206
FXUS07 KWBC 161331
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EST THU NOV 16 2023
30-DAY OUTLOOK DISCUSSION FOR DECEMBER 2023
EL NIñO CONDITIONS ARE CURRENTLY OBSERVED, AND EQUATORIAL SEA SURFACE
TEMPERATURES (SSTS) ARE ABOVE AVERAGE ACROSS THE CENTRAL AND EASTERN EQUATORIAL
PACIFIC OCEAN. THE TROPICAL PACIFIC ATMOSPHERE IS CONSISTENT WITH EL NIñO, AND
AS SUCH WE EXPECT EL NIñO TO BE THE DOMINANT TROPICAL-BASED TELECONNECTION FOR
DECEMBER. THE MADDEN JULIAN OSCILLATION (MJO) RECENTLY WEAKENED ACCORDING TO
THE REAL-TIME MULTIVARIATE (RMM) INDEX AND CPC'S 200-HPA VELOCITY POTENTIAL
INDEX, BUT IS FORECAST TO STRENGTHEN LATER IN NOVEMBER. A STRENGTHENING MJO
COULD RESULT IN MORE VARIABILITY OVER THE WESTERN CONUS DURING THROUGH
MID-DECEMBER. IN ADDITION TO THESE INFLUENCING FACTORS, THE DECEMBER
TEMPERATURE AND PRECIPITATION OUTLOOKS CONSIDER LOCAL SST ANOMALIES, DYNAMICAL
MODEL GUIDANCE FROM THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME), COPERNICUS
MODEL SUITE (C3S), AND THE CLIMATE FORECAST SYSTEM VERSION 2 (CFSV2), AS WELL
AS STATISTICAL MODELS THAT INCLUDE THE INFLUENCE OF TREND AND ENSO. WEEK 3-4
OUTPUTS FROM CFSV2, ECMWF, AND GEFSV12 FROM MID-NOVEMBER FOR THE EARLY PART OF
DECEMBER WERE ALSO CONSIDERED.
THE DECEMBER 2023 TEMPERATURE OUTLOOK FAVORS A BROAD AREA OF ABOVE NORMAL
TEMPERATURES FOR THE EASTERN CONUS, FROM THE NORTHERN GREAT PLAINS TO THE LOWER
MISSISSIPPI VALLEY AND EASTWARD TO THE COAST. THE HIGHEST PROBABILITIES FOR
ABOVE-NORMAL TEMPERATURES ARE OVER THE UPPER MISSISSIPPI VALLEY AND GREAT
LAKES, WHERE THE IMPACTS OF TREND AND ENSO ARE MAXIMIZED. NMME OUTPUTS SUPPORT
THE AREA OF ABOVE-NORMAL TEMPERATURES EAST OF THE MISSISSIPPI RIVER, BUT WITH
LOWER PROBABILITIES THAN THE STATISTICAL TOOLS (CCA, CA, OCN). ACROSS THE GREAT
PLAINS TO THE ROCKIES, TRENDS ARE WEAK AND THE DYNAMICAL MODEL SIGNALS ARE
MIXED, SO EQUAL CHANCES (EC) IS INDICATED. OCN INDICATES WARMTH ACROSS THE
SOUTHWEST WHILE ENSO-OCN FAVORS BELOW-NORMAL TEMPERATURES IN THE FOUR CORNERS
REGION. LAGGED COMPOSITES OF PREDICTED MJO ACTIVITY WOULD FAVOR A HIGHLY
VARIABLE PATTERN ACROSS THE ROCKIES, FURTHER CONTRIBUTING TO THE EC OUTLOOK
THERE. ACROSS NORTHERN CALIFORNIA AND THE PACIFIC NORTHWEST, THE STATISTICAL
TOOLS AND DYNAMICAL MODELS BOTH INDICATE ABOVE-NORMAL TEMPERATURES, BUT THE
SPATIAL PATTERNS IN THE TOOLS ARE NOT ALIGNED, INDICATING UNCERTAINTY IN THE
OUTPUT AND LIKELY UNCERTAINTY IN THE FORCING, SO EC IS INDICATED THERE. ACROSS
ALASKA, RECENT SST OBSERVATIONS ARE SHOWING ABOVE-NORMAL SSTS AND LOWER SEA ICE
COVERAGE, BOTH OF WHICH WOULD FAVOR ABOVE-NORMAL TEMPERATURES FOR WESTERN AND
NORTHERN ALASKA. NMME AND WEEK3/4 MODEL GUIDANCE ALSO SUPPORT BROAD SCALE
ABOVE-NORMAL TEMPERATURES ACROSS MOST OF ALASKA, THOUGH TEMPERED BY MEAN
TROUGHING ASSOCIATED WITH THE PREDICTED PHASES OF MJO EARLY IN THE MONTH.
THE STRONGEST SIGNAL FOR ABOVE-NORMAL PRECIPITATION IS ACROSS THE SOUTHEAST,
CONSISTENT WITH NMME AND STATISTICAL TOOL GUIDANCE, AS WELL AS WEEK-3/4
GUIDANCE. A STORM TRACK ACROSS THE SOUTHEAST IS CONSISTENT WITH THE WINTER TIME
RESPONSE TO EL NIñO. THE ENSO-OCN TOOL INDICATED A WET START TO THE MONTH FROM
TEXAS TO SOUTH DAKOTA, AND THE OCN INDICATES A STRONG WET TREND IN THE NORTHERN
PLAINS. MJO COMPOSITES INDICATE VARIABILITY IN STORM TRACK DURING THE MONTH,
WITH EARLY MONTH TROUGHING ACROSS THE WESTERN CONUS THAT EVOLVES INTO AN
ENHANCED JET BY MID MONTH. THAT TRANSITION AND PROGRESSIVE PATTERN RESULTS IN
EC OVER MOST OF THE WESTERN CONUS, THOUGH NORTH OF THE MEAN TROUGH LIKELY EARLY
IN THE MONTH IS AN AREA ACROSS THE NORTHERN GREAT PLAINS WHERE BELOW-NORMAL
PRECIPITATION IS LIKELY FOR THE MONTH AS A WHOLE. MEAN TROUGHING TO THE WEST OF
ALASKA FROM MJO COMPOSITES, TRENDS, AND SST PATTERNS INDICATE ABOVE-NORMAL
PRECIPITATION FOR WESTERN AND NORTHERN MAINLAND ALASKA IS THE MOST LIKELY
OUTCOME.
FORECASTER: MATTHEW ROSENCRANS
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.
AN UPDATED MONTHLY OUTLOOK... FOR DEC WILL BE ISSUED ON THU NOVEMBER 30 2023
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1991-2020 BASE PERIOD.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page