR NOV WILL BE ISSUED ON WED OCTOBER 31 2007 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD. 
 
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