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FXUS07 KWBC 301901
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT WED SEP 30 2026
30-DAY OUTLOOK DISCUSSION FOR OCT 2026
THE UPDATED SET OF TEMPERATURE AND PRECIPITATION OUTLOOKS FOR OCTOBER 2026 ARE
BASED PRIMARILY ON THE LATEST WPC WEEK-1 AND CPC WEEK-2 AND WEEKS 3-4 GUIDANCE,
ALONG WITH THE LATEST DYNAMICAL MODEL INPUT FROM THE ECENS AND GEFS ENSEMBLE
SYSTEMS. OTHER CONSIDERATIONS INCLUDE THE VERY ACTIVE TROPICAL CYCLONE SEASON
IN THE EASTERN AND CENTRAL PACIFIC, THE CURRENT EL NINO, CLIMATOLOGY, AND
PRECIPITATION 7-DAY AND 30-DAY DEPARTURES FROM NORMAL. EXPERIMENTAL GEFS AND
CFS PERIOD-WEIGHTED TEMPERATURE AND PRECIPITATION FORECASTS WERE ALSO
CONSIDERED, AS WELL AS EXPERIMENTAL AIMS2S MODEL GUIDANCE.
THE UPDATED TEMPERATURE OUTLOOK FOR OCTOBER FAVORS ABOVE NORMAL MONTHLY MEAN
TEMPERATURES FOR NEARLY ALL AREAS WEST OF THE CONTINENTAL DIVIDE. EAST OF THE
DIVIDE, ANOMALOUS WARMTH IS FAVORED FOR THE NORTHERN AND CENTRAL PLAINS, THE
UPPER MISSISSIPPI VALLEY, AND IN THE VICINITY OF THE GULF COAST. THE HIGHEST
CHANCES OF ABOVE NORMAL TEMPERATURES ARE INDICATED OVER CALIFORNIA AND PARTS OF
WESTERN NEVADA AND SOUTHERN OREGON, AS WELL AS OVER MOST OF THE FLORIDA
PENINSULA. THE BROAD COVERAGE OF FAVORED ABOVE NORMAL TEMPERATURES IS GENERALLY
CONSISTENT WITH OFFICIAL WPC WEEK-1 AND CPC WEEK-2 AND WEEKS 3-4 TEMPERATURE
GUIDANCE, AS WELL AS AN EXTENDED PERIOD OF MID-LEVEL RIDGING AND 500-HPA
POSITIVE HEIGHT ANOMALIES FOR THE WEST. AIMS2S SUBSEASONAL-TO-SEASONAL
TEMPERATURE GUIDANCE ALSO LENDS SUPPORT TO THIS OUTLOOK, THOUGH IT DIFFERS BY
PREDICTING A COOL-DOWN RELATIVE TO NORMAL DURING THE LATTER HALF OF OCTOBER
ACROSS THE GULF COAST REGION AND SOUTHEAST. IN ALASKA, EXPERIMENTAL GEFS AND
CFS PERIOD-WEIGHTED GUIDANCE, IN ADDITION TO CPCS EXTENDED-RANGE TEMPERATURE
OUTLOOKS, FAVORS ABOVE NORMAL TEMPERATURES OVER THE EASTERN INTERIOR,
SOUTHCENTRAL AND SOUTHEASTERN ALASKA. ELSEWHERE, WHICH INCLUDES A SIZABLE
PORTION OF THE LOWER 48 STATES, AND WESTERN AND NORTHERN ALASKA, EQUAL CHANCES
(EC) OF ABOVE, NEAR, AND BELOW NORMAL TEMPERATURES IS FAVORED.
THE UPDATED PRECIPITATION OUTLOOK FOR OCTOBER FAVORS ABOVE NORMAL PRECIPITATION
FOR MOST OF THE SOUTHERN TIER OF THE CONTIGUOUS U.S. (CONUS), FROM SOUTHERN
ARIZONA EASTWARD ACROSS THE SOUTHERN PLAINS, LOWER MISSISSIPPI AND TENNESSEE
VALLEYS, AND THE SOUTHEAST. MAXIMUM PROBABILITIES RANGING FROM 50 TO AS MUCH AS
80-PERCENT ARE CONCENTRATED CLOSER TO THE GULF COAST AND THE TEXAS HILL
COUNTRY. THIS WET PATTERN IS HEAVILY FRONT-LOADED (WITHIN THE FIRST 7-10 DAYS
OF OCTOBER) AND IS ASSOCIATED WITH SEVERAL HIGH PRESSURE SYSTEMS AND THEIR
ACCOMPANYING SURGES OF COOLER CANADIAN AIR MOVING SOUTHWARD TO NEAR THE GULF
COAST. THE RESPECTIVE COLD FRONTS REPRESENTING THE LEADING EDGES OF THESE
COOLER SURGES ARE FORECAST TO STALL ACROSS THE DEEP SOUTH, ACCOMPANIED BY
EASTERLY SURFACE FLOW AND INCREASINGLY MOIST CONDITIONS. IN ADDITION, MANY OF
THE MODELS AND TOOLS USED SUPPORT THIS ANOMALOUSLY WET OUTCOME. DESPITE THIS
BEING EARLY IN THE FALL SEASON, THE SOUTHERN STORM TRACK COMMONLY OBSERVED WITH
STRONG EL NINOS IS ALREADY BEGINNING TO TAKE SHAPE. BELOW NORMAL PRECIPITATION
IS FAVORED FROM THE UPPER MISSISSIPPI VALLEY/WESTERN GREAT LAKES REGION
WEST-SOUTHWESTWARD ACROSS THE NORTHERN AND CENTRAL ROCKIES, AND THE NORTHERN
AND CENTRAL GREAT BASIN TO NEARLY ALL OF THE WEST COAST. THIS IS ASSOCIATED
WITH EXTENSIVE AND PROLONGED MID-LEVEL HIGH PRESSURE AND THE EXPECTATION OF
WIDESPREAD POSITIVE 500-HPA HEIGHT ANOMALIES. IN THE PACIFIC NORTHWEST,
CONDITIONS LOOK ABNORMALLY DRY AT LEAST THROUGH THE FIRST HALF OF OCTOBER,
ACCORDING TO WPCS OFFICIAL WEEK-1 PRECIPITATION OUTLOOK AND CPCS OFFICIAL
WEEK-2 PRECIPITATION OUTLOOK. LATER IN OCTOBER, THE POSSIBILITY OF A PERSISTENT
NORTHEAST PACIFIC MID-LEVEL TROUGH SHIFTING EASTWARD WARRANTS AT LEAST A
NON-DRY (I.E. EC) OUTLOOK FOR THE WESTERNMOST REACHES OF WASHINGTON STATE.
ACROSS THE SOUTHWEST, THE MONSOON IS TYPICALLY WINDING DOWN IN OCTOBER.
HOWEVER, THERE IS ALWAYS THE TROPICAL CYCLONE WILDCARD TO CONSIDER, WHERE A
LATE SEASON TROPICAL CYCLONE OVER THE EASTERN PACIFIC AND/OR RELATED GULF SURGE
FROM THE GULF OF CALIFORNIA BRINGS ABUNDANT MOISTURE INTO THE AMERICAN
SOUTHWEST. THIS FALL, GIVEN THE CURRENT STRENGTH OF EL NINO AND THE VERY ACTIVE
TROPICAL CYCLONE SEASON THUS FAR, THE POSSIBILITY OF A TROPICAL SYSTEM
AFFECTING THE SOUTHWEST EXTENDS INTO THE AUTUMN SEASON EVEN LATER THAN USUAL.
THE PRECIPITATION OUTLOOK FOR ALASKA SEEMS RELATIVELY STRAIGHTFORWARD GIVEN THE
INCREASED LIKELIHOOD OF A MID-LEVEL TROUGH POSITIONED FROM ABOUT THE BERING SEA
TO THE CENTRAL GULF OF ALASKA, WHICH IS A HIGHLY FAVORABLE PATTERN THAT
PROMOTES INCREASED PRECIPITATION OVER THE SOUTHERN PORTION OF THE STATE. THIS
WIDESPREAD ONSHORE FLOW PATTERN IS CLEARLY INDICATED BY THE AIMS2S TOOL, AND
THE GEFS/ECENS WEEK-2 PRECIPITATION DEPARTURE FORECASTS WHICH TAKES US AT LEAST
INTO MID-OCTOBER. ELSEWHERE, WHICH INCLUDES A LARGE PORTION OF THE CONUS,
WESTERN AND NORTHERN ALASKA, AND THE ALEUTIANS, EQUAL CHANCES (EC) OF ABOVE,
NEAR, AND BELOW NORMAL PRECIPITATION IS FAVORED.
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PREVIOUS MID-MONTH DISCUSSION BELOW
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THE OCTOBER 2026 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON THE: NORTH
AMERICAN MULTI-MODEL ENSEMBLE (NMME) AND INTERNATIONAL MULTI-MODEL ENSEMBLE
(IMME), CONSOLIDATION (DYNAMICAL AND STATISTICAL TOOLS), AND EL NINO
COMPOSITES. DUE TO THE STRONG AND DOMINANT EL NINO, THE MADDEN-JULIAN
OSCILLATION (MJO) WAS NOT A FACTOR IN THE OCTOBER FORECAST. THE WEST PACIFIC IS
LIKELY TO REMAIN ACTIVE WITH A NUMBER OF TROPICAL CYCLONES (TCS) HEADING INTO
OCTOBER. IF A TC RECURVES NORTHEASTWARD INTO THE HIGHER LATITUDES OF THE NORTH
PACIFIC, IT COULD DISRUPT THE DOWNSTREAM LONGWAVE PATTERN WHICH INCREASES
FORECAST UNCERTAINTY. ALTHOUGH SOIL MOISTURE HAS A DECLINING INFLUENCE ON
SURFACE TEMPERATURES DURING THE FALL, THE INTENSIFYING DROUGHT CONDITIONS WITH
LOW SOIL MOISTURE WILL HAVE A WARMING EFFECT ON SURFACE TEMPERATURES ACROSS THE
SOUTHERN GREAT PLAINS, OZARKS REGION, LOWER MISSISSIPPI VALLEY, AND PARTS OF
THE SOUTHEAST.
