PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830AM EDT THURSDAY SEP 20 2012

30-DAY OUTLOOK DISCUSSION FOR OCTOBER 2012

ENSO NEUTRAL CONDITIONS CONTINUED DURING THE MONTH OF SEPTEMBER. POSITIVE 
EQUATORIAL PACIFIC SEA SURFACE TEMPERATURE (SST) ANOMALIES HAVE BEEN OBSERVED 
IN THE CENTRAL AND EASTERN PACIFIC WITH WEEKLY NINO3.4 VALUES GENERALLY AROUND 
+0.5 C. EL NINO CONDITIONS ARE LIKELY LATER IN THE FALL.

THE OCTOBER 2012 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON A NUMBER 
OF FACTORS WHICH INCLUDE CLIMATE MODELS SUCH AS THE CFSV2 AND NMME, SOIL 
MOISTURE CONDITIONS, SEA SURFACE TEMPERATURES (SST), AND RECENT OBSERVED 
TEMPERATURE AND PRECIPITATION PATTERNS. 

THE OCTOBER 2012 TEMPERATURE OUTLOOK DEPICTS ENHANCED ODDS FOR ABOVE-NORMAL 
MEAN TEMPERATURES ACROSS MOST OF THE CONTIGUOUS UNITED STATES FROM THE ROCKIES 
TO NEW ENGLAND, AND NORTHERN ALASKA. THIS IS BASED ON CONSISTENT SIGNATURES 
FROM CLIMATE MODEL FORECASTS (CFSV2 AND NMME), AND THE CAS WHICH ACTS ON VERY 
LOW SOIL MOISTURE CONDITIONS ACROSS A LARGE AREA OF THE EAST-CENTRAL CONUS. 
STATISTICAL TOOLS INDICATE WARMTH TO EXTEND ALSO INTO THE SOUTHWEST, AND THIS 
IS IN PART DUE TO LONG TERM TEMPERATURE TRENDS.  BELOW-NORMAL OCTOBER MEAN 
TEMPERATURES ARE FAVORED FOR ALL COASTAL REGIONS FROM SOUTHERN ALASKA TO 
CALIFORNIA, 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 OCTOBER MEAN TEMPERATURES ARE 
INDICATED.

THE OCTOBER 2012 PRECIPITATION OUTLOOK FAVORS ABOVE-MEDIAN PRECIPITATION FOR 
SOUTHWESTERN SECTIONS OF TEXAS AND FOR SOUTHERN SECTIONS OF NEW MEXICO 
PRIMARILY SUPPORTED FROM THE CFSV2. SOME OF THE DYNAMICAL MODELS ARE PREDICTING 
ENHANCED CHANCES FOR BELOW-MEDIAN PRECIPITATION FOR THE NW CORNER OF THE CONUS 
AND FROM THE MIDWEST THROUGH THE GREAT LAKES TO NEW ENGLAND.  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: ED O'LENIC


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 OCT WILL BE ISSUED ON SUN SEPTEMBER 30 2012


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

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