PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
CLIMATE PREDICTION CENTER NCEP
NATIONAL WEATHER SERVICE  WASHINGTON DC
3 PM EDT THURSDAY APRIL 12 2001

30-DAY OUTLOOK DISCUSSION FOR MAY 2001
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CENTRAL EQUATORIAL PACIFIC SSTS REMAIN BELOW NORMAL AND THE CIRCULATION IN THE
TROPICAL PACIFIC BASIN CONTINUES TO EXHIBIT CHARACTERISTICS FOUND DURING COLD 
(LA NINA) EPISODES. RECENT ANALYSES AND BOTH STATISTICAL AND DYNAMIC MODELS
INDICATE THAT THE LA NINA WILL CONTINUE TO WEAKEN OVER THE NEXT SEASON.
HOWEVER COOLER THAN AVERAGE SSTS WILL PROBABLY PERSIST IN THE NINO 3.4 REGION 
THROUGH MAY 2001 - ALTHOUGH AT THIS TIME OF YEAR THERE WOULD BE LITTLE EFFECT ON 
THE CLIMATE OF THE MAINLAND U.S.  WE CONSIDERED THE FOLLOWING TOOLS:  - THE CCA 
- THE OCN - COLD ENSO COMPOSITES AND THE CONSTRUCTED ANALOGUE FOR SOIL MOISTURE 
(CAS).  ON THE MONTHLY TIME SCALE NONE OF THESE TOOLS HAVE VERY HIGH SKILL.

WARMER THAN NORMAL TEMPERATURES ARE PREDICTED FROM THE SOUTHWEST EASTWARD 
THROUGH MOST OF TEXAS AND THE GULF STATES TO FLORIDA AND SOUTHWESTERN GEORGIA. 
THE TOOLS ARE IN SOME AGREEMENT IN THE SOUTHWEST AND NORTHWEST BUT OTHERWISE 
SHOW MIXED SIGNALS.  THE CAS TOOL RATHER UNREALISTICALLY FAVORS COOLER THAN 
AVERAGE CONDITIONS ACROSS THE SOUTHERN PART OF THE COUNTRY WHILE THE OTHER 
TOOLS INDICATED WARMER THAN NORMAL FOR MUCH OF THAT REGION.  THE CAS TOOL 
AGREED WITH OTHER INDICATIONS FOR WARMTH IN THE PACIFIC NORTHWEST - WHICH 
SEEMS REASONABLE GIVEN THE DEFICIENT MOUNTAIN SNOWPACK AND LONG TERM DRYNESS 
IN THAT REGION. 
  
MOST OF THE REMAINING NORTHERN TWO-THIRDS OF THE LOWER 48 STATES WHERE 
INDICATIONS FROM THE VARIOUS TOOLS WERE VERY WEAK WAS GIVEN CLIMATOLOGICAL 
PROBABILITIES.  TOOLS ALSO GAVE MIXED SIGNALS FOR SOUTHERN AND SOUTHWESTERN 
COASTAL SECTIONS OF ALASKA - WITH CCA STILL PREDICTING BELOW NORMAL.  GIVEN
THAT THE WATER TEMPERATURES ARE ABOVE NORMAL OVER THE NORTHERN GULF OF ALASKA
AND SOUTHERN BERING SEA WITH DEFICIENT SEA ICE AND THAT TEMPERATURES HAVE BEEN 
RUNNING MUCH ABOVE NORMAL FOR MOST OF THE WINTER IN SPITE OF FORECASTS OF 
BELOW NORMAL FROM CCA THROUGHOUT THAT TIME PERIOD WE DECIDED TO GIVE CL TO THE 
SOUTHWESTERN PART OF THE STATE AND PERSIST ABOVE NORMAL IN THE INTERIOR AND 
NORTHERN SECTIONS - WHICH ALSO AGREED WITH INDICATIONS FROM OCN.

THE PRECIPITATION OUTLOOK REFLECTS SOME RESIDUAL COLD EPISODE FEATURES WHICH 
CAN STILL BE EXPECTED EVEN IN THE LATTER PART OF SPRING.  THUS WE CONTINUED 
THE BELOW MEDIAN PRECIPITATION FORECAST IN FLORIDA AND EXTENDED THE AREA 
NORTHWARD IN AGREEMENT WITH BOTH OCN AND CAS INDICATIONS.  OCN AND CAS ALSO 
SUGGEST BELOW MEDIAN IN PARTS OF TEXAS.  THE FORECAST OF ABOVE MEDIAN COMES 
NOT FROM LA NINA BUT FROM OCN - WHICH HAS BEEN FAIRLY RELIABLE AT THIS TIME OF 
YEAR ON THAT FEATURE IN RECENT YEARS - AND PRECIPITATION HAS BEGUN TO INCREASE 
THERE RECENTLY.  HOWEVER IT WILL BE OF LITTLE CONSEQUENCE SINCE THE NORMALS 
DECLINE RAPIDLY THIS TIME OF YEAR.  THE REMAINDER OF THE LOWER 48 STATES AND 
MOST OF ALASKA HAD WEAK OR MIXED SIGNALS FROM THE TOOLS - EXCEPT FOR BELOW 
MEDIAN IN PARTS OF CENTRAL AND NORTHERN ALASKA.  THUS WE OPTED FOR CL IN THE 
WEAKLY INDICATED REGIONS. 

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 - THE NEXT 0.5 MONTH LEAD-TIME MONTHLY OUTLOOK WILL BE ISSUED
THURSDAY MAY 17 2001.

NOTE - THE NEW 1971-2000 BASE PERIOD MEANS WILL BE IMPLEMENTED WITH THE NEXT 
SET OF LONG LEAD OUTLOOKS RELEASED ON MAY 17 2001.

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