February 19, 2015 - Climate Predcition Center Forecast through May 31, 2015

PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 
830AM EST THURSDAY FEB 19 2015 
 
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS 
 
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS CONTINUE TO SHOW MIXED SIGNALS 
REGARDING THE STATE OF ENSO. SEA-SURFACE TEMPERATURES (SSTS) REMAINED NEAR TO 
ABOVE-AVERAGE FOR ALL BUT FAR EASTERN SECTIONS OF THE EQUATORIAL PACIFIC. 
THROUGH EARLY FEBRUARY, THE ATMOSPHERIC RESPONSE TO THE RELATIVELY WARM WATER 
CONTINUES TO BE WEAK. TAKEN AS A WHOLE, THE ENSO SYSTEM REMAINS IN AN 
ENSO-NEUTRAL STATE, WITH SOME ASPECTS OF A WEAK WARM EVENT. THE CHANCES OF EL 
NINO DEVELOPING DURING THE NEXT 2 MONTHS ARE BETWEEN 50-60 PERCENT, WITH A 
RETURN TO ENSO-NEUTRAL CONDITIONS FAVORED THEREAFTER. HOWEVER, THIS IS EXPECTED 
TO HAVE LITTLE IMPACT ON THIS SET OF OUTLOOKS. 
 
THE TEMPERATURE OUTLOOK FOR MARCH-MAY (MAM) 2015 INDICATES ELEVATED CHANCES OF 
ABOVE-NORMAL MEAN TEMPERATURES ACROSS ALASKA AND THE WESTERN LOWER 48 STATES. 
INCREASED ODDS FOR BELOW-NORMAL MEAN TEMPERATURES ARE INDICATED OVER MUCH OF 
THE SOUTHERN PLAINS AND LOWER MISSISSIPPI RIVER VALLEY. 
 
THE MAM 2015 PRECIPITATION OUTLOOK INDICATES ELEVATED ODDS OF ABOVE-MEDIAN 
PRECIPITATION OVER PARTS OF THE SOUTHWEST, THE CENTRAL AND SOUTHERN ROCKIES, 
THE SOUTHERN HIGH PLAINS AND SOUTHERN TEXAS, THE SOUTHERN ATLANTIC COAST 
INCLUDING FLORIDA, AND MUCH OF THE SOUTHERN COAST OF ALASKA. CHANCES FOR 
BELOW-MEDIAN PRECIPITATION ARE ELEVATED ALONG THE PACIFIC NORTHWEST COAST. 
 
IN AREAS WHERE THE LIKELIHOODS OF SEASONAL MEAN TEMPERATURES AND SEASONAL 
ACCUMULATED PRECIPITATION AMOUNTS ARE SIMILAR TO CLIMATOLOGICAL PROBABILITIES, 
EQUAL CHANCES (EC) IS INDICATED. 
 
BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS 
NOTE: FOR GRAPHICAL DISPLAYS OF THE FORECAST TOOLS DISCUSSED BELOW SEE: 
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/TOOLS/BRIEFING 
 
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS 
 
THE CONTINUED LACK OF ROBUST COUPLING BETWEEN THE OCEAN AND ATMOSPHERE IN THE 
TROPICAL PACIFIC HAS PROLONGED BORDERLINE CONDITIONS BETWEEN ENSO-NEUTRAL AND A 
WEAK EL NINO. OCEANIC PARAMETERS FAVOR A WEAK EL NINO, WHILE ATMOSPHERIC 
PARAMETERS FAVOR ENSO-NEUTRAL. SSTS IN THE WESTERN AND CENTRAL EQUATORIAL 
PACIFIC ARE ABOVE-AVERAGE, AND SSTS IN THE EASTERN PORTION OF THE BASIN ARE 
NEAR TO BELOW-AVERAGE. THE LATEST WEEKLY SST INDICES ARE +0.9C FOR THE NINO 4 
REGION, +0.5C FOR NINO 3.4, +0.3C FOR NINO3, AND -0.8C FOR NINO 1+2. 
 
A NETWORK OF MOORED BUOYS ACROSS THE EQUATORIAL PACIFIC USED TO MONITOR THE 
STATE OF ENSO REVEALS WELL ABOVE-AVERAGE TEMPERATURES (AS MUCH AS 4-6 DEGREES C 
ABOVE-AVERAGE) DOWN TO A DEPTH OF 200 METERS NEAR AND EAST OF THE DATE LINE. 
BELOW-AVERAGE TEMPERATURES (AS MUCH AS 2-4 DEGREES C BELOW-AVERAGE) ARE 
OBSERVED ACROSS THE EASTERN EQUATORIAL PACIFIC BETWEEN ABOUT 110W-90W, DOWN TO 
A DEPTH OF 100 METERS. THE NEAR-EQUATORIAL UPPER-OCEAN HEAT CONTENT ANOMALIES 
(FROM THE DATE LINE TO 100W, UPPERMOST 300 METERS) HAD DECLINED TO NEAR ZERO IN 
EARLY JANUARY, BUT HAVE SINCE REBOUNDED IN EARLY FEBRUARY TO ABOUT +0.7C. THE 
OCEANIC COMPONENT OF THE GLOBAL CLIMATE SYSTEM IS CONSISTENT WITH A WEAK EL 
NINO. 
 
ON THE OTHER HAND, THE ATMOSPHERIC CIRCULATION IS MORE CONSISTENT WITH THE 
NEUTRAL PHASE OF ENSO. OUTGOING LONGWAVE RADIATION (OLR) MEASUREMENTS INDICATE 
THAT CONVECTION IS ENHANCED OVER THE WESTERN EQUATORIAL PACIFIC, AND SUPPRESSED 
OVER INDONESIA, NORTHERN AUSTRALIA, AND EAST OF THE DATE LINE. LOW-LEVEL 
(850-HPA) TRADE WINDS FOR THE PAST MONTH HAVE BEEN AVERAGING CLOSE TO NORMAL 
ACROSS THE EQUATORIAL PACIFIC, WHILE THE UPPER-LEVEL (200-HPA) WIND PATTERN 
DEPICTS A LARGE ANTICYCLONIC CIRCULATION CENTERED NEAR HAWAII, AND ENHANCED 
EASTERLIES NEAR THE EQUATOR FROM ABOUT 140W TO THE DATE LINE. 
 
ACCORDING TO THE JOINT INSTITUTE FOR THE STUDY OF THE ATMOSPHERE AND OCEAN 
(JISAO) IN SEATTLE, THE CALCULATED VALUE OF THE PACIFIC DECADAL OSCILLATION 
(PDO) INDEX FOR JANUARY 2015 IS +2.45. THE RECENT DECEMBER 2014 PDO INDEX VALUE 
OF +2.51 IS THE LARGEST DECEMBER VALUE ON RECORD (SINCE 1900) AND THE HIGHEST 
FOR ANY MONTH SINCE AUGUST 1997. 
 
PROGNOSTIC DISCUSSION OF SST FORECASTS 
 
THE IRI/CPC NINO 3.4 SST ANOMALY FORECAST PLUME OF VARIOUS DYNAMICAL AND 
STATISTICAL MODELS INDICATES MOST MODELS PREDICT A RANGE OF SST ANOMALIES FROM 
NEAR 0.0C TO +1.5C, WITH THE DYNAMICAL MODELS FAVORING THE HIGHER END OF THE 
RANGE, AND THE STATISTICAL MODELS FAVORING THE LOWER END OF THE RANGE. THE COLA 
CCSM3 IS THE HIGH-END OUTLIER, PEAKING NEAR +1.8C BY JAS AND ASO. THE CDC LIM 
IS THE LOW-END OUTLIER, BOTTOMING OUT AT -0.25C IN ASO. THE CFSV2 SST ANOMALY 
PREDICTIONS FOR NINO 3.4 RANGE FROM NEAR 0.0C TO +2.5C, WITH THE ENSEMBLE MEAN 
SLOWLY INCREASING FROM ABOUT +0.8C IN MAM TO +1.4C BY SON. 
 
THE CPC CONSOLIDATION (CON) SST FORECAST STARTS OFF AT +0.4C IN MAM AND 
DECLINES VERY SLIGHTLY TO ABOUT +0.2C IN SON. THE BOX AND WHISKERS PLOT SHOWS 
RAPIDLY INCREASING UNCERTAINTY BY AUTUMN, WITH PREDICTED SST ANOMALY VALUES 
RANGING ANYWHERE FROM +2.5C TO -2.0C DURING OND AND NDJ. 
 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS 
 
THE PRIMARY TOOLS USED FOR THE FIRST 5 OUTLOOKS ARE THE CFS, THE NMME AND IMME 
(AND THEIR CONSTITUENT INPUTS), CCA, SMLR, OCN, AND THE CPC CONSOLIDATION. FOR 
LEADS 6-13, THE PRIMARY TOOL USED IS THE CPC CONSOLIDATION, A SKILL-WEIGHTED 
AND CALIBRATED MEAN OF THE CFS, CCA, SMLR, AND OCN, WHICH IS HELPFUL IN 
INCORPORATING LONGER-TERM TRENDS. ANOTHER TOOL BEING UTILIZED IS THE 
CONSTRUCTED ANALOG BASED ON SSTS (CA-SST), WHICH IS AVAILABLE FOR ALL LEADS. 
THE CURRENT AND ANTICIPATED STATES OF ENSO WERE ALSO CONSIDERED, AS WERE 
OBSERVED TEMPERATURE AND PRECIPITATION PATTERNS OVER THE UNITED STATES DURING 
THE PAST 90-DAYS. 
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - MAM 2015 TO MAM 2016 
 
TEMPERATURE 
 
FOR LEAD 1 (MAM 2015), ENHANCED PROBABILITIES FOR BELOW-NORMAL SEASONAL MEAN 
TEMPERATURES ARE INDICATED OVER THE SOUTHERN PLAINS AND LOWER MISSISSIPPI 
VALLEY. THIS SIGNAL IS EVIDENT IN THE NMME, CFS, GFDL AND NASA MODELS, AS WELL 
AS THE CA-SST TOOL. PROBABILITIES ARE ENHANCED FOR ABOVE-NORMAL TEMPERATURES IN 
ALASKA AND THE WESTERN CONUS, WITH PROBABILITIES NEAR 60 PERCENT ALONG THE 
SOUTHERN COAST OF ALASKA, AND THE COASTS OF WASHINGTON AND OREGON. THIS LARGE 
EXTENT OF PREDICTED ABOVE-NORMAL SEASONAL MEAN TEMPERATURES IS FAVORED BY 
NEARLY ALL OF THE VARIOUS TOOLS. THE NMME, IMME, CFS, AND OTHER SOLUTIONS 
EXTEND THIS RELATIVE WARMTH EASTWARD ACROSS THE NORTH-CENTRAL CONUS, BUT THIS 
IS DEEMED TOO UNCERTAIN, ESPECIALLY IN LIGHT OF HIGHER FREQUENCY CLIMATE 
SIGNALS (INTRA-SEASONAL VARIABILITY) THAT SUGGEST THIS AREA MAY BE OPEN TO 
LONGER PERIODS OF COLD AIR INTRUSIONS. IN WESTERN NORTH AMERICA, HOWEVER, THE 
LOW-FREQUENCY SEASONAL SIGNAL APPEARS STABLE ENOUGH TO WARRANT THE HIGHER 
PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES. 
 
FOR LEADS 2-6, THE PREVIOUS SET OF OUTLOOKS WAS MODIFIED ACCORDING TO THE 
LATEST DYNAMICAL MODEL OUTPUT. THE MOST RELIABLE SIGNALS ARE FOR ABOVE-NORMAL 
TEMPERATURES ACROSS ALASKA AND THE WESTERN CONUS, ASSOCIATED WITH THE LOWER 
FREQUENCY SIGNAL OF LONG-TERM RIDGING OVER WESTERN NORTH AMERICA. IN GENERAL, 
THE DYNAMICAL SOLUTIONS FAVOR ENHANCED ODDS OF ABOVE-NORMAL TEMPERATURES ACROSS 
THE GREAT LAKES REGION AND NORTHEAST DURING AMJ AND MJJ, AND MUCH OF THE 
ATLANTIC AND GULF COAST REGIONS DURING JJA, JAS AND ASO. THE ELEVATED ODDS OF 
ABOVE-NORMAL MEAN TEMPERATURES CONTINUES IN THE NORTHEAST DURING SON AND OND 
2015, BASED LARGELY ON HISTORICAL TEMPERATURE TRENDS. THE SPATIAL COVERAGE OF 
EXPECTED ABOVE-NORMAL MEAN TEMPERATURES IN THE WESTERN CONUS GRADUALLY 
DIMINISHES IN SIZE DURING THE AUTUMN AND WINTER, TO INCLUDE ONLY THE SOUTHWEST 
DURING THE LAST 4 SEASONS. 
 