THE OCTOBER TEMPERATURE OUTLOOK GENERALLY USED THE CONSOLIDATION TOOL AS A
GUIDE, WHICH REPRESENTS A COMBINATION OF DYNAMICAL MODEL OUTPUT AND STATISTICAL
TOOLS WHICH INCLUDE IMPACTS FROM THE PHASE OF THE EL NINO SOUTHERN OSCILLATION
(ENSO) AND LONG-TERM TREND. ABOVE-NORMAL TEMPERATURES ARE FAVORED ALONG THE
WEST COAST AND FOR MUCH OF THE CENTRAL AND EASTERN CONTIGUOUS U.S. (CONUS). THE
EQUAL CHANCES (EC) OF BELOW, NEAR, OR ABOVE-NORMAL TEMPERATURES ACROSS THE
INTERIOR WEST IS DUE TO CONFLICTING SIGNALS BETWEEN THE COOLER EL NINO
COMPOSITES AND WARMER DYNAMICAL MODELS. THE OUTLOOK LEANS SLIGHTLY TOWARDS
ABOVE NORMAL (33-40% CHANCE) ACROSS PARTS OF ARIZONA AND NEW MEXICO BASED ON
THE LONG-TERM TREND. ABOVE-NORMAL TEMPERATURE PROBABILITIES ARE INCREASED TO
MORE THAN 50% FOR THE LOWER MISSISSIPPI VALLEY GIVEN THE INTENSIFYING DROUGHT
AND LOW SOIL MOISTURE HAVING A WARMING EFFECT HEADING INTO OCTOBER. THE OTHER
AREA WITH HIGHER FORECAST CONFIDENCE IS SOUTHEASTERN ALASKA WITH THE CALIBRATED
NMME AND IMME DEPICTING GREATER THAN A 50% CHANCE OF ABOVE-NORMAL TEMPERATURES.
THE LACK OF SEA ICE SUPPORTS ABOVE-NORMAL TEMPERATURES FOR THE NORTH SLOPE OF
ALASKA. THE INCREASED CHANCE THAT A RECURVING TC IN THE WEST PACIFIC AFFECTS
THE LONGWAVE PATTERN DOWNSTREAM OVER NORTH AMERICA IS A SOURCE OF FORECAST
UNCERTAINTY, LIMITING THE COVERAGE OF ABOVE-NORMAL TEMPERATURE PROBABILITIES
EXCEEDING 50 PERCENT.
DURING THE FIRST HALF OF OCTOBER, THE GEFS AND ECMWF MODELS ARE IN GOOD
AGREEMENT WITH A 500-HPA TROUGH NEAR THE WEST COAST AND ANOMALOUS MID-LEVEL
RIDGING OVER THE EASTERN TWO-THIRDS OF THE CONUS. THIS LONGWAVE PATTERN WOULD
YIELD A RELATIVELY WET START TO THE MONTH FOR THE SOUTHWEST. ON THE MONTHLY
TIME SCALE, THE CFS MODEL ALONG WITH THE NMME AND IMME SUPPORT ELEVATED
ABOVE-NORMAL PRECIPITATION PROBABILITIES FROM THE SOUTHWEST EASTWARD TO THE
CENTRAL TO SOUTHERN GREAT PLAINS AND PARTS OF THE GULF COAST. THIS FAVORED
WETNESS ALSO EXTENDS WEST TO INCLUDE SOUTHERN CALIFORNIA DUE TO GOOD MODEL
CONSISTENCY FROM PAST DAILY CFS MODEL RUNS AND THE LIKELIHOOD OF A CONTINUED
ACTIVE EAST PACIFIC HURRICANE SEASON. ALTHOUGH EL NINO COMPOSITES WOULD SUPPORT
THE OCTOBER OUTLOOK LEANING ON THE DRIER SIDE FOR THE PACIFIC NORTHWEST AND
NORTHERN INTERMOUNTAIN WEST, EC IS FORECAST FOR THESE AREAS DUE TO A LACK OF
SUPPORT FROM THE CALIBRATED DYNAMICAL MODEL OUTPUT AND THE ENSO-OCN TOOL.
ELSEWHERE ACROSS THE LOWER 48 STATES, EC IS ALSO FORECAST WITH GENERALLY WEAK
SIGNALS AMONG THE TOOLS AT THIS TIME LEAD. BASED ON MODEL GUIDANCE FAVORING
ABOVE-NORMAL PRECIPITATION DURING THE FIRST HALF OF THE MONTH ALONG WITH THE
IMME ON THE MONTHLY TIME SCALE, ELEVATED ABOVE-NORMAL PRECIPITATION
PROBABILITIES (33-40%) ARE FORECAST ACROSS PARTS OF SOUTHEASTERN ALASKA AND
COASTAL SOUTHERN ALASKA.
FORECASTER: ANTHONY ARTUSA
THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1991 AND 2020, 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 15 2026
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1991-2020 BASE PERIOD.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
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