PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830AM EDT THURSDAY JUN 18 2015

30-DAY OUTLOOK DISCUSSION FOR JULY 2015

SEA SURFACE TEMPERATURES (SSTS) IN EARLY JUNE ARE CURRENTLY MORE THAN ONE 
DEGREE C ABOVE NORMAL ALONG THE EQUATOR IN THE PACIFIC OCEAN FROM THE SOUTH 
AMERICAN COAST WESTWARD TO JUST EAST OF THE INTERNATIONAL DATE LINE. WITHIN 
THIS AREA THERE ARE SOME PLACES WERE THE SST ANOMALIES ARE OVER +2.0 DEGREES C. 
ABOVE NORMAL SSTS EXTEND NORTHWARD FROM THE EQUATOR TO COVER AN EXTENSIVE AREA 
TO THE WEST OF NORTH AMERICA. SUBSURFACE OCEAN WATER TEMPERATURES ARE ALSO 
CONSIDERABLY ABOVE NORMAL THROUGHOUT THE EASTERN EQUATORIAL PACIFIC OCEAN.  
RECENT ATMOSPHERIC OBSERVATIONS OVER THE EASTERN AND CENTRAL TROPICAL PACIFIC 
OCEAN SUGGEST STRONG OCEAN-ATMOSPHERE COUPLING, WITH UNUSUALLY ACTIVE 
CONVECTION TOGETHER WITH LARGE SCALE WESTERLY WIND ANOMALIES AT LOW LEVELS, AND 
EASTERLY ANOMALIES AT UPPER LEVELS. TOGETHER THESE SUGGEST THE DEVELOPMENT OF 
MODERATE STRENGTH EL NINO CONDITIONS. STATISTICAL AND DYNAMIC MODELS FOR SST 
PREDICTION SUGGEST THAT THE EL NINO CONDITIONS WILL PERSIST OR STRENGTHEN IN 
THE COMING MONTHS. EL NINO APPEARS TO BE CONTRIBUTING TO CLIMATE ANOMALIES OVER 
PARTS OF NORTH AMERICA IN THE PAST MONTH OR TWO, AND ARE EXPECTED TO CONTINUE 
TO HAVE AN INFLUENCE IN JULY.

DYNAMICAL MODEL FORECASTS INITIALIZED IN THE LAST FEW MONTHS HAVE SHOWN 
CONSIDERABLE CONSISTENCY IN THEIR PREDICTIONS FOR NORTH AMERICAN SURFACE 
TEMPERATURE AND PRECIPITATION. THEIR PREDICTIONS HAVE BEEN QUITE SUCCESSFUL IN 
SUGGESTING ELEVATED ODDS OF WET CONDITIONS IN MUCH OF WESTERN AND CENTRAL CONUS 
IN THE LATE SPRING. THE MODEL PREDICTIONS AGREE REASONABLY WELL WITH THE 
TEMPERATURE AND PRECIPITATION ANOMALIES OBSERVED IN ASSOCIATION WITH PAST EL 
NINOS. THUS, THE OUTLOOK FOR JULY 2015 IS BASED HEAVILY ON THE FORECAST FROM 
THE CFSV2, AND PROBABILITIES FROM THE MODEL CONSENSUS OF CLIMATE MODELS RUN AS 
PART OF THE NMME AND IMME.  

THE FORECAST SUGGESTS ELEVATED CHANCES OF ABOVE-NORMAL TEMPERATURES IN THE 
WESTERN CONUS AND ALASKA. BELOW NORMAL TEMPERATURES ARE FAVORED IN AREAS THAT 
HAVE EXPERIENCED RECENT SURPLUS RAINFALL IN THE CENTRAL AND SOUTHERN PORTIONS 
OF THE ROCKY MOUNTAINS AND GREAT PLAINS, INCLUDING MUCH OF TEXAS. THIS AREA IS 
LIKELY ASSOCIATED WITH THE COOLING EFFECTS OF ABOVE AVERAGE SOIL MOISTURE, 
TOGETHER WITH INCREASED CHANCES FOR A CONTINUATION OF RELATIVELY WET CONDITIONS 
IN THE NEXT MONTH. THERE IS A FAIR CONSENSUS AMONG CLIMATE MODELS FOR ABOVE 
NORMAL TEMPERATURES IN THE EASTERN CONUS, HOWEVER THE CONFIDENCE IS LOW 
CONSIDERING THAT PAST EL NINO SUMMERS GENERALLY FAVOR COOL CONDITIONS FOR MUCH 
OF THE EAST AND NORTH CENTRAL CONUS. THE AREA FAVORING ABOVE NORMAL 
TEMPERATURES WAS RESTRICTED TO AREAS EAST OF THE APPALACHAIN MOUNTAINS WHERE 
THE YEAR-TO-YEAR TEMPERATURE VARIABILITY IS LOWER IN RELATION TO POSSIBLE 
CLIMATE SIGNALS.  

THERE CONTINUES TO BE A STRONG CONSENSUS AMONG MODELS FOR ABOVE-MEDIAN 
PRECIPITATION AMOUNTS OVER A WIDE AREA OF THE CENTRAL AND WESTERN CONUS. SOME 
EARLY TROPICAL STORM ACTIVITY HAS ALREADY BEEN OBSERVED IN EARLY JUNE IN THE 
EASTERN PACIFIC OFF THE COAST OF MEXICO, AND HAS BEEN CONTRIBUTING TO ANOMALOUS 
MOISTURE IN PARTS OF THE WESTERN CONUS. MODEL FORECASTS SUGGEST A CONTINUATION 
OF ENHANCED CHANCES OF ABOVE MEDIAN PRECIPITATION THAT APPEARS AS A NORTHWARD 
EXTENSION OF A LARGE AREA OF FORECAST ABOVE MEDIAN RAINFALL IN THE TROPICAL 
EASTERN PACIFIC. ENSO COMPOSITES GENERALLY FAVOR A WEAK SOUTHWEST MONSOON IN 
THE WESTERN PART OF THE MONSOON REGION, SO THE MODEL FORECASTS FOR ABOVE MEDIAN 
PRECIPITATION AMOUNTS IN ARIZONA MAY DEPEND ON HIT-OR-MISS RESIDUAL MOISTURE 
FROM TROPICAL STORMS, AND AS SUCH MAY BE UNRELIABLE IN WESTERN REGIONS OF THE 
DESERT SOUTHWEST. THE CFSV2 MODEL INDICATES BELOW MEDIAN PRECIPITATION FOR 
SOUTH TEXAS EXTENDING INTO PARTS OF THE SOUTHEASTERN CONUS. THIS AREA SEEMS A 
REASONABLE EXTENSION OF DRY CONDITIONS EXPECTED OVER THE CARIBBEAN IN EL NINO 
SUMMERS, HOWEVER MODEL CONSENSUS IN THE EASTERN PART OF THE AREA AND IN FLORIDA 
WAS LOW. THERE IS ALSO SOME WEAK CONSENSUS AMONG THE NMME FOR BELOW MEDIAN 
PRECIPITATION AMOUNTS OVER PARTS OF THE ALASKA PANHANDLE.

IN AREAS WHERE THERE ARE NO STATISTICALLY SIGNIFICANT CLIMATE SIGNALS, SUCH 
THAT THE LIKELIHOODS OF MONTHLY MEAN TEMPERATURES OR MONTHLY ACCUMULATED 
PRECIPITATION AMOUNTS ARE EQUAL TO CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES 
(EC) IS INDICATED.

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 JUL WILL BE ISSUED ON TUE JUNE 30 2015


THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.

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