344
FXUS07 KWBC 301901
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SUN APR 30 2023
30-DAY OUTLOOK DISCUSSION FOR MAY 2023
THE MAY 2023 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE UPDATED CONSIDERING
CURRENT WEATHER PREDICTION CENTER (WPC) OUTLOOKS FOR WEEK 1, CLIMATE PREDICTION
CENTER (CPC) EXTENDED RANGE AND SUBSEASONAL OUTLOOKS, DYNAMICAL MODEL GUIDANCE
FOR WEEK 2 AND WEEKS 3-4, CURRENT SOIL MOISTURE CONDITIONS, BACKGROUND CLIMATE
STATES, AND RECENT CLIMATE FORECAST SYSTEM VERSION 2 (CFSV2) MONTHLY FORECASTS
OF TEMPERATURE AND PRECIPITATION. SEA SURFACE TEMPERATURE (SST) ANOMALIES ARE
NEAR-TO-ABOVE AVERAGE ACROSS MOST OF THE PACIFIC OCEAN AND RECENT WEEKLY SST
DEPARTURES IN THE NINO1+2 REGION REACHED 2.5 DEGREES CELSIUS ABOVE NORMAL. EL
NIñO SOUTHERN OSCILLATION (ENSO) NEUTRAL CONDITIONS ARE OBSERVED IN THE
EQUATORIAL PACIFIC, AND AS SUCH, ENSO DID NOT PLAY A SIGNIFICANT ROLE IN THE
UPDATED MAY 2023 OUTLOOKS. WELL ORGANIZED MADDEN JULIAN OSCILLATION (MJO)
ACTIVITY HAS CONTINUED DURING THE LATTER PARTS OF APRIL AND RECENT FORECASTS OF
THE REALTIME MULTIVARIATE MJO (RMM) INDEX INDICATE POTENTIAL CONTINUATION
THROUGH AT LEAST MID-MAY. AS THE ATMOSPHERIC RESPONSE TO THE LA NINA CONTINUES
TO WANE, MJO IS EXPECTED TO BE THE DOMINANT DRIVER OF TROPICAL CONVECTIVE
ANOMALIES, HOWEVER, EXTRATROPICAL LINKAGES BECOME LESS CLEAR DURING BOREAL
SPRING. THOUGH THE EXTRATROPICAL INFLUENCE FROM THE MJO MAY BE WEAK DURING
SPRING, IT IS CONSIDERED IN THE UPDATED OUTLOOKS.
A LARGELY PERSISTENT PATTERN IS FORECAST IN THE 6-10 AND 8-14 DAY PERIODS
(EARLY MAY) DEPICTING TROUGHING OVER THE WEST COAST, RIDGING OVER THE ROCKIES,
AND TROUGHING OVER THE EAST COAST. THE TROUGHING OVER THE EAST COAST IS
FORECAST TO PROGRESS OVER THE NORTH ATLANTIC BY MID-MAY, WHILE THE TROUGH OVER
THE WEST COAST HAS BEEN AND IS EXPECTED TO REMAIN MORE STATIONARY. GIVEN THE
PERSISTENT EARLY MAY PATTERN, THE UPDATED MAY 2023 TEMPERATURE OUTLOOK HAS A
FEW CHANGES FROM THE MID-MONTH OUTLOOK, PARTICULARLY OVER THE EASTERN
CONTIGUOUS UNITED STATES (CONUS) WHERE TROUGHING IS EXPECTED TO LEAD TO COOLER
TEMPERATURES TO START THE MONTH.
A WEAK TILT TOWARD BELOW NORMAL TEMPERATURES IS INDICATED OVER THE INTERIOR
EASTERN CONUS BENEATH THE PERSISTENT EARLY-MAY TROUGH, AND WHERE EQUAL-CHANCES
(EC) OF ABOVE AND BELOW NORMAL TEMPERATURES WERE INDICATED IN THE PRIOR MAY
2023 TEMPERATURE OUTLOOK. THOUGH WE EXPECT COOLER TEMPERATURES IN EARLY MAY,
THE EXPECTED INFLUENCE FROM CONTINUED MJO ACTIVITY IS ABOVE NORMAL TEMPERATURES
OVER THE CENTRAL AND EASTERN CONUS, AND LONGER LEAD FORECASTS (WEEK 3-4) TILT
WEAKLY WARM AS THE TROUGHING PROGRESSES OVER THE NORTH ATLANTIC. AS SUCH,
PROBABILITIES ARE LOW FOR BELOW NORMAL TEMPERATURES. THE REGION OF ABOVE NORMAL
TEMPERATURES ALONG THE EAST COAST IN THE INITIAL MAY 2023 OUTLOOK IS
SIGNIFICANTLY SMALLER, AND EC IS INDICATED ALONG THE COAST CONSIDERING THE
STRONG MODEL AGREEMENT FROM EARLIER NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME)
AND COPERNICUS MODEL SUITE (C3S) GUIDANCE ON ABOVE NORMAL PROBABILITIES, BOTH
OF WHICH ARE AT ODDS WITH UPDATED GUIDANCE FAVORING A COOLER START TO MAY. MORE
RECENT FORECASTS SHOW CONFLICTING SIGNALS OVER TX WHERE PROBABILITIES OF ABOVE
NORMAL TEMPERATURES WERE ORIGINALLY INDICATED, WITH SOME SHORT TERM AND WEEK
3-4 GUIDANCE FAVORING ABOVE NORMAL TEMPERATURES, AND CFSV2 MONTHLY FORECASTS
FAVORING BELOW NORMAL TEMPERATURES. AS SUCH, EC IS FAVORED OVER TEXAS. ENHANCED
PROBABILITIES OF ABOVE NORMAL TEMPERATURES REMAIN OVER NEW ENGLAND AND FLORIDA
WHERE DYNAMICAL MODELS CONSISTENTLY FORECAST ABOVE NORMAL TEMPERATURES
THROUGHOUT MAY. THE AREA OF ABOVE NORMAL PROBABILITIES OVER THE PACIFIC
NORTHWEST IS EXPANDED INTO THE WESTERN NORTHERN PLAINS GIVEN THE PERSISTENT
RIDGING AND CONSISTENT MODEL FORECASTS. THE REGION OF BELOW NORMAL
PROBABILITIES IS MAINTAINED AND EXPANDED OVER THE WEST COAST INTO THE SOUTHWEST
UNDER AND AHEAD OF PERSISTENT TROUGHING AND GIVEN EARLIER MODEL SOLUTIONS WHICH
FAVORED COOLER TEMPERATURES OVER PARTS OF THE WEST COAST. EC IS NOW FAVORED
OVER THE EASTERN NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY WHERE CFSV2
INDICATES EC, AND OTHER MODEL SOLUTIONS SHOW WEAK OR CONFLICTING FORECASTS
THROUGHOUT THE MONTH. PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE MAINTAINED
OVER THE NORTH SLOPE OF ALASKA, AND A SMALL AREA OF BELOW NORMAL PROBABILITIES
IS INTRODUCED OVER THE SOUTH COAST GIVEN THE TRANSITION TO TROUGHING OVER THE
WESTERN CONUS AND COOLER SST ANOMALIES OFF THE WEST COAST OF ALASKA.
