PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 
830AM EDT THURSDAY MAY 16 2013 
 
30-DAY OUTLOOK DISCUSSION FOR JUNE 2013 
 
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: ANTHONY ARTUSA 
 
 
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 JUN WILL BE ISSUED ON FRI MAY 31 2013 
 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. 
 
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