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FXUS05 KWBC 161231
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU MAY 16 2024
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS
AT PRESENT, AN EL NIñO ADVISORY REMAINS IN EFFECT BUT ATMOSPHERIC AND OCEANIC
PATTERNS ASSOCIATED WITH EL NIñO ARE DECREASING. EL NIñO SOUTHERN OSCILLATION
(ENSO) NEUTRAL CONDITIONS ARE EXPECTED FOR THE APRIL-MAY-JUNE (AMJ) SEASON AS A
WHOLE, AND THERE ARE APPROXIMATELY EVEN CHANCES OF ENSO NEUTRAL OR LA NIñA
CONDITIONS BY THE JUNE-JULY-AUGUST (JJA) SEASON. A LA NIñA CLIMATE STATE IS
MORE LIKELY TO DEVELOP BY JULY-AUGUST-SEPTEMBER (JAS) WITH A PROBABILITY OF
ALMOST 70 PERCENT, AND WOULD BE EXPECTED TO CONTINUE THROUGH WINTER, ONCE IN
PLACE. THE JJA 2024 TEMPERATURE OUTLOOK FAVORS BELOW-NORMAL TEMPERATURES FOR
THE SOUTHWESTERN COAST OF MAINLAND ALASKA, WHILE ABOVE-NORMAL TEMPERATURES ARE
FAVORED FOR CENTRAL AND EASTERN ALASKA. ABOVE-NORMAL TEMPERATURES ARE LIKELY
FOR THE WESTERN CONTIGUOUS U.S. (CONUS) AND ACROSS THE SOUTHERN PLAINS INTO THE
WESTERN GULF COAST REGION. ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED FOR THE
EASTERN CONUS WITH PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES EXCEEDING 50
PERCENT FOR THE NORTHEAST. EQUAL CHANCES (EC) OF BELOW, NEAR, AND ABOVE-NORMAL
SEASONAL MEAN TEMPERATURES ARE INDICATED FOR PARTS OF THE NORTHERN CENTRAL
CONUS.
THE JJA 2024 PRECIPITATION OUTLOOK SLIGHTLY FAVORS ABOVE-NORMAL PRECIPITATION
ACROSS MOST OF ALASKA. THE OUTLOOK FAVORS BELOW-NORMAL PRECIPITATION ACROSS
MOST OF THE WEST FROM THE PACIFIC COAST ACROSS THE ROCKY MOUNTAINS, WHILE EC IS
PREDICTED FOR THE CLIMATOLOGICALLY DRIER REGION OVER CALIFORNIA, NEVADA, AND
ARIZONA. ABOVE-NORMAL PRECIPITATION IS FAVORED FOR A LARGE AREA OF THE EASTERN
CONUS STRETCHING FROM THE GULF COAST NORTHEASTWARD ACROSS THE LOWER MISSISSIPPI
VALLEY AND THE SOUTHEAST, INTO THE OHIO VALLEY, MID-ATLANTIC, AND SOUTHERN NEW
ENGLAND. FOR THE REMAINING AREAS OF THE CENTRAL 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
ALTHOUGH THE CURRENT INTERANNUAL CLIMATE STATE IS EL NIñO, AS REPRESENTED BY
THE MOST RECENT SEASONAL MEAN NIñO 3.4 INDEX VALUE OF +1.1 DEGREES CELSIUS, THE
MOST RECENT WEEKLY MEAN SEA SURFACE TEMPERATURE (SST) ANOMALY FOR THE NIñO 3.4
REGION IS ONLY +0.3 C, AS THE EQUATORIAL PACIFIC IS COOLING. A SUBSTANTIAL
RESERVOIR OF COLDER THAN AVERAGE OCEAN TEMPERATURES REMAINS BELOW THE SURFACE
NEAR THE DATE LINE AT A DEPTH OF 100 TO 200 METERS EXTENDING INTO THE EASTERN
PACIFIC AT A DEPTH OF ABOUT 150 METERS TO THE SURFACE. NEGATIVE SST ANOMALIES
ARE OBSERVED NEAR THE EQUATOR IN THE EAST-CENTRAL PACIFIC WITH ANOMALIES
EXCEEDING -1.0 DEGREES C IN SOME LOCATIONS. OUTGOING LONGWAVE RADIATION (OLR)
ANOMALIES ARE WEAK ACROSS THE TROPICAL PACIFIC INDICATING NEAR AVERAGE
CONVECTION AND PRECIPITATION. LOW-LEVEL (850-HPA) WINDS WERE NEAR AVERAGE OVER
MOST OF THE TROPICAL PACIFIC OCEAN. CROSS EQUATORIAL UPPER-LEVEL (200-HPA) WIND
ANOMALIES WERE OBSERVED NEAR THE DATE LINE AND OVER EAST-CENTRAL EQUATORIAL
PACIFIC. MOST RECENT, SHORT TERM, ATMOSPHERIC AND OCEANIC ANOMALIES ARE MORE
INDICATIVE OF ENSO NEUTRAL CONDITIONS THAN THE CURRENT EL NIñO INTERANNUAL
STATE.
SIGNIFICANT INCREASES IN SOIL MOISTURE WERE OBSERVED IN THE LAST FOUR WEEKS
OVER THE NORTH-CENTRAL CONUS, AND POSITIVE SOIL MOISTURE ANOMALIES ARE OBSERVED
OVER MUCH OF THE REGION. POSITIVE SST ANOMALIES ARE CURRENTLY OBSERVED ALONG
THE GULF COAST AND NEAR THE ATLANTIC COAST OF THE SOUTHEAST. SST ANOMALIES ARE
NEAR AVERAGE ALONG MOST OF THE WEST COAST. NEGATIVE SST ANOMALIES ARE OBSERVED
ALONG THE WEST COAST OF MAINLAND ALASKA. SURFACE BOUNDARY CONDITIONS, SUCH AS
SOIL MOISTURE ANOMALIES, AND NEAR COASTAL SST ANOMALIES CAN INFLUENCE LOCAL
TEMPERATURE AND PRECIPITATION OVER THE NEXT SEASON. SOIL MOISTURE ANOMALIES
HAVE A GREATER INFLUENCE ON SURFACE TEMPERATURES OVER THE GREAT PLAINS IN THE
SUMMER MONTHS.
PROGNOSTIC DISCUSSION OF SST FORECASTS
SST FORECASTS FROM MOST NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) DYNAMICAL
MODELS AND FROM MOST STATISTICAL MODELS, INCLUDING THE CPC CONSTRUCTED ANALOG
(CA) AND CANONICAL CORRELATION ANALYSIS (CCA) PREDICT INCREASINGLY NEGATIVE
AVERAGE SST ANOMALIES FOR THE NIñO 3.4 REGION THROUGH THE COMING SEASONS INTO
NEXT WINTER. SOME INDIVIDUAL MODELS OF THE NMME AND OF THE INTERNATIONAL
MULTI-MODEL ENSEMBLE (IMME OR C3S) FAVOR ENSO NEUTRAL SSTS IN THE NIñO 3.4
REGION THROUGH AUTUMN, WHILE THE CONSOLIDATED NMME MODELS INDICATES
APPROXIMATELY A -1.1 DEGREE C ANOMALY, CONSIDERED TO BE A MODERATE LA NIñA
EVENT. THE CPC NIñO 3.4 SST CONSOLIDATION FORECAST PREDICTS A PEAK ANOMALY OF
-1.1 DEGREES C FOR THE NOVEMBER-DECEMBER-JANUARY (NDJ) SEASON. THE CPC ENSO
OUTLOOK PREDICTS GREATER THAN AN 80 PERCENT CHANCE OF LA NIñA FORMING BY
METEOROLOGICAL BOREAL AUTUMN, SEPTEMBER-OCTOBER-NOVEMBER (SON), AND CONTINUING
THROUGH WINTER INTO EARLY 2025.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
THE SEASONAL TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED PRIMARILY ON
FORECAST TOOLS DERIVED FROM THE NMME, INCLUDING CALIBRATED VERSIONS, SUCH AS
THE PROBABILITY ANOMALY CORRELATION (PAC) AND THE CALIBRATION, BRIDGING AND
MERGING (CBAM), WHICH CALIBRATES THE DYNAMICAL MODEL FORECAST USING BAYESIAN
JOINT PROBABILITY (BJP) MODELS, AS WELL AS GENERATING STATISTICAL OR “BRIDGING”
BJP MODELS OF TEMPERATURE AND PRECIPITATION FROM DYNAMICAL MODEL NIñO 3.4
ANOMALY FORECAST PREDICTORS. AN ENSO-OCN FORECAST TOOL IS USED TO REPRESENT THE
COMBINED INFLUENCE OF THE EL NIñO SOUTHERN OSCILLATION (ENSO) AND DECADAL
TIMESCALE TRENDS IN TEMPERATURE AND PRECIPITATION, USING THE OPTIMUM CLIMATE
NORMAL (OCN). LA NIñA IMPACTS ARE CONSIDERED IN THE OUTLOOKS FROM JJA 2024
THROUGH MARCH-APRIL-MAY (MAM) 2025, WITH LA NIñA IMPACTS POSSIBLE LATE IN THE
JJA 2024 SEASON DESPITE EQUAL CHANCES OF ENSO NEUTRAL OR LA NIñA FOR THE SEASON
AS A WHOLE. 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 THAT
UTILIZES PAC CALIBRATION IS USED THROUGHOUT THE OUTLOOKS FROM JJA 2024 TO JJA
2025.
PROGNOSTIC DISCUSSION OF OUTLOOKS - JJA 2024 TO JJA 2025
TEMPERATURE
THE JJA 2024 SEASONAL TEMPERATURE OUTLOOK FAVORS BELOW NORMAL TEMPERATURES FOR
THE SOUTHWESTERN COAST OF MAINLAND ALASKA AND THE ALASKA PENINSULA, SUPPORTED
BY DYNAMICAL MODEL FORECASTS FROM THE NMME AND BELOW AVERAGE SSTS NEAR THE
COAST. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR EASTERN ALASKA AS IN MOST
DYNAMICAL MODEL FORECASTS AND THE CONSOLIDATION. ABOVE NORMAL TEMPERATURES ARE
LIKELY FOR MOST OF THE WESTERN CONUS, WITH PROBABILITIES EXCEEDING 60 PERCENT
FOR PARTS OF THE SOUTHWEST, SUPPORTED BY THE CONSOLIDATION, RELATED TO
SIGNIFICANT DECADAL TRENDS IN SUMMER TEMPERATURES AND REINFORCED BY A BELOW
NORMAL PRECIPITATION FORECAST. PROBABILITIES FAVORING ABOVE NORMAL TEMPERATURES
ARE REDUCED FOR THE CALIFORNIA COAST, WHERE MODELS PREDICT POTENTIAL BELOW
NORMAL TEMPERATURES IN JUNE. ABOVE NORMAL TEMPERATURES ARE FAVORED ACROSS THE
SOUTHERN HALF OF THE GREAT PLAINS AND FOR MOST OF THE EASTERN CONUS IN THE JJA
2024 SEASONAL OUTLOOK, IN AGREEMENT WITH MOST FORECAST TOOLS. EC IS FORECAST
FOR THE NORTHERN CENTRAL CONUS, WHERE SOME MODELS SUCH AS THE CBAM INDICATE THE
POTENTIAL FOR BELOW NORMAL TEMPERATURES, AND POSITIVE SOIL MOISTURE ANOMALIES
MAY HELP MAINTAIN BELOW OR NEAR NORMAL TEMPERATURES, EARLY IN THE SEASON.
THE TEMPERATURE OUTLOOKS FOR THE NEXT TWO SEASONS, THROUGH SUMMER INTO EARLY
AUTUMN, FAVOR ABOVE NORMAL TEMPERATURES ACROSS THE ENTIRE CONUS, DRIVEN BY
STRONG DECADAL TEMPERATURE TRENDS IN THESE SEASONS, AND LESSER IMPACTS OF A
POTENTIAL LA NIñA. THE TEMPERATURE OUTLOOK FOR ALASKA DURING THIS PERIOD 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. A MORE CANONICAL LA NIñA TEMPERATURE
PATTERN IS FAVORED OVER THE CONUS FROM LATE AUTUMN THROUGH WINTER, WITH BELOW
NORMAL TEMPERATURES FAVORED FOR PARTS OF THE PACIFIC NORTHWEST FROM NDJ
2024-2025 THROUGH MAM 2025, AND ABOVE NORMAL TEMPERATURES MORE LIKELY ACROSS
THE SOUTHERN TIER OF THE CONUS, INCLUDING MOST OF THE SOUTHWEST, THE GULF
COAST, AND THE EASTERN SEABOARD. DECADAL TEMPERATURE TRENDS FAVOR ABOVE NORMAL
TEMPERATURES ACROSS MOST OF THE CONUS FOR THE LONGER LEADS, EXCLUDING PARTS OF
THE NORTHERN CENTRAL CONUS, WHERE TRENDS ARE WEAKER.
