PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 
300PM EDT FRIDAY MAY 31 2013 
 
30-DAY OUTLOOK DISCUSSION FOR JUNE 2013 
 
ATMOSPHERIC AND OCEANIC CONDITIONS OVER THE TROPICAL PACIFIC CONTINUE TO 
INDICATE ENSO-NEUTRAL CONDITIONS. EQUATORIAL SEA SURFACE TEMPERATURES (SSTS) 
REMAIN NEAR LONG-TERM CLIMATOLOGICAL NORMAL VALUES WEST OF ABOUT 135W 
LONGITUDE, BUT HAVE COOLED DURING THE MONTH OF MAY AND BECOME BELOW NORMAL OVER 
THE EASTERN PACIFIC FROM ABOUT 135W TO THE SOUTH AMERICAN COAST. WHILE THE 
AVERAGE SUBSURFACE OCEAN TEMPERATURES TO A DEPTH OF 300 METERS IN THE 
EQUATORIAL PACIFIC ARE ONLY SLIGHTLY BELOW NORMAL, THERE IS A LARGE VOLUME OF 
WARMER THAN NORMAL WATER BELOW THE SURFACE TO THE WEST OF THE DATE LINE, AND A 
REGION OF COOLER THAN NORMAL WATER HAS DEVELOPED IN THE LAST MONTH TO THE EAST 
OF 120W FROM THE SURFACE TO ABOUT 100 METERS DEPTH. DURING THE LAST MONTH 
TROPICAL CONVECTION WAS ENHANCED IN THE REGION AROUND THE MARITIME CONTINENT 
AND SUPPRESSED OVER THE CENTRAL AND EASTERN EQUATORIAL PACIFIC. THE 
MADDEN-JULIAN OSCILLATION (MJO) IS NOT CURRENTLY ACTIVE. 
 
THE JUNE 2013 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE UPDATED AT THE END OF 
THE MONTH OF MAY USING THE LATEST GUIDANCE FROM DYNAMICAL WEATHER PREDICTION 
MODELS, INCLUDING CALIBRATED FORECASTS FROM THE NCEP GLOBAL ENSEMBLE FORECAST 
SYSTEM (GEFS) USING REFORECASTS AND THE NORTH AMERICAN ENSEMBLE FORECAST SYSTEM 
(NAEFS) FOR THE FIRST TWO WEEKS OF JUNE AND FROM THE NCEP CLIMATE FORECAST 
SYSTEM (CFSV2) FOR THE COMING MONTH. ADDITIONALLY, CLIMATE FORCING MECHANISMS 
SUCH AS UNUSUALLY DRY SOIL CONDITIONS AND DECADAL-TIMESCALE CLIMATE TRENDS ALSO 
PLAYED A ROLE IN THE MONTHLY UPDATE. 
 
THE REVISED TEMPERATURE OUTLOOK FOR JUNE 2013 INDICATES A GREATER PROBABILITY 
FOR ABOVE NORMAL MEAN TEMPERATURES FOR PARTS OF THE PACIFIC NORTHWEST AND GREAT 
BASIN AND DECREASED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES IN THE CENTRAL 
AND SOUTHERN PLAINS. ABOVE NORMAL MEAN MONTHLY TEMPERATURES ARE LESS LIKELY IN 
THE GREAT PLAINS WITH CURRENT MODEL PREDICTIONS OF BELOW NORMAL TEMPERATURES IN 
THE NEXT TWO WEEKS. BOTH SHORTER TERM AND MONTHLY MODEL FORECASTS PREDICT AN 
INCREASED PROBABILITY OF ABOVE NORMAL TEMPERATURES IN THE WEST. THE FORECAST 
FOR THE CALIFORNIA COAST CONTINUES TO INDICATE EQUAL CHANCES OF ABOVE, NEAR AND 
BELOW NORMAL TEMPERATURES, WITH BELOW NORMAL SSTS EXPECTED TO MODERATE MONTHLY 
MEAN TEMPERATURES. 
 
THE REVISED PRECIPITATION OUTLOOK FOR JUNE 2013 INDICATES INCREASING 
PROBABILITIES OF ABOVE MEDIAN PRECIPITATION FOR PARTS OF THE SOUTHEAST AND 
ESPECIALLY FLORIDA AND FOR THE ALASKAN PANHANDLE. THE PROBABILITIES OF BELOW 
MEDIAN PRECIPITATION FOR THE SOUTHWEST AND THE SOUTHERN PLAINS HAVE DECREASED. 
DYNAMICAL MODEL FORECASTS FOR THE FIRST TWO WEEKS OF JUNE INDICATE GREATER 
CHANCES OF ABOVE MEDIAN PRECIPITATION FOR THE ALASKAN PANHANDLE, THE SOUTHERN 
AND CENTRAL PLAINS, AND THE SOUTHEAST EARLY IN THE MONTH, REDUCING THE ODDS OF 
BELOW MEDIAN TOTAL PRECIPITATION IN SOME AREAS. IN THE SOUTHWEST, THE CHANCES 
OF BELOW MEDIAN PRECIPITATION IN REGIONS THAT HAVE A RELATIVELY DRY CLIMATOLOGY 
ARE DECREASED. 
 
*** THE HALF-MONTH LEAD MONTHLY OUTLOOK DISCUSSION FOR JUNE 2013 FOLLOWS. *** 
 
ENSO-NEUTRAL CONDITIONS CONTINUE ACROSS THE TROPICAL PACIFIC BASIN. EQUATORIAL 
SEA SURFACE TEMPERATURES (SSTS) FROM ABOUT 135W WESTWARD ACROSS THE CENTRAL AND 
WESTERN PACIFIC ARE CLOSE TO LONG-TERM AVERAGES. FROM ABOUT 135W EASTWARD TO 
THE SOUTH AMERICAN COAST, SSTS ARE GENERALLY 1-2 DEGREES C BELOW AVERAGE. THE 
SUBSURFACE TEMPERATURE ANOMALY PATTERN IS WEAK AND LARGELY NON-DESCRIPT EAST OF 
THE DATE LINE, WHILE WEST OF THE DATE LINE A LARGE VOLUME OF RELATIVELY WARM 
WATER (COMPARED TO NORMAL) IS OBSERVED AT DEPTHS RANGING FROM 50-250 METERS. 
THROUGHOUT THE MONTH OF APRIL, THE NEAR-EQUATORIAL UPPER-OCEAN HEAT CONTENT 
REMAINED SLIGHTLY BELOW AVERAGE. THE OBSERVED TROPICAL CONVECTION PATTERN FOR 
THE PAST 30 DAYS SHOWS ENHANCED CONVECTIVE ACTIVITY OVER THE FAR WESTERN 
PACIFIC AND ADJACENT PORTIONS OF THE MARITIME CONTINENT REGION, AND SUPPRESSED 
CONVECTIVE ACTIVITY ACROSS THE CENTRAL AND EAST-CENTRAL TROPICAL PACIFIC, FROM 
ABOUT 170E TO 120W. 
 
THE JUNE 2013 TEMPERATURE AND PRECIPITATION OUTLOOKS UTILIZED STATISTICAL AND 
DYNAMICAL GUIDANCE, WHICH INCLUDED THE CLIMATE FORECAST SYSTEM MODEL (CFSV2), 
THE NATIONAL MULTI-MODEL ENSEMBLE (NMME), THE CONSTRUCTED ANALOG ON SOIL 
MOISTURE (CAS), THE SCREENING MULTIPLE LINEAR REGRESSION (SMLR), THE CANONICAL 
CORRELATION ANALYSIS (CCA), AND THE OPTIMAL CLIMATE NORMALS (OCN). 
 