ENHANCED PROBABILITIES OF BELOW NORMAL PRECIPITATION OVER THE GREAT LAKES IN
THE MID-MONTH OUTLOOK ARE EXPANDED INTO THE UPPER AND MIDDLE MISSISSIPPI, OHIO,
AND TENNESSEE VALLEY REGIONS IN THE UPDATED PRECIPITATION OUTLOOK, AHEAD OF THE
ANTICIPATED EARLY MAY CENTRAL CONUS RIDGING. THE TILT TOWARDS ABOVE NORMAL
PRECIPITATION IS MAINTAINED OVER THE GULF STATES AND EXPANDED INTO PARTS OF
EASTERN TEXAS GIVEN RECENT MONTHLY CFSV2 FORECASTS AND SHORT TERM FORECASTS
THAT FAVOR ABOVE NORMAL PRECIPITATION IN THE REGION; HOWEVER, MOST MODELS SHOW
A SHARP TRANSITION FROM BELOW NORMAL TO ABOVE NORMAL PRECIPITATION OVER THE
GULF STATES. GIVEN WEST COAST TROUGHING, A TILT TOWARD ABOVE NORMAL
PRECIPITATION IS NOW INDICATED OVER THE WESTERN CONUS, WITH PROBABILITIES
REACHING 50 TO 60 PERCENT WHERE DYNAMICAL MODELS AGREE AND PROBABILITIES ARE
STRONGEST. THE AREA OF BELOW NORMAL PRECIPITATION IS REMOVED OVER THE PACIFIC
NORTHWEST CONSISTENT WITH UPDATED MODEL FORECASTS AND EC OF ABOVE AND BELOW
NORMAL PRECIPITATION IS NOW INDICATED. PROBABILITIES FOR ABOVE NORMAL
PRECIPITATION REMAIN CONFIDENT IN MODELS OVER WESTERN ALASKA.
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****** PREVIOUS MID-MONTH DISCUSSION BELOW ******
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THE MAY 2023 TEMPERATURE AND PRECIPITATION OUTLOOKS INCLUDE THE LATEST
STATISTICAL AND DYNAMICAL MODEL GUIDANCE, IMPACTS FROM DECADAL TRENDS, LOCAL
SEA SURFACE TEMPERATURE (SST) ANOMALIES, SURFACE MOISTURE CONDITIONS, AND
POTENTIAL INFLUENCE FROM THE MADDEN JULIAN OSCILLATION (MJO). MJO IS CURRENTLY
ACTIVE IN RECENT OBSERVATIONS, AND REALTIME MULTIVARIATE MJO (RMM) INDEX
FORECASTS FROM THE GLOBAL ENSEMBLE FORECAST SYSTEM (GEFS) AND EUROPEAN CENTRE
FOR MEDIUM-RANGE WEATHER FORECASTS (ECMWF) MODELS DEPICT CONTINUED MJO ACTIVITY
THROUGH THE NEXT WEEK, WITH SOME INDICATION OF A DISRUPTION OF THE SIGNAL IN
WEEK 2 GIVEN INTERFERENCE FROM ROSSBY AND KELVIN WAVE ACTIVITY. SOME ENSEMBLE
MEMBERS, PARTICULARLY FROM GEFS, FAVOR CONTINUATION OF THE MJO INTO EARLY MAY
THOUGH THE PHASE SPEED AND AMPLITUDE OF THE MJO IS UNCERTAIN AT THIS TIME. MJO
PLAYED A MARGINAL ROLE IN THIS FORECAST GIVEN ITS UNCERTAIN EVOLUTION, AND WILL
BE CONSIDERED MORE HEAVILY FOR THE MONTHLY UPDATE. EL NIñO SOUTHERN OSCILLATION
(ENSO) CONDITIONS ARE CURRENTLY NEUTRAL, BUT NEAR TO ABOVE AVERAGE SEA SURFACE
TEMPERATURE (SST) ANOMALIES HAVE EXPANDED ACROSS THE EQUATORIAL PACIFIC IN THE
PAST FEW WEEKS WITH SST ANOMALIES IN THE EASTERN PACIFIC (NINO1+2) REACHING 2.7
DEGREES CELSIUS ABOVE NORMAL. THOUGH WARM SST ANOMALIES HAVE BECOME MORE
PROMINENT IN THE EASTERN PACIFIC, TRANSITION TO EL NIñO CONDITIONS HAS NOT YET
OCCURRED AND TELECONNECTIONS ARE NOT ANTICIPATED TO IMPACT THE MAY FORECAST AT
THIS TIME. DYNAMICAL MODEL GUIDANCE FROM THE NORTH AMERICAN MULTI-MODEL
ENSEMBLE (NMME), COPERNICUS MODEL SUITE (C3S), AND THE CLIMATE FORECAST SYSTEM
VERSION 2 (CFSV2) WERE CONSIDERED FOR THE OUTLOOK AS WELL AS STATISTICAL
MODELS. WEEK 3-4 FORECASTS FROM CFSV2, ECMWF, AND GEFSV12 FOR THE EARLY PART OF
MAY WERE ALSO CONSIDERED.
WITH ENSO NEUTRAL CONDITIONS IN THE EQUATORIAL PACIFIC AND AN UNCERTAIN MJO
EVOLUTION, AS WELL AS EXPECTED LARGER INFLUENCE FROM DAILY WEATHER PATTERNS ON
THE LARGE-SCALE CLIMATE SIGNAL DURING THE BOREAL SPRING, TOOLS SUPPORTING THE
TEMPERATURE AND PRECIPITATION OUTLOOKS ARE GENERALLY UNCERTAIN OR HAVE MIXED
RESULTS PARTICULARLY FOR PRECIPITATION. AS SUCH, PROBABILITIES ARE MODERATED IN
THE OFFICIAL OUTLOOKS, AND EQUAL CHANCES OF ABOVE, MEDIAN, OR BELOW NORMAL
TEMPERATURE (PRECIPITATION) (EC) IS INDICATED WHERE TOOLS DISAGREE OR SIGNALS
ARE WEAK.
THE MAY 2023 TEMPERATURE OUTLOOK DEPICTS ABOVE NORMAL TEMPERATURE PROBABILITIES
STRETCHING FROM TEXAS ALONG THE EAST COAST OF THE CONTIGUOUS UNITED STATES
(CONUS). NMME AND C3S BOTH FAVOR ABOVE NORMAL PROBABILITIES OVER EASTERN PARTS
OF THE CONUS, AND THIS TILT TOWARD ABOVE NORMAL PROBABILITIES IS ADDITIONALLY
SUPPORTED BY THE WEEKS 3-4 OUTLOOK AND TOOLS WHICH GENERALLY FEATURE ENHANCED
PROBABILITIES OF ABOVE NORMAL TEMPERATURES OVER THE GULF STATES AND EAST COAST
IN EARLY PARTS OF MAY. PROBABILITIES ARE ENHANCED ALONG PARTS OF THE COAST AND
NEW ENGLAND GIVEN ANOMALOUSLY WARM COASTAL SSTS. 40 TO 50 PERCENT PROBABILITIES
OF ABOVE NORMAL TEMPERATURES ARE INDICATED OVER TEXAS WHERE SOIL MOISTURE IS
ANOMALOUSLY DRY. GREAT LAKES TEMPERATURES ARE ABOVE NORMAL, AND AS SUCH A
SLIGHT TILT TOWARD ABOVE NORMAL TEMPERATURES IS FAVORED OVER THE LOWER GREAT
LAKES WHERE DYNAMICAL MODELS ALSO HAD AGREEMENT, HOWEVER, MUCH OF THE UPPER
GREAT LAKES AND OHIO RIVER VALLEY REGIONS HAD CONFLICTING SIGNALS AMONGST THE
TOOLS. MOREOVER, UNCERTAINTY IN THE PHASE SPEED AND AMPLITUDE OF THE POTENTIAL
MJO COULD LEAD TO DIFFERING TELECONNECTIONS OVER THE EASTERN CONUS. AS SUCH, EC
IS INDICATED OVER THE UPPER GREAT LAKES AND OHIO RIVER VALLEY. WEAK
PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE INDICATED OVER PARTS OF THE
PACIFIC NORTHWEST WHERE STATISTICAL GUIDANCE AND RECENT CFSV2 SOLUTIONS AGREE.
