MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1149 AM EST MON JAN 05 2015 VALID JAN 05/1200 UTC THRU JAN 09/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...MID-LEVEL VORTICITY ACCELERATING THROUGH THE NORTHEASTERN U.S. THIS AFTERNOON... PRELIMINARY PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH SEVERAL SHORTWAVES ACCOMPANYING A STRONG UPPER JET MAXIMA WILL RACE THROUGH THE NORTHEASTERN U.S. THIS AFTERNOON BEFORE EXITING OFFSHORE LATER IN THE DAY. THERE ARE NO NOTABLE DIFFERENCES IN THE GUIDANCE SO A GENERAL MODEL CONSENSUS IS RECOMMENDED. ...CLIPPER SYSTEM CROSSING THE MIDDLE MS VALLEY TONIGHT... ...WEAKENING AREA OF LOW PRESSURE... PRELIMINARY PREFERENCE: A NON-00Z CMC MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE BROAD CYCLONIC FLOW ANCHORING THE NORTHERN ROCKIES EASTWARD TO THE CENTRAL/EASTERN CONUS WILL ALLOW A FAST-MOVING CLIPPER SYSTEM TO TRACK THROUGH THE MIDDLE MS VALLEY LATER TONIGHT. THE WAVE OF LOW PRESSURE CROSSING IA/MO SHOW A SLIGHT VARIANCE IN TIMING WITH THE 00Z ECMWF/CMC BEING A TAD SLOWER. ALTHOUGH THE 00Z ECMWF DOES SEEM TO ADJUST LATER ON. THIS WAVE DOES QUICKLY WEAKEN WHILE MIGRATING INTO THE OH VALLEY/MID-ATLANTIC REGION. OVERALL...WILL LEAN AWAY FROM THE SLOWER 00Z CMC AND FAVOR A MODEL COMPROMISE OF THE REMAINING MODELS. ...STRONG HEIGHT FALLS MOVING FROM THE UPPER MIDWEST TOWARD THE EASTERN SEABOARD... ...POSSIBLY RECORD BREAKING DOME OF HIGH PRESSURE BUILDING ACROSS THE CENTRAL U.S... PRELIMINARY PREFERENCE: A NON-00Z UKMET MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE THE NEXT SHOT OF ARCTIC AIR WILL BE ACCOMPANIED BY A STRONG AXIS OF HEIGHT FALLS TRACKING THROUGH THE UPPER MIDWEST/GREAT LAKES BY TUESDAY EVENING. THIS COLD SHOT WILL DRAG SUB-490 DM 1000-500 MB THICKNESSES TO AREAS OF THE GREAT LAKES AND NORTHEASTERN U.S. THROUGHOUT THE PERIOD. EXCEPT FOR SOME SUBTLE TIMING DIFFERENCES...THE MODEL SPREAD IS NOT THAT SIGNIFICANT THROUGH WEDNESDAY AS THE UPPER TROF CROSSES THE EASTERN SEABOARD. THIS IS WELL DEPICTED IN THE SPAGHETTI PLOTS WITH LITTLE CHANGE NOTED IN THE PAST FEW MODEL CYCLES. REGARDING THE POSSIBLY RECORD BREAKING MSLP VALUES EXPECTED TO AFFECT THE CENTER OF THE COUNTRY...THE 00Z UKMET APPEARED TOO WEAK NOT DEPICTING VALUES IN THE 1058-1060 MB RANGE ON WEDNESDAY MORNING. WILL RECOMMEND A NON-00Z UKMET MODEL COMPROMISE GIVEN THIS FACT. ...NEXT SYSTEM CROSSING THE NORTHERN TIER BY THURSDAY EVENING... PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE THE LAST SHORTWAVE IN THE CHAIN WILL QUICKLY WORK ITS WAY INTO THE NORTH-CENTRAL U.S. BY LATE THURSDAY. CONTRARY TO OTHER SYSTEMS ON THE MAP...THERE IS A GREATER AMOUNT OF DIVERSITY WITH THE SOLUTIONS REGARDING THIS FEATURE. THE 00Z ECMWF/ECMWF MEAN ARE MUCH MORE PROGRESSIVE WHILE THE 00Z CMC/UKMET EACH SHOW A PAIR OF STRONGER EMBEDDED SHORTWAVES WORKING THEIR WAY THROUGH THE UPPER GREAT LAKES BY 09/0000Z. ON THE SLOWER SIDE OF THE EQUATION ARE THE 12Z NAM/GFS/GFS-PARALLEL AND 06Z GEFS/09Z SREF MEANS. WILL SPLIT THE DIFFERENCE BETWEEN THE SLOW AND FAST SIDE FAVORING A BLEND OF THE 12Z GFS/00Z ECMWF WITH SLIGHTLY BELOW AVERAGE CONFIDENCE. ...QUASI-STATIONARY UPPER LOW ALONG BAJA CA... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE DETACHED FROM THE PREVAILING WESTERLIES WILL BE A QUASI-STATIONARY UPPER LOW ROUGHLY MEANDERING ABOUT BAJA CA. THIS CIRCULATION IS CURRENTLY SPINNING WEST OF THE SOUTHERN TIP OF BAJA CA BASED ON THE LATEST WATER VAPOR IMAGERY. THERE IS SOME VARIABILITY IN THE FORECAST SOLUTIONS BUT ALL SEEM TO BE WELL WITHIN THE ENVELOPE OF ENSEMBLE SPREAD. A GENERAL MODEL COMPROMISE APPEARS WARRANTED HERE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER