PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EDT WED MAR 31 2010

30-DAY OUTLOOK DISCUSSION FOR APRIL 2010

EL NINO CONDITIONS CONTINUE ACROSS THE EQUATORIAL PACIFIC OCEAN WITH SEA 
SURFACE TEMPERATURE (SST) DEPARTURES OF +1.0 DEGREE C OR GREATER ACROSS MUCH OF 
THE CENTRAL PACIFIC. OCEAN SUB-SURFACE TEMPERATURE ANOMALIES ALSO REMAIN 
POSITIVE FROM THE SURFACE TO A DEPTH OF APPROXIMATELY 130 M EAST OF THE 
DATELINE ALONG THE EQUATOR ACROSS THE PACIFIC, THEREFORE EL NINO CONDITIONS ARE 
EXPECTED TO CONTINUE EASILY THROUGH APRIL 2010.

CURRENT ATMOSPHERIC CONDITIONS IN THE TROPICS ARE CONSISTENT WITH EL NINO. 
ENHANCED TROPICAL CONVECTION ACROSS THE PACIFIC OCEAN NEAR THE DATE LINE IS 
EVIDENT AS WELL AS ANOMALOUS LOW-LEVEL WESTERLY WIND ANOMALIES ACROSS PORTIONS 
OF THE WEST-CENTRAL PACIFIC DURING THE PAST 30 DAYS. BASED ON THE 
AFOREMENTIONED OCEANIC AND ATMOSPHERIC CONDITIONS, EL NINO REMAINS A FACTOR IN 
THE APRIL 2010 MONTHLY OUTLOOK FOR THE US. 

WE NEED TO POINT OUT THAT THE ENSO IMPACT DEPENDS ON SEASON. WE MAY SEE 
CONTINUED EL NINO TYPE FORCING IN THE TROPICS AND A DIRECT OR DELAYED 
ATMOSPHERIC RESPONSE IN THE MID-LATITUDE FOR APRIL, BUT LESS SO THAN IN MARCH. 
SOME ENSO IMPACTS OVER THE US EXPERIENCED DURING LAST WINTER MAY CARRY OVER IN 
LAGGED FASHION INTO APRIL AND LATER THROUGH SOIL MOISTURE ANOMALIES, AS WELL AS 
BY WIDESPREAD NEGATIVE SST ANOMALIES IN THE GULF OF MEXICO AND SOUTHWEST 
ATLANTIC.

BOTH STATISTICAL AND DYNAMICAL FORECAST TOOLS WERE CONSIDERED FOR THE OUTLOOK 
ALTHOUGH THE STATISTICAL TOOLS MAY HAVE LITTLE SIGNAL FOR A PERIOD AS SHORT AS 
MONTH. THE CFS INDICATES A STRONG EL NINO PATTERN THAT IS QUITE CONSISTENT WITH 
EL NINO COMPOSITES. WE AMENDED THE ENSO COMPOSITES IN AREAS WHERE STRONG SOIL 
MOISTURE ANOMALIES MAY IMPACT APRIL TEMPERATURE. THIS WOULD BE MAINLY IN STATES 
WHERE VEGETATION IS GREENING, I.E. ACROSS THE SOUTH, NOT IN THE DAKOTAS

UNFORTUNATELY THE END-OF-MONTH UPDATE IS RADICAL. THE FLOW PATTERN HAS CHANGED 
JUST A FEW DAYS AGO FROM WHAT MIGHT BE CONSIDERED A PERSISTENT EL NINO 
RESPONSE. MANY OF THE INDICATIONS BASED ON NWP FOR THE FIRST PART OF THE MONTH, 
WEEK 1 ESPECIALLY, ARE ALMOST COMPLETEY AT ODDS WITH THE LONG LEAD APRIL 
FORECAST ISSUED A FEW WEEKS AGO. WE DELETED THE WARMTH AND DRYNESS IN THE 
NORTHWEST AND ALSO AK, REDUCED THE COLD IN THE CENTER AND SOUTHEAST OF THE 
COUNTRY, EXPANDED WARMTH IN THE NORTHEAST SOUTHWARD AND SHIFTED THE ABOVE 
MEDIAN PRECIPITATION AREA FAR NORTHWARD. ELEMENTS PRESENT IN THE LONG LEAD 
FORECAST THAT WE KEPT ARE WARMTH IN THE NORTHERN GREAT LAKES, COOLNESS ALONG 
THE GULF COAST, DRYNESS IN THE EASTERN GREAT LAKES AND ABOVE MEDIAN 
PRECIPITATION IN SOME PARTS OF THE SOUTH. THESE ELEMENTS ARE EITHER SUPPORTED 
BY OR NOT STRONGLY AT ODD WITH NWP FOR THE EARLY PART OF THE MONTH. ON THE 
WHOLE A LOW CONFIDENCE SITUATION.

THE APRIL FORECAST CALLS FOR ABOVE AVERAGE TEMPERATURE IN THE NORTHEASTERN 
QUADRANT OF THE COUNTRY. BELOW AVERAGE TEMPERATURE ARE FAVORED IN FLORIDA AND 
ALONG THE IMMEDIATE GULF COAST WESTWARD TO TEXAS AS WELL AS IN MUCH OF THE 
WEST. PROBABILITIES ARE ONLY MODEST. 

BELOW MEDIAN PRECIPITATION IS EXPECTED ONLY IN A SMALL AREA IN THE EASTERN 
GREAT LAKES. ABOVE MEDIAN PRECIPITATION IS EXPECTED ALONG THE WEST COAST IN 
OREGON AND NORTHERN CALIFORNIA. ABOVE MEDIAN PRECIPITATION IS ALSO EXPECTED IN 
A LARGE AREA IN THE NORTH CENTER OF THE COUNTRY. PROBABILITIES ARE ONLY MODEST. 



  
 


FORECASTER: HUUG VAN DEN DOOL

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

THE NEXT MONTHLY OUTLOOK...FOR MAY 2010...WILL BE ISSUED ON THU APR 15 2010

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

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