566
FXUS05 KWBC 201231
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU JUN 20 2024
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS
THE FINAL EL NIñO ADVISORY WAS RECENTLY ISSUED IN THE 17 JUNE 2024 EL NIñO
SOUTHERN OSCILLATION (ENSO) OUTLOOK. CURRENTLY, ENSO-NEUTRAL CONDITIONS ARE
PRESENT WITH EQUATORIAL SEA SURFACE TEMPERATURES (SSTS) ABOVE AVERAGE IN THE
WEST-CENTRAL PACIFIC OCEAN, NEAR AVERAGE IN THE EAST-CENTRAL PACIFIC OCEAN, AND
BELOW-AVERAGE IN THE FAR EASTERN PACIFIC OCEAN. A LA NIñA WATCH IS NOW IN
EFFECT AS LA NIñA IS FAVORED TO DEVELOP DURING JULY-SEPTEMBER (JAS, 65% CHANCE)
AND PERSIST INTO THE NORTHERN HEMISPHERE WINTER 2024-25 (85% CHANCE DURING
NOVEMBER-JANUARY, NDJ).
THE JAS 2024 TEMPERATURE OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES FOR MUCH OF
THE CONTIGUOUS UNITED STATES (CONUS), WITH THE STRONGEST PROBABILITIES REACHING
70 TO 80% OVER PARTS OF THE FOUR CORNERS REGION. ENHANCED PROBABILITIES OF
ABOVE NORMAL TEMPERATURES REACHING 60 TO 70% ARE FOUND OVER THE GULF COAST. IN
CONTRAST, EQUAL-CHANCES (EC) OF ABOVE, NEAR, AND BELOW NORMAL TEMPERATURES ARE
FAVORED OVER THE WEST COAST OF THE CONUS. BELOW NORMAL TEMPERATURES ARE
INDICATED OVER SOUTHWESTERN ALASKA, TRANSITIONING TO ABOVE NORMAL OVER THE
NORTHEAST PART OF THE STATE.
BELOW NORMAL PRECIPITATION IS FAVORED OVER PARTS OF THE WESTERN AND CENTRAL
CONUS IN JAS 2024, EXCEPTING OVER THE WEST COAST WHERE EC IS FAVORED. ABOVE
NORMAL PRECIPITATION IS FORECAST FOR SOUTHEASTERN TEXAS, THE GULF STATES, AND
ALONG THE EASTERN SEABOARD INTO NEW ENGLAND WITH THE HIGHEST PROBABILITIES (50
TO 60%) ALONG PARTS OF THE GULF COAST AND FLORIDA. ABOVE NORMAL PRECIPITATION
IS ALSO INDICATED OVER WESTERN ALASKA. FOR THE REMAINING AREAS OF THE CONUS,
WHERE POSSIBLE SEASONAL TOTAL PRECIPITATION AMOUNTS ARE PREDICTED TO BE SIMILAR
TO CLIMATOLOGICAL PROBABILITIES, EC IS FORECAST.
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
ENSO-NEUTRAL CONDITIONS RETURNED DURING THE PAST MONTH, AND SSTS IN THE NIñO3.4
REGION RECENTLY DROPPED TO 0.0 DEGREES CELSIUS. SSTS IN NIñO4 REMAIN MILDLY
ABOVE NORMAL AT 0.6 DEGREES CELSIUS, WHILE NIñO3 HAS DROPPED TO -0.2 DEGREES
CELSIUS AND NIñO1+2 TO -0.6 DEGREES CELSIUS. MORE GENERALLY, IN THE LAST FOUR
WEEKS, EQUATORIAL SSTS WERE ABOVE AVERAGE IN THE WEST-CENTRAL PACIFIC OCEAN AND
NEAR-TO-BELOW-AVERAGE SSTS WERE EVIDENT IN THE EAST-CENTRAL AND EASTERN PACIFIC
OCEAN. COLLECTIVELY, THE COUPLED OCEAN-ATMOSPHERE SYSTEM REFLECTED ENSO-NEUTRAL
CONDITIONS, AND THERE HAS BEEN A SLIGHT SLOWDOWN IN THE RATE OF COOLING SINCE
LAST MONTH.
