270
FXUS07 KWBC 292002
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST THU FEB 29 2024
30-DAY OUTLOOK DISCUSSION FOR MARCH 2024
MUCH OF THE FORECAST THINKING FROM THE MIDDLE OF FEBRUARY FOR THE MARCH
TEMPERATURE AND PRECIPITATION OUTLOOKS REMAINS IN PLACE FOR THIS END OF THE
MONTH UPDATE. OVERALL, ANY SIGNIFICANT OUTLOOK CHANGES ARE LIMITED TO ALASKA
AND THE NORTHERN AND CENTRAL FAR WEST IN THE TEMPERATURE OUTLOOK. THE PRIMARY
CHANGES IN THE UPDATED PRECIPITATION OUTLOOK ARE FOR INCREASES IN FORECAST
COVERAGE AND ODDS FOR ABOVE-NORMAL MONTHLY PRECIPITATION AMOUNTS IN MANY AREAS.
A BRIEF SUMMARY UPDATE OF THE CLIMATE PREDICTORS OUTLINED IN THE MID-MONTH
DISCUSSION AS IMPORTANT FOR THE FORECAST REMAIN GENERALLY UNCHANGED. THE MJO
REMAINS ACTIVE WITH THE ENHANCED CONVECTION PHASE ENTERING AND FURTHER
RE-ORGANIZING IN THE INDIAN OCEAN AND MODEL FORECASTS OF THE RMM INDEX ARE
QUITE IMPRESSIVE AND CONSISTENT AMONG ENSEMBLE MODEL PREDICTIONS.
ALTHOUGH ANOTHER SSW IS FORECAST WITHIN THE NEXT SEVERAL DAYS, PREVIOUS EVENTS
THIS WINTER HAVE NOT HAD MUCH DURATION NOR IMPACTS IN THE TROPOSPHERE AND IT IS
UNCLEAR WHETHER THIS LATEST PREDICTED WARMING WILL BE ANY DIFFERENT. THE TWO
WEEK FORECASTS OF THE AO INDEX (PHASE AND AMPLITUDE) HAVE BEEN EXTREMELY POOR
THIS WINTER FROM BOTH THE GEFS AND ECMWF ENSEMBLE PREDICTION SYSTEMS. GIVEN
THESE FACTORS, IT IS NOT POSSIBLE TO RELIABLY INCLUDE ANY POTENTIAL SSW RELATED
IMPACTS THAT MAY OCCUR IN LATE MARCH FOR THE UPDATED TEMPERATURE OUTLOOK.
THE MJO IS FORECAST OVER THE NEXT TWO WEEKS TO STRENGTHEN IN AMPLITUDE AND
COHERENCE AND PROPAGATE EASTWARD ACROSS THE MARITIME CONTINENT DURING THE FIRST
HALF OF MARCH. THIS EVOLUTION FAVORS RIDGING FOR EASTERN NORTH AMERICA AND
ABOVE-NORMAL TEMPERATURES FOR THE EASTERN CONUS ENTERING MID-MARCH WHICH MAY
CONTINUE FOR THE FOLLOWING 1-2 WEEKS. THIS COMBINED WITH FORECAST RIDGING AND
VERY LARGE POSITIVE TEMPERATURE ANOMALIES DURING THE FIRST TWO WEEKS OF MARCH -
AS INDICATED BY SHORT-, MEDIUM- AND EXTENDED-RANGE MODEL GUIDANCE - SUPPORTS
HIGH ODDS FOR ABOVE-NORMAL MONTHLY MEAN TEMPERATURES FOR THE GREAT LAKES, OHIO
VALLEY, MID-ATLANTIC AND NORTHEAST.
BOTH TROUGHING DURING THE FIRST 1-2 WEEKS OF MARCH OVER THE SOUTHWEST CONUS AND
MJO CONSIDERATIONS (SIMILAR FORCING) IS THE REASON FOR EXPANDING THE
HIGHLIGHTED AREA OF FAVORED BELOW-NORMAL TEMPERATURES IN THE SOUTHWEST U.S. AT
MID-MONTH TO NOW INCLUDE CALIFORNIA, NEVADA AND UTAH AND REMOVING FAVORED
ABOVE-NORMAL TEMPERATURES FOR NORTHERN AND CENTRAL AREAS OF THE FAR WEST. MODEL
PREDICTIONS DURING THE FIRST COUPLE OF WEEKS IN MARCH WARRANT A CHANGE IN THE
OUTLOOK FOR ALASKA FOR ENHANCED ODDS FOR BELOW-NORMAL TEMPERATURES IN THE
MONTHLY UPDATE. LARGE DEFICITS IN SNOW COVER AND SNOW DEPTH COMPARED TO NORMAL
ALSO CONTRIBUTE TO ENHANCED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES FOR THE
NORTHERN TIER OF THE U.S. FROM THE HIGH PLAINS TO THE NORTHEAST.
