PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EST THU JAN 17 2019


30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2019

THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR FEBRUARY 2019 ARE BASED ON THE 
BACKGROUND ENSO STATE, POTENTIAL MJO ACTIVITY, AS WELL AS DYNAMICAL MODEL 
GUIDANCE.  DYNAMICAL MODEL GUIDANCE AND STATISTICAL TOOLS THAT TYPICALLY 
SUPPORT THE WEEK 3-4 PERIOD, WHICH COVERS THE FIRST HALF THE MONTH, WERE ALSO 
USED.  

THE OBSERVED TEMPERATURE ANOMALY PATTERN DURING EARLY DECEMBER OVER THE CONUS 
EXHIBITED A DIPOLE STRUCTURE WITH COLDER THAN NORMAL EAST AND WARMER THAN 
NORMAL WEST. THE PATTERN THEN FLIPPED DURING LATER DECEMBER. JANUARY STARTED 
WITH A WARM EAST, BUT IS LIKELY TO FINISH WITH A COOLER THAN AVERAGE EAST AND 
WARMER THAN AVERAGE WESTERN CONUS.  THE MJO LIKELY PLAYED A ROLE IN THESE NOTED 
SWITCHES, AND THE MJO IS PREDICTED TO REMAIN ACTIVE INTO FEBRUARY, THOUGH THE 
AMOUNT OF INFLUENCE CAN VARY MONTH TO MONTH DUE TO SEVERAL FACTORS. THE COLDER 
EASTERN CONUS ANTICIPATED IN LATER JANUARY IS CONSISTENT WITH A SUDDEN 
STRATOSPHERIC WARMING EVENT THAT TOOK PLACE IN EARLY JANUARY.  ATTRIBUTION OF 
THE PATTERN IS STILL ONGOING.

THE COLDER THAN NORMAL CONDITIONS ACROSS THE EASTERN CONUS ARE LIKELY TO 
CONTINUE FOR THE FIRST HALF OF FEBRUARY, WITH TEMPERATURES DURING THE LATTER 
HALF OF THE MONTH BEING LESS CERTAIN. DYNAMICAL MODELS DEPICTING THE FULL MONTH 
OUTLOOK INDICATE NEAR TO BELOW NORMAL CONDITIONS FOR MUCH OF THE EASTERN CONUS, 
WITH THE STRONGEST SIGNALS FOR COLD FROM THE GREAT LAKES TO TENNESSEE VALLEY 
AND TO THE SOUTHEAST. THE MULTIPLE LINEAR REGRESSION (MLR) TOOL THAT EXPLICITLY 
ACCOUNTS FOR THE MJO INFLUENCE INDICATES WARMER SIGNALS OVER THE EASTERN CONUS, 
SO THE PROBABILITIES IN THE OFFICIAL OUTLOOK ARE TEMPERED FROM THAT IN MANY OF 
THE DYNAMICAL MODELS, ESPECIALLY THOSE TOOLS GEARED TOWARD THE FIRST HALF THE 
MONTH.  ACROSS THE WESTERN CONUS, A FORECAST FOR ABOVE NORMAL TEMPERATURES IS 
SUPPORTED BY DYNAMICAL MODEL PREDICTIONS AND TRENDS. THE MLR TOOL HAS A MUCH 
WEAKER SIGNAL ACROSS THE WESTERN CONUS, SO PLAYS LESS OF A ROLE.  ACROSS 
ALASKA, TRENDS AND DYNAMICAL MODEL GUIDANCE FAVOR ABOVE NORMAL TEMPERATURES, 
THOUGH THE EXACT PLACEMENT OF THE AREAS WITH THE HIGHEST ODDS HAVE VARIED WITH 
RECENT MODEL RUNS. THE OFFICIAL OUTLOOK PLACES THE HIGHEST ODDS ACROSS SOUTHERN 
ALASKA AND THE ALASKA PANHANDLE AS THOSE LOCATIONS ARE LIKELY TO EXPERIENCE 
SOUTHERLY MEAN FLOW AT THE SURFACE. THERE IS SOME POTENTIAL FOR PERIODS OF COLD 
AIR TO SPILL INTO THE ALASKA PANHANDLE IF RIDGING OVER WESTERN CANADA SLIPS 
WESTWARD.

THE PRECIPITATION OUTLOOK LARGELY REFLECTS DYNAMICAL MODEL GUIDANCE AND TRENDS, 
AS EXPRESSED IN BOTH THE SEASONAL OCN AND THE MLR TOOL.  A MEAN STORM TRACK 
INTO SOUTHERN ALASKA FAVORS ABOVE NORMAL PRECIPITATION FOR SOUTHERN ALASKA AND 
THE ALASKA PANHANDLE, WITH THE MEAN STORM TRACK THEN DIPPING DOWN OVER THE 
NORTHERN GREAT PLAINS. ANOMALOUS RIDGING IS LIKELY TO PREVAIL ALONG THE WEST 
COAST DURING THE EARLY PORTIONS OF FEBRUARY, LIMITING THE POTENTIAL FOR LONG 
PERIODS OF WET WEATHER DURING A CLIMATOLOGICALLY WET PERIOD, SO BELOW NORMAL 
PRECIPITATION IS FAVORED FOR MUCH OF OREGON, CALIFORNIA, PORTIONS OF THE GREAT 
BASIN, AND PARTS OF THE SOUTHWEST. MEAN NORTHERLY FLOW, SUPPORTING THE COLDER 
THAN NORMAL TEMPERATURE OUTLOOK, ALSO FAVORS BELOW NORMAL PRECIPITATION FROM 
THE GREAT LAKES TO THE TENNESSEE VALLEY. ALONG THE GULF COAST AND EAST COAST, 
THE PLACEMENT OF THE MEAN FRONTAL ZONE COULD RESULT IN ABOVE NORMAL 
PRECIPITATION, BUT UNCERTAINTY IS TOO HIGH TO DEPICT A SIGNAL.

FORECASTER: MATTHEW ROSENCRANS

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 THU JANUARY 31 2019

THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.
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