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FXUS07 KWBC 181230
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU SEP 18 2025
30-DAY OUTLOOK DISCUSSION FOR OCTOBER 2025
THE OCTOBER 2025 TEMPERATURE AND PRECIPITATION OUTLOOKS CONSIDERED THE EVOLVING
STATE OF THE EL NINO - SOUTHERN OSCILLATION (ENSO), STRENGTH AND FORECAST OF
THE MADDEN-JULIAN OSCILLATION (MJO) AS WELL AS OTHER COHERENT SUBSEASONAL
TROPICAL VARIABILITY, ANOMALOUS LAND SURFACE CONDITIONS (SOIL MOISTURE,
VEGETATION EXTENT) AND BOTH REMOTE AND NEAR COASTAL EXTRATROPICAL SEA SURFACE
TEMPERATURES (SSTS).
DYNAMICAL MODEL GUIDANCE FROM THE WEEK 3-4 TIME PERIOD WAS EVALUATED AND
UTILIZED FROM THE ECMWF, GEFS AND CFS. MONTHLY INTEGRATIONS FROM THE NMME AND
C3S ENSEMBLE SYSTEM SUITES WERE ALSO USED, BOTH ENSEMBLE MEAN AND INDIVIDUAL
PARTICIPANT MODEL SOLUTIONS. I NOTE THAT THE SPEAR NMME CONTRIBUTING MODEL
CONTINUES TO BE UNAVAILABLE FROM NOAA GFDL.
THE OCTOBER TEMPERATURE OUTLOOK FAVORS MONTHLY MEAN ABOVE-NORMAL TEMPERATURES
FOR MUCH OF THE COUNTRY. THIS INCLUDES THE WESTERN CONUS WHERE FORECAST
GUIDANCE, STRONGLY POSITIVE TEMPERATURE TRENDS, LARGE REGIONS OF ANOMALOUS
SURFACE DRYNESS (SOIL AND VEGETATION) AS WELL AS ANOMALOUSLY WARM LOCAL COASTAL
AND GREATER NORTH PACIFIC SSTS SUPPORT THIS FORECAST. FOR SOUTHERN TEXAS AND
THE EASTERN U.S., BOTH STATISTICALLY AND DYNAMICAL FORECAST GUIDANCE, POSITIVE
TEMPERATURE TRENDS IN SOME AREAS AND IN THE CASE OF THE OHIO VALLEY AND
MID-SOUTH RAPIDLY DEVELOPING DROUGHT CONDITIONS LEAD TO THE WARMER-THAN-NORMAL
FORECAST.
FOR ALASKA, A NUMBER OF FACTORS AT PLAY MAKE THE FORECAST FOR THIS REGION
ESPECIALLY CHALLENGING THIS MONTH. SOME FORECAST GUIDANCE FAVORS TROUGHING
ENTERING OCTOBER IN PROXIMITY TO THE STATE AND SO POTENTIAL BELOW-NORMAL
TEMPERATURES. BUT THIS IS OFFSET BY ABOVE-NORMAL SSTS IN MANY COASTAL AREAS
AROUND THE STATE AS WELL AS QUITE STRONG POSITIVE TEMPERATURE TRENDS RELATED TO
THE NEGATIVE TREND IN SEA ICE ADVANCE AND COVERAGE. FOR THESE REASONS, AN AREA
OF FAVORED NEAR-NORMAL MONTHLY MEAN TEMPERATURES IS FORECAST FOR THE
WEST-CENTRAL COASTAL AREAS, WHILE ONLY MODEST ODDS FOR ABOVE-NORMAL
TEMPERATURES ARE FORECAST FOR THE NORTH SLOPE OF ALASKA AND FOR MUCH OF THE
SOUTH COASTAL AREAS OF THE STATE.
FOR MUCH OF THE INTERIOR PORTION OF THE CONUS, EQUAL-CHANCES (EC) IS FORECAST
AS THE HIGHEST OUTLOOK UNCERTAINTY IS LOCATED IN THIS REGION. IN THIS AREA,
WEAK SHORT-TERM CLIMATE SIGNALS AND HIGHLY CONFLICTING FACTORS THAT INCLUDE
DYNAMICAL MODEL GUIDANCE, SOIL MOISTURE CONDITIONS AND UNCERTAIN IMPACT FROM
THE EVOLVING LA NINA STATE (I.E. LA NINA WATCH CURRENTLY IN PLACE).