THE PRECIPITATION OUTLOOK FOR THE MONTHLY UPDATE IS LARGELY UNCHANGED FROM THE
MID-MONTH FIRST RELEASE. ALL FACTORS DISCUSSED AT MID-MONTH REMAIN ON TRACK AND
THE LATEST GUIDANCE ACROSS TIME SCALES IS CONSISTENT IN MOST WAYS WITH THE
ORIGINAL OUTLOOK. THE CHANGES ARE MAINLY RELATED TO INCREASES IN FORECAST
COVERAGE AND PROBABILITIES FOR ABOVE-NORMAL MONTHLY TOTAL PRECIPITATION AMOUNTS
FOR THE REGIONS FROM THE WEST COAST TO THE CENTRAL GREAT PLAINS AND FROM THE
CENTRAL GULF COAST INTO THE SOUTHEAST. THE MAIN SIGNIFICANT CHANGE IS THE
REMOVAL OF FAVORED BELOW-NORMAL PRECIPITATION FOR THE EXTREME PACIFIC NORTHWEST
WHERE AN ACTIVE PERIOD DURING THE FIRST 2 WEEKS OF MARCH IS LIKELY TO LEAD TO
SIGNIFICANT PRECIPITATION AMOUNTS.
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PREVIOUS DISCUSSION FROM MID-MONTH OUTLOOK BELOW
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A NUMBER OF CLIMATE FACTORS ARE CONSIDERED IN PREPARING THE MARCH 2024
TEMPERATURE AND PRECIPITATION OUTLOOKS. IN ADDITION TO THE ONGOING, ALBEIT
WEAKENING EL NINO, AN ONGOING MJO EVENT CONTINUES. TO FURTHER COMPLICATE
MATTERS, THERE ARE INDICATIONS OF A WEAKENING IN THE STRATOSPHERIC POLAR VORTEX
POTENTIALLY LEADING TO A SUDDEN STRATOSPHERIC WARMING (SSW) SOMETIME DURING THE
SECOND HALF OF FEBRUARY. MOREOVER, EL NINO WINTERTIME RESIDUAL IMPACTS ARE ALSO
CONSIDERED IN DEVELOPING THE OUTLOOK.
EVEN THOUGH EL NINO OCEANIC CONDITIONS HAVE PEAKED - SSTS ARE DECREASING AND
OCEANIC HEAT CONTENT ALONG THE EQUATOR WITH DEPTH IN THE PACIFIC BASIN HAS
DECREASED CONSIDERABLY, THE INDUCED ATMOSPHERIC RESPONSE CAN OFTEN LINGER AND
SO COMMON EL NINO IMPACTS ARE LIKELY TO CONTINUE AT TIMES THROUGH MARCH AND
POTENTIALLY INTO APRIL. SO THE MARCH 2024 TEMPERATURE AND PRECIPITATION
OUTLOOKS CONTINUED TO CONSIDER EL NINO AS PART OF THE LARGE SCALE BASE STATE
AND SO POTENTIAL IMPACTS.
THE MJO HAS BEEN QUITE ACTIVE THE LAST SEVERAL WEEKS, BUT ITS CURRENT COHERENCY
IS BEING IMPACTED BY MULTIPLE MODES OF BOTH SUBSEASONAL [I.E., ATMOSPHERIC
KELVIN WAVES AND EQUATORIAL ROSSBY WAVES (KW/ERW)] AND INTER-ANNUAL FORCING
(I.E. ENSO). WITH THIS THE CASE, SOME STANDARD REALTIME METRICS OF THE MJO
AMPLITUDE AND PHASE ARE DISTURBED AND AT TIMES LESS CLEAR WHEN MONITORING. BUT
GIVEN RECENT PACIFIC OCEAN JET STRENGTH AND EXTENSIONS AND MONITORING THE
CIRCULATION ONLY PORTION OF THE SIGNAL (E.G., 200-HPA VELOCITY POTENTIAL) IT
APPEARS THE MJO REMAINS ACTIVE AND HAS ENTERED AND IS CROSSING THE WESTERN
HEMISPHERE. MODEL PREDICTIONS OF THE RMM INDEX, VARY HIGHLY, BUT MOST GENERALLY
FAVOR CONTINUE EASTWARD PROPAGATION OF A SIGNAL ACROSS AFRICA BACK TOWARDS THE
INDIAN OCEAN OVER THE NEXT COUPLE OF WEEKS. IF THIS BECOMES THE CASE AND
ENHANCED CONVECTION REDEVELOPS IN THE EASTERN INDIAN OCEAN AND MARITIME
CONTINENT, RIDGING AND ABOVE-NORMAL TEMPERATURES FOR THE EASTERN HALF OF THE
CONUS WOULD TEND TO BE FAVORED. WEAK SIGNALS OR TROUGHING WOULD BE MOST LIKELY
AT MODEST ODDS ACROSS THE WESTERN CONUS.
RECENT MONITORING OF THE STRATOSPHERE AND MODEL PREDICTIONS OF THE 10-HPA ZONAL
WIND INDICATE A POTENTIAL FOR A SSW AND POTENTIAL COUPLING WITH THE TROPOSPHERE
AND A TENDENCY TO FAVOR A NEGATIVE AO FOR PERIODS DURING THE MONTH OF MARCH.
HOWEVER, THERE REMAINS HIGH UNCERTAINTY IN THE EVENTUAL EVOLUTION AFTER ANY SSW
EVENT AND SO FOLLOW ON -AO POTENTIAL. EVEN WITH A SSW EVENT, THERE ALWAYS
REMAINS CONSIDERABLE VARIABILITY IN HOW THE VORTEX IS IMPACTED (I.E. DISPLACED
VORTEX VS. A SPLIT VORTEX) AND THE HEMISPHERE (EASTERN VS. WESTERN) WHERE THE
ODDS ARE THE GREATEST FOR MORE FREQUENT ARCTIC AIR OUTBREAKS DURING MARCH.
IN MID-FEBRUARY, SUBSTANTIAL SNOW DEFICITS ARE EVIDENT FROM THE NORTHERN HIGH
PLAINS EASTWARD TO THE GREAT LAKES AND NORTHEAST - COMMON AFTER EL NINO
WINTERS. INCREASED WETNESS AND SNOWPACK HAS DEVELOPED IN RECENT WEEKS FOR
PORTIONS OF THE WESTERN CONUS PRIMARILY IN CALIFORNIA, NEVADA, AND THE CENTRAL
AND SOUTHERN ROCKIES AS A RESULT OF ACTIVE PACIFIC STORMINESS.
WEIGHING ALL THESE FACTORS, THE MARCH 2024 TEMPERATURE OUTLOOK FAVORS
ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE FAR WEST, PACIFIC NORTHWEST EASTWARD
ACROSS THE NORTHERN PLAINS, GREAT LAKES AND FOR MUCH OF THE EASTERN CONUS. EL
NINO AND NEGATIVE SNOW DEPARTURES SUPPORT THE FORECAST FOR MUCH OF THIS
HIGHLIGHTED AREA. POTENTIAL MJO INFLUENCE SUPPORTS THE EXTENSION OF FAVORED
ABOVE-NORMAL WARMTH FOR THE EASTERN THIRD OF THE CONUS. LOWER ODDS FOR
ABOVE-NORMAL TEMPERATURES IN THE NORTHERN PLAINS AND WESTERN GREAT LAKES, LARGE
AREA OF EQUAL-CHANCES (EC) IN THE INTERIOR OF THE CONUS AND SLIGHTLY FAVORED
BELOW-NORMAL TEMPERATURES FOR PARTS OF THE SOUTHEAST AND TEXAS ARE IN DEFERENCE
TO POTENTIAL INFLUENCE FROM NEGATIVE AO PERIODS. ELEVATED ODDS FOR ABOVE-NORMAL
PRECIPITATION ALSO CONTRIBUTES SLIGHTLY TO THE BELOW-NORMAL TEMPERATURE
FORECAST IN THIS REGION. POTENTIAL TROUGHING ASSOCIATED WITH THE MJO AND
ELEVATED CHANCES FOR ABOVE-NORMAL PRECIPITATION IN SOME AREAS SUPPORT A SLIGHT
TILT TOWARD BELOW-NORMAL TEMPERATURES FOR PARTS OF THE SOUTHWEST. ABOVE-NORMAL
TEMPERATURES ARE MOST LIKELY FOR THE ENTIRE STATE OF ALASKA.
FOR PRECIPITATION, EL NINO BACKGROUND CONDITIONS AND POTENTIAL MJO INFLUENCE AT
TIMES IN MARCH, FAVOR ABOVE-NORMAL MONTHLY TOTAL PRECIPITATION AMOUNTS FROM
CALIFORNIA EASTWARD ACROSS THE CENTRAL ROCKIES TO THE NORTH-CENTRAL PLAINS.
DYNAMICAL MODEL GUIDANCE (NMME, C3S) AND LONG TERM POSITIVE PRECIPITATION
TRENDS ALSO SUPPORT THIS FORECAST. EL NINO CONSIDERATIONS AND DYNAMICAL MODEL
GUIDANCE SUPPORT ELEVATED ODDS FOR ABOVE-NORMAL PRECIPITATION FOR THE GULF
COAST, THE SOUTHEAST AND MUCH OF THE EASTERN SEABOARD AS WELL AS SMALLER
REGIONS OF FAVORED BELOW-NORMAL PRECIPITATION FOR PARTS OF THE PACIFIC
NORTHWEST AND CENTRAL GREAT LAKES. THE MAJORITY OF DYNAMICAL MODEL GUIDANCE
FAVORED BELOW-NORMAL MONTHLY PRECIPITATION AMOUNTS FOR SOUTHERN TEXAS. FOR
ALASKA, ABOVE-NORMAL PRECIPITATION IS MOST LIKELY FOR MOST OF THE SOUTHERN
PORTION OF THE STATE.
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.
THE NEXT MONTHLY OUTLOOK...FOR APR ... WILL BE ISSUED ON THU MAR 21 2024
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1991-2020 BASE PERIOD.
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