PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EDT THU APR 15 2004

30-DAY OUTLOOK DISCUSSION FOR MAY 2004
                                                                               .
SST ANOMALIES CURRENTLY AVERAGE WITHIN .5 DEGREE C OF NORMAL IN THE EASTERN AND 
CENTRAL EQUATORIAL PACIFIC OCEAN... AND CLOSER TO AROUND PLUS 0.5 DEGREE C 
NEAR AND JUST WEST OF THE DATE LINE.  THE VARIOUS STATISTICAL AND NUMERICAL 
MODELS FOR EQUATORIAL PACIFIC SSTS ARE MOSTLY PREDICTING THE TEMPERATURES TO 
REMAIN WITHING THE ENSO-NEUTRAL RANGE... ALTHOUGH A FEW OF THE RECENTLY 
INITIALIZED RUNS ARE SUGGESTING THAT SST ANOMALIES COULD BRIEFLY REACH WEAK EL 
NINO LEVELS BY EARLY SUMMER...  BUT PROBABLY NOT REMAIN THERE FOR LONG.  THE 
CONSENSUS OPINION IS THAT SST ANOMALIES WILL REMAIN WITHIN THE NEUTRAL ENSO 
RANGE IN MAY.  NO IMPACTS OF ENSO ON THE U.S. CLIMATE ARE EXPECTED DURING MAY.  

WITH LITTLE FORCING FROM EQUATORIAL SSTS - ENSO-NEUTRAL CONDITIONS - THIS 
MONTHS NUMERICAL CLIMATE PREDICTION MODELS HAVE CONSIDERABLE SPREAD IN THEIR 
SOLUTIONS AND THEIR RELIABILITY IS NOT EXPECTED TO BE VERY HIGH.  THEREFORE THE 
ANOMALY PATTERNS PREDICTED BY SOME OF THE MODELS WITH BETTER TRACK RECORDS ARE 
REFLECTED ONLY WHERE THERE IS SUPPORT FROM OTHER TOOLS.  THE TEMPERATURE 
FORECAST FOR MAY IS BASED PRIMARILY ON LONG-TERM TRENDS AS REFLECTED IN THE OCN 
TOOL... THE CCA TOOL BASED ON RECENT OBSERVED SEASONAL MEAN PATTERNS OF 
ATMOSPHERIC AND SURFACE PARAMETERS... AND NOW THAT WE ARE ENTERING THE WARM 
SEASON... THE CAS CONSTRUCTED ANALOG SOIL MOISTURE TOOL BASED ON THE LATEST 
AVAILABLE OBSERVATIONS.  THIS LATTER TOOL WAS THE PRIMARY DETERMINANT OF THE 
PRECIPITATION FORECAST FOR MAY... AS OCN AND CCA HAD FEW RELIABLE SIGNALS.

ABOVE NORMAL TEMPERATURES OVER THE SOUTHWEST AND GREAT BASIN ARE PREDICTED ON 
THE BASIS OF CCA AND OCN... WITH CAS ENCOURAGING THE EXTENSION OF THE AREA OF 
FORECAST WARMTH FARTHER NORTH IN THE GREAT BASIN AND TO THE WESTERN SLOPES OF 
THE ROCKIES THAN CCA AND OCN ALONE WOULD INDICATE.  RECENT ABNORMALLY HEAVY 
PRECIPITATION AND A CAS FORECAST OF BELOW NORMAL TEMPERATURES OVER THE RIO 
GRANDE BASIN IS THE REASON FOR THE BREAK IN THE AREA OF FORECAST 
ABOVE NORMAL TEMPERATURES IN THAT REGION... WHERE CCA AND OCN HAVE SOME OF 
THEIR STRONGEST AND MOST SIGNIFICANT SIGNALS FOR WARMTH.  

THE AREA OF ABOVE NORMAL TEMPERATURES FORECAST OVER THE LOWER MISSISSIPI VALLEY 
AND THE TENNESSEE AND OHIO VALLEYS IS DUE PRIMARILY TO CAS... WITH SOME SUPPORT 
FROM OCN NEAR THE GULF COAST AND FROM ONE OF THE BETTER MODELS OVER THE OHIO 
VALLEY.  RECENT VERY HEAVY RAINS OVER FLORIDA... ALONG WITH SIGNIFICANTLY BELOW 
NORMAL SSTS ESPECIALLY EAST OF THE STATE... ARE THE REASONS THAT ALL BUT THE 
EXTREME SOUTHERN TIP OF THE FLORIDA PENINSULA WAS GIVEN A FORECAST OF EC THIS 
TIME.  BELOW NORMAL TEMPERATURES INDICATED OVER NORTHEASTERN MONTANA... MOST OF 
THE DAKOTAS AND THE EXTREME UPPER MISSISSIPPI VALLEY ARE FROM OCN WITH SUPPORT 
FROM SOME OF THE DYNAMICAL MODELS.   

THE MODELS CONTINUE TO INDICATE ABNORMALLY DRY CONDITIONS OVER MUCH OF THE 
SOUTHEAST... WITH SUPPORT FROM THE CAS STATICSTICAL TOOL EXCEPT OVER THE 
FLORIDA PENINSULA.  CAS IS THE MAIN REASON FOR THE DRYNESS FORECAST OVER THE 
LOWER MISSISSIPPI VALLEY.  THE AREAS OF ABNORMAL WETNESS PREDICTED FOR THE 
SOUTHERN PLAINS AND DRYNESS INDICATED FOR PARTS OF THE GREAT BASIN... ROCKIES 
AND NORTHERN GREAT PLAINS ARE BASED ALMOST ENTIRELY ON CAS... WHILE THE AREA 
OF ABOVE MEDIAN PRECIPITATION SHOWN OVER THE PACIFIC NORTHWEST WEST OF THE 
CASCADES IS FROM CAS WITH A LITTLE SUPPORT FROM OCN.  

FORECASTER: A. J. WAGNER

NOTE - THIS CLIMATE OUTLOOK IS INTENDED FOR USE ONLY PRIOR TO THE START OF THE 
VALID PERIOD.  WITHIN THE VALID PERIOD OBSERVATIONS AND SHORT AND MEDIUM RANGE 
FORECASTS SHOULD BE CONSULTED.

NOTE -  AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL
PROBABILTIES) ARE NOW LABELED EC (EQUAL CHANCES).  
  
NOTE - THE NEXT 0.5 MONTH LEAD-TIME MONTHLY OUTLOOK WILL BE ISSUED 
THURSDAY MAY 20 2004.
  
NOTE - THE NEW 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE 
WITH THE MAY 17 2001 FORECAST RELEASE.


$$