452
FXUS07 KWBC 211333
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EST THU JAN 21 2021
30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2021
THE FEBRUARY 2021 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON WEEKS 3
TO 4 FORECASTS FROM THE CFS AND ECMWF MODELS, THE NORTH AMERICAN MULTI-MODEL
ENSEMBLE (NMME), TYPICAL INFLUENCES FROM THE ONGOING LA NIA, AND DECADAL
TRENDS. BELOW AVERAGE SEA SURFACE TEMPERATURES (SSTS) ACROSS THE EQUATORIAL
PACIFIC ALONG WITH A STRONG COUPLING WITH THE ATMOSPHERE REPRESENT LA NIA
CONDITIONS. ALTHOUGH DYNAMICAL MODELS DEPICT A STRENGTHENING MADDEN-JULIAN
OSCILLATION (MJ0) DURING LATE JANUARY INTO EARLY FEBRUARY, LA NIA IS LIKELY TO
BE THE MAJOR TROPICAL FORCING DUE TO THE WELL-ESTABLISHED ANOMALOUS ENHANCED
(SUPPRESSED) CONVECTION OVER THE MARITIME CONTINENT (EQUATORIAL CENTRAL
PACIFIC).
DESPITE HIGH LATITUDE BLOCKING WITH A PERSISTENT NEGATIVE ARCTIC OSCILLATION
(AO), 30-DAY TEMPERATURES SINCE MID-DECEMBER HAVE AVERAGED ABOVE NORMAL FOR
NEARLY ALL OF THE CONUS. THIS MILD TEMPERATURE PATTERN WAS DUE IN PART TO
ENHANCED PACIFIC FLOW OVERSPREADING THE HIGHER LATITUDES OF NORTH AMERICA AND
CROSS POLAR FLOW GENERALLY LIMITED TO THE EASTERN HEMISPHERE. WEEK-2 MODEL
GUIDANCE (JAN 28-FEB 3) REMAINS CONSISTENT THAT AN AMPLIFIED AND FULL-LATITUDE
500-HPA RIDGE BECOMES CENTERED OVER THE ALEUTIANS AND EXTENDS POLEWARD. THE
WEEK 3-4 ECMWF MODEL INDICATES THIS ANOMALOUS RIDGING PERSISTING THROUGH AT
LEAST EARLY FEBRUARY, WHICH IS LIKELY TO PROMOTE CROSS POLAR FLOW AND RESULT IN
BELOW NORMAL TEMPERATURES ACROSS PARTS OF ALASKA. BASED ON GOOD MODEL
CONTINUITY WITH THIS FEATURE AND SUPPORT FROM A NUMBER OF INPUTS TO THE NMME,
BELOW NORMAL TEMPERATURES ARE FAVORED FOR SOUTHEASTERN MAINLAND ALASKA AND THE
ALASKA PANHANDLE. ALTHOUGH THE SOURCE REGION IS EXPECTED TO BECOME MORE
FAVORABLE FOR ARCTIC AIR TO SHIFT SOUTH ACROSS THE WESTERN AND NORTH-CENTRAL
CONUS DURING THE NEXT MONTH, THE NMME SUPPORTS EQUAL CHANCES (EC) OF BELOW,
NEAR, OR ABOVE NORMAL TEMPERATURES FOR MUCH OF THE WEST AND NORTHERN GREAT
PLAINS. SPARSE SNOW COVER ACROSS THE CANADIAN PRAIRIES AND NORTHERN GREAT
PLAINS MAY BE A LIMITING FACTOR TO ANOMALOUSLY COLD TEMPERATURES HEADING INTO
FEBRUARY. BELOW NORMAL TEMPERATURES ARE SLIGHTLY FAVORED FOR PARTS OF THE
PACIFIC NORTHWEST AND NORTHERN ROCKIES, DUE TO THE PREDICTED CLOSE PROXIMITY OF
ANOMALOUS COLD DURING THE FIRST HALF OF FEBRUARY AND THIS IS ALSO CONSISTENT
WITH LA NIA COMPOSITES.
THE LARGEST PROBABILITIES (ABOVE 50 PERCENT) OF ABOVE NORMAL TEMPERATURES ARE
FORECAST FROM THE RIO GRANDE VALLEY EASTWARD TO THE GULF COAST, BASED ON THE
WEEK 3-4 MODEL GUIDANCE, CALIBRATED NMME, AND LA NIA COMPOSITES. ALTHOUGH A
HIGH LATITUDE BLOCK OVER THE DAVIS STRAIT AND NEGATIVE PHASE OF THE NAO ARE
FORECAST TO PROMOTE PERIODS OF BELOW NORMAL TEMPERATURES ALONG THE EAST COAST
DURING THE REMAINDER OF JANUARY, THE GFS ENSEMBLE MEMBERS DEPICT A TRANSITION
TO A NEUTRAL OR EVEN POSITIVE PHASE OF THE NAO BY THE BEGINNING OF FEBRUARY. AS
THE NEGATIVE NAO DIMINISHES DURING THE NEXT TWO WEEKS, LA NIA IS EXPECTED TO
BECOME A MORE DOMINANT FACTOR WHICH INCREASES PROBABILITIES OF ABOVE NORMAL
TEMPERATURES ACROSS THE SOUTHEAST. ABOVE NORMAL TEMPERATURES ARE ONLY SLIGHTLY
FAVORED FOR THE NORTHEAST, GREAT LAKES, AND UPPER MISSISSIPPI VALLEY DUE TO
LOWER FORECAST CONFIDENCE AND THE POTENTIAL FOR A VARIABLE TEMPERATURE PATTERN
DURING FEBRUARY. IT REMAINS UNCLEAR WHEN OR EVEN IF THE RECENT STRATOSPHERIC
WARMING EVENT WOULD INFLUENCE TEMPERATURES ACROSS THE CONUS AND THIS WILL BE
REASSESSED FOR THE UPDATED OUTLOOK RELEASED ON JANUARY 31.
THE PRECIPITATION OUTLOOK FOR FEBRUARY IS CONSISTENT WITH LA NIA COMPOSITES
AND SUPPORTED BY THE NMME. BELOW NORMAL PRECIPITATION IS MOST LIKELY ACROSS THE
SOUTHERN TIER OF THE CONUS, WHILE ABOVE NORMAL PRECIPITATION IS FAVORED FROM
THE PACIFIC NORTHWEST EASTWARD TO THE UPPER AND MIDDLE MISSISSIPPI VALLEY AND
GREAT LAKES. ELEVATED PROBABILITIES OF BELOW NORMAL PRECIPITATION, FORECAST FOR
SOUTHEASTERN MAINLAND ALASKA AND THE ALASKA PANHANDLE, ARE CONSISTENT WITH
BELOW NORMAL TEMPERATURES FAVORED FOR THESE AREAS. A MAJORITY OF INPUTS TO THE
NMME SUPPORT INCREASED PROBABILITIES OF ABOVE NORMAL PRECIPITATION ACROSS THE
ALEUTIANS. PROBABILITIES THROUGHOUT THE FORECAST DOMAIN ARE TEMPERED DUE TO
LARGE UNCERTAINTIES DURING THIS MONTHLY OUTLOOK TIME RANGE.
FORECASTER: BRAD PUGH
THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, 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.
AN UPDATED MONTHLY OUTLOOK... FOR FEB WILL BE ISSUED ON SUN JANUARY 31 2021
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.
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