MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 223 PM EST THU DEC 11 2014 VALID DEC 11/1200 UTC THRU DEC 15/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 12Z MODEL GUIDANCE (12Z ECMWF ONLY AVAILABLE THROUGH 72 HOURS) ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...BROAD UPPER LOW LINGERING ACROSS THE NORTHEASTERN U.S... FINAL PREFERENCE: BLEND OF THE 12Z GFS/ECMWF FORECAST CONFIDENCE: AVERAGE AN EXPANSIVE REGION OF CYCLONIC FLOW CONTINUES TO ANCHOR ITSELF ACROSS THE NORTHEASTERN U.S. THIS CIRCULATION SHOULD LINGER ANOTHER COUPLE OF DAYS BEFORE EXITING OFF THE NEW ENGLAND COAST. GENERAL AGREEMENT IS NOTED IN THE MODELS ALTHOUGH THE 12Z CMC DOES END UP SOUTHWEST OF THE CONSENSUS BY EARLY SATURDAY. THE MULTI-DAY TRENDS IN THE SPAGHETTI PLOTS SUGGEST A SHIFT IN THE FASTER/MORE OFFSHORE DIRECTION. THE 12Z NAM WHICH IS CLOSER TO THE COAST APPEARS TO BE A WEST OUTLIER TOWARD THE END OF THE PERIOD. A COMBINATION OF THE 12Z GFS/ECMWF APPEARS TO BE A NICE MIDDLE GROUND SOLUTION WHICH AGREES WITH THE ENSEMBLE MEANS. ...ADDITIONAL SHORTWAVE ENERGY DROPPING THROUGH THE SOUTHERN PLAINS ON FRIDAY... FINAL PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE SHORTWAVE ENERGY SLIDING SOUTHWARD FROM UPPER MIDWEST/MIDDLE MS VALLEY WILL EVENTUALLY REACH THE SOUTHERN/CENTRAL PLAINS BY THE END OF THE WORK WEEK. THE SYSTEM GETS STRETCHED OUT AND SHEARED BY THE TIME IT REACHES THE EASTERN GULF COAST TOWARD THE END OF THE PERIOD. MODELS ARE IN MUCH BETTER AGREEMENT THAN THEY WERE YESTERDAY REGARDING HOW QUICKLY THIS FEATURE MOVES TOWARD THE EAST. A GENERAL MODEL COMPROMISE WILL SUFFICE HERE. ...STRONG WESTERN U.S. TROF... ...HEIGHT FALLS SPREADING INTO THE CENTER OF THE COUNTRY BY SUNDAY... FINAL PREFERENCE: BLEND OF THE 12Z UKMET/00Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE A POWERFUL UPPER TROF WILL MIGRATE EASTWARD IN TWO PARTS WITH A COMPACT CLOSED LOW INITIALLY LIFTING TOWARD THE PACIFIC NORTHWEST DURING THE NEXT 6 TO 12 HOURS. THE REMAINDER OF THE HEIGHT FALLS ARE FORECAST TO MOVE TOWARD THE CA COAST REACHING THE DESERT SOUTHWEST BY FRIDAY AFTERNOON. THE 12Z UKMET MAY BE A HAIR QUICK WITH THE PASSAGE OF THE UPPER TROF. DIFFERENCES CONTINUE TO GROW IN NUMBER AS THE UPPER TROF MOVES TOWARD THE FOUR CORNERS REGION WITH THE 12Z GFS/ECMWF BEING ON THE FASTER SIDE OF THE ENVELOPE. THE PREVIOUS FOUR SPAGHETTI PLOTS SHOWS A TREND IN THE SLOWER DIRECTION. WILL REVERT SLIGHTLY FROM THE PRIOR SOLUTION AND NOT INCLUDE THE MOST RECENT 12Z ECMWF GIVEN ITS FASTER TREND. PLAN ON STICKING CLOSER TO THE PREVIOUS 00Z ECMWF ENSEMBLE MEAN WHICH IS SUPPORTED BY THE 12Z UKMET. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER