PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 
830AM EDT THURSDAY APR 17 2014 
 
30-DAY OUTLOOK DISCUSSION FOR MAY 2014 
 
RECENT ATMOSPHERIC AND OCEANIC CONDITIONS IN THE TROPICAL PACIFIC BASIN 
CONTINUE TO INDICATE ENSO-NEUTRAL CONDITIONS IN EARLY APRIL. PACIFIC SEA 
SURFACE TEMPERATURE (SST) ANOMALIES HAVE BEEN STEADILY RISING ALONG EQUATOR 
THROUGHOUT MUCH OF THE CENTRAL AND EASTERN PACIFIC OCEAN AND ARE NOW ABOVE 
AVERAGE EXCEPT ALONG THE SOUTH AMERICAN COAST.  THERE ARE MANY INDICATORS THAT 
SUGGEST THAT THE ENSO STATE IS EVOLVING TOWARD EL NINO. THESE INCLUDE RECENTLY 
OBSERVED WESTERLY WIND ANOMALIES OVER MUCH OF THE CENTRAL AND WESTERN 
EQUATORIAL PACIFIC, A MARKED INCREASE IN SUB-SURFACE OCEANIC HEAT CONTENT IN 
THE PAST FEW WEEKS, AND A SLOW PROGRESSION OF ENHANCED CONVECTION ALONG THE 
EQUATOR TOWARD THE CENTRAL PACIFIC. IN ADDITION, THERE IS AN INCREASING 
CONSENSUS AMONG DYNAMICAL AND STATISTICAL FORECASTS THAT POSITIVE SST ANOMALIES 
IN THE ENSO CRITICAL REGIONS OF THE PACIFIC WILL REACH MINIMAL THRESHOLDS FOR 
EL NINO CONDITIONS BY SUMMER 2014. COMPOSITES OF PAST YEARS IN WHICH EL NINO 
CONDITIONS DEVELOPED IN SUMMER WERE CONSIDERED FOR THE MAY OUTLOOK. 
 
THE MAY OUTLOOK FOR MONTHLY MEAN TEMPERATURES INDICATES ELEVATED CHANCES FOR 
BELOW-NORMAL TEMPERATURES FOR PORTIONS OF THE NORTHERN ROCKIES, THE NORTHERN 
GREAT PLAINS, AND THE UPPER GREAT LAKES. THIS IS DUE TO INDICATIONS FROM THE 
BOTH SMLR AND CFS, AND IS CONSISTENT WITH TEMPERATURES FROM COMPOSITES OF PAST 
YEARS WITH DEVELOPING EL NINO CONDITIONS. ABOVE-NORMAL SOIL MOISTURE CONTENT IN 
THE NORTHERN ROCKIES MAY ALSO ENHANCE THE CHANCES FOR BELOW-NORMAL 
TEMPERATURES. THE CHANCES FOR BELOW-NORMAL TEMPERATURES NEAR THE SHORES OF THE 
GREAT LAKES ARE FURTHER ENHANCED BY THE SIGNIFICANTLY BELOW-NORMAL WATER 
TEMPERATURES THAT ARE EXPECTED TO PERSIST INTO MAY. MOST TOOLS INDICATE 
ENHANCED ODDS FOR ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE SOUTHWESTERN 
QUARTER OF THE CONUS AND PARTS OF THE SOUTHERN GREAT PLAINS. DRY SOIL MOISTURE 
CONDITIONS ARE EXPECTED TO HELP INCREASE THE ODDS OF ABOVE NORMAL TEMPERATURES 
IN THESE REGIONS. ABOVE-NORMAL SSTS NEAR SOUTHERN FLORIDA HELP ELEVATE CHANCES 
FOR ABOVE-NORMAL AIR TEMPERATURES THERE. MANY MODELS AND STATISTICAL TOOLS 
POINT TO AN INCREASED CHANCE FOR ABOVE-NORMAL TEMPERATURES ALONG THE WEST COAST 
OF NORTH AMERICA AND MOST OF ALASKA. IN AREAS WHERE CLIMATE SIGNALS ARE WEAK 
AND/OR NOT RELIABLE, EQUAL CHANCES (EC) OF BELOW-, NEAR- AND ABOVE-NORMAL MEAN 
MONTHLY TEMPERATURES ARE INDICATED. 
 
THE NMME, IMME AND CFS, FAVOR BELOW-MEDIAN PRECIPITATION IN THE PACIFIC 
NORTHWEST AND ALSO THE ALASKA PANHANDLE. THE NMME FAVORS ABOVE-MEDIAN 
PRECIPITATION AMOUNTS NEAR FLORIDA. COMPOSITES BASED ON YEARS WITH DEVELOPING 
EL NINO CONDITIONS ALSO SUPPORT DRY TENDENCIES IN THE PACIFIC NORTHWEST, AND 
TENDENCIES FOR WET CONDITIONS IN FLORIDA. ELSEWHERE, THE LACK OF CONSISTENT 
SIGNALS AMONG TOOLS SUGGEST EQUAL CHANCES (EC) FOR BELOW- NEAR- OR ABOVE-MEDIAN 
PRECIPITATION AMOUNTS. IT IS NOTEWORTHY THAT THE VARIOUS MODELS IN THE NMME 
SHOW NO CONSISTENT SIGNAL FOR THE SOUTHERN HIGH PLAINS AND WEST TEXAS IN SPITE 
OF VERY DRY INITIAL SOIL MOISTURE CONDITIONS IN SOME OF THESE REGIONS. 
 
THE MAIN FACTORS THAT USUALLY INFLUENCE THE MONTHLY CLIMATE OUTLOOK INCLUDE: 
1) EL NINO AND LA NINA - WHICH COMPRISE ENSO. IMPACTS OF THESE EVENTS ARE 
SUMMARIZED BY SEPARATING 3-MONTH OBSERVATIONS FROM THREE OR MORE DECADES INTO 
EL NINO, NEUTRAL AND LA NINA SETS, AVERAGING EACH SEPARATELY, AND THEN 
COMPUTING ANOMALIES. THESE ARE CALLED "COMPOSITES" AND USED AT TIMES TO 
SUBJECTIVELY MODIFY THE FORECAST. 
2) TRENDS - APPROXIMATED BY THE OCN TOOL AS THE DIFFERENCE BETWEEN THE MOST 
RECENT 10-YEAR MEAN OF TEMPERATURE OR 15-YEAR MEAN OF PRECIPITATION FOR A GIVEN 
LOCATION AND TIME OF YEAR AND THE 30-YEAR CLIMATOLOGY PERIOD (CURRENTLY 
1981-2010). 
3) THE TROPICAL 30-60 DAY OSCILLATION - CALLED THE MADDEN JULIAN OSCILLATION 
(MJO) - AFFECTS CLIMATE VARIABILITY WITHIN SEASONS. 
4) THE ARCTIC OSCILLATION (AO), THE SIMILAR NORTH ATLANTIC OSCILLATION (NAO), 
AND THE PACIFIC NORTH AMERICAN (PNA) PATTERNS - WHICH AFFECT THE TEMPERATURE 
ANOMALY PATTERN ESPECIALLY DURING BOREAL WINTER AND ARE GENERALLY CONSIDERED TO 
HAVE LOW PREDICTABILITY. 
5) THE PACIFIC DECADAL OSCILLATION (PDO) - AN ENSO-LIKE PATTERN OF CLIMATE 
VARIABILITY AFFECTING THE TROPICS AND THE NORTH PACIFIC AND NORTH AMERICAN 
REGIONS, BUT WHICH VARIES ON A MUCH LONGER TIME-SCALE THAN ENSO. 
6) PERSISTENTLY DRY OR WET SOILS IN THE SPRING AND SUMMER AND SNOW AND ICE 
COVER ANOMALIES IN THE WINTER. THESE FACTORS TEND TO PERSIST FOR LONG PERIODS 
AND ACT AS A KIND OF MEMORY IN THE CLIMATE SYSTEM. 
7) STATISTICAL FORECAST MODELS - CANONICAL CORRELATION ANALYSIS (CCA), 
SCREENING MULTIPLE LINEAR REGRESSION (SMLR), CONSTRUCTED ANALOG (CA), AND 
ENSEMBLE CCA (ECCA). 
8) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM 
VERSION 2 (CFS) AND FOR THE ZERO-LEAD UPDATE FORECASTS THE NCEP GLOBAL ENSEMBLE 
FORECAST SYSTEM (GEFS).  AN EXPERIMENTAL FORECAST SYSTEM, THE NATIONAL 
MULTI-MODEL ENSEMBLE (NMME), COMPRISED OF SEVERAL DYNAMICAL MODELS IS ALSO USED. 
 
 
FORECASTER: DAVID UNGER 
 
 
THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING 
THE WORLD METEOROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3 
COMPLETE DECADES AS THE CLIMATE REFERENCE PERIOD.  THE PROBABILITY ANOMALIES 
FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT 
SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS. 
 
 
 
AN UPDATED MONTHLY OUTLOOK... FOR MAY WILL BE ISSUED ON WED APRIL 30 2014 
 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. 
 
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