PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 300 PM EST WED FEB 28 2018 30-DAY OUTLOOK DISCUSSION FOR MARCH 2018 THE UPDATED, 0-LEAD MARCH 2018 FORECASTS EXHIBIT SOME LARGE CHANGES RELATIVE TO THE 0.5-MONTH LEAD FORECASTS DUE TO SHORT-TERM WEATHER AND SUBSEASONAL CLIMATE VARIABILITY. THE BACKGROUND ENSO STATE REMAINS IN PLAY, AND THE MJO IS CURRENTLY ACTIVE OVER THE INDIAN OCEAN, BUT FORECAST TO WEAKEN OVER THE NEXT WEEK TO TEN DAYS. THE CURRENT 500-HPA HEIGHT PATTERN OVER NORTH AMERICA FEATURES ANOMALOUS RIDGING NEAR THE ALEUTIANS AND A VERY HIGH AMPLITUDE BLOCK OVER GREENLAND. THESE LOW-FREQUENCY FEATURES ARE FORECAST TO REMAIN INTACT OVER THE NEXT TWO WEEKS, THE LATTER SLOWLY SHIFTING WESTWARD WITH TIME TO NEAR HUDSON BAY. VARIOUS DYNAMICAL MODEL FORECASTS AND TELECONNECTIONS UPON THESE HEIGHT CENTERS FAVOR BELOW-NORMAL TEMPERATURES AND ABOVE-NORMAL PRECIPITATION OVER MUCH OF THE WEST, AND ABOVE-NORMAL TEMPERATURES OVER NEW ENGLAND AND THE NORTHERN GREAT LAKES. AS THE MONTH PROGRESSES, EXTRATROPICAL TELECONNECTIONS FROM THE MJO FAVOR A GENERAL WARMING TREND RELATIVE TO NORMAL OVER THE EASTERN AND CENTRAL CONUS. THE MARCH OUTLOOKS ARE CONSTRUCTED BY STARTING WITH A NEW CALIBRATED CFS MONTHLY FORECAST SYSTEM THAT ACCOUNTS FOR DECREASING SKILL WITH LEAD TIME. THIS IS THEN TWEAKED BY TAKING INTO ACCOUNT THE ECMWF MONTHLY FORECAST INITIALIZED ON 26 FEB AS WELL AS THE CURRENT WPC AND CPC FORECAST SUITE THAT COVERS THE FIRST TWO WEEKS OF THE MONTH. LASTLY, STATISTICAL GUIDANCE THAT UTILIZES THE MJO, ENSO, AND LONG-TERM TRENDS ARE CONSIDERED FOR THE SECOND HALF OF THE MONTH. THE TEMPERATURE OUTLOOK DEPICTS THE HIGHEST AMPLITUDE PROBABILITIES ACROSS PARTS OF THE NORTHERN CONUS DUE TO THE HIGH-AMPLITUDE CIRCULATION PATTERN FORECAST DURING THE FIRST HALF OF THE MONTH. UNCERTAINTY IS HIGHEST OVER THE CENTRAL AND SOUTHEASTERN CONUS WHERE PERIODS OF BELOW-NORMAL TEMPERATURES ARE FAVORED EARLY IN THE MONTH, BUT MJO, LONG-TERM TRENDS, AND DYNAMICAL FORECAST GUIDANCE FAVORS ABOVE-NORMAL TEMPERATURES LATER IN THE MONTH. ABOVE-NORMAL TEMPERATURES ARE FAVORED OVER PARTS OF SOUTHWEST AND SOUTHERN HIGH PLAINS BASED ON DYNAMICAL MODEL GUIDANCE AND STATISTICAL GUIDANCE EMPHASIZING ENSO AND LONG-TERM TRENDS. BELOW-NORMAL TEMPERATURES ARE FAVORED OVER SOUTHERN ALASKA WHERE THE WEEK-2 FORECAST STRONGLY FAVORS COLDER-THAN-NORMAL TEMPERATURES. LONG-TERM TRENDS AND REDUCED SEA ICE COVERAGE RELATIVE TO NORMAL CONTRIBUTE TO PROBABILITIES FAVORING ABOVE-NORMAL TEMPERATURES OVER NORTHWESTERN ALASKA. THE PRECIPITATION OUTLOOK CENTERS ON FOUR REGIONS OVER THE CONUS THAT ARE EXPECTED TO SEE ENHANCED PRECIPITATION EARLY IN THE MONTH, NAMELY, MUCH OF THE WESTERN CONUS, THE UPPER AND LOWER MISSISSIPPI VALLEY, AND PARTS OF THE NORTHEAST. LOWER-FREQUENCY CLIMATE FORCING FROM ENSO, MJO, AND LONG-TERM TRENDS FAVORS BELOW-NORMAL PRECIPITATION OVER PARTS OF FLORIDA, THE SOUTHWEST, AND SOUTHERN HIGH PLAINS. THE OHIO VALLEY AND THE NORTHERN PLAINS TILT TOWARD ABOVE-NORMAL PRECIPITATION BASED ON THESE LOW-FREQUENCY CLIMATE FACTORS. THE AFOREMENTIONED BLOCK OVER NORTHEASTERN NORTH AMERICA FAVORS BELOW-NORMAL PRECIPITATION OVER FAR NORTHERN NEW ENGLAND AND THE NORTHERN GREAT LAKES. OVER ALASKA, A RELATIVELY WET PATTERN IS FORECAST EARLY IN THE MONTH FOR THE WESTERN PART OF THE STATE, WHILE FORECAST RIDGING NEAR THE ALEUTIANS FAVORS BELOW-NORMAL PRECIPITATION OVER THE SOUTHERN PART OF THE STATE. THE ORIGINAL DISCUSSION FOLLOWS BELOW: ---------------------------------------------------------------------- LA NINA CONDITIONS CONTINUE INTO MID-FEBRUARY, WITH NEGATIVE SST ANOMALIES OBSERVED ACROSS THE CENTRAL AND EASTERN PACIFIC OCEAN FROM NEAR THE DATE LINE TO THE COAST OF SOUTH AMERICA. THE COUPLED ATMOSPHERIC RESPONSE TO LA NINA REMAINS READILY OBSERVED, WITH POSITIVE OLR ANOMALIES DUE TO REDUCED CONVECTION NEAR THE DATE LINE AND NEGATIVE OLR ANOMALIES DUE TO ENHANCED CONVECTION OVER PARTS OF THE MARITIME CONTINENT. THE MJO REMAINED ACTIVE OVER THE PAST SEVERAL WEEKS; THE ENHANCED PHASE PROPAGATED ACROSS THE WEST PACIFIC OF LATE AND EASTWARD PROPAGATION HAS SLOWED. THE CURRENT MJO STATE FAVORS BELOW-NORMAL TEMPERATURES OVER MUCH OF THE CONUS IN EARLY MARCH. ADDITIONALLY, A SUDDEN STRATOSPHERIC WARMING OCCURRED ON FEBRUARY 12. EMPIRICALLY, THIS FAVORS A MODEST SHIFT IN THE LOW-FREQUENCY AO TOWARD THE NEGATIVE PHASE. THE RECENT RUNS OF THE GEFS AND CFS FORECAST A TRANSITIONS TOWARD A STRONGLY NEGATIVE AO REGIME, WITH HIGH-LATITUDE BLOCKING FORECAST NEAR THE DAVIS STRAIT. THE ECWMF SHOWS A SIMILAR EVOLUTION, BUT WITHOUT THE ASSOCIATED TELECONNECTION PATTERN OVER THE EASTERN CONUS. DYNAMICAL MODEL GUIDANCE INITIALIZED IN EARLY FEBRUARY SEEMS TO EMPHASIZE LA NINA AND LONG-TERM TRENDS, A REASONABLE STARTING PLACE FOR THE MARCH OUTLOOK. THE FEBRUARY TEMPERATURE OUTLOOK STARTS WITH THE CALIBRATED DYNAMICAL MODEL GUIDANCE, BUT MAKES RATHER SUBSTANTIAL CHANGES BASED ON THE LATEST CFS FORECASTS AND EMPIRICAL FORECAST MODELS THAT ARE CONSISTENT WITH A STRONG NEGATIVE AO PROJECTION DURING THE EARLY PART OF THE MONTH. ANY MJO IMPACTS DURING THE SECOND HALF OF THE MONTH ARE A BIT OF A WILD CARD GIVEN UNCERTAINTY IN MJO EVOLUTION DURING LATE FEBRUARY AND EARLY MARCH. THE FEBRUARY TEMPERATURE OUTLOOK INDICATES INCREASES IN THE PROBABILITIES OF BELOW-NORMAL TEMPERATURES OVER MUCH OF THE NORTHWESTERN AND NORTH-CENTRAL CONUS, AND WITH REASONABLY LARGE PROBABILITIES FOR A 0.5-MONTH LEAD OUTLOOK. THIS SIGNAL IS CONSISTENT WITH LA NINA, EARLY MONTH MJO IMPACTS, AND A COMBINATION OF DYNAMICAL MODEL GUIDANCE. OVER THE FAR SOUTHERN AND EASTERN PARTS OF THE CONUS, ABOVE-NORMAL TEMPERATURES ARE FAVORED. THE SIGNAL IS STRONGEST OVER NEW ENGLAND WHERE THE LATEST MODEL GUIDANCE SUGGESTS THE HIGHEST PROBABILITIES. THIS IS ALSO CONSISTENT WITH TELECONNECTIONS UPON A BLOCKING PATTERN OVER DAVIS STRAIT. LONG-TRENDS AND LA NINA FAVOR ABOVE-NORMAL TEMPERATURES OVER THE SOUTHWEST, BUT THIS IS TEMPERED BY THE LATEST DYNAMICAL MODEL GUIDANCE THAT SUGGESTS A RELATIVELY COLD START TO THE MONTH. EQUAL CHANCES OF ABOVE-, NEAR-, AND BELOW-NORMAL TEMPERATURES IS FORECAST OVER A LARGE SWATH OF THE CONUS FROM THE SOUTH-CENTRAL U.S. EASTWARD. OVER THIS REGION THERE ARE CONFLICTING SIGNALS BETWEEN THE LOW-FREQUENCY TRENDS AND ENSO AND HIGHER-FREQUENCY AO AND MJO CONTRIBUTIONS. ABOVE-NORMAL TEMPERATURES ARE FAVORED OVER WESTERN ALASKA WHERE THE MAJORITY OF FORECAST TOOLS ARE IN GOOD AGREEMENT. THE FEBRUARY PRECIPITATION OUTLOOK, LIKE THE TEMPERATURE OUTLOOK, ATTEMPTS TO COMBINE THE INFLUENCE OF LA NINA WITH THE LATEST CFS GUIDANCE AND THE AO AND MJO FOOTPRINTS EARLY IN THE MONTH. ABOVE-NORMAL PRECIPITATION IS FAVORED OVER THE NORTHERN ROCKIES, AND EXTENDED EASTWARD INTO PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS. ABOVE-NORMAL PRECIPITATION IS ALSO FAVORED OVER PARTS OF THE INTERIOR SOUTHEAST; THIS REGION IS SHIFTED SOUTHEAST OF THE CANONICAL LA NINA FOOTPRINT BASED ON THE MJO AND AO. BELOW-NORMAL PRECIPITATION IS FAVORED ACROSS THE SOUTHERN TIER OF THE CONUS EXCEPT FOR MUCH OF THE GULF COAST. THIS IS BROADLY CONSISTENT WITH LA NINA AND BASED ON THE PREPONDERANCE OF DYNAMICAL MODEL GUIDANCE. EQUAL CHANCES IS FORECAST FOR LARGE SECTIONS OF THE CENTRAL AND EASTERN CONUS WHERE THE VARIOUS AFOREMENTIONED CLIMATE SIGNALS CONFLICT, AS DOES THE LATEST CFS WITH COUPLED MODEL INITIALIZED AT THE BEGINNING OF THE MONTH. ANOMALOUS RIDGING CENTERED JUST SOUTH OF ALASKA FAVORS A NORTHWARD SHIFTED STORM TRACK, AND THUS A NORTH-SOUTH DIPOLE IN PROBABILITIES FAVORING ABOVE- AND BELOW-NORMAL PRECIPITATION. FORECASTER: STEPHEN BAXTER 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 APR ... WILL BE ISSUED ON THU MAR 15 2018 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. $$