THE JUNE TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL TEMPERATURES WEST OF THE 
CONTINENTAL DIVIDE, EXCLUDING NEAR THE PACIFIC COAST WHERE EQUAL CHANCES (EC) 
OF BELOW, NEAR, AND ABOVE-NORMAL TEMPERATURES ARE FAVORED. ABOVE-NORMAL 
TEMPERATURES ARE ALSO FAVORED EAST OF THE DIVIDE OVER THE CENTRAL AND INTERIOR 
SOUTHERN GREAT PLAINS. THIS PREDICTED PATTERN HAS GOOD SUPPORT FROM THE NMME, 
AS WELL AS FROM ITS CONSTITUENT CLIMATE MODELS. THE AREAS OF EC ANTICIPATED 
ALONG THE WEST COAST AND TEXAS COAST ARE DUE TO THE EXPECTED PERSISTENCE OF 
ABNORMALLY COOL SSTS. IN THE EASTERN HALF OF THE CONTIGUOUS U.S., WHERE 
STATISTICAL AND DYNAMICAL MODEL RUNS EXHIBITED CONFLICTING AND/OR WEAK SIGNALS, 
A FORECAST OF EC WAS ASSIGNED. ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED OVER 
NORTHERN ALASKA, BASED PRIMARILY ON THE TRADITIONAL STATISTICAL TOOLS (SMLR, 
CCA, AND OCN) WHICH TEND TO EMPHASIZE LONGER-TERM TRENDS. ELSEWHERE ACROSS 
ALASKA, EQUAL CHANCES (EC) OF BELOW, NEAR, AND ABOVE-NORMAL TEMPERATURES IS 
PREDICTED. 
 
THE JUNE PRECIPITATION OUTLOOK SHOWS ENHANCED ODDS OF BELOW-MEDIAN AMOUNTS OF 
PRECIPITATION OVER THE PACIFIC NORTHWEST, CALIFORNIA, NEVADA, AND MUCH OF BOTH 
THE ROCKIES AND CENTRAL AND SOUTHERN PLAINS. THIS FORECAST IS BASED LARGELY ON 
THE NMME AND RECENTLY OBSERVED PRECIPITATION PATTERNS. UNSEASONABLY WET 
CONDITIONS IN THE PAST FEW WEEKS ACROSS COLORADO AND EASTERN UTAH LEAD TO A 
MORE CAUTIOUS EC FORECAST (AS OPPOSED TO INCREASED ODDS OF BELOW-MEDIAN 
PRECIPITATION) IN THIS AREA. MOST OF THE AVAILABLE DYNAMICAL AND STATISTICAL 
GUIDANCE INDICATES HIGHER PROBABILITIES FOR BELOW-MEDIAN PRECIPITATION OVER NEW 
MEXICO, AND MUCH MORE UNCERTAINTY FOR ARIZONA. THIS SUGGESTS ANY MOISTURE 
ASSOCIATED WITH THE ONSET OF THE SUMMER MONSOON MAY BE DIRECTED MOSTLY TOWARD 
ARIZONA. FOR THE EASTERN HALF OF THE CONUS AND ALASKA, THE CLIMATE MODELS 
SHOWED WEAK AND/OR CONFLICTING SIGNALS, DEEMED TOO UNRELIABLE TO INCLUDE IN THE 
OFFICIAL OUTLOOK. THEREFORE, EC IS FAVORED IN THESE AREAS. 
 
THE MAIN FACTORS WHICH 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) PERSISTANTLY 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 (CFS) 
AND FOR ZERO-LEAD UPDATE FORECASTS THE NCEP GLOBAL ENSEMBLE FORECAST SYSTEM 
(GEFS). THE EARLIER VERSION OF THE CFS MODEL WAS DISCONTINUED AS OF OCTOBER, 
2012. AN EXPERIMENTAL FORECAST SYSTEM, THE NATIONAL MULTI-MODEL ENSEMBLE 
(NMME), COMPRISED OF SEVERAL DYNAMICAL MODELS IS ALSO USED. 
 
 
FORECASTER: DAN COLLINS 
 
 
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. 
 
 
 
THE NEXT MONTHLY OUTLOOK...FOR JUL ... WILL BE ISSUED ON THU JUN 20 2013 
 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. 
 
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