FOR PRECIPITATION, THE OCTOBER 2025 OUTLOOK IS QUITE CONSERVATIVE DUE TO A
NUMBER OF FACTORS INCLUDING THE TIME WITHIN THE OVERALL ANNUAL CYCLE WHERE THE
SIGNAL-TO-NOISE RATIO AND SO FORECAST PREDICTABILITY IS THE LEAST. IN ADDITION
TO ABOVE, OUTSIDE OF A JUST A FEW REGIONS IN THE U.S., IMPACTS FROM ONGOING
CLIMATE DRIVERS ARE GENERALLY WEAK AND LARGELY UNCLEAR, FORECAST GUIDANCE IS
STRONGLY CONFLICTED AND HISTORICAL OUTLOOK SKILL FOR MANY TOOLS IS QUITE LOW
WITH POOR RELIABILITY.
DYNAMICAL MODEL GUIDANCE DURING THE FIRST 2 WEEKS OF OCTOBER FROM WEEK 3-4
ENSEMBLE MODELING SYSTEMS INDICATES AN ACTIVE PATTERN FOR THE NORTHEAST PACIFIC
AND SO ABOVE-NORMAL MONTHLY TOTAL PRECIPITATION AMOUNTS ARE FAVORED FOR THE
SOUTH-CENTRAL AND SOUTHEAST COASTAL AREAS OF ALASKA AND FOR SOME AREAS IN THE
PACIFIC NORTHWEST AND NORTHERN ROCKIES. THIS IS CONSISTENT WITH THE PACIFIC
OCEAN-ATMOSPHERE STATE EVOLVING TO A POTENTIAL LA NINA EVENT ENTERING AUTUMN
AND EARLY WINTER.
DURING EARLY OCTOBER, INDICATIONS FROM SOME MODEL GUIDANCE FOR NORTHWARD
SHIFTED WESTERLIES, ON AVERAGE, FAVOR BELOW-NORMAL PRECIPITATION FOR AREAS OF
THE SOUTH-CENTRAL U.S., LOWER MISSISSIPPI VALLEY AND LOWER OHIO VALLEY. THIS IS
ALSO CONSISTENT WITH EVOLVING POTENTIAL LA NINA CONDITIONS ENTERING FALL.
SLIGHTLY ELEVATED ODDS FOR ABOVE-NORMAL PRECIPITATION IS ALSO FORECAST FOR THE
FLORIDA PENINSULA AND EXTREME SOUTHERN GEORGIA DUE MODEL GUIDANCE SUGGESTING A
CONTINUATION OF A WEAKNESS IN SUBTROPICAL RIDGING IN THE EAST-CENTRAL GULF OF
AMERICA AND ASSOCIATED MOISTURE IMPACTING THIS AREA. ALSO, THERE IS THE
POTENTIAL FOR TROPICAL CYCLONES OR DISTURBANCES FROM THE GULF OF AMERICA AND
WESTERN CARIBBEAN TO IMPACT THIS AREA AS THIS MOISTURE CAN IMPACT FAR EASTERN
GULF COAST STATES AND FLORIDA DURING THE MONTH OF OCTOBER.
THE OUTLOOK DEPICTS AN ABOVE-NORMAL AMOUNT OF COVERAGE OF EC DUE TO SOME OF THE
FACTORS NOTED ABOVE. THESE AREAS INCLUDE THE SOUTHWEST, MUCH OF THE ROCKIES,
NORTHERN PLAINS, MIDWEST, MID-ATLANTIC AND NORTHEAST. ADDITIONAL CLARITY IN
FORECAST FACTORS OVER THE NEXT TWO WEEKS MAY ALLOW GREATER NON-EC OUTLOOK
COVERAGE WHEN THE OCTOBER 2025 UPDATED MONTHLY OUTLOOK IS RELEASED ON THE LAST
DAY OF SEPTEMBER.
FORECASTER: JON GOTTSCHALCK
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 TUE SEPTEMBER 30 2025
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1991-2020 BASE PERIOD.
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