PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 
300 PM EDT FRI SEP 30 2016 
 
30-DAY OUTLOOK DISCUSSION FOR OCTOBER 2016 
 
THE OCTOBER TEMPERATURE AND PRECIPITATION OUTLOOKS ARE UPDATED PRIMARILY BASED 
ON SHORT, MEDIUM AND EXTENDED RANGE MODEL GUIDANCE TO ADJUST THE PREVIOUS 
MID-SEPTEMBER OUTLOOK. 
 
ON AVERAGE, FORECAST RIDGING WITH POSITIVE HEIGHT DEPARTURES AND MEAN ANOMALOUS 
SOUTHWESTERLY FLOW EARLY IN THE MONTH ACROSS EASTERN NORTH AMERICA CONTRIBUTES 
TO FAVORED ABOVE NORMAL MONTHLY MEAN TEMPERATURES FOR AREAS OF THE CENTRAL AND 
EASTERN CONUS. THE HIGHEST PROBABILITIES ARE LOCATED IN PROXIMITY TO THE GREAT 
LAKES WHERE SHORT-, MEDIUM- AND EXTENDED RANGE GUIDANCE ARE CONSISTENT WITH 
INDICATING ABOVE NORMAL TEMPERATURES. THE CFS MONTH LONG FORECASTS PERSIST THIS 
SIGNAL IN THIS AREA AS WELL FOR THE REMAINDER OF THE MONTH. 
 
EARLY IN THE MONTH, A TROUGH IS ANTICIPATED TO IMPACT THE WESTERN CONUS AND 
BELOW NORMAL TEMPERATURES ARE FAVORED FOR VARIOUS PORTIONS OF THE INTERIOR WEST 
ADDING SOME UNCERTAINTY FOR THE FORECAST OF MEAN TEMPERATURES FOR THE MONTH AS 
A WHOLE. CONSEQUENTLY, THE AREA DEPICTED WITH EQUAL CHANCES FOR ABOVE, BELOW OR 
NEAR NORMAL MONTHLY MEAN TEMPERATURES ARE SHIFTED WESTWARD FROM THE PREVIOUS 
OUTLOOK. WEEK 3-4 MODEL GUIDANCE INDICATES ABOVE AVERAGE TEMPERATURES RETURNING 
FOR THE WEST COAST AND AREAS ALONG THE NORTHERN TIER OF THE WESTERN CONUS SO 
WEAK PROBABILITIES FOR THE ABOVE NORMAL CATEGORY REMAIN IN THESE AREAS. WEEK 
3-4 MODEL GUIDANCE IS LESS CLEAR ACROSS THE SOUTHWEST AS HIGHLIGHTED BY THE 
MONTHLY CFS FORECAST. 
 
ANTICIPATED MEAN POSITIVE 500-HPA HEIGHT DEPARTURES, SOUTHERLY FLOW AND ABOVE 
NORMAL OCEAN TEMPERATURES IN NEARBY WATERS FAVOR ABOVE NORMAL TEMPERATURES FOR 
THE ENTIRE STATE OF ALASKA. EQUAL CHANCES (EC) FOR ABOVE, BELOW OR NEAR NORMAL 
MONTHLY MEAN TEMPERATURES ARE INDICATED IN THE WHITE REGIONS LABELED WITH EC. 
 
THE ABOVE MEDIAN PRECIPITATION AREA ACROSS THE CENTRAL PLAINS IN THE ORIGINAL 
OUTLOOK HAS BEEN EXPANDED AND SHIFTED NORTH AND WEST IN THE UPDATED OUTLOOK AS 
THIS IS MORE CONSISTENT WITH ANTICIPATED MEAN TROUGHING AT VARIOUS TIMES DURING 
THE OUTLOOK PERIOD. EARLY IN THE MONTH, A TROUGH IS FAVORED TO IMPACT THE 
WESTERN CONUS AND SUPPORT PRECIPITATION IN THE HIGHLIGHTED REGION. MORE ACTIVE 
WEATHER IS NOW ANTICIPATED ACROSS THE PACIFIC NORTHWEST OVER THE FORECAST 
PERIOD AND SO ELEVATED ODDS FOR ABOVE MEDIAN PRECIPITATION ARE NOW INDICATED 
FOR SOME AREAS IN THE UPDATED OUTLOOK. THE CFS MONTHLY FORECAST INDICATES 
MODESTLY HIGH PROBABILITIES ACROSS THE HIGHLIGHTED AREA FOR THE MONTH OF 
OCTOBER AS A WHOLE AS WELL. 
 
ANTICIPATED MEAN RIDGING AND ALL INDICATIONS FROM SHORT, MEDIUM AND EXTENDED 
RANGE GUIDANCE CONTINUE TO SUPPORT DRY CONDITIONS FOR AREAS OF THE INTERIOR 
SOUTHEAST DURING THE MONTH SO THIS AREA REMAINS AND IS SLIGHTLY EXPANDED IN THE 
FORECAST UPDATE. A SUBSTANTIAL WILDCARD IN THE OUTLOOK IS THE EVOLUTION OF 
HURRICANE MATTHEW AND ANY POTENTIAL IMPACT TO AREAS OF THE SOUTHEAST AND 
EASTERN SEABOARD. THERE IS HIGH UNCERTAINTY FOR THE TRACK OF MATTHEW DURING THE 
EARLY PORTIONS OF OCTOBER. LATEST FORECASTS KEEP THE SYSTEM OFF THE EASTERN 
SEABOARD BUT THERE IS CONSIDERABLE FORECAST SPREAD IN ENSEMBLE MODEL GUIDANCE. 
 
ABOVE MEDIAN PRECIPITATION IS FAVORED FOR SOUTHWESTERN PORTIONS OF ALASKA 
PRIMARILY DURING THE FIRST 10 DAYS OF THE PERIOD. EQUAL CHANCES (EC) FOR ABOVE, 
BELOW OR NEAR MEDIAN MONTHLY PRECIPITATION AMOUNTS ARE INDICATED IN THE WHITE 
REGIONS LABELED WITH EC. 
 
************ PREVIOUS DISCUSSION IS BELOW *************************** 
 
A REVIEW OF TROPICAL SEASONAL AND INTRASEASONAL CLIMATE CONDITIONS DURING EARLY 
TO MID SEPTEMBER INDICATE CONTINUED ENSO-NEUTRAL CONDITIONS AND INCOHERENT MJO 
ACTIVITY. ALTHOUGH EQUATORIAL CENTRAL AND EASTERN PACIFIC SEA SURFACE 
TEMPERATURES (SST) ARE BELOW NORMAL ON AVERAGE, THEY REMAIN GENERALLY WEAKLY SO 
ACROSS SUBSTANTIAL PORTIONS OF THE BASIN. NEGATIVE ANOMALIES OF EQUATORIAL 
OCEAN HEAT CONTENT (OCEAN TEMPERATURE DEPARTURES TO A DEPTH OF 300 METERS) HAVE 
SLOWLY DECREASED SINCE MAY. ALTHOUGH SUPPRESSED CONVECTION IS INDICATED ACROSS 
PORTIONS OF THE CENTRAL PACIFIC, SUBSTANTIAL LOWER- AND UPPER-LEVEL WIND 
ANOMALIES, CONSISTENT WITH LA NINA, ARE LACKING. IN ADDITION TO THESE LATEST 
OBSERVATIONS, DYNAMICAL MODEL GUIDANCE OF FORECASTS OF NINO3.4 SST HAVE TRENDED 
TOWARD ENSO-NEUTRAL CONDITIONS FOR THE AUTUMN AND WINTER MONTHS AND THE ODDS 
FOR LA NINA HAVE DECREASED. THE LA NINA WATCH IS NO LONGER IN PLACE AND 
ENSO-NEUTRAL CONDITIONS ARE FAVORED THROUGH OCTOBER. 
 
MJO INDICES (CPC VELOCITY POTENTIAL AND RMM) INDICATE NO APPRECIABLE COHERENT 
MJO ACTIVITY DURING THE PAST MONTH AND FORECASTS DO NOT DEPICT CLEAR, LONG TERM 
STRENGTHENING AT THE CURRENT TIME AND THE MJO DID NOT PLAY A ROLE IN THE 
HALF-MONTH-LEAD OCTOBER OUTLOOK. 
 
THE OCTOBER 2016 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE PRIMARILY BASED ON 
AVAILABLE DYNAMICAL MODEL GUIDANCE, ALTHOUGH STATISTICAL BASED TOOLS WERE 
UTILIZED AS WELL INCLUDING THOSE TARGETING AUTUMN SEASON LONGER TERM TRENDS. 
COASTAL SST DEPARTURES FROM NORMAL ALSO PLAYED A ROLE IN THE OUTLOOK PRIMARILY 
FOR AREAS NEAR ALASKA AND NEW ENGLAND. 
 
THE OCTOBER TEMPERATURE OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES FOR MOST OF 
THE FORECAST DOMAIN. THERE IS NEARLY UNANIMOUS SUPPORT FOR ANOMALOUS WARMTH AS 
DEPICTED ON THE OUTLOOK MAP FROM THE NMME AND IMME MODEL SUITE WHICH INCLUDES 
THE CFS AND ECMWF MODELING SYSTEMS, AMONG SEVERAL OTHER PARTICIPANT MODELS. THE 
PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE THE LARGEST FOR AREAS IN 
ALASKA, THE SOUTHWEST AND NEW ENGLAND. STRONGLY ABOVE NORMAL SSTS SURROUNDING 
WESTERN AND SOUTHERN ALASKA AND LONG TERM TRENDS ACROSS THE NORTH SLOPE 
INCREASE ODDS FOR ABOVE NORMAL TEMPERATURES IN THESE AREAS. STRONGLY POSITIVE 
LONG TERM TEMPERATURE TRENDS AND STATISTICAL GUIDANCE INCREASE PROBABILITIES 
FOR AREAS IN THE SOUTHWEST AND NEW ENGLAND. 
 
AVAILABLE WEEK 3-4 SPECIFIC MODEL GUIDANCE DOES SHOW AREAS OF FAVORED NEAR TO 
BELOW NORMAL TEMPERATURES AND GREATER UNCERTAINTY IN GENERAL ACROSS THE 
INTERIOR OF THE CONUS IN EARLY OCTOBER SO PROBABILITIES FOR ABOVE NORMAL 
TEMPERATURES ARE LESS FOR PARTS OF THE CENTRAL AND NORTHERN PLAINS AND 
SOUTHEAST. MOREOVER, THIS UNCERTAINTY AND CONSIDERABLY WEAKER SIGNALS FOR 
ANOMALOUS WARMTH FROM THE NMME AND IMME DYNAMICAL MODEL SUITE SUPPORT EQUAL 
CHANCES (EC) FOR ABOVE, NEAR OR BELOW NORMAL TEMPERATURES ACROSS THE SOUTH 
CENTRAL PART OF THE CONUS. 
 
THERE IS HIGH UNCERTAINTY FOR THE PRECIPITATION OUTLOOK, AS IS TYPICAL FOR THIS 
TIME OF THE YEAR. THERE ARE SOME SIGNALS THAT CAN BE HIGHLIGHTED, HOWEVER, 
BASED ON THE CURRENTLY FAVORED FORECAST PATTERN. ANOMALOUS SOUTHERLY FLOW 
ACROSS THE GULF OF ALASKA FAVORS ABOVE MEDIAN PRECIPITATION FOR THE SOUTHERN 
AREAS OF ALASKA INCLUDING THE PANHANDLE REGION. DYNAMICAL MODEL GUIDANCE ACROSS 
TIME SCALES FAVORS BELOW-MEDIAN PRECIPITATION FOR PARTS OF THE PACIFIC 
NORTHWEST AND INTERIOR SOUTHEAST DURING THE MONTH OF OCTOBER. ABOVE-MEDIAN 
PRECIPITATION FAVORED BY THE MONTHLY CFS FORECAST AND POTENTIAL TROUGHING 
ACROSS AREAS OF THE CENTRAL CONUS IS THE REASON FOR ENHANCED ODDS FOR ABOVE 
MEDIAN PRECIPITATION DEPICTED IN THE CENTRAL PLAINS. EQUAL CHANCES FOR ABOVE, 
NEAR OR BELOW-MEDIAN PRECIPITATION ARE INDICATED IN REMAINING AREAS. 
 
 
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. 
 
 
 
THE NEXT MONTHLY OUTLOOK...FOR NOV ... WILL BE ISSUED ON THU OCT 20 2016 
 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. 
 
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