MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 156 AM EST TUE JAN 3 2017 VALID JAN 3/0000 UTC THRU JAN 6/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION ALONG WITH FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SHORTWAVE CURRENTLY OVER TENNESSEE REACHING NEW ENGLAND WEDNESDAY MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ PREFERENCE: 00Z NAM/00Z GFS/00Z ECMWF COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE A COMPACT SOUTHERN-STREAM SHORTWAVE TRACKING FROM THE DEEP SOUTH TO THE NORTHEAST U.S. IS FORECAST TO ACQUIRE NEGATIVE TILT AS IT LIFTS NORTHWARD. AT THE SURFACE, MILLER TYPE-B CYCLOGENESIS IS EXPECTED WITH THE INITIAL SURFACE LOW TRACKING WEST OF THE APPALACHIANS, AND A NEW COASTAL LOW DEVELOPING NEAR THE NEW ENGLAND COAST AND INTENSIFYING. A STRONG COLD FRONT WILL THEN CLEAR THE EAST COAST AFTER THIS STORM SYSTEM DEPARTS. THE MODELS HAVE COME INTO BETTER AGREEMENT WITH THIS SYSTEM, ALTHOUGH THE 00Z UKMET IS FASTER WITH THE PROGRESSION OF THE SECONDARY SURFACE LOW NEAR MAINE AND NORTH OF THE MODEL CONSENSUS. THE GFS, NAM, AND ECMWF ARE CLOSEST TO THE ENSEMBLE MEANS AND MAKE THE MOST SENSE WITH THEIR SOLUTIONS. UPPER MIDWEST DISTURBANCE EVOLVING INTO CLOSED LOW OVER QUEBEC ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z ECMWF CONFIDENCE: AVERAGE A NORTHERN STREAM SHORTWAVE TROUGH OVER NORTH DAKOTA AND MINNESOTA AT THE BEGINNING OF THE PERIOD IS PROGGED TO EVOLVE INTO A CLOSED MID-LEVEL LOW OVER EASTERN ONTARIO AND QUEBEC BY WEDNESDAY NIGHT. THE SURFACE REFLECTION OF THIS WILL LIKELY BE AN INVERTED TROUGH OVER THE NORTHERN GREAT LAKES THAT DEVELOPS INTO A STRENGTHENING SURFACE LOW OVER QUEBEC BY THURSDAY MORNING THAT JOINS FORCES WITH THE NEW ENGLAND LOW DESCRIBED IN THE PREVIOUS SECTION. THE 00Z GFS IS MORE AMPLIFIED COMPARED TO ITS EARLIER RUNS AND THE OTHER MODEL GUIDANCE, WITH THE CLOSED LOW FARTHER SOUTH OVER SOUTHERN QUEBEC. THE UKMET IS CLOSER TO THE MODEL CONSENSUS COMPARED TO ITS EARLIER RUN. THE NAM APPEARS TO BE SLOWER WITH THE TROUGH AXIS ACROSS THE GREAT LAKES REGION. THE 00Z ECMWF BEST FITS THE POSITION OF BOTH THE GEFS AND EC ENSEMBLE MEANS. POSITIVELY-TILTED TROUGH DROPPING ACROSS THE NORTHERN PLAINS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z EC MEAN/00Z NAM/18Z GEFS MEAN CONFIDENCE: SLIGHTLY BELOW AVERAGE BY WEDNESDAY MORNING, A SECONDARY TROUGH AND SHORTWAVE IMPULSE DIVING SOUTHWARD FROM CENTRAL CANADA SHOULD REACH THE NORTHERN PLAINS AND THEN THE UPPER MIDWEST BY THURSDAY MORNING. THIS WILL HELP TO REINFORCE THE LARGE SCALE TROUGH OVER THE NORTH-CENTRAL U.S. AND INTO CANADA FOR THE END OF THE WEEK. THE GFS AND THE GEFS MEAN ARE ON THE LESS AMPLIFIED SIDE OF THE GUIDANCE, WHILST THE 00Z ECMWF AND ITS MEAN ARE MORE AMPLIFIED. THE UKMET BECOMES MORE AMPLIFIED AS THE TROUGH CROSSES THE UPPER MIDWEST. LARGE UPPER LEVEL TROUGH OVER THE NORTHWESTERN U.S. STATES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z UKMET/12Z EC MEAN CONFIDENCE: NEAR AVERAGE A MID-LEVEL TROUGH ORIENTED ROUGHLY WEST TO EAST ACROSS THE PACIFIC NORTHWEST AND NORTHERN ROCKIES IS FORECAST TO REMAIN QUASI-STATIONARY THROUGH THURSDAY MORNING BEFORE FINALLY PUSHING SOUTHEASTWARD BY THE END OF THE FORECAST PERIOD. SHORTWAVE ENERGY WITH THE TROUGH WILL ALLOW FOR THE WESTERN PORTION TO EVOLVE INTO A CLOSED LOW OVER WASHINGTON AND OREGON BEFORE TRANSITIONING BACK INTO AN OPEN WAVE ALOFT. A SURFACE LOW TRACKING INLAND FROM THE PACIFIC WILL LIKELY SETTLE OVER THE INTERMOUNTAIN WEST ALONG A STRONG FRONTAL BOUNDARY. DECENT MODEL AGREEMENT EXISTS THROUGH THE FIRST 36 HOURS OF THE FORECAST. THE 00Z ECMWF IS NOT AS FAST TO DROP THE CLOSED LOW SOUTHEASTWARD ACROSS THE INTERMOUNTAIN WEST COMPARED TO ITS 12Z RUN, BUT IT IS STILL FASTER THAN THE EC MEAN. THE 00Z GFS STAYS AMPLIFIED LONGER THAN THE MODEL CONSENSUS AND ALSO DEVIATES FROM THE GEFS MEAN. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... Hamrick