582  
FXUS07 KWBC 151902  
PMD30D  
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
830 AM EST THU FEB 15 2018  
 
30-DAY OUTLOOK DISCUSSION FOR MARCH 2018  
 
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 MARCH 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 MARCH 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 MARCH 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.  
 
AN UPDATED MONTHLY OUTLOOK... FOR MAR WILL BE ISSUED ON WED FEBRUARY 28 2018  
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.  

 
 
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