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Official 90-day Outlooks are issued once each month near mid-month at 8:30am Eastern Time. Please consult the schedule of 30 & 90-day outlooks for exact release dates.

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    0.5mn OND 2014
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    0.5mn Oct 2014


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HOME> Outlook Maps>Seasonal Forecast Discussion
 
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830AM EDT THURSDAY SEP 18 2014

30-DAY OUTLOOK DISCUSSION FOR OCTOBER 2014

THROUGH THE EARLY PORTION OF SEPTEMBER, RECENT ATMOSPHERIC AND OCEANIC
CONDITIONS CONTINUE TO INDICATE ENSO NEUTRAL CONDITIONS. AFTER A SLIGHT PAUSE
DURING LATE JULY AND EARLY AUGUST, SEA SURFACE TEMPERATURES (SST) ACROSS THE
EQUATORIAL CENTRAL PACIFIC OCEAN ARE AGAIN SHOWING AN UPWARD TREND WITH
ANOMALIES AVERAGED ACROSS THE NINO3.4 REGION NOW NEAR +0.5 DEGREES C THIS PAST
WEEK. EQUATORIAL OCEAN TEMPERATURES FROM THE SURFACE TO 300 M DEPTH ALSO
INDICATE A RESERVOIR OF ABOVE AVERAGE OCEAN TEMPERATURES OVER MUCH OF THE
CENTRAL PACIFIC OCEAN WITH THE GREATEST DEPARTURES CENTERED NEAR 100 M DEPTH
FROM 170W TO 110W. STATISTICAL AND DYNAMICAL MODEL FORECASTS FOR NINO3.4 SST
CONTINUE TO INDICATE PRIMARILY A WEAK EL NINO EVENT PEAKING IN LATE AUTUMN OR
EARLY WINTER. THE OCTOBER OUTLOOK DID TAKE INTO CONSIDERATION POTENTIAL EL NINO
CONDITIONS, MAINLY FOR ADDITIONAL SUPPORT TO OTHER FORECAST GUIDANCE.

OTHER RECENT CLIMATE CONDITIONS OR FACTORS CONSIDERED FOR THE OCTOBER OUTLOOK
INCLUDED POSITIVE SST ANOMALIES IN PROXIMITY TO MOST AREAS OF COASTAL ALASKA
AND THE U.S. WEST COAST, AS WELL AS BELOW NORMAL ARCTIC SEA ICE ALONG THE NORTH
SLOPE OF ALASKA. SOIL MOISTURE CONDITIONS ACROSS THE FAR WEST AND SOUTHWEST
ALSO PLAYED A ROLE IN THE OUTLOOK. THE CURRENT WEAK MJO ACTIVITY WAS CONSIDERED
FOR THE OCTOBER OUTLOOK ALTHOUGH TELECONNECTIONS DURING THIS TIME OF THE YEAR
ARE DIFFICULT TO ASSESS AND THIS PLAYED A MINOR ROLE.

MODEL GUIDANCE FROM THE CFS, NMME AND IMME WERE UTILIZED AS WELL IN PREPARING
THE INITIAL OCTOBER OUTLOOK. MORE TRADITIONAL STATISTICAL FORECAST TOOLS
OFFERED LITTLE SIGNAL OTHER THEN FOR TEMPERATURE IN ALASKA AND THE NORTHEAST
CONUS.

THE OCTOBER TEMPERATURE OUTLOOK INDICATES AN INCREASED LIKELIHOOD FOR
ABOVE-NORMAL MONTHLY MEAN TEMPERATURES FOR THE ENTIRE STATE OF ALASKA AND THE
WEST COAST STATES. FOR ALASKA, THE OUTLOOK IS BASED ON SEVERAL FACTORS THAT
INCLUDE A GENERAL CONSENSUS AMONGST THE DYNAMICAL MODEL GUIDANCE FOR
ABOVE-NORMAL UPPER-LEVEL HEIGHTS, ESPECIALLY FROM THE CFS, STRONGLY POSITIVE
SST ANOMALIES IN NEIGHBORING WATERS AND BELOW NORMAL ARCTIC SEA ICE ALONG THE
NORTH COAST. CONSISTENT RUN-TO-RUN FORECAST RIDGING BY THE CFS, CONTINUED DRY
SOIL MOISTURE CONDITIONS AND ABOVE NORMAL COASTAL SSTS ARE THE BASIS FOR THE
FORECAST FOR THE WEST COAST STATES. A COMBINATION OF EL NINO CONSIDERATIONS,
POTENTIAL ANTECEDENT WETNESS FROM ABOVE AVERAGE SEPTEMBER RAINFALL AND FAVORED
ABOVE-MEDIAN PRECIPITATION DURING OCTOBER ARE THE BASIS FOR ELEVATED ODDS OF
BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE SOUTHWEST, CENTRAL ROCKIES AND
CENTRAL HIGH PLAINS. DYNAMICAL MODEL GUIDANCE OF THE NMME AND IMME AND
PARTICIPANT MEMBERS FAVOR ELEVATED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES
FOR AREAS IN THE GREAT BASIN AND FOR AN AREA FROM EAST TEXAS NORTH AND EAST TO
INCLUDE THE MID-ATLANTIC AND NORTHEAST.

THE MONTHLY OUTLOOK FOR OCTOBER 2014 INDICATES A GREATER THAN NORMAL LIKELIHOOD
OF ABOVE-MEDIAN PRECIPITATION FOR MUCH OF THE SOUTHWEST AND CENTRAL ROCKIES,
SOUTHERN ALASKA (INCLUDING THE PANHANDLE) AND FOR THE UPPER MIDWEST AND WESTERN
GREAT LAKES REGION. BELOW MEDIAN MONTHLY PRECIPITATION AMOUNTS ARE MOST LIKELY
FOR PARTS OF THE PACIFIC NORTHWEST.

IN THE SOUTHWEST CONUS, MODEL FORECASTS CONTINUE TO INDICATE A CONTINUATION OF
THE PATTERN THAT HAS OCCURRED OFTEN THIS SUMMER TO DATE, NAMELY AN ENHANCED
ITCZ, ACTIVE TROPICAL CYCLONE SEASON AND FREQUENT MOISTURE SURGES INTO THE
SOUTHWEST CONUS. IT IS DIFFICULT TO ARGUE AGAINST THIS CONTINUING INTO OCTOBER
GIVEN REMAINING ABOVE NORMAL SSTS IN THE REGION AND CONTINUED FREQUENT TROPICAL
CYCLONE DEVELOPMENT. TWO OTHER HIGHLIGHTED AREAS, ABOVE-MEDIAN (BELOW-MEDIAN)
MONTHLY PRECIPITATION TOTALS FOR SOUTHERN ALASKA (PACIFIC NORTHWEST) ARE SHOWN
IN A CONSENSUS OF THE MODEL GUIDANCE CONSISTENT WITH A MEAN TROUGH-RIDGE
PATTERN ACROSS THE NORTH PACIFIC - WESTERN NORTH AMERICA REGION AS WELL AS
COMPOSITES BASED ON EL NINO CONDITIONS FOR OCTOBER. FAVORED ABOVE MEDIAN
PRECIPITATION IN THE UPPER MIDWEST REGION IS BASED LARGELY ON MODEL GUIDANCE
WHICH SHOWS A TREND TOWARD TROUGHING AND ENHANCED PRECIPITATION IN THIS AREA.
IF THE MJO REMAINS ACTIVE, WHICH IS UNCERTAIN, IT WOULD TEND TO ALSO FAVOR
ABOVE MEDIAN PRECIPITATION IN THIS AREA LATER IN OCTOBER.

IN AREAS WHERE CLIMATE SIGNALS ARE WEAK SUCH THAT THE LIKELIHOODS OF MONTHLY
MEAN TEMPERATURES OR MONTHLY ACCUMULATED PRECIPITATION AMOUNTS ARE SIMILAR 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: JON GOTTSCHALCK


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 TUE SEPTEMBER 30 2014


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

$$

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