MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 157 PM EST THU JAN 14 2016 VALID JAN 14/1200 UTC THRU JAN 18/0000 UTC ..SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/CMC AND ECMWF ...UPPER TROUGH CROSSING THE INTERMOUNTAIN WEST TODAY... ...ENERGY EJECTING ACROSS THE PLAINS/MIDWEST/GREAT LAKES... ...SURFACE LOW CROSSING THE NORTHERN PLAINS TO THE GREAT LAKES... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE CONTINUES TO SHOW A PROGRESSIVE SHORTWAVE TROUGH CROSSING THE INTERMOUNTAIN WEST THROUGH TODAY...BEFORE THEN AMPLIFYING SOMEWHAT OUT ACROSS THE PLAINS FRI. THEREAFTER THE ENERGY IS FORECAST TO LIFT NORTHEAST ACROSS THE OH VALLEY AND LOWER GREAT LAKES REGION. ALL THE WHILE...LOW PRESSURE WILL DEVELOPING ACROSS THE FAR NORTHERN HIGH PLAINS AND WILL GRADUALLY DEEPEN AS IT MOVES EAST TOWARD THE UPPER MS VALLEY AND GREAT LAKES REGION THROUGH SAT. THE MODELS HAVE CONVERGED RATHER NICELY ON TIMING AND DEPTH...AND SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED. ...SHORTWAVE TRACKING THROUGH THE GULF COAST THROUGH TONIGHT... ...SURFACE LOW DEVELOPING IN THE GULF OF MEXICO TODAY... ...DEEPENING LOW CENTER TRACKING UP THE EAST COAST FRI AND SAT... PREFERENCE: BLEND OF THE 12Z UKMET AND 12Z ECMWF CONFIDENCE: BELOW AVERAGE THE GUIDANCE TAKES THE UPPER TROUGH EXITING OUT OF NORTHERN MEXICO GRADUALLY EAST ACROSS THE GULF COAST STATES TODAY AND TONIGHT BEFORE BEGINNING TO LIFT NORTHEAST ACROSS THE SOUTHEAST AND MID-ATLANTIC THROUGH FRI. THE ENERGY WILL FOSTER SURFACE CYCLOGENESIS OVER THE GULF OF MEXICO BY LATER TODAY AND THIS WAVE IS EXPECTED TO DEEPEN RATHER RAPIDLY ALONG THE EAST COAST FRI AND SAT. SOME OF THIS DEEPENING WILL BE TIED INTO THE AFOREMENTIONED ENERGY APPROACHING THE GREAT LAKES REGION AND SOME INTERACTION BETWEEN THE TWO. AFTER SEEING THE GUIDANCE SHIFT RIGHT OVER THE LAST COUPLE OF MODEL CYCLES WITH THE LOW TRACK ALONG THE EAST COAST...THE 12Z GFS AND THE 12Z GEM REGIONAL HAVE SHIFTED THE TRACK A BIT TO THE LEFT OVER THE SOUTHEAST AND MID-ATLANTIC. THE NON-NCEP GUIDANCE INCLUDING UKMET AND CMC ARE ALREADY A BIT LEFT WITH THE TRACK OVER THE SOUTHEAST...BUT THEY HAVE TRENDED EVEN FARTHER LEFT AND ESPECIALLY THE 12Z UKMET WHICH IS NOW FARTHEST LEFT OF ALL THE MODELS. THE 12Z ECMWF HAS TRENDED SIGNIFICANTLY TO THE LEFT AND IS ONLY A TAD EAST OF THE 12Z UKMET OVER THE SOUTHEAST AND ALSO THE MID-ATLANTIC REGION THROUGH FRI NIGHT. THE NON-NCEP MODELS COLLECTIVELY ARE A TAD LEFT OF THE NCEP MODELS OVER THE SOUTHEAST AND MID-ATLANTIC. THEREAFTER...THE GUIDANCE HAS COME INTO BETTER AGREEMENT WITH A TRACK BACK TO THE LEFT WITH THE DEEPENING LOW CENTER AND THUS A TRACK A BIT CLOSER INTO SOUTHERN NEW ENGLAND ON SAT. THE 12Z GEFS MEAN HAS SHIFTED FARTHER LEFT OFFSHORE NEW ENGLAND...BUT IS NOT AS CLOSE AS THE DETERMINISTIC GFS. BY SAT...THE 12Z GFS IS THE FARTHEST WEST MODEL WITH THE 12Z ECMWF AND 12Z UKMET WELL CLUSTERED A LITTLE FARTHER EAST. THESE MODELS TAKE THE LOW CENTER VERY CLOSE TO THE BENCHMARK. THE 12Z CMC AND 12Z NAM ULTIMATELY END UP A BIT RIGHT OF THE LATEST MODEL CONSENSUS. THE 12Z GEFS MEAN SHARES DECENT AGREEMENT WITH THE UKMET/ECMWF CAMP...WITH THE 00Z ECENS MEAN A TAD FARTHER EAST AND CLOSER TO THE NAM/CMC CAMP. BASED ON THE LATEST TRENDS/CLUSTERING...A BLEND OF THE 12Z ECMWF AND 12Z UKMET WILL BE PREFERRED. CONFIDENCE REMAINS LIMITED BASED ON RATHER POOR RUN TO RUN MODEL CONTINUITY. ...DEEP VORTEX OVER SOUTHERN ONTARIO BY LATE SAT... PREFERENCE: BLEND OF THE 12Z GFS/12Z ECMWF AND 12Z UKMET CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS SHOW A DEEP VORTEX OVER SOUTHERN HUDSON BAY THAT WILL PIVOT SOUTH/SOUTHWEST DOWN INT5O SOUTHERN ONTARIO BY SAT IN CONNECTION TO SOME HIGHER LATITUDE RIDGING OVER THE DAVIS STRAIT THAT WILL SHIFT WEST INTO NORTHERN CANADA. THEREAFTER THE DEEP LOW CENTER WILL SLIP SOUTHEAST INTO THE GREAT LAKES REGION. THE STRONGER MODEL CLUSTERING THROUGH THE PERIOD RESIDES WITH THE 12Z GFS/12Z ECMWF AND 12Z UKMET. THE 12Z NAM APPEARS TO GRADUALLY BECOME A LITTLE TOO SLOW WITH THE HEIGHT FALL EVOLUTION...AND THE 12Z CMC MAY BE A TAD TOO DEEP. THE ENSEMBLE MEANS FAVOR THE GFS/ECMWF AND UKMET CLUSTER AND THUS THIS CLUSTER WILL BE PREFERRED. ...UPPER TROUGH MOVING INTO THE PACIFIC NORTHWEST BY TONIGHT... ...ENERGY DIGGING SOUTHEAST TOWARD THE SOUTHERN PLAINS BY SAT... ...DEVELOPING LOW PRESSURE OVER THE GULF OF MEXICO... PREFERENCE: BLEND OF THE 12Z GFS/12Z UKMET AND 12Z ECMWF CONFIDENCE: BELOW AVERAGE THE MODELS AGREE IN BRINGING AN UPPER TROUGH ACROSS THE PACIFIC NORTHWEST BY TONIGHT AND THEN WITH THE ENERGY DROPPING SOUTHEAST THROUGH THE INTERMOUNTAIN WEST THROUGH FRI. THE GUIDANCE ALL AGREES IN TAKING THE ENERGY SOUTHEAST THROUGH THE SOUTHERN PLAINS ON SAT...WITH SOME AMPLIFICATION EXPECTED. THE AMPLIFICATION OF THIS ENERGY SHOULD FOSTER SURFACE LOW PRESSURE DEVELOPMENT OVER THE WESTERN GULF OF MEXICO ON SAT. THE 12Z NAM TENDS TENDS TO BE A BIT FLATTER AND LESS-DEVELOPED WITH THE LOW DEVELOPMENT OVER THE GULF OF MEXICO BY SAT AND THEN ON SUN IT IS FASTER AND FARTHER NORTH WITH ITS TRACK THAT IMPACTS THE SOUTHEAST U.S. AND FL PENINSULA. THE 12Z UKMET GRADUALLY BECOMES THE DEEPEST SOLUTION OVER THE GULF OF MEXICO WITH A STRONGER IMPACT ON FL BY SUN...AND ITS TRACK IS CLOSE TO THAT OF THE 12Z GFS WITH THE GFS A LITTLE WEAKER. THE 12Z ECMWF IS A BIT SLOWER THAN THE MODEL CONSENSUS. THE 12Z CMC SPLITS THE DIFFERENCE BETWEEN THE FLATTER/FASTER NAM AND THE UKMET/GFS CLUSTER. THE LATEST GEFS MEAN WOULD TEND TO SUPPORT A BLEND OF THE GFS/UKMET AND ECMWF...AND SO A BLEND OF THESE SOLUTIONS WILL BE PREFERRED. CONFIDENCE WILL BE LIMITED GIVEN THE MASS FIELD MODEL SPREAD. ...UPPER TROUGH/PACIFIC FRONT NEARING THE WEST COAST SAT MORNING... PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF CONFIDENCE: AVERAGE THE 12Z UKMET AGAIN APPEARS TO BE TOO FAST WITH THE PROGRESSION OF THE NEXT PACIFIC SHORTWAVE TROUGH TO COME INTO THE PACIFIC NORTHWEST BY THIS WEEKEND. THE 12Z CMC IS NOW THE SLOWEST AND STRONGEST WITH THIS FEATURE...WITH THE 12Z NAM/12Z GFS AND 12Z ECMWF SPLITTING THE DIFFERENCE. THE 12Z GFS AND 12Z ECMWF CLUSTER THE BEST AND HAVE BETTER ENSEMBLE SUPPORT AND SO A BLEND OF THESE TWO SOLUTIONS WILL BE PREFERRED. ...UPPER TROUGH/PACIFIC FRONT NEARING THE WEST COAST LATE SUN... PREFERENCE: BLEND OF THE 12Z GFS/12Z UKMET AND 12Z ECMWF CONFIDENCE: AVERAGE THE MODELS SHOW ANOTHER SHORTWAVE TROUGH AND FRONT ARRIVING BY LATE SUN ACROSS THE PACIFIC NORTHWEST. THE 12Z CMC NOW SHOWS A NOTABLY DEEPER SOLUTION AND ESPECIALLY AT THE SURFACE WITH ITS STRONG SURFACE LOW SOUTH OF THE MODEL CONSENSUS OFFSHORE WA STATE AND BRITISH COLUMBIA BY EARLY SUN. THE MODEL CONSENSUS TAKES THE BULK OF THE SHORTWAVE ENERGY AND THE DEEPER SURFACE LOW FARTHER NORTHEAST AND OFFSHORE CENTRAL BRITISH COLUMBIA BY LATE SUN. THE 12Z NAM IS LIKELY TOO FAR NORTH WITH ITS LOW TRACK...BUT THE 12Z CMC REMAINS A SOUTHERLY OUTLIER. THE 12Z GFS/12Z UKMET AND 12Z ECMWF NOW CLUSTER TOGETHER RATHER WELL AND THIS MODEL CONSENSUS WILL BE PREFERRED AND IS REASONABLY WELL SUPPORTED BY THE 12Z GEFS MEAN. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON