MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1213 PM EDT SUN OCT 11 2015 VALID OCT 11/1200 UTC THRU OCT 15/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. CUT-OFF CYCLONE TO LIFT/SHEAR TO THE NORTHEAST TUES/WED WEAK SURFACE WAVE LIFTING NORTH INTO NEW ENGLAND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 12Z GFS/NAM CONFIDENCE: SLIGHTLY ABOVE AVERAGE OVERALL EVOLUTION APPEARS AGREEABLE WITH THE UPPER LOW...THE 00Z ECMWF RUN DID APPEAR TO HAVE A BIT OF CONVECTIVE FEEDBACK INTO MONDAY NIGHT OFF THE NC COAST...THIS INTENSIFIED A SURFACE SOLUTION THAT ADVANCES TOWARD NEW ENGLAND BY TUESDAY. THIS IS NOT WELL SUPPORTED BY ITS 00Z ECWMF ENSEMBLE AND IS GENERALLY FASTER THAN THE REST OF THE DETERMINISTIC RUNS. THE 12Z NAM IS A BIT FAST BUT A BIT WEAKER AND MORE REALISTIC IN THE WAVES STRENGTH AND QPF MAGNITUDE. THE 00Z CMC ALSO SUPPORTS A FARTHER WEST TRACK BUT IS A BIT SLOWER DUE TO A SLOWER UPSTREAM TROF...WHICH IS THE CMC TENDENCY. THE 00Z UKMET ALSO IS A BIT EAST OF BEST PACKING/TRACK OF THE WEAK SURFACE LOW/WAVE. THE 12Z GFS IS A MIDDLE GROUND OF ALL THE SOLUTIONS WITH SUPPORT OF THE 09Z SREF/00Z AND 06Z GEFS AND A LARGE PORTION OF THE ECMWF ENSEMBLE SUITE. TO BEST REPRESENT THE BEST MIDDLE GROUND...A BLEND OF THE 12Z GFS/NAM IS PREFERRED WHEN INCLUDING QPF AND MASS FIELDS BUT A BLEND THE OVERALL PATTERN/SOLUTION SEEMS WELL HANDLED TO BOOST OVERALL CONFIDENCE BUT SMALL DETAILS PARTICULARLY AT THE SURFACE AND QPF MAKES CONFIDENCE ONLY SLIGHTLY ABOVE AVERAGE. DEEP CYCLONE MOVING THROUGH SOUTHERN CANADA THROUGH MON COLD FRONT ADVANCING THROUGH EASTERN THIRD OF THE U.S. EXITING THE COAST WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF OPERATIONAL MODELS WITH INCREASED WEIGHTING TOWARD 12Z GFS/00Z ECMWF CONFIDENCE: ABOVE AVERAGE THE OVERALL AGREEMENT IN THE MAIN ENSEMBLE MEANS (00Z ECENS/06Z GEFS/09Z SREF) BRING HIGH CONFIDENCE IN THE FORECAST OF THE DEEP CYCLONE AND ASSOCIATED EASTWARD PROGRESSION OF THE COLD FRONT ACROSS THE U.S. THE 00Z CMC CONTINUES TO RETAIN MORE DEPTH TO THE SURFACE OCCLUSION MORE AS IT SHIFTS NORTH OF LAKE SUPERIOR ALLOWING THE LOW TO LAG THE REST OF THE WELL PACKED GUIDANCE. BY DAY 3... THE 12Z NAM APPEARS TO BE A BIT BROADER (E-W) WITH THE TROF OVER THE THE MID-ATLANTIC AND STARTS TO LAG THE 00Z ECMWF...THIS SHIFT WAS FOLLOWED BY THE 12Z GFS THOUGH TO A LESSER EXTENT. THE 00Z UKMET BECOMES A BIT FAST...PER USUAL. OVERALL THIS SUPPORTS INCREASED WEIGHTING TO THE 12Z GFS/00Z ECMWF...BUT OVERALL DIFFERENCES APPEAR IN THE MESOSCALE TO INCLUDE THE 00Z CMC/UKMET AND THE 12Z NAM INTO A PREFERENCE OF OPERATIONAL MODEL BLEND AT ABOVE AVERAGE CONFIDENCE. SYSTEM MOVING ACROSS WESTERN/CENTRAL CANADA - REINFORCING EASTERN TROF WED SURFACE WAVE/WARM FRONT CROSSING THE NRN PLAINS INTO LOWER OHIO RIVER VALLEY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF OPERATIONAL MODELS CONFIDENCE: SLIGHTLY ABOVE AVERAGE VERY FLAT SHORTWAVE ENERGY REPRESENTED MORE BY THE SPEED MAX ALOFT AND WEAK SURFACE WAVES TRACKING ACROSS THE NORTHERN PORTION OF THE CENTRAL CANADIAN PROVIDENCES AND ANOTHER PARALLELING IT OUT OF SOUTHERN SASKATCHEWAN THROUGH THE LOWER OHIO RIVER VALLEY BY WED. THE 00Z UKMET AS USUAL...LEADS THE RELATIVELY TIGHT PACKING...WITH THE 12Z GFS/NAM LAGGING A BIT. GIVEN HOW WEAK THE WAVE IS...THE ENSEMBLES GENERALLY AVERAGE THE WAVE OUT A BIT MORE BUT ARE IN GENERAL AGREEMENT WITH THE PLACEMENT SEEN IN THE 12Z GFS/NAM AND 00Z ECMWF/CMC. THE 00Z UKMET NOT TOO OUT OF PHASE TO SUPPORT ITS INCLUSION BUT AT A BIT LOWER WEIGHTING. AS SUCH AN OPERATIONAL MODEL BLEND IS PREFERRED BUT GIVEN HOW WEAK THE WAVE IS AND MODERATE SPREAD DO NOT FEEL THE CONFIDENCE IS AT MAXIMUM...SO IT IS SLIGHTLY ABOVE AVERAGE. UPPER LOW OFFSHORE BAJA CALIFORNIA SURFACE LOW MOVING NORTHWEST OFFSHORE BAJA CA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET BLEND CONFIDENCE: ABOVE AVERAGE REASONABLE AGREEMENT CONTINUES TO EXIST PARTICULARLY WITH THE UPPER LOW AS IT MOVES NORTH...AS THERE IS A BIT MORE SPREAD IN AT 7H AND BELOW. THE 00Z UKMET ALONG WITH THE 09Z SREF ARE ON THE NORTHEAST SIDE OF THE GENERAL DETERMINISTIC AND ENSEMBLE COLLECTIVE. THE 00Z ECMWF IS A NORTHEAST MEMBER OF THE 00Z ECMWF SURFACE LOW CLUSTER...BUT STILL AGREEABLE WITH THE OVERALL ECENS MEAN. MAYBE A BIT TOO RESTRICTIVE...BUT A NON-UKMET BLEND IS PREFERRED TO BUILD A STRONGER AGREEMENT IN THE BLEND. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA