MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 222 AM EST MON FEB 01 2016 VALID FEB 01/0000 UTC THRU FEB 04/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 0Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ MID-LEVEL SHORTWAVE AND SURFACE LOW MOVING INTO SOUTHEAST CANADA ASSOCIATED FRONTAL PASSAGE THROUGH THE EAST COAST TODAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE MODELS REMAIN IN GOOD AGREEMENT WITH THE SHORTWAVE AND ASSOCIATED SURFACE LOW MOVING INTO SOUTHEAST CANADA AND THE COLD FRONT MOVING ACROSS THE EAST COAST. ONLY MINOR TIMING DIFFERENCES...AND THUS WILL CONTINUE TO PREFER A DETERMINISTIC MODEL BLEND. SURFACE LOW TRACKING THROUGH THE SOUTHWEST INTO THE THE SOUTHERN PLAINS MONDAY EVENING NORTHEAST INTO THE GREAT LAKES BY TUESDAY EVENING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 0Z ECMWF/GFS CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE LARGE SCALE AGREEMENT CONTINUES TO BE ABOVE AVERAGE WITH THIS SYSTEM AS THE LONG WAVE TROUGH MOVES INTO THE PLAINS. SURFACE LOW PRESSURE NEAR THE FOUR CORNERS REGION AT 12Z MONDAY WILL REFORM ACROSS NORTHEAST NM AND SOUTHEAST CO DURING THE DAY MONDAY...BEFORE EJECTING EAST INTO KS...AND EVENTUALLY NORTHEAST INTO THE GREAT LAKES REGION BY TUESDAY NIGHT. STILL SOME SUBTLE DIFFERENCES IN HOW THE MODELS HANDLE THE SHORTWAVE ENERGY WITHIN THE TROUGH AND THUS THE RESULTANT SURFACE LOW TRACK THROUGH 12Z TUESDAY. THE 0Z GFS AND 12Z UKMET ARE ON THE NORTHERN EDGE OF THE GUIDANCE...WITH THE 0Z NAM...AND 12Z ECMWF AND GEM SLIGHTLY SOUTH. IN THE LARGE SCHEME OF THINGS THIS DIFFERENCE IS MINOR...BUT COULD HAVE A PRETTY BIG IMPACT ON THE NORTHWARD EXTENT OF HIGHER SNOWFALL. THE TWO CAMPS OF MODELS HAVE BEEN PRETTY CONSISTENT WITH THEIR SOLUTIONS...AND AT THIS TIME THINK A SOLUTION IN BETWEEN IS MOST LIKELY AT THIS TIME. THUS FOR THE DAY 1 PERIOD A CONSENSUS BETWEEN THE NORTH GFS/UKMET AND SOUTH NAM/ECMWF/GEM IS PREFERRED. MAY GIVE A SLIGHT LEAN TO THE NORTHERN SOLUTIONS...AS THEY HAVE SUPPORT FROM THE NEW HIGH RES ARW AND NMMB SOLUTIONS. AS WE HEAD FROM TUESDAY INTO WEDNESDAY THE LOW TRACKS FROM KS TO MI...AND MODEL AGREEMENT REMAINS PRETTY GOOD. THE 0Z NAM REMAINS A SUPPRESSED/SOUTHEAST OUTLIER WITH THIS SYSTEM...AND HAS LITTLE SUPPORT FROM THE GLOBAL DETERMINISTIC GUIDANCE...AND EVEN THE SREF MEAN IS CONSIDERABLY NORTHWEST OF THE NAM. THUS WILL CONTINUE TO LEAN AGAINST THE NAM SOLUTION AFTER DAY 1. THE 12Z GEM ALSO REMAINS A BIT FURTHER SOUTH AND SLOWER THAN THE BEST MODEL CLUSTERING. THE 0Z GFS AND 12Z ECMWF/UKMET CONTINUE TO BE IN GOOD AGREEMENT ON THE TRACK OF THIS SYSTEM...AND HAVE CONSISTENTLY BEEN IN GOOD AGREEMENT. THE ONLY DIFFERENCE IS WITH THE TIMING OF THE SYSTEM...WITH THE ECMWF CONSISTENTLY SLOWER AND THE GFS/UKMET QUICKER. 18Z GEFS AND 12Z ECMWF ENSEMBLE MEANS SUGGEST A TIMING IN BETWEEN THE TWO CAMPS IS MOST LIKELY. THUS WILL CONTINUE TO PREFER A CONSENSUS OF THE GFS/ECMWF/UKMET BLEND FOR THIS SYSTEM AFTER DAY 1. 07Z UPDATE: THE NEW 0Z UKMET CAME IN A BIT NORTHWEST OF THE OTHER DETERMINISTIC GUIDANCE. CAN NOT COMPLETELY RULE THIS SOLUTION OUT...BUT IT DOES LIE ON THE NORTHWEST EDGE OF THE 12Z GLOBAL ENSEMBLE SPREAD...AND THUS APPEARS LESS LIKELY AT THIS TIME. THE 0Z GEM REMAINS A SUPPRESSED/SOUTHEAST OUTLIER. THE 0Z ECMWF/GFS REMAIN IN GOOD AGREEMENT ON THE TRACK OF THE SYSTEM...ALONG WITH THE 0Z GEFS MEAN...12Z ECMWF MEAN AND 21Z SREF MEAN. GIVEN THIS GOOD AND CONSISTENT AGREEMENT...WILL CHANGE THE PREFERENCE TO A GFS/ECMWF BLEND FOR THE ENTIRE SYSTEM. THIS COMPROMISES ON THE SLOWER ECMWF AND QUICKER GFS PROGRESSION. THIS PREFERENCE ON CONSENSUS TIMING ALSO HOLDS FOR THE COLD FRONT PROGRESSING TOWARDS THE EAST COAST ASSOCIATED WITH THIS SYSTEM ON WEDNESDAY. WHILE THE 0Z NAM INITIALLY APPEARS WITHIN THE RANGE OF PLAUSIBLE SOLUTIONS...IT PRETTY QUICKLY MOVES OUTSIDE THE BETTER DETERMINISTIC AND ENSEMBLE CLUSTERING AND CONTINUES TO NOT BE PREFERRED. SHORTWAVE SHEARING THROUGH THE MEAN PACIFIC RIDGE TOWARD THE NORTHWEST TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 0Z GFS/NAM/ECMWF CONFIDENCE: ABOVE AVERAGE A HIGHLY ELONGATED TROUGH MOVES THROUGH A WELL ESTABLISHED/STRONG MEAN PACIFIC RIDGE MONDAY INTO TUESDAY...AND GENERALLY SHEARS OUT WITH LITTLE IMPACT TO SIGNIFICANT WEATHER...HOWEVER THE SOUTHERN AND CENTRAL ENERGY OF THE WAVE SLIDE ALONG THE EASTERN SIDE OF THE RIDGE TO HELP REINFORCE THE BASE (AND WESTERN SIDE) OF THE LARGER SCALE TROUGH ACROSS THE SOUTHWEST BY TUE EVENING/WED MIDDAY ACROSS NEW MEXICO. MODELS REMAIN IN GOOD AGREEMENT WITH THIS FEATURE. THE 12Z UKMET IS ON THE DEEPER/STRONGER EDGE OF THE DETERMINISTIC AND ENSEMBLE SPREAD AND APPEARS TO OFFER A LESS LIKELY SOLUTION...WITH BETTER CLUSTERING AROUND THE NAM/GFS/ECMWF/GEM. THUS WILL PREFER A NON UKMET SOLUTION AT THIS TIME. 07Z UPDATE: THE 0Z UKMET REMAINS A BIT DEEPER THAN THE CONSENSUS...AND THE NEW 0Z GEM NOW APPEARS INITIALLY TOO FLAT/WEAK WITH THE SHORTWAVE ENERGY REINFORCING THE TROUGH. THE 0Z GFS/NAM/ECMWF SHOW THE BEST CLUSTERING AND AGREEMENT IN THE MIDDLE OF THE MODEL SPREAD. NEXT DEEPER TROF AND FRONT NEARING THE PACIFIC NORTHWEST COAST WED INTO THURS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ PREFERENCE: 0Z GFS/ECMWF CONSENSUS CONFIDENCE: AVERAGE MAINLY JUST SOME TIMING ISSUES WITH THIS SYSTEM WITH THE SHORTWAVE ENERGY AND ASSOCIATED FRONTAL PASSAGE. THE 0Z GFS IS ON THE QUICKER SIDE OF THE GUIDANCE...WITH THE 12Z ECMWF ON THE SLOWER SIDE OF THINGS. THE 0Z NAM AND 12Z GEM HANDLE THE ENERGY A BIT DIFFERENTLY THAN THE OTHER DETERMINISTIC GUIDANCE...AND ARE CONSIDERED LESS LIKELY SOLUTIONS AT THIS TIME. BOTH THE GEFS AND ECMWF ENSEMBLES SEEM TO SUPPORT THE SLOWER ECMWF MORE THAN THE QUICKER SOLUTIONS WITH REGARDS TO THE SHORTWAVE ENERGY...ALTHOUGH THE ECMWF DOES SEEM LIKE IT COULD BE A BIT TOO SLOW WITH THE FRONTAL PROGRESSION INTO THE NORTHWEST ON WEDNESDAY. THUS A SOLUTION BETWEEN THE 0Z GFS AND 12Z ECMWF MAY BE OPTIMAL AT THIS TIME...WHICH IS PRETTY CLOSE TO THE 12Z UKMET SOLUTION. 07Z UPDATE: MODELS CONTINUE TO HANDLE THE EVOLUTION OF THE SHORTWAVE ENERGY MOVING TOWARD THE PACIFIC NORTHWEST DIFFERENTLY. ALL END UP HAVING A FRONT MOVE ASHORE WITH INCREASING IMPACTS ON SENSIBLE WEATHER...BUT THE TIMING REMAINS DIFFERENT. SEEMS TO BE BETTER DETERMINISTIC CLUSTERING AROUND THE QUICKER SOLUTION LEAVING THE ECMWF A BIT OF A SLOW OUTLIER. HOWEVER GIVEN THAT THIS SLOWER SOLUTION HAS SOME SUPPORT FROM ENSEMBLE MEANS...IT CAN NOT BE RULED OUT. SO WILL CONTINUE FAVORING A SOLUTION BETWEEN THE SLOWER ECMWF AND QUICKER GFS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... CHENARD