PROGNOSTIC DISCUSSION FOR REVISED MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EDT SAT MAY 31 2008

30-DAY OUTLOOK DISCUSSION FOR JUNE 2008

SEA SURFACE TEMPERATURES (SST) ALONG THE EQUATOR IN THE EAST CENTRAL PACIFIC OCEAN 
REMAIN BELOW NORMAL BUT THE MAGNITUDE OF THE ANOMALIES HAVE SLOWLY DIMINISHED IN 
THE LAST TWO WEEKS.  SST ANOMALIES IN THE NINO 3.4 REGION (BETWEEN 5 N AND 5 S, 
AND 170W AND 120W) WERE ABOUT .8 DEGREES C BELOW NORMAL IN MID-MAY, AND NOW ARE 
AROUND -.4 C.  THE ATMOSPHERIC CIRCULATION THROUGHOUT THE TROPICAL PACIFIC OCEAN 
CONTINUES TO REFLECT LA NINA CONDITIONS, WITH ENHANCED LOW LEVEL EASTERLIES ALONG 
THE EQUATOR, AND SUPPRESSED CONVECTION IN THE CENTRAL EQUATORIAL PACIFIC.  MOST 
NUMERICAL AND STATISTICAL MODELS CONTINUE TO WEAKEN SST ANOMALIES IN THE NINO 3.4 
REGION OVER THE NEXT FEW MONTHS.  THE LATEST CFS MODEL FORECAST SHOWS RAPID 
WEAKENING OF THE SST ANOMALIES... HOWEVER THE MJO IS CURRENTLY ACTIVE AND MAY 
INFLUENCE THE CFS FORECASTS AS WELL AS PRODUCE SUBSTANTIAL SHORT TERM FLUCTUATIONS 
IN WEEKLY MEAN SSTS THE NEAR FUTURE.  THE MONTHLY MEAN SST ANOMALY IN THE NINO 3.4 
REGION IS EXPECTED TO REMAIN NEGATIVE, BUT BE SMALLER THAN IN MAY.  THUS LA NINA 
IS EXPECTED TO HAVE NEGLIGIBLE IMPACT ON U.S. TEMPERATURES AND PRECIPITATION IN 
JUNE.

SSTS ALONG THE WESTERN COAST OF NORTH AMERICA ARE BELOW NORMAL AND ARE EXPECTED TO 
FAVOR BELOW NORMAL AIR TEMPERATURES ALONG IMMEDIATE COASTAL AREAS FROM THE SOUTH 
COAST OF ALASKA TO SOUTHERN CALIFORNIA.  THE CFS, CCA, AND OCN INDICATE ABOVE 
NORMAL TEMPERATURES IN THE SOUTHWESTERN U.S. AND THE GREAT BASIN. THE CFS 
CONTINUES TO SUGGEST ELEVATED CHANCES OF A LONG WAVE UPPER LEVEL RIDGE JUST OFF 
THE WEST COAST WITH A TROUGH IN THE EAST AS IT DID IN ITS MID-MAY RUNS... HOWEVER 
SHORT TERM FORECASTS SUGGEST THAT THE MEAN TROUGH WILL BE FARTHER WEST THAN THE 
CFS INDICATES... INCREASING THE CHANCES FOR BELOW NORMAL MONTHLY MEAN TEMPERATURES 
FROM THE THE PACIFIC NORTHWEST TO THE NORTHERN GREAT PLAINS... AND SUBSTANTIALLY 
DECREASING THE CHANCES OF ABOVE NORMAL TEMPERATURES IN THE GREAT BASIN FROM THE 
FORECAST RELEASED IN MID-MAY.  ABOVE NORMAL TEMPERATURES ARE EXPECTED FOR PORTIONS 
OF THE SOUTHERN GREAT BASIN AND SOUTHWESTERN STATES DUE PRIMARILY TO TRENDS.  MEAN 
UPPER LEVEL HEIGHTS OVER THE EASTERN U.S. ARE EXPECTED TO BE ABOVE NORMAL IN THE 
FIRST HALF OF JUNE... AND THIS WILL INCREASE THE ODDS OF THE MONTHLY MEAN 
TEMPERATURES FINISHING THE MONTH IN THE ABOVE NORMAL CATEGORY IN NEW ENGLAND AND 
PARTS OF THE MID-ATLANTIC STATES.  SOIL MOISTURE IS MUCH ABOVE NORMAL FROM THE 
MIDDLE-MISSISSIPPI VALLEY TO THE OHIO RIVER VALLEY, WHICH FAVORS BELOW NORMAL 
TEMPERATURES DUE TO INCREASED EVAPORATIVE COOLING... HOWEVER THE AREA OF 
ANTICIPATED BELOW NORMAL TEMPERATURES WAS SHIFTED NORTHWESTWARD FROM THE OUTLOOK 
RELEASED IN MID-MAY DUE TO SHORT TERM FORECASTS OF A WARM START TO THE MONTH IN 
PARTS OF THE EASTERN CONUS.  

LOCAL SOIL MOISTURE CONDITIONS ARE ASSOCIATED WITH INCREASED CHANCES FOR ABOVE 
MEDIAN RAINFALL FOR THE MIDDLE MISSISSIPPI AND PORTIONS OF THE OHIO RIVER VALLEYS.  
THIS IS SUPPORTED BY SHORT TERM FORECASTS OF ABOVE MEDIAN PRECIPITATION IN THE
AREA.  DRY CONDITIONS ARE FORECAST IN PARTS OF THE WEST BY THE CFS MODEL AND THE 
CAS SOIL MOISTURE ANALOG TOOL.   HOWEVER WITH A MEAN UPPER LEVEL TROUGH EXPECTED 
OVER THE NORTHERN ROCKIES EARLY IN THE MONTH, PRECIPITATION CHANCES ARE EXPECTED 
TO BE HIGH ENOUGH TO COUNTERACT DRY SIGNALS FROM THESE MODELS OVER THE NORTHERN 
ROCKIES AND THE PACIFIC NORTHWEST, SO THE AREA OF EXPECTED DRY CONDITIONS WAS 
TRIMMED BACK ON THIS OUTLOOK FROM THE EARLIER MONTHLY OUTLOOK.  SHORT TERM 
FORECAST SHOW INCREASED CHANCES OF SIGNIFICANT PRECIPITATION FROM THE NORTHERN 
PLAINS TO THE UPPER MISSISSIPPI VALLEY... SO THE REGION OF EXPECTED ABOVE MEDIAN 
RAINFALL WAS EXTENDED NORTHWESTWARD FROM THE AREA INDICATED IN THE JUNE OUTLOOK 
ISSUED TWO WEEKS AGO.   

FORECASTER: DAVID UNGER

NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES).

THE NEXT MONTHLY OUTLOOK...FOR JULY 2008...WILL BE ISSUED ON THU JUN 19 2008

THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD.

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