HIGHER ELEVATIONS WHERE SNOW COVER REMAINS, INCLUDING THE CASCADES, MAY SEE
POCKETS OF BELOW NORMAL TEMPERATURES EARLIER IN MAY. SNOW COVER IS ANOMALOUSLY
HIGH OVER PARTS OF EASTERN NORTH DAKOTA AND WESTERN MONTANA. GIVEN FORECASTS
FOR THE REMAINDER OF APRIL AND BEGINNING OF MAY THAT TILT TOWARD COOLER
TEMPERATURES WHICH COULD DELAY SNOW MELT, BELOW NORMAL TEMPERATURE
PROBABILITIES ARE INDICATED FOR PARTS OF THE NORTH CENTRAL CONUS. BELOW NORMAL
TEMPERATURES OVER THIS REGION ARE ALSO SUPPORTED BY RECENT CFSV2 RUNS AND BELOW
NORMAL DECADAL TEMPERATURE TRENDS. BELOW NORMAL TEMPERATURE PROBABILITIES ARE
ALSO FAVORED FOR PARTS OF THE WEST COAST WHERE THERE IS GOOD AGREEMENT AMONG
MODELS, ALSO SUPPORTED BY ANOMALOUSLY COLD WEST COAST SSTS.
TOOLS ARE SOMEWHAT INCONSISTENT OVER ALASKA, PARTICULARLY THE SOUTHERN HALF OF
THE STATE. STATISTICAL TOOLS DEPICT ABOVE NORMAL TEMPERATURES OVER AK, WHILE
C3S FAVORS BELOW NORMAL TEMPERATURES OVER THE SOUTHWESTERN COAST WHERE SST
ANOMALIES ARE BELOW NORMAL, AND CFSV2 FAVORS A TRANSITION TO EC OR BELOW NORMAL
TEMPERATURES ALONG THE SOUTH COAST. THE AREA OF HIGHEST AGREEMENT IS FOR ABOVE
NORMAL TEMPERATURES OVER THE NORTH SLOPE, BUT ANOMALOUSLY HIGH SNOW COVER OVER
THE BROOKS RANGE WILL LIKELY LEAD TO COOLER TEMPERATURES AND EC IS INDICATED
FOR THE REMAINDER OF THE STATE.
DISAGREEMENT AMONG MODELS AND TOOLS IS RELATIVELY HIGHER FOR PRECIPITATION, AND
AS SUCH PROBABILITIES ARE LOW AND A LARGE AREA OF EC IS FAVORED IN THE MAY 2023
PRECIPITATION OUTLOOK. A TILT TOWARD BELOW NORMAL PRECIPITATION IS FAVORED OVER
THE PACIFIC NORTHWEST AND PARTS OF THE NORTHERN ROCKIES, CONSISTENT WITH
FORECASTED WARMER TEMPERATURES. BELOW NORMAL PRECIPITATION IS ALSO INDICATED
FOR PARTS OF THE GREAT LAKES WHERE THERE WAS AGREEMENT AMONG MODELS. MODELS
WERE ALSO CONSISTENT ON FORECASTING ABOVE NORMAL PRECIPITATION OVER THE
SOUTHEAST, ADDITIONALLY SUPPORTED BY DECADAL TRENDS. SOIL MOISTURE IS
ANOMALOUSLY HIGH OVER PARTS OF THE LOWER MISSISSIPPI VALLEY WHICH SUPPORTS
EXPANSION OF THE REGION OF ABOVE NORMAL PRECIPITATION PROBABILITIES. TOOLS AND
DYNAMICAL MODELS FORECAST WEAK OR INCONSISTENT SIGNALS ACROSS MUCH OF ALASKA,
HOWEVER, THE AREA OF HIGHEST CONSISTENCY WAS OVER THE SOUTHWESTERN COAST WHERE
ABOVE NORMAL PRECIPITATION PROBABILITIES ARE INDICATED.
FORECASTER: JOHNNA INFANTI
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.
THE NEXT MONTHLY OUTLOOK...FOR JUN ... WILL BE ISSUED ON THU MAY 18 2023
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1991-2020 BASE PERIOD.
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