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FXUS07 KWBC 171231
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU SEP 17 2026
30-DAY OUTLOOK DISCUSSION FOR OCT 2026
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: BRAD PUGH
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.
AN UPDATED MONTHLY OUTLOOK... FOR OCT WILL BE ISSUED ON WED SEPTEMBER 30 2026
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1991-2020 BASE PERIOD.
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