018
FXUS07 KWBC 211243
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EDT THU AUG 21 2008
30-DAY OUTLOOK DISCUSSION FOR SEPTEMBER 2008
ENSO-NEUTRAL CONDITIONS CONTINUED DURING JULY 2008, AS SEA SURFACE TEMPERATURES
(SSTS) IN THE CENTRAL EQUATORIAL PACIFIC OCEAN REMAINED NEAR-AVERAGE. SSTS IN
THE EASTERN PACIFIC ARE ABOVE AVERAGE... BUT THE ACTUAL SSTS ARE NOT WARM
ENOUGH TO SUPPORT CONVECTION. THE ATMOSPHERIC CIRCULATION OVER THE WESTERN AND
CENTRAL TROPICAL PACIFIC CONTINUES TO REFLECT SOME ASPECTS OF LA NINA. ENHANCED
LOW-LEVEL EASTERLY WINDS AND UPPER-LEVEL WESTERLY WINDS PERSIST IN THIS REGION,
WHILE CONVECTION REMAINS GENERALLY SUPPRESSED OVER THE CENTRAL PACIFIC. THE
CONSOLIDATION OF NUMERICAL AND STATISTICAL NINO 3.4 FORECASTS INDICATES ENSO
NEUTRAL CONDITIONS THROUGH THE NORTHERN HEMISPHERE FALL. THE JUST CONCLUDED LA
NINA IS NOT EXPECTED TO HAVE ANY IMPACTS ON U.S. TEMPERATURE OR PRECIPITATION
DURING SEPTEMBER.
BELOW NORMAL SST ANOMALIES ALONG THE PACIFIC COAST OF NORTH AMERICA FROM OREGON
TO ALASKA TILT THE ODDS TOWARD BELOW AVERAGE AIR TEMPERATURES FOR THE COASTAL
AREAS FROM THE SOUTHERN COAST OF ALASKA TO WESTERN WASHINGTON AND OREGON. AN
ENHANCED PROBABILITY OF ABOVE NORMAL TEMPERATURES IS FORECAST FOR THE
SOUTHWESTERN U.S. THIS IS DUE MOSTLY TO LATE SUMMER-EARLY FALL TEMPERATURE
TRENDS IN THESE REGIONS AS INDICATED IN THE CAS AND OCN TOOLS.
LITTLE DEFINITIVE GUIDANCE IS PROVIDED BY THE TRADITIONAL STATISTICAL TOOLS FOR
THE SEPTEMBER PRECIPITATION FORECAST WITH THE EXCEPTION OF A LARGE PART OF THE
PACIFIC NORTHWEST... WHERE THE OCN FAVORS BELOW NORMAL PRECIPITATION. IN
ADDITION, THE EXPECTED ACTIVE HURRICANE SEASON INCREASES THE PROBABILITY OF
ABOVE MEDIAN PRECIPITATION ALONG BOTH THE GULF COAST AND THE SOUTH ATLANTIC
COAST DURING THE MONTH.
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 SUN AUGUST 31 2008
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD.
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