FROM SON 2015 TO MAM 2016, THERE ARE ENHANCED ODDS OF ABOVE-NORMAL TEMPERATURES 
ACROSS NORTHERN ALASKA, PRIMARILY DUE TO STRONG TRENDS IN SURFACE TEMPERATURE 
AND SEA ICE COVER. 
 
PRECIPITATION 
 
FOR MAM 2015, THERE ARE ELEVATED ODDS OF ABOVE-MEDIAN PRECIPITATION FOR PARTS 
OF THE SOUTHWEST, THE CENTRAL AND SOUTHERN ROCKIES, THE SOUTHERN HIGH PLAINS 
AND SOUTHERN TEXAS, THE SOUTHERN ATLANTIC COAST INCLUDING FLORIDA, AND MUCH OF 
THE SOUTHERN COAST OF ALASKA. ODDS FOR BELOW-MEDIAN PRECIPITATION ARE ELEVATED 
ALONG THE PACIFIC NORTHWEST COAST. THIS OUTLOOK IS PRIMARILY BASED ON THE NMME, 
IMME, CFS, AND TO SOME DEGREE THE GFDL, CANCM4 AND NASA MODELS. IT IS ALSO 
CONSISTENT WITH THE EXPECTATION OF A VERY STABLE, LOW-FREQUENCY SIGNAL IN THE 
VICINITY OF WESTERN NORTH AMERICA, FAVORING A RIDGE. 
 
THROUGH THE SPRING AND EARLY PORTIONS OF THE SUMMER, THE STRONGEST SIGNAL IN 
THE MODELS IS FOR ENHANCED ODDS OF ABOVE-MEDIAN PRECIPITATION OVER THE 
SOUTHWEST. THE OUTLOOK THERE IS HIGHLY UNCERTAIN, ESPECIALLY DURING AMJ, A 
CLIMATOLOGICALLY DRY TIME OF YEAR ACROSS THAT REGION. FROM JAS TO NDJ, 
PRECIPITATION SIGNALS ACROSS THE U.S. ARE TOO WEAK TO JUSTIFY ANY ONE OF THE 
THREE CATEGORIES (BELOW, NEAR, OR ABOVE-MEDIAN), SO EQUAL CHANCES (EC) IS 
INDICATED. FROM DJF 2015-16 TO FMA 2016, HISTORICAL TRENDS SLIGHTLY FAVOR 
BELOW-MEDIAN PRECIPITATION IN THE SOUTHEAST, DUE IN PART TO THE DOMINANCE OF LA 
NINA EVENTS DURING THE PAST 15 YEARS. FOR MAM 2016, THIS HISTORICAL TREND IS 
NOT AS CLEAR, SO EC IS FAVORED. 
 
FORECASTER: ANTHONY ARTUSA 
 
THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING 
THE WORLD METEROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3 
COMPLETE DECADES AS THE CLIMATIC 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. 
 
FOR A DESCRIPTION OF OF THE STANDARD FORECAST TOOLS - THEIR SKILL- AND THE 
FORECAST FORMAT PLEASE SEE OUR WEB PAGE AT 
HTTP:/WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/DISC.HTML 
(USE LOWER CASE LETTERS) 
INFORMATION ON THE FORMATION OF SKILL OF THE CAS FORECASTS MAY BE FOUND AT: 
HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML (USE LOWERCASE LETTERS) 
NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR 
VALID PERIOD.  WITHIN ANY GIVEN VALID PERIOD OBSERVATIONS AND SHORT AND MEDIUM 
RANGE FORECASTS SHOULD BE CONSULTED. 
 
THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCE OF THE NEW SET NEXT 
MONTH ON MAR 19 2015 
 
 
1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 
FORECAST RELEASE. 
$$