PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300PM EDT TUESDAY JUL 31 2012

30-DAY OUTLOOK DISCUSSION FOR AUGUST 2012

THE UPDATED AUGUST 2012 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON A 
NUMBER OF FACTORS, SUCH AS THE MOST RECENT EXTENDED-RANGE MODEL GUIDANCE, 
CLIMATE MODELS SUCH AS THE CFSV2 AND NMME, SOIL MOISTURE CONDITIONS, SEA 
SURFACE TEMPERATURES (SST), AND RECENT OBSERVED TEMPERATURE AND PRECIPITATION 
PATTERNS.

ENSO NEUTRAL CONDITIONS CONTINUED DURING THE MONTH OF JULY. POSITIVE EQUATORIAL 
PACIFIC SEA SURFACE TEMPERATURE (SST) ANOMALIES HAVE INCREASED ACROSS THE 
EASTERN PACIFIC OCEAN, EXCEEDING +1.0 C IN LATE JULY. SST ANOMALIES ARE SMALL 
ACROSS MUCH OF THE WESTERN AND CENTRAL PACIFIC WHERE DEPARTURES FROM NORMAL ARE 
WITHIN 0.5 C. AT DEPTH, OCEAN TEMPERATURES ARE GENERALLY ABOVE AVERAGE WITH THE 
LARGEST POSITIVE ANOMALIES (3 TO 4 CELSIUS DEGREES) CENTERED FROM 125W-110W AT 
50 METER DEPTH.  

THE UPDATED AUGUST 2012 TEMPERATURE OUTLOOK DEPICTS ENHANCED ODDS FOR 
ABOVE-NORMAL MEAN TEMPERATURES ACROSS MOST OF THE CONTIGUOUS UNITED STATES AND 
NORTHERN ALASKA. THIS IS BASED ON CONSISTENT SIGNATURES FROM CLIMATE MODEL 
FORECASTS (CFSV2 AND NMME), VERY LOW SOIL MOISTURE CONDITIONS ACROSS THE 
EAST-CENTRAL CONUS, LONG TERM TEMPERATURE TRENDS, AND TEMPERATURE OBSERVATIONS 
OVER THE PAST 30-DAYS. THE LARGEST PROBABILITIES ARE INDICATED OVER THE MIDDLE 
MISSISSIPPI VALLEY AND ADJACENT PORTIONS OF THE CENTRAL PLAINS, WHICH HAVE VERY 
LOW SOIL MOISTURE VALUES AND SEVERE REDUCTIONS IN EVAPOTRANSPIRATION, BOTH OF 
WHICH CAN RESULT IN PERPETUATING THE REGIONAL DROUGHT. IN NORTHERN ALASKA, ODDS 
FAVOR ABOVE-NORMAL TEMPERATURES DUE PRIMARILY TO THE CFSV2 AND ABNORMALLY WARM 
SSTS. BELOW-NORMAL AUGUST MEAN TEMPERATURES ARE FAVORED FOR THE COASTAL REGIONS 
OF BOTH THE PACIFIC NORTHWEST AND SOUTHERN ALASKA, SUPPORTED IN PART BY THE 
CFSV2 AND ABNORMALLY COOL SSTS. ELSEWHERE THERE ARE EITHER VERY WEAK OR 
CONFLICTING SIGNALS AMONG TOOLS, AND SO EQUAL CHANCES FOR BELOW-, NEAR-, OR 
ABOVE-NORMAL AUGUST MEAN TEMPERATURES ARE INDICATED.

THE AUGUST 2012 PRECIPITATION OUTLOOK FAVORS ABOVE-MEDIAN PRECIPITATION FOR 
MUCH OF THE SOUTHWEST U.S. IN RELATION TO AN ACTIVE MONSOON, AND NORTHWESTERN 
PORTIONS OF ALASKA. THIS HAS SOME SUPPORT FROM THE CFSV2 MODEL, AND ALSO FROM 
SHORT-TERM (NEXT 5-DAYS) PRECIPITATION FORECASTS. ODDS FOR BELOW-MEDIAN 
PRECIPITATION ARE ELEVATED OVER A LARGE PORTION OF BOTH THE MISSISSIPPI VALLEY 
AND GREAT PLAINS REGION, EXTENDING AS FAR WEST AS EASTERN NEW MEXICO. THIS IS 
LARGELY ATTRIBUTED TO REINFORCING, NEGATIVE FEEDBACKS ASSOCIATED WITH DRY SOILS 
DURING THE SUMMER SEASON, AND IS CONSISTENT WITH RAINFALL OBSERVATIONS FOR THE 
PAST 30-DAYS. ODDS FOR BELOW-MEDIAN PRECIPITATION ARE ALSO ELEVATED OVER THE 
PACIFIC NORTHWEST, THE ALASKA PANHANDLE, AND SOUTHWEST PORTIONS OF ALASKA 
INCLUDING THE EASTERN ALEUTIANS. THIS IS DUE PRIMARILY TO THE CFSV2 MODEL AND 
RECENT TRENDS IN EXTENDED-RANGE GUIDANCE. ELSEWHERE, WHERE THERE ARE EITHER 
WEAK OR CONFLICTING SIGNALS AMONG THE TOOLS, EQUAL CHANCES (EC) OF BELOW-, 
NEAR-, AND ABOVE-MEDIAN PRECIPITATION IS PROJECTED.

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 UPGRADED VERSION OF THE CFS (CFSV2) BECAME OPERATIONAL IN LATE 
MARCH OF 2011. BOTH VERSIONS OF CFS ARE CURRENTLY RUN IN PARALLEL. 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.



THE NEXT MONTHLY OUTLOOK...FOR SEP ... WILL BE ISSUED ON THU AUG 16 2012


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

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