PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 300 PM EST SAT DEC 31 2016 30-DAY OUTLOOK DISCUSSION FOR JANUARY 2017 THE MAJOR CLIMATE FACTORS IMPACTING THE JANUARY OUTLOOK HAVE NOT CHANGED SIGNIFICANTLY. RECENT SST ANOMALIES OVER THE CENTRAL PACIFIC REMAINED NEGATIVE, WITH WEEKLY VALUES NEAR THE THRESHOLD FOR LA NINA. THE ATMOSPHERIC PATTERN REMAINS INCONSISTENT WITH A ROBUST MJO, SO THE MJO WILL LIKELY NOT PLAY A ROLE IN THE JANUARY TEMPERATURE AND PRECIPITATION PATTERNS. EXTRATROPICAL MODES OF VARIABILITY ARE LIKELY TO DOMINATE THE PATTERN OVER NORTH AMERICA. SINCE THOSE MODES HAVE LOWER LEVELS OF PREDICTABILITY BEYOND ABOUT 14 DAYS, THE UNCERTAINTY IN THE LATTER HALF OF JANUARY REDUCES THE OVERALL CONFIDENCE. THE TEMPERATURE OUTLOOK REMAINS LARGELY THE SAME, THOUGH THE SIGNALS FOR BELOW NORMAL TEMPERATURES ACROSS THE NORTHWEST QUADRANT OF THE CONUS ARE MORE CERTAIN, SO PROBABILITIES ARE INCREASED. THE ANOMALIES FORECAST DURING THE FIRST 7 DAYS OF THE MONTH ARE LIKELY TO BE QUITE LARGE, SO EVEN WITH NEAR OR ABOVE NORMAL TEMPERATURES DURING THE LATTER HALF OF THE MONTH, THE MONTHLY VALUES ARE LIKELY TO BE BELOW AVERAGE FOR THE NORTHWESTERN PORTION OF THE CONUS. THAT SIGNAL FOR BELOW NORMAL TEMPERATURES EXTENDS OVER SOUTHEAST ALASKA AND THE ALASKA PANHANDLE. WARMTH EARLY IN THE PERIOD AND A PERSISTENT SIGNAL FROM ABOVE NORMAL SEA SURFACE TEMPERATURES FAVORS ABOVE NORMAL TEMPERATURES FOR WESTERN ALASKA. ABOVE NORMAL TEMPERATURES ARE STILL FAVORED FOR MUCH OF THE SOUTHERN CONUS AND THE NORTHEAST, WITH THE LATEST MODEL RUNS FAVORING ABOVE NORMAL TEMPERATURES OVER THE MID-ATLANTIC RATHER THAN NEW ENGLAND. ABOVE NORMAL TEMPERATURES ACROSS THE SOUTHERN TIER IS CONSISTENT WITH THE SEASONAL SIGNALS, SO THAT SIGNAL WAS INCORPORATED INTO THE OUTLOOKS. THE PRECIPITATION OUTLOOK IS MODIFIED TO REFLECT THE SHORTER TERM OUTLOOKS FOR HEAVY PRECIPITATION ACROSS THE SOUTHEAST DURING THE FIRST 7 DAYS OF THE MONTH, ALTHOUGH THE CLIMATE SIGNALS STILL FAVOR BELOW NORMAL PRECIPITATION FOR SOME OF THE SOUTHEAST, SO THE PROBABILITIES ARE KEPT LOWER. A STORM SYSTEM EARLY IN THE PERIOD, COMBINED WITH THE OUTLOOKS THROUGH 14 DAYS, FAVOR ABOVE MEDIAN PRECIPITATION ACROSS THE GREAT BASIN, CENTRAL AND NORTHERN ROCKIES, AND PACIFIC NORTHWEST. SIGNALS FOR THE LATTER HALF OF JANUARY FAVOR ABOVE MEDIAN PRECIPITATION FOR THE PACIFIC NORTHWEST AND NORTHERN ROCKIES, SO THE HIGHEST PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION ARE ACROSS THE NORTHERN PORTION OF THE WESTERN CONUS. ----------- PREVIOUS MESSAGE (FROM DECEMBER 15) --------------- THE JANUARY 2017 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON DYNAMICAL MODEL OUTPUTS, STATISTICAL TOOLS, TYPICAL PATTERNS ASSOCIATED WITH TROPICAL SST VARIABILITY, AND THE LIKELY STATES OF PATTERNS OF EXTRATROPICAL VARIABILITY. LA NINA CONDITIONS CONTINUE OVER THE TROPICAL PACIFIC, AND ARE EXPECTED TO CONTINUE THROUGH JANUARY 2017, THOUGH IMPACTS ON THE MONTHLY TIMESCALE FROM ENSO ARE LESS ROBUST THAN SEASONAL IMPACTS. CLIMATE SIGNALS ASSOCIATED WITH LA NINA ARE CONSIDERED AS A PORTION OF THE OUTLOOK. THE MJO IS NOT CURRENTLY ACTIVE, AND THE UNCERTAINTY FOR INTRASEASONAL VARIABILITY IS HIGH, SO THE MJO DID NOT PLAY A ROLE IN THE OUTLOOK. ITS EVOLUTION WILL BE CLOSELY MONITORED FOR THE REVISED OUTLOOK AT THE END OF DECEMBER. THE DYNAMICAL MODEL OUTLOOKS FOR JANUARY 2017 EXHIBITED GOOD AGREEMENT, WHERE AS LAST MONTH THE OUTLOOKS FOR DECEMBER HAD BETTER AGREEMENT, SO THE CONFIDENCE IN THE OUTLOOK IS SLIGHTLY LOWER, RESULTING IN LOW TO MODERATE COVERAGE. LA NINA CONDITIONS WOULD FAVOR ABOVE NORMAL TEMPERATURES OVER THE SOUTHERN CONUS WITH BELOW NORMAL TEMPERATURES OVER MUCH OF THE NORTHERN CONUS. THE SPATIAL COVERAGE OF WHERE BELOW NORMAL TEMPERATURES ARE FAVORED OVER THE NORTHERN ROCKIES AND NORTHERN GREAT PLAINS IS SMALLER THAN A TYPICAL SEASONAL FOOTPRINT OF LA NINA, DUE TO LOWER PREDICTABILITY AND DYNAMICAL MODEL GUIDANCE. SOME STATISTICAL TOOLS FAVOR BELOW NORMAL TEMPERATURES EXTENDING INTO NORTHERN COLORADO. SOME DYNAMICAL MODELS INDICATE A SLIGHT TILT TOWARD A NEGATIVE ARCTIC OSCILLATION THROUGHOUT THE WINTER, WHICH FAVORS PERIODS OF COLDER AIR MOVING SOUTHWARD OVER THE GREAT PLAINS, SO PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE LOWER THAN INDICATED IN MODEL GUIDANCE OVER THE GREAT PLAINS AND MID-ATLANTIC. ABOVE NORMAL SSTS FAVOR ABOVE NORMAL TEMPERATURES FOR WESTERN ALASKA AND THE ALEUTIANS. THE PRECIPITATION OUTLOOK FOR JANUARY 2017 REFLECTS CALIBRATED NMME OUTPUT AND IS CONSISTENT WITH TRADITIONAL LA NINA IMPACTS DURING DJF AND JFM. COVERAGE AND PROBABILITIES FOR THE CATEGORIES ARE LOWER THAN IF LA NINA WAS THE ONLY FACTOR, AS SIGNALS IN THE DYNAMICAL MODELS ARE WEAKER, AND LA NINA IMPACTS ON A SINGLE MONTH OF A SEASON ARE LESS PRONOUNCED THAN IMPACTS ON AN ENTIRE SEASON. BELOW MEDIAN PRECIPITATION IS FAVORED FOR THE SOUTHERN CONUS, WITH ABOVE MEDIAN PRECIPITATION FAVORED ALONG THE ROCKIES AND OVER THE GREAT LAKES REGION, WITH A MORE ACTIVE NORTHERN STORM TRACK. ABOVE NORMAL SSTS, BELOW NORMAL SEA ICE COVERAGE IN THE BERING SEA, AND MODEL GUIDANCE FAVOR ABOVE MEDIAN PRECIPITATION FOR WESTERN ALASKA. 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. THE NEXT MONTHLY OUTLOOK...FOR FEB ... WILL BE ISSUED ON THU JAN 19 2017 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. $$