STARTING IN NOVEMBER 2023, POSITIVE SUBSURFACE TEMPERATURE ANOMALIES WEAKENED
TO NEAR ZERO. FROM LATE JANUARY TO MID-APRIL 2024, NEGATIVE TEMPERATURE
ANOMALIES EMERGED AT THE SURFACE AND STRENGTHENED. OVER THE LAST MONTH,
NEGATIVE ANOMALIES HAVE WEAKENED SLIGHTLY, BUT DOMINATE THE EASTERN HALF OF THE
EQUATORIAL PACIFIC OCEAN.
THE MADDEN JULIAN OSCILLATION (MJO) RECENTLY WEAKENED AND THERE WAS LITTLE
ACTIVITY DURING THE FIRST HALF OF JUNE, AND DYNAMICAL MODEL FORECASTS OF THE
REALTIME MULTIVARIATE MJO INDEX THROUGH THE END OF JUNE ARE GENERALLY
INCOHERENT. AS LA NIñA IS FAVORED TO DEVELOP DURING JAS 2024 AND PERSIST
THROUGH WINTER 2025, LA NIñA IS CONSIDERED THE DOMINANT EXTRATROPICAL INFLUENCE
ON THE FORECAST.
OUTSIDE OF THE EQUATORIAL PACIFIC, SST ANOMALIES ARE BELOW NORMAL NEAR THE
ALASKA COAST, PARTICULARLY OFF THE WEST COAST OF THE STATE. WEAK, BELOW NORMAL
SST ANOMALIES ARE ALSO OBSERVED ALONG THE WEST COAST OF THE CONUS, THOUGH THEY
ARE WEAK AND SPOTTY. STRONG ABOVE NORMAL SST ANOMALIES ARE PRESENT IN THE GULF
OF MEXICO AND UP MUCH OF THE EAST COAST OF THE CONUS. SOIL MOISTURE VARIES
ACROSS MUCH OF THE CONUS BUT IS NOTABLY ANOMALOUSLY LOW OVER MUCH OF NEW MEXICO
AND SOUTHWESTERN TEXAS.
PROGNOSTIC DISCUSSION OF SST FORECASTS
THE CPC NIñO3.4 SST CONSOLIDATION FORECAST FAVORS A TRANSITION TO A LA NIñA
STATE BY JAS 2024. BELOW ZERO SST ANOMALIES ARE FORECAST IN THE MEAN OF MOST
INPUTS TO THE CONSOLIDATION THROUGH APRIL-JUNE 2025 (AMJ). FORECAST PLUMES OF
THE NIñO3.4 INDEX FROM THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) GENERALLY
INDICATE BELOW ZERO SST ANOMALIES FROM JULY 2024 THROUGH JANUARY 2025, THOUGH
SOME MODELS AND ENSEMBLE MEMBERS INDICATE ENSO-NEUTRAL CONDITIONS - FOR
EXAMPLE, THE GFDL-SPEAR MODEL HAS A NUMBER OF ENSEMBLE MEMBERS WITH ANOMALIES
THAT STAY NEAR OR SLIGHTLY ABOVE ZERO DEGREES CELSIUS. THE CPC PROBABILISTIC
ENSO OUTLOOK FAVORS ENSO-NEUTRAL IN MAY-JULY 2024 (MJJ) AND JUNE-AUGUST 2024
(JJA), WITH CHANCES OF LA NIñA DEVELOPING IN JAS (65% CHANCE) AND PERSISTING
THROUGH THE NORTHERN HEMISPHERE WINTER 2024-25.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
DYNAMICAL MODEL FORECASTS FROM THE COPERNICUS (C3S) AND NMME MULTI-MODEL
ENSEMBLE SYSTEMS ARE USED FOR THE FIRST THREE AND SIX LEADS RESPECTIVELY, AS
WELL AS INDIVIDUAL MODEL FORECASTS FROM THE CLIMATE FORECAST SYSTEM VERSION 2
(CFSV2) AND EUROPEAN CENTRE FOR MEDIUM RANGE WEATHER FORECASTS (ECMWF) MODELS
AS AVAILABLE. THE OBJECTIVE, HISTORICAL SKILL WEIGHTED CONSOLIDATION THAT
COMBINES BOTH DYNAMICAL AND STATISTICAL FORECAST TOOLS WAS ALSO CONSIDERED
THROUGHOUT ALL LEADS. THE CALIBRATION, BRIDGING AND MERGING (CBAM) TOOL
ANCHORED TO THE NMME FORECASTS AND "BRIDGED" TO THE NIñO3.4 INDEX IS ALSO
UTILIZED.
LA NIñA IMPACTS WERE CONSIDERED GIVEN THE FORECASTED EVENT FROM JAS THROUGH
ROUGHLY MARCH-APRIL-MAY (MAM) 2025 AS APPROPRIATE FOR THE REGION, VARIABLE, AND
SEASON, AND LA NIñA COMPOSITES AND CORRELATIONS OF TEMPERATURE AND
PRECIPITATION WITH THE NIñO3.4 REGION WERE USED TO DETERMINE TYPICAL LA NIñA
IMPACTS. STATISTICAL GUIDANCE SUCH AS THE GLOBAL SST BASED CONSTRUCTED ANALOG
(CA) AND LONG TERM (DECADAL) TEMPERATURE AND PRECIPITATION TRENDS PLAYED A ROLE
IN MANY OF THE OUTLOOK SEASONS, PARTICULARLY BEYOND LEAD 6 WHEN DYNAMICAL MODEL
GUIDANCE IS UNAVAILABLE. COASTAL SSTS AND SOIL MOISTURE ANOMALIES ARE
CONSIDERED AT EARLY LEADS. LONGER LEAD OUTLOOKS, BEGINNING IN APRIL-MAY-JUNE
(AMJ) 2025 ARE BASED PRIMARILY ON DECADAL TEMPERATURE AND PRECIPITATION TRENDS.
A CONSOLIDATION OF MULTIPLE STATISTICAL AND DYNAMICAL FORECAST TOOLS IS USED
THROUGHOUT THE OUTLOOKS FROM JAS 2024 TO JAS 2025.
PROGNOSTIC DISCUSSION OF OUTLOOKS - JAS 2024 TO JAS 2025
TEMPERATURE
THE JAS 2024 TEMPERATURE OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES FOR MUCH OF
THE CONUS, WITH HIGHER PROBABILITIES REACHING 70 TO 80% OVER PARTS OF THE FOUR
CORNERS REGION WHERE THERE WAS STRONG MODEL AGREEMENT, THE DECADAL TEMPERATURE
TREND IS ABOVE NORMAL, AND THERE ARE FAVORED ODDS OF BELOW NORMAL
PRECIPITATION. ABOVE NORMAL TEMPERATURE PROBABILITIES ARE ALSO ENHANCED ALONG
THE EXTREME GULF COAST, REACHING 60 TO 70%, OWING TO STRONGLY POSITIVE SST
ANOMALIES IN THE GULF OF MEXICO AND AROUND FLORIDA. ENHANCED PROBABILITIES,
REACHING 50 TO 60% ARE FAVORED ALONG THE EASTERN SEABOARD INTO NEW ENGLAND AND
PARTS OF THE EASTERN GREAT LAKES DUE TO MODEL AGREEMENT, WARM COASTAL SSTS, AND
ABOVE NORMAL DECADAL TEMPERATURE TREND OVER NEW ENGLAND. THOUGH STILL ABOVE
NORMAL, PROBABILITIES ARE RELATIVELY WEAKER OVER EASTERN PARTS OF THE NORTHERN
PLAINS STRETCHING SOUTHWARD TO THE SOUTHERN PLAINS WHERE WE MIGHT EXPECT SOME
MINOR MODULATION OF TEMPERATURES GIVEN THE FORECASTED LA NIñA, THOUGH NOT
ENOUGH TO TILT THE ODDS TOWARD BELOW NORMAL. EC IS FAVORED OVER THE WEST COAST
GIVEN COOLER SST ANOMALIES (LEADING TO AN ENHANCED SEABREEZE) AND DUE TO THE
POTENTIAL FOR EARLY IMPACTS OF LA NIñA OVER THE PACIFIC NORTHWEST AS THE JAS
SEASON PROGRESSES. SSTS ARE ANOMALOUSLY COLD ALONG THE SOUTHERN AND WESTERN
COAST OF ALASKA LEADING TO A SLIGHT TILT TOWARD BELOW NORMAL TEMPERATURES OVER
THE SOUTHWESTERN PART OF THE STATE, WHICH IS ALSO COINCIDENT WITH EXPECTED
EARLY LA NIñA TELECONNECTIONS. PROBABILITIES TRANSITION TO ABOVE NORMAL TOWARD
THE NORTHEASTERN PART OF ALASKA GIVEN FORECASTS FROM NMME AND C3S.
THE NEXT TWO SEASONS, AUGUST-OCTOBER (ASO) 2024 AND SEPTEMBER-NOVEMBER (SON)
2024 ALSO DEPICT FAVORED PROBABILITIES OF ABOVE NORMAL TEMPERATURES ACROSS THE
MAJORITY OF THE CONUS, AGAIN DRIVEN BY MODEL AGREEMENT AND STRONG DECADAL
TRENDS PARTICULARLY OVER THE WESTERN CONUS AND NEW ENGLAND. AREAS OF EXCEPTION
ARE THE WEST COAST AND PACIFIC NORTHWEST IN ASO AND THE PACIFIC NORTHWEST IN
SON WHERE EC IS FAVORED GIVEN EXPECTED IMPACTS FROM LA NIñA AND THE COOLER
COASTAL SSTS. THE TEMPERATURE OUTLOOK FOR ALASKA FAVORS BELOW NORMAL
TEMPERATURES FOR PARTS OF SOUTHERN ALASKA AND ABOVE NORMAL TEMPERATURES FOR
NORTHERN ALASKA, INFLUENCED BY LA NIñA AND DECADAL TRENDS, RESPECTIVELY. THIS
TEMPERATURE PATTERN ESSENTIALLY CONTINUES IN THE OUTLOOKS FOR ALASKA INTO EARLY
SPRING OF 2025, AS LA NIñA IS PREDICTED TO CONTINUE, AFTER WHICH, ABOVE NORMAL
TEMPERATURES ARE INCREASINGLY FAVORED FOR ALASKA AT LONGER LEADS, RELATED TO
DECADAL TRENDS.
LA NIñA IMPACTS ARE THE KEY DRIVER OF THE FORECAST DURING WINTER AND EARLY
SPRING 2024-2025, AND THE FORECASTS GENERALLY DEPICT BELOW NORMAL TEMPERATURE
PROBABILITIES OVER THE PACIFIC NORTHWEST AND STRETCHING INTO PARTS OF THE
CENTRAL PLAINS FROM NDJ 2024-2025 THROUGH MAM 2025, WITH ABOVE NORMAL
TEMPERATURES OVER THE SOUTHERN TIER OF THE CONUS. FOR LONGER LEADS BEGINNING IN
AMJ 2025 THROUGH JAS 2025, THE FORECAST IS DOMINATED BY TEMPERATURE TRENDS,
WHERE ABOVE NORMAL TEMPERATURES ARE FAVORED ACROSS MUCH OF THE CONUS EXCEPTING
PARTS OF THE NORTHERN PLAINS WHERE TRENDS ARE WEAKER.
PRECIPITATION
THE JAS 2024 PRECIPITATION OUTLOOK FAVORS BELOW NORMAL PRECIPITATION OVER PARTS
OF THE WESTERN AND CENTRAL CONUS. EC IS INDICATED OVER THE SOUTHERN WEST COAST
AND PARTS OF WESTERN NEVADA, AS THESE REGIONS ARE CLIMATOLOGICALLY DRIER, AND
OVER THE PACIFIC NORTHWEST WHERE MODEL FORECASTS ARE WEAK AND INCONSISTENT. 50
TO 60% CHANCES OF BELOW NORMAL PRECIPITATION ARE FAVORED OVER EASTERN ARIZONA,
WESTERN NEW MEXICO, AND PARTS OF THE FOUR CORNERS REGION WHERE DYNAMICAL MODEL
AGREEMENT WAS STRONGEST AND IN AGREEMENT WITH EARLY IMPACTS OF LA NIñA FOR
SOME REGIONS. GIVEN ANOMALOUSLY LOW SOIL MOISTURE OVER PARTS OF EASTERN NEW
MEXICO AND WESTERN TEXAS, 40 TO 50% PROBABILITIES OF BELOW NORMAL PRECIPITATION
ARE INDICATED. ENHANCED PROBABILITIES FOR ABOVE NORMAL PRECIPITATION ARE
DEPICTED OVER THE SOUTHEAST AND ALONG THE EASTERN SEABOARD TO NEW ENGLAND, WITH
THE HIGHEST PROBABILITIES REACHING 50 TO 60% OVER THE COASTAL GULF STATES,
FLORIDA, AND COASTAL SOUTH CAROLINA OWING TO A FORECASTED ABOVE NORMAL
HURRICANE SEASON AND GIVEN EARLY IMPACTS OF LA NIñA. PROBABILITIES REMAIN
ENHANCED, REACHING 40 TO 50% ABOVE NORMAL, ALONG THE EAST COAST INTO COASTAL
NEW ENGLAND GIVEN THE CHANCE OF STORMINESS CONTINUING ALONG THE COAST. THIS
PATTERN IS GENERALLY FAVORED FOR THE CONUS INTO ASO 2024. ABOVE NORMAL
PRECIPITATION IS FORECAST FOR MUCH OF ALASKA IN JAS 2024 BASED MAINLY ON NMME
AND C3S, EXCLUDING THE NORTHEASTERN PART OF THE STATE WHERE MODEL SIGNALS WERE
WEAK.
BEGINNING IN LATE FALL 2024 INTO WINTER AND EARLY SPRING 2025, A CANONICAL LA
NIñA PRECIPITATION PATTERN IS FAVORED OVER THE CONUS. ABOVE NORMAL
PRECIPITATION IS INDICATED OVER THE NORTH COAST OF ALASKA AND THE PACIFIC
NORTHWEST STRETCHING INTO THE CENTRAL PLAINS AND SHIFTING EASTWARD TO THE GREAT
LAKES AS THE FORECAST PROGRESSES THROUGH FEBRUARY-APRIL (FMA) 2025. BELOW
NORMAL PRECIPITATION IS FAVORED ACROSS THE SOUTHERN TIER OF THE CONUS AND SOUTH
COAST OF ALASKA THROUGH ROUGHLY FEBRUARY-APRIL (FMA) 2024. THE REMAINING LEADS,
MAM 2025 THROUGH JAS 2025 ARE BASED MAINLY ON DECADAL TRENDS WHICH FAVOR DRIER
CONDITIONS OVER THE SOUTHWEST (MAM 2025), AND OVER THE NORTHERN AND CENTRAL
PLAINS FROM AMJ 2025 THROUGH JAS 2025. A SMALL REGION OF ABOVE NORMAL
PRECIPITATION IS FAVORED OVER SOUTHERN NEW ENGLAND AND THE MID-ATLANTIC IN JAS
2025 GIVEN DECADAL TRENDS. ABOVE NORMAL PRECIPITATION IS FAVORED FOR PARTS OF
THE NORTH SLOPE OF ALASKA, DUE TO POSITIVE DECADAL TRENDS IN PRECIPITATION,
SHIFTING TO THE SOUTH COAST BY JAS 2025.
FORECASTER: JOHNNA INFANTI
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 JUL 18 2024
1991-2020 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 20, 2021
FORECAST RELEASE.
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