PRECIPITATION
THE JJA AND JAS SEASONAL PRECIPITATION OUTLOOKS FAVOR ABOVE NORMAL
PRECIPITATION FOR MOST OF ALASKA, EXCLUDING THE WESTERN ALEUTIANS AND SOUTHEAST
ALASKA, WITH DYNAMICAL MODELS PREDICTING SOUTHERLY FLOW INTO THE STATE. BELOW
NORMAL PRECIPITATION IS FAVORED FOR MOST OF THE WESTERN CONUS, EXCLUDING ONLY
CLIMATOLOGICAL DRIER REGIONS OF CALIFORNIA, NEVADA AND ARIZONA, SUPPORTED BY
MOST TOOLS AND THE CONSOLIDATION, AND CONSISTENT WITH POTENTIAL EARLY IMPACTS
OF LA NIñA IN SOME AREAS. ABOVE NORMAL PRECIPITATION IS FAVORED FROM THE GULF
COAST REGION ACROSS THE LOWER MISSISSIPPI VALLEY, THE OHIO VALLEY,
MID-ATLANTIC, AND SOUTHERN NEW ENGLAND, CONSISTENT OVERALL WITH THE
PRECIPITATION CONSOLIDATION, DECADAL TRENDS, AND POTENTIAL EARLY TROPICAL
ACTIVITY RELATED TO LA NIñA AND ABOVE AVERAGE TROPICAL SSTS.
THE NEXT SEVERAL SEASONAL PRECIPITATION OUTLOOKS INDICATE AN EVOLUTION OF THE
PRECIPITATION PATTERN OVER THE CONUS, SHIFTING AREAS OF FAVORED BELOW NORMAL
PRECIPITATION SOUTHWARD AWAY FROM THE NORTHERN TIER AND WEST COAST, AND
EASTWARD TOWARDS THE MISSISSIPPI VALLEY. ABOVE NORMAL PRECIPITATION IS FAVORED
OVER THE NORTHWEST BY THE SEPTEMBER-OCTOBER-NOVEMBER (SON) SEASON INTO WINTER,
CONSISTENT WITH A PREDICTED LA NIñA. DURING THE WINTER SEASON, AREAS OF FAVORED
ABOVE NORMAL PRECIPITATION SHIFT EASTWARD INTO THE NORTHERN PLAINS AND
SOUTHEASTWARD INTO THE CENTRAL MISSISSIPPI AND OHIO VALLEYS. WINTER INTO EARLY
SPRING SEASONAL OUTLOOKS FAVOR BELOW NORMAL PRECIPITATION ACROSS MUCH OF THE
SOUTHERN TIER OF THE CONUS FROM SOUTHERN CALIFORNIA AND THE SOUTHWEST TO THE
GULF COAST AND SOUTHEAST AND FOR THE SOUTH COAST OF ALASKA, FOLLOWING A
CANONICAL LA NIñA PRECIPITATION PATTERN, AS REPRESENTED BY REGRESSIONS OF
PRECIPITATION ONTO NIñO 3.4 SST ANOMALIES. THE LAST THREE PRECIPITATION
OUTLOOKS FAVOR BELOW NORMAL PRECIPITATION FOR PARTS OF THE NORTHWESTERN CONUS,
DUE TO DECADAL TRENDS FAVORING DRIER CONDITIONS. BEGINNING IN
OCTOBER-NOVEMBER-DECEMBER (OND) 2024 THROUGH ALL LONGER LEADS, ABOVE NORMAL
PRECIPITATION IS FAVORED FOR PARTS OF THE NORTH SLOPE OF ALASKA, DUE TO
POSITIVE DECADAL TRENDS IN PRECIPITATION AND ADJACENT SSTS.
FORECASTER: DAN COLLINS
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 JUN 20 2024
1991-2020 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 20, 2021
FORECAST RELEASE.
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