066
FXUS05 KWBC 201231
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU JUL 20 2023
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS
THE AUGUST-SEPTEMBER-OCTOBER (ASO) 2023 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL
SEASONAL MEAN TEMPERATURES ACROSS A MAJORITY OF THE U.S. THE HIGHEST
PROBABILITIES (MORE THAN 60 PERCENT) OF ABOVE-NORMAL TEMPERATURES ARE FORECAST
ACROSS PARTS OF THE SOUTHWEST. THE ASO PRECIPITATION OUTLOOK DEPICTS ELEVATED
PROBABILITIES OF BELOW-NORMAL PRECIPITATION FOR PARTS OF THE SOUTHWEST AND
PACIFIC
NORTHWEST, WHILE ABOVE-NORMAL PRECIPITATION IS FAVORED ACROSS MUCH OF THE
CENTRAL AND SOUTHERN GREAT PLAINS, PARTS OF THE MIDDLE TO LOWER MISSISSIPPI
VALLEY, THE TENNESSEE VALLEY, AND THE CENTRAL ATLANTIC COAST FROM THE CAROLINAS
TO SOUTHERN VIRGINIA. EQUAL CHANCES (EC) ARE FORECAST IN AREAS WHERE THE
LIKELIHOOD OF SEASONAL MEAN TEMPERATURES OR SEASONAL ACCUMULATED PRECIPITATION
AMOUNTS ARE EXPECTED TO BE SIMILAR TO CLIMATOLOGICAL PROBABILITIES.
EL NIñO CONDITIONS ARE PRESENT AND EQUATORIAL SEA SURFACE TEMPERATURES (SSTS)
ARE ABOVE AVERAGE ACROSS THE CENTRAL AND EASTERN EQUATORIAL PACIFIC OCEAN. EL
NIñO IS EXPECTED TO STRENGTHEN AND PERSIST THROUGH THE WINTER 2023-24.
BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS
NOTE: FOR GRAPHICAL DISPLAYS OF THE FORECAST TOOLS DISCUSSED BELOW SEE:
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/TOOLS/BRIEFING
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS
OCEANIC AND ATMOSPHERIC OBSERVATIONS ACROSS THE EQUATORIAL PACIFIC REFLECT EL
NIñO CONDITIONS. THE OBSERVED WEEKLY SSTS, CENTERED ON JULY 12, FEATURE
POSITIVE ANOMALIES THROUGHOUT THE EQUATORIAL PACIFIC WITH THE LARGEST ANOMALIES
OF MORE THAN +1 DEGREE C GENERALLY EAST OF 160°W. THE LARGEST ANOMALIES ARE
SPREADING WESTWARD ALONG THE EQUATOR. THE LATEST WEEKLY SST DEPARTURE FOR THE
NIñO 3.4 REGION IS AT +1.1 DEGREES C. EQUATORIAL UPPER-OCEAN HEAT ANOMALIES
(AVERAGED BETWEEN 180 TO 100 °W AND 0-300M DEPTH) REMAIN STRONGLY POSITIVE.
LOW-LEVEL (850-HPA) WIND ANOMALIES DURING THE LAST MONTH WERE SMALL IN
AMPLITUDE ALONG THE EQUATOR WITH A SPATIALLY SMALL AREA OF EASTERLY ANOMALIES
ALONG 5°S FROM 180 TO 120°W. CONSISTENT WITH EL NIñO CONDITIONS, NEGATIVE OLR
ANOMALIES (ENHANCED CONVECTION) WERE LOCATED EAST OF PAPUA NEW GUINEA AND ALSO
JUST NORTH OF THE EQUATOR ACROSS THE EASTERN PACIFIC. THOSE NEGATIVE ANOMALIES
ARE FURTHER EAST COMPARED TO THE LAST MONTH. POSITIVE OLR ANOMALIES (SUPPRESSED
CONVECTION) WERE OBSERVED THROUGHOUT MUCH OF SOUTHEAST ASIA AND THE SOUTHWEST
PACIFIC.
THE REAL-TIME MULTIVARIATE (RMM) INDEX DEPICTS A WEAK MADDEN-JULIAN OSCILLATION
(MJO) DURING EARLY JULY. THE 200-HPA VELOCITY POTENTIAL ANOMALY FIELD FEATURES
A COHERENT WAVE-1 STRUCTURE, BUT IT DOES APPEAR TO HAVE INFLUENCES FROM HIGHER
FREQUENCY MODES. DYNAMICAL MODEL FORECASTS INDICATE THAT THE MJO IS LIKELY TO
REMAIN WEAK, AND IS NOT CONSIDERED TO BE A FACTOR IN THE EARLIEST LEAD OF THE
SEASONAL OUTLOOKS
NEGATIVE SST ANOMALIES HAVE PERSISTED IN THE CHUKCHI SEA, WHILE SSTS IN THE
BERING STRAIT ARE ABOVE NORMAL DURING THE FIRST HALF OF JULY. BELOW-AVERAGE
SSTS ARE PERSISTENT IN MUCH OF THE BERING SEA AND GULF OF ALASKA AND ALONG MUCH
OF THE WEST COAST OF THE CONUS. THE NORTHERN GULF OF MEXICO WARMED RECENTLY
WITH ABOVE-NORMAL SSTS OBSERVED DURING EARLY JULY. POSITIVE SST ANOMALIES
WEAKENED ACROSS THE EASTERN TROPICAL ATLANTIC SINCE MAY.
PROGNOSTIC DISCUSSION OF SST FORECASTS
THE CPC SST CONSOLIDATION FOR THE NIñO 3.4 REGION INDICATES AN INCREASE IN THE
MAGNITUDE OF POSITIVE ANOMALIES THIS SUMMER AND FALL TO AROUND +1 DEGREE C,
FOLLOWED BY A DECLINE TO MORE NEUTRAL ENSO CONDITIONS DURING SPRING 2024. THE
CFSV2 CONTINUES TO DEPICT A STRONG EL NIñO BY ASO, WHILE THE NORTH AMERICAN
MULTI-MODEL ENSEMBLE (NMME) MEAN KEEPS THE ANOMALIES BELOW 1.5 DEGREES C. THE
STATISTICAL TOOLS VARY WITH THE STRENGTH OF THE EL NIñO DURING THE NEXT SIX
MONTHS. AS OF EARLY JULY, NOAA’S CPC FORECAST CALLS FOR MORE THAN A 90 PERCENT
CHANCE OF EL NIñO PERSISTING THROUGH JFM 2024 WITH A 52 PERCENT CHANCE OF A
STRONG EL NIñO (> 1.5 DEGREES C) DURING OND 2023.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
TOOLS USED FOR THE SEASONAL OUTLOOKS INCLUDED DYNAMICAL MODEL GUIDANCE SUCH AS
THE NMME, THE CALIBRATION, BRIDGING, AND MERGING (CBAM) POST-PROCESSING OF THE
NMME, AND THE COPERNICUS CLIMATE CHANGE SERVICE (C3S) SEASONAL MODEL
CONTRIBUTIONS. IN ADDITION, THE CONSOLIDATION TOOL, WHICH INCLUDES NMME INPUT
AND VARIOUS STATISTICAL TOOLS WERE USED. CURRENT SOIL MOISTURE CONDITIONS WERE
A CONSIDERATION ACROSS THE MIDWEST AND CORN BELT IN THE ASO TEMPERATURE
OUTLOOK. EL NIñO TEMPERATURE AND PRECIPITATION CORRELATIONS WERE RELIED UPON
FROM ASO 2023 THROUGH FMA 2024 AND THESE COMPOSITES WERE WEIGHED MOST HEAVILY
FROM NDJ 2023-24 THROUGH JFM 2024. DECADAL TRENDS IN TEMPERATURE AND
PRECIPITATION WERE A FACTOR AT ALL TIME LEADS BUT RELIED UPON THE MOST AT THE
LONGER LEADS, WHEN DYNAMICAL MODEL GUIDANCE IS NOT AVAILABLE.
PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2023 TO ASO 2024
TEMPERATURE
ABOVE-NORMAL TEMPERATURES ARE FAVORED THROUGHOUT A MAJORITY OF THE U.S. DURING
ASO WITH THE HIGHEST PROBABILITIES (ABOVE 60 PERCENT) FORECAST FOR A PORTION OF
THE SOUTHWEST. FOR MUCH OF THE WEST, GULF COAST, AND EAST, PROBABILITIES ARE
GREATER THAN 50 PERCENT FOR ABOVE-NORMAL TEMPERATURES, CONSISTENT WITH
DYNAMICAL MODEL GUIDANCE AND DECADAL TRENDS. CBAM, TRENDS, AND CORRELATIONS
WITH NINO 3.4 SUPPORT FAVORING BELOW-NORMAL TEMPERATURES IN THE CENTRAL PLAINS.
MANY OF THE TOOLS ALSO INDICATE A WEAK MONSOON, SO PROBABILITIES FOR
ABOVE-NORMAL TEMPERATURES EXCEED 60 PERCENT IN THE FOUR CORNERS REGION.
COMPARED TO THE PREVIOUS OUTLOOK, ABOVE-NORMAL TEMPERATURE PROBABILITIES WERE
DECREASED ACROSS THE CORN BELT AND GREAT LAKES, CONSISTENT WITH CORRELATIONS
WITH A MODERATE EL NIñO AND THE LATEST NMME OUTPUT. THE CONSOLIDATION TOOL AND
EL NIñO COMPOSITES SUPPORT ABOVE-NORMAL TEMPERATURE PROBABILITIES ACROSS MUCH
OF ALASKA. ABOVE-NORMAL TEMPERATURES REMAIN THE MOST LIKELY OUTCOME THROUGHOUT
MUCH OF THE U.S. FOR SON AND OND 2023, WITH EQUAL CHANCES OVER THE NORTHERN AND
CENTRAL PLAINS AND THE UPPER GREAT LAKES. BEGINNING IN NDJ 2023-24 THROUGH JFM
2024, PREDICTED EL NIñO CONDITIONS RESULT IN ENHANCED CHANCES FOR ABOVE-NORMAL
TEMPERATURES ACROSS THE NORTHERN TIER OF THE CONUS WITH AN INCREASING COVERAGE
OF EC ACROSS CALIFORNIA, THE SOUTHWEST, SOUTHERN GREAT PLAINS, AND LOWER
MISSISSIPPI VALLEY. DURING THE WINTER 2023-24, ABOVE-NORMAL TEMPERATURES ARE
FAVORED ACROSS THE EAST BASED ON THE STATISTICAL CONSOLIDATION. FROM MAM TO ASO
2024, THE TEMPERATURE OUTLOOK IS CONSISTENT WITH DECADAL TRENDS.
PRECIPITATION
DURING ASO 2023, BELOW-NORMAL PRECIPITATION IS FAVORED FOR THE PACIFIC
NORTHWEST, THOUGH THE SIGNAL IS WEAKER THAN INDICATED LAST MONTH FOR LEAD 2, AS
INDICATED BY THE LATEST NMME GUIDANCE AND TRENDS. BELOW-NORMAL PRECIPITATION,
ASSOCIATED WITH AN ANOMALOUSLY WEAK MONSOON AND AS INDICATED IN THE SST-CA,
OCN, AND NMME, IS LIKELY FOR THE SOUTHWEST. CORRESPONDINGLY, ABOVE-NORMAL
PRECIPITATION IS LIKELY OVER THE CENTRAL AND SOUTHERN PLAINS, AS A DIPOLE IN
PRECIPITATION BETWEEN THE SOUTHWEST AND PLAINS IS COMMON DURING THE SUMMER
MONTHS. ABOVE-NORMAL PRECIPITATION IS WEAKLY FAVORED OVER THE SOUTHEAST, ON THE
SOUTHERN FLANK OF AN ANOMALOUS TROUGH, LIKELY OVER THE GREAT LAKES. ANOMALOUS
TROUGHING IN THE GREAT LAKES IS ASSOCIATED WITH EL NIñO AND INDICATED IN MANY
OF THE NMME MODELS. THE OUTLOOK FOR SON MAINTAINS MOST OF THOSE SIGNALS, EXCEPT
FOR THE SIGNAL IN THE PLAINS AS SON ARE NOT THE CORE MONSOON MONTHS. DURING OND
THE AREA WHERE ABOVE-NORMAL PRECIPITATION IS FAVORED EXPANDS FROM THE SOUTHEAST
TO THE SOUTHERN PLAINS, ASSOCIATED WITH LIKELY IMPACTS FROM THE PREDICTED
STATES OF ENSO. CORRESPONDINGLY ODDS FOR BELOW-NORMAL PRECIPITATION EXPAND IN
THE NORTHWEST.
DURING NDJ 2023 TO JFM 2024, THE OUTLOOKS LARGELY FAVOR ABOVE-NORMAL
PRECIPITATION ACROSS THE SOUTHERN TIER AND BELOW-NORMAL PRECIPITATION ACROSS
THE NORTHERN TIER OF THE CONUS. THAT PATTERN IS LARGELY ALIGNED WITH ENSO
IMPACTS AND MODEL GUIDANCE. FROM FMA 2024 THROUGH ASO 2024, THE OUTLOOKS
PRIMARILY REFLECT THE CONSOLIDATION OF AVAILABLE TOOLS, WHICH LARGELY FOLLOWS
TRENDS AND ENSO IMPACTS.
DURING ASO, TRENDS AND MODEL GUIDANCE FAVOR ABOVE-NORMAL PRECIPITATION FOR
WESTERN AND NORTHERN MAINLAND ALASKA, CONSISTENT WITH ENSO IMPACTS AND ICE EDGE
RETREAT. ODDS ARE MITIGATED BY TRENDS OVER WESTERN ALASKA. DURING SON AND OND,
TRENDS INDICATE A WET SIGNAL AGAIN, SO COVERAGE OF ABOVE-NORMAL PRECIPITATION
IS FAVORED OVER A LARGER AREA. DURING WINTER 2023/2024, SIGNALS FOR
PRECIPITATION IN ALASKA ARE WEAK, SO MUCH OF THE STATE HAS EC INDICATED, EXCEPT
THE NORTH SLOPE WHERE TRENDS FAVOR ABOVE-NORMAL PRECIPITATION.
FORECASTER: MATTHEW ROSENCRANS
THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1991 AND 2020, FOLLOWING
THE WORLD METEROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3
COMPLETE DECADES AS THE CLIMATIC 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.
FOR A DESCRIPTION OF OF THE STANDARD FORECAST TOOLS - THEIR SKILL- AND THE
FORECAST FORMAT PLEASE SEE OUR WEB PAGE AT
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/LONG_RANGE/TOOLS.HTML
(USE LOWER CASE LETTERS)
INFORMATION ON THE FORMATION OF SKILL OF THE CAS FORECASTS MAY BE FOUND AT:
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/SOILMST_MONITORING/US/OUTLOOK/OUTLOOK.SHTM
L
(USE LOWERCASE LETTERS)
NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR
VALID PERIOD. WITHIN ANY GIVEN VALID PERIOD OBSERVATIONS AND SHORT AND MEDIUM
RANGE FORECASTS SHOULD BE CONSULTED.
THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCE OF THE NEW SET NEXT
MONTH ON AUG 17 2023
1991-2020 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 20, 2021
FORECAST RELEASE.
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