MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1201 AM EST THU JAN 14 2016 VALID JAN 14/0000 UTC THRU JAN 17/1200 UTC ..SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...SYSTEM LIFTING OUT OF EASTERN MX... ...RESULTANT SURFACE LOW MOVING EAST OF THE CAROLINA COAST BY LATE FRIDAY... PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF WITH THE 18Z GEFS MEAN FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE AN UPPER LOW CURRENTLY MOVING THROUGH CENTRAL MX IS ACCOMPANIED BY QUITE THE SUBTROPICAL JET PER WATER VAPOR IMAGERY AND RECENT 00Z RAOBS. THIS SYSTEM IS EXPECTED TO MIGRATE EASTWARD WHICH WILL SPREAD HEAVY RAINFALL ALONG MUCH OF THE GULF COAST REGION. THE PROGRESSIVE NATURE OF THE SOUTHERN STREAM WILL QUICKLY LIFT THIS SHORTWAVE INTO THE COASTAL CAROLINAS BY 16/0000Z. THE RESULTANT SURFACE CYCLONE IS EXPECTED TO DEEPEN RAPIDLY WITH A SOMEWHAT UNCERTAIN TRACK FORECAST. ON THE WESTERN SIDE OF THE SPREAD ARE THE 12Z CMC/UKMET AND 21Z SREF MEAN. THERE IS QUITE A BIT OF ENSEMBLE SPREAD NOTED IN THE SPAGHETTI LOW PLOTS BUT THESE SOLUTIONS ARE ON THE EXTREME WESTERN SIDE HERE. THE 12Z ECMWF ENSEMBLE MEAN IS TO THE WEST OF THE 18Z GEFS MEAN WHILE THE DETERMINISTIC RUNS OF EACH ARE NEARLY IN PHASE WITH ONE ANOTHER WHICH GENERALLY MIMICS THE 18Z GEFS MEAN. THE PREFERENCE WILL BE A MIX OF THE 00Z GFS/12Z ECMWF WITH THE 18Z GEFS MEAN. ...MIGRATORY SHORTWAVE ADVANCING FROM THE WESTERN U.S. TO THE OH VALLEY THROUGH FRIDAY... ...SURFACE CYCLONE TRACKING FROM THE DAKOTAS TO THE LOWER GREAT LAKES... PRELIMINARY PREFERENCE: A NON-12Z CMC MODEL COMPROMISE FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE A VERY PROGRESSIVE UPPER PATTERN WILL HELP TRACK AN ELONGATED SHORTWAVE CURRENTLY OVER THE CENTRAL GREAT BASIN QUICKLY TOWARD THE OH VALLEY THE NEXT COUPLE OF DAYS. AS THE FEATURE MOVES THROUGH THE MO VALLEY ON FRIDAY MORNING...THE 12Z CMC IS NOTABLY SLOWER WITH THE SOUTHERN EXTENT OF THE ENERGY. IN SPITE OF THE SOME DISAGREEMENTS IN TIMING...MUCH OF THE GUIDANCE IS PRETTY WELL CLUSTERED WITH THE SURFACE CYCLONE. AT THIS POINT...ANY SOLUTION EXCEPT THE 12Z CMC APPEARS FEASIBLE. THUS...WILL RECOMMEND A NON-12Z CMC MODEL COMPROMISE. ...PROGRESSIVE IMPULSE MIGRATING FROM THE OR/CA BORDER TO THE EASTERN GULF COAST... ...ATTENDANT SURFACE WAVE FORMING IN THE GULF OF MX... PRELIMINARY PREFERENCE: 18Z GEFS MEAN FORECAST CONFIDENCE: BELOW AVERAGE A QUICK-MOVING SYSTEM EMERGES ON THE MAP AS IT CROSSES THE OREGON COAST BY 15/0000Z. DURING THE EARLY STAGES OF EVOLUTION...THE 12Z CMC IS SLOWER COMPARED TO OTHER SOLUTIONS. GENERAL MODEL AGREEMENT CARRIES THIS SYSTEM DOWNSTREAM TOWARD THE BIG BEND OF TX BY SATURDAY MORNING. MOST NOTABLY...THE 12Z ECMWF IS WELL OFF TO THE SOUTHWEST WHICH IS EVEN AWAY FROM ITS ENSEMBLE MEAN. OTHER MODELS DO SHOW A RATHER PRONOUNCED SHORTWAVE RACING ACROSS THE LONE STAR STATE WITH A SURFACE LOW POSSIBLY CROSSING THE NORTHERN GULF OF MX ON SATURDAY. THERE ARE QUITE A FEW ENSEMBLE MEMBERS AGREEING WITH SUCH DEVELOPMENT THIS WEEKEND. THE BIGGEST OUTLIER IS THE 12Z ECMWF WHICH GENERALLY IS MORE DIFFUSE WITH THE INITIAL SYSTEM WHILE ALLOWING AN ELONGATED SHORTWAVE TO HANG BACK OVER THE CENTRAL GULF OF MX EARLY SUNDAY. WILL PLAY THIS FEATURE MORE CONSERVATIVELY GIVEN SUCH UNCERTAINTIES. AFTER COORDINATION WITH WPC MEDIUM RANGE...THE PREFERENCE WILL BE THE 18Z GEFS MEAN. ...ADDITIONAL SYSTEM REACHING THE WEST COAST BY 16/1800Z... PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/18Z GEFS MEAN FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE THE CONTINUED PROGRESSIVE FLOW ACROSS THE MID-LATITUDES WILL ALLOW ANOTHER SHORTWAVE TO REACH THE WEST COAST BY MIDDAY SATURDAY. RECENT ENSEMBLE SPAGHETTI PLOTS SHOW PRONOUNCED TIMING ISSUES WITH THE 12Z UKMET ON THE FAR EASTERN SIDE OF THE SPREAD. THE 00Z NAM SOMEWHAT MOVES IN THAT DIRECTION AS WELL. GIVEN THE FAST-MOVING FLOW ON THE MAP...WOULD PREFER TO NOT BE AS SLOW AS THE 12Z ECMWF/CMC. THE 00Z GFS/18Z GEFS MEAN WOULD PRESENT A NICE COMPROMISE HERE WHILE ALSO ERRING ON THE SLIGHTLY QUICKER SIDE OF THE ENVELOPE. ...BROAD UPPER LOW ANCHORING THE NORTHEAST PACIFIC BY LATE IN THE WEEKEND... ...SURFACE BOUNDARIES/DEEP LOW CENTER... PRELIMINARY PREFERENCE: 18Z GEFS MEAN FORECAST CONFIDENCE: BELOW AVERAGE ON THE HEELS OF THE NEXT PACIFIC SYSTEM...A MORE ELONGATED UPPER LOW BEGINS TO TAKE SHAPE OVER THE NORTHEAST PACIFIC BY LATE IN THE WEEKEND. THERE ARE A MYRIAD OF SOLUTIONS NOTED REGARDING THE SURFACE LOW TRACK ACROSS THE EASTERN PACIFIC. GIVEN THE VARIETY OF FORECASTS AT HAND...WILL TAKE THE ENSEMBLE ROUTE AND UTILIZE THE 18Z GEFS MEAN TO BE CONSISTENT WITH THE DOWNSTREAM PREFERENCE. ...DEEP UPPER LOW DROPPING DOWN INTO THE GREAT LAKES LATE IN THE PERIOD... PRELIMINARY PREFERENCE: 18Z GEFS MEAN FORECAST CONFIDENCE: BELOW AVERAGE TOWARD THE END OF THE PERIOD...A RATHER ROBUST UPPER LOW DIVES DOWN INTO THE GREAT LAKES REGION. THERE ARE A VARIETY OF SOLUTIONS PORTRAYED BY THE DETERMINISTIC GUIDANCE SO FEEL MORE INCLUDED TO GO WITH ENSEMBLE MEANS. PER PREVIOUS PREFERENCES/RATIONALE...WILL FAVOR THE 18Z GEFS MEAN HERE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER