MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1157 PM EST TUE JAN 14 2014 VALID JAN 15/0000 UTC THRU JAN 18/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...SHORTWAVE LIFTING ALONG COASTAL NEW ENGLAND THROUGH WEDNESDAY MORNING... ...ASSOCIATED SURFACE COASTAL LOW... PRELIMINARY PREFERENCE: COMPROMISE BETWEEN THE 00Z GFS AND 18Z GEFS MEAN FORECAST CONFIDENCE: HIGH A PROGRESSIVE SHORTWAVE LIFTING UP COASTAL NEW ENGLAND WILL QUICKLY CARRY ITS ASSOCIATED PRECIPITATION SHIELD INTO FAR EASTERN CANADA BY ROUGHLY 15/1200Z. THE DIFFERENCES ALOFT ARE QUITE MINIMAL BUT THERE ARE SURPRISINGLY SOME MINOR MODEL UNCERTAINTY WITH THE PLACEMENT OF THE COASTAL WAVE. WILL FOLLOW THE 00Z GFS/18Z GEFS MEAN HERE AS ITS POSITION WAS CLOSEST TO THE WPC 00Z SURFACE ANALYSIS. OTHER GUIDANCE WERE DISPLACED TO THE SOUTH OF THIS VERIFIED SOLUTION. ...CLOSED LOW/SURFACE CYCLONE CROSSING THE LOWER GREAT LAKES OVERNIGHT... ...AMPLIFIED TROF DIGGING ACROSS THE SOUTHEASTERN U.S. BY 16/0600Z... ...SERIES OF SURFACE LOWS MOVING NORTHWARD OVER THE WESTERN ATLANTIC... PRELIMINARY PREFERENCE: GENERAL MODEL CONSENSUS FOR THE GREAT LAKES...BLEND OF THE 00Z GFS/12Z ECMWF FOR THE SOUTHEASTERN U.S. SYSTEM FORECAST CONFIDENCE: HIGH...THEN BECOMING AVERAGE INITIALLY A SYSTEM WILL CROSS THE LOWER GREAT LAKES REGION WITH THE LOBE OF MID-LEVEL ENERGY EVENTUALLY LIFTING UP INTO WESTERN QUEBEC BY 16/0000Z. AS THIS SYSTEM IS PRIMARILY ONLY AN ISSUE THE NEXT 12 TO 18 HOURS...SOLUTIONS ARE NEARLY COMPARABLE SO A GENERAL CONSENSUS CAN BE UTILIZED IN THIS CASE. LOOKING AHEAD...THERE ARE DEFINITELY MORE SUFFICIENT MODEL DIFFERENCES AS ANOTHER TROF BEGINS TO DIG INTO THE DEEP SOUTH BY LATE WEDNESDAY. BY 16/0000Z...THE 00Z NAM IS A HAIR SLOWER ALOFT WHICH REMAINS MORE IN LINE WITH THE 18Z GEFS/21Z SREF MEANS AS THE TROF BECOMES NEGATIVELY-TILTED OFFSHORE OF THE SOUTHEASTERN U.S. MEANWHILE...ON THE FASTER SIDE OF THE ENVELOPE ARE THE 12Z CMC/UKMET. AS THE SYSTEM LIFTS QUICKLY TO THE NORTH...THE FLATTER 00Z GFS SOLUTION ALLOWS IT TO BECOME MUCH MORE PROGRESSIVE BY LATE THURSDAY. AT THE SURFACE...THE SOLUTIONS ARE RATHER COMPLEX AS THE GUIDANCE FORECAST A NUMBER OF SURFACE LOWS RISING NORTHWARD WELL OFFSHORE OF THE EASTERN SEABOARD. THE OVERALL IMPACTS APPEAR MINIMAL GIVEN THE OFFSHORE TRACK. AS THIS IS THE CASE...WILL NOT WORRY AS MUCH ABOUT THESE LOW ONCE THEY ARE INTO THE OPEN ATLANTIC. WILL GO AHEAD AND SPLIT THE DIFFERENCE BETWEEN THE FASTER 00Z GFS AND SLOWER 12Z ECMWF. ...AMPLIFIED TROF REACHING THE UPPER MIDWEST/GREAT LAKES BY THURSDAY MORNING... ...ACCOMPANYING SURFACE LOW WHICH GRADUALLY FILLS OVER THE GREAT LAKES... ...POTENTIAL LOW DEVELOPMENT OVER THE MID-ATLANTIC BY FRIDAY EVENING... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET WITH THE 12Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE A PRONOUNCED UPPER TROF DROPPING DOWN INTO NORTH-CENTRAL U.S. WILL CARRY A SURFACE LOW THAT SHOULD GRADUALLY FILL AS IT MOVES TOWARD THE GREAT LAKES REGION. THE ONCE SUB-980 MB SURFACE CYCLONE OVER NORTHERN SASKATCHEWAN ON 15/1800Z WILL FILL RATHER QUICKLY REACHING THE LOW/MID 990 MB RANGE 24 HOURS LATER. THE LONGWAVE TROF DIGGING DOWN INTO THE UPPER MIDWEST/GREAT LAKES WILL CONSIST OF A NUMBER OF EMBEDDED SHORTWAVE LIMITED FORECASTABILITY AS GUIDANCE SHOW A VARIETY OF POTENTIAL SOLUTIONS. BY 16/1800Z...THE ENSEMBLE MEANS ARE AT ODDS WITH ONE ANOTHER WITH THE 12Z ECMWF ENSEMBLE MEAN BEING THE SLOWEST...THE 18Z GEFS MEAN THE QUICKEST WHILE THE 21Z SREF MEAN IS SANDWICHED IN THE CENTER. THE 18Z GEFS MEAN GETS PARTICULARLY QUICK BY THE END OF THE SHORT RANGE PERIOD. THE RUN-TO-RUN TRENDS IN THE ENSEMBLES SHOW THE ECMWF MEMBERS SLOWING WHILE THE OTHERS SPED UP. WPC WILL LEAN ON THE SLOWER SOLUTIONS WITH THE BELIEVE THAT THE GEFS/SREF IDEA IS TOO QUICK. THE BEST SOLUTION HERE WILL UTILIZE THE 12Z ECMWF/UKMET WITH THE 12Z ECMWF ENSEMBLE MEAN. THIS COVERS THE SURFACE EVOLUTION BY LATE FRIDAY/EARLY SATURDAY AS WELL. ...SECONDARY SHORTWAVE CROSSING THE UPPER MIDWEST BY LATE FRIDAY/EARLY SATURDAY... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE IN THE WAKE ALL OF THE DOWNSTREAM ENERGY AMPLIFYING OVER THE EASTERN U.S...A WEAKER IMPULSE EMBEDDED WITHIN THE BROAD NORTHWESTERLY FLOW WILL MOVE INTO THE UPPER MIDWEST/MIDDLE MS VALLEY BY 18/1200Z. THE 00Z NAM IS DEFINITELY THE DEEPEST SOLUTION AT THE SURFACE ALTHOUGH THE 18Z GEFS MEAN DOES SHOW A HINT AT SUCH AN INTENSITY AS WELL. THE 12Z CMC/UKMET SHOW NO REAL SIGNS OF A DEFINED SURFACE WAVE. GIVEN THE PREFERRED SOLUTION DOWNSTREAM WAS TO GO SLOWER...WILL STAY CONSISTENT WITH THIS IDEA WHICH WOULD FAVOR THE 12Z ECMWF/ECMWF ENSEMBLE MEAN IN THIS CASE. RUN-TO-RUN CONTINUITY IS NOT VERY GOOD OVERALL SO THE CONFIDENCE IS BELOW AVERAGE. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER