MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 147 AM EST FRI FEB 14 2014 VALID FEB 14/0000 UTC THRU FEB 17/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z CMC/UKMET/ECMWF ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...VIGOROUS UPPER LOW LIFTING THROUGH COASTAL NEW ENGLAND OVERNIGHT... ...DEEPENING SURFACE CYCLONE AFFECTING THE NORTHEASTERN U.S... FINAL PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH A DYNAMIC UPPER LOW WHICH HAS SPREAD WIDESPREAD WINTRY PRECIPITATION ACROSS THE NORTHEASTERN U.S. WILL CONTINUE TO LIFT NORTHWARD WHILE GAINING ADDITIONAL STRENGTH. AS THIS OCCURS...A COASTAL LOW WILL RAPIDLY DEEPEN ALONG THE EASTERN SEABOARD WITH THE MODELS IN SUFFICIENT AGREEMENT WITH THE EVOLUTION OF THIS SYSTEM. THUS...THE PREFERENCE WILL BE A GENERAL MODEL CONSENSUS SOLUTION. ...SHORTWAVE TRACKING ACROSS THE GREAT LAKES EARLY IN THE PERIOD... FINAL PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH AN AXIS OF WEAK HEIGHT FALLS ARE EXPECTED TO SLIDE ACROSS THE GREAT LAKES EARLY THIS MORNING WITH THE ENERGY GRADUALLY SHEARING AS IT BECOMES SOMEWHAT ABSORBED BY THE CLOSED LOW ALONG THE EASTERN SEABOARD. GIVEN THE FORECAST IS PRIMARILY DURING THE FIRST 18 HOURS...MODELS AGREE WITH ONE ANOTHER ENOUGH TO SUPPORT A GENERAL MODEL CONSENSUS HERE. ...CLIPPER SYSTEM SLIDING THROUGH THE LOWER TN VALLEY BY 15/0600Z... ...COASTAL LOW EMERGING OFF THE OUTER BANKS/VA CAPES... FINAL PREFERENCE: BLEND OF THE 00Z NAM/ECMWF FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE A MULTITUDE OF SHORTWAVES SEEN ON WATER VAPOR IMAGERY TRACKING THROUGH THE NORTHERN HIGH PLAINS WILL QUICKLY BEGIN TO NOSE SOUTH AND EAST WHILE AMPLIFYING PRETTY DRAMATICALLY BY FRIDAY EVENING. MODELS AGREE THAT THIS CLIPPER SYSTEM WILL BECOME NEGATIVELY-TILTED AS IT EMERGES OFF THE COASTAL CAROLINAS EARLY SATURDAY WHICH SHOULD HELP INVIGORATE AN AREA OF SURFACE LOW PRESSURE. WITH REGARD TO THE REMAINING 00Z GUIDANCE ARRIVING...THE 00Z UKMET HAS PICKED UP A BIT OF SPEED WHICH BRINGS IN CLOSER TO THE CONSENSUS THROUGH 15/1200Z. OVERALL...THE ENSEMBLE LOW PLOTS LOOK RATHER MESSY SHOWING THE INHERENT UNCERTAINTY IN THE FORECAST. A MAJORITY OF THE MEMBERS DEPICT THE LOW TRACKING EAST OF THE 40N/70W BENCHMARK ALTHOUGH THE 00Z GFS SUGGESTS A SCENARIO WHERE THE SYSTEM CROSSES DIRECTLY OVER THIS SPOT. WHILE POSSIBLE...IT STILL LOOKS LIKE A MINORITY SOLUTION WITHIN THE BROAD SPREAD. EVEN THOUGH THE 00Z GEFS MEAN NOW SUPPORTS THE 00Z GFS...STILL WOULD LIKE TO SEE ANOTHER MODEL JOIN THIS SOLUTION BEFORE BECOMING SOLD ON IT. WILL PREFER THE TRACK SUGGESTED BY THE 00Z NAM/ECMWF. THE INITIAL GAP BETWEEN THE 00Z NAM AND 00Z ECMWF HAS BEEN BRIDGED A BIT AS THE 00Z ECMWF TRENDED A TAD SLOWER. ...WEAKLY AMPLIFIED UPPER TROF CROSSING THE LOWER MID-ATLANTIC BY MIDDAY SUNDAY... FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF FORECAST CONFIDENCE: AVERAGE ON THE HEELS OF THE CLIPPER SYSTEM WILL BE ANOTHER AREA OF SHORTWAVE ENERGY RACING THROUGH THE MIDDLE MS VALLEY BY MIDDAY SATURDAY. GIVEN THE PROGRESSIVE PATTERN DEPICTED...THE 00Z NAM SEEMS A BIT SLOWER THAN THE CONSENSUS. THE 18Z GEFS MEAN WHICH HAD SUPPORTED THIS NAM IDEA HAS BACKED OFF WITH THE 00Z GEFS MEAN JOINING THE 00Z GFS. THE 00Z GFS NOW SUPPORTS THE IDEA OF THE 00Z ECMWF/12Z ECMWF ENSEMBLE MEAN PRETTY WELL SO WILL RECOMMEND A COMBINATION OF THESE TWO. ...PAIR OF SYSTEMS TRACKING ACROSS THE NORTHERN/CENTRAL PLAINS EARLY NEXT WEEK... FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF WITH THE 12Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE A FAIRLY PRONOUNCED UPPER TROF WILL SWING EASTWARD TOWARD THE PACIFIC NORTHWEST COAST BY LATE SATURDAY NIGHT BEFORE THE HEIGHT FALLS EVENTUALLY PROGRESS INLAND. AS THIS OCCURS...THE SYSTEM APPEARS TO SPLIT INTO A PAIR OF WAVES...EACH WITH A DEFINED LOW TRACK. A SLEW OF MODEL DIFFERENCES ARE NOTED WITH THE TIMING AND THE OVERALL EVOLUTION OF THE STREAMS WHICH APPEAR TO HAVE ENOUGH SEPARATION TO NOT INTERACT. IN TERMS OF TIMING...THE 00Z UKMET IS THE SLOWEST PIECE GUIDANCE WHICH MAKES SENSE AS IT TENDED TO WRAP UP THE INITIAL PACIFIC CYCLONE MORE THAN OTHER MODELS. A VARIETY OF SOLUTIONS ARE ADVERTISED BY EARLY MONDAY SO THE CONFIDENCE IS RATHER LOW WITH ANY PREFERENCE. ONE THING TO NOTE IS THE PAST FEW CYCLES OF THE ENSEMBLE LOW PLOTS SHOW THE ECMWF ENSEMBLE MEMBERS HAVE FAVORED A LOW POSITION ACROSS OK/KS ON MONDAY MORNING. MEANWHILE...THE 18Z GEFS MEAN SHOWS A FASTER SOLUTION WHICH THE 00Z GFS HAS BACKED OFF ON AND SLOWED A BIT MORE TOWARD THE ECMWF SUITE. THE PREFERENCE WILL LEAN ON THE STABILITY OF THE ECMWF ENSEMBLE MEAN BUT ADD THE 00Z GFS/ECMWF IN SPITE OF THEIR TIMING DIFFERENCES IN THE NORTHERN STREAM. FEEL THERE IS ENOUGH UNCERTAINTY THAT MODELS ARE STILL WAFFLING BETWEEN VARIOUS SOLUTIONS AT THIS TIME. ...NEXT PACIFIC SYSTEM IMPACTING THE PACIFIC NORTHWEST EARLY MONDAY... FINAL PREFERENCE: BLEND OF THE 00Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: AVERAGE AS ZONAL FLOW BECOMES REESTABLISHED ACROSS THE WESTERN U.S...ANOTHER MYRIAD OF IMPULSES BEGIN TO TRACK INTO THE PACIFIC NORTHWEST/UPPER INTERMOUNTAIN WEST BY EARLY NEXT WEEK. OVERALL...THERE ARE ENOUGH DETAIL DIFFERENCES THAT A COMBINATION OF THE ENSEMBLE MEANS WILL BE THE BEST WAY TO RESOLVE THIS ISSUE. FOR NOW WILL LEAN ON THE 00Z GEFS/12Z ECMWF ENSEMBLE MEANS WITH AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... 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