MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1253 AM EDT THU SEP 11 2014 VALID SEP 11/0000 UTC THRU SEP 14/1200 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. ...SHORTWAVE LIFTING THROUGH THE GREAT LAKES EARLY THIS MORNING... ...STRENGTHENING SURFACE WAVE... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE A POTENT SHORTWAVE WILL CONTINUE TO MOVE NORTH AND EAST INTO WESTERN QUEBEC THIS MORNING. THE ASSOCIATED COLD FRONT SHOULD MARCH EASTWARD REACHING THE I-95 CORRIDOR BY THIS AFTERNOON/EVENING. WHILE THERE SUBTLE DIFFERENCES IN THE SOLUTIONS...A GENERAL MODEL COMPROMISE WILL SUFFICE. ...DEEP UPPER TROF CROSSING THE MIDDLE OF THE U.S... ...STRONG DOME OF HIGH PRESSURE SURGING SOUTHWARD... PRELIMINARY PREFERENCE: BLEND OF THE 00Z NAM WITH THE 12Z ECMWF/UKMET FORECAST CONFIDENCE: AVERAGE A BROAD AMPLIFIED TROF WILL USHER IN MUCH COOLER AIR INTO THE CENTRAL U.S. AS 1000-500 DM THICKNESSES BEGIN TO CRASH BEHIND THE AXIS OF HEIGHT FALLS. BY EARLY FRIDAY...THE 18Z GEFS/21Z SREF MEANS ARE A BIT FASTER WITH THE NORTHERN EXTENT OF THE UPPER TROF. WHILE THE GFS SUITE HAS SLOWED DOWN RELATIVE TO ITS QUICKER SOLUTIONS THE PAST FEW DAYS...IT STILL APPEARS TO BE A HAIR FASTER OVERALL. WPC WILL LEAN ON A CONSENSUS FORMED BY THE 00Z NAM AND 12Z ECMWF/UKMET. ...SECONDARY TROF REACHING THE NORTHERN PLAINS BY LATE IN THE WEEKEND... PRELIMINARY PREFERENCE: BLEND OF THE 00Z NAM/12Z ECMWF FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE ON THE WINGS OF THE INITIAL HEIGHT FALLS...ANOTHER SHORTWAVE IS EXPECTED TO TRACK THROUGH THE NORTHERN TIER OF THE COUNTRY BY THE WEEKEND. THE 12Z CMC/UKMET SHOW MORE ADDITIONAL ON THE WESTERN EXTENT OF THE LONGWAVE TROF WHICH DOES NOT APPEAR TO AGREE WITH THE ENSEMBLE MEANS. MEANWHILE...THE 00Z GFS IS FLATTER AND DOES NOT EXTENT THE TROF AXIS AS FAR SOUTH AS OTHER MODELS. CHOOSE TO STAY CLOSER TO THE PREFERENCE DOWNSTREAM BUT NOT INCLUDE THE 12Z UKMET DUE TO ITS AFOREMENTIONED DIFFERENCE. A BLEND OF THE 00Z NAM/12Z ECMWF WILL BE RECOMMENDED. ...EASTERLY WAVE APPROACHING SOUTH TX BY LATE TONIGHT... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF WITH THE 12Z ECMWF ENSEMBLE/18Z GEFS MEANS FORECAST CONFIDENCE: BELOW AVERAGE AN EASTERLY WAVE TRACKING ACROSS THE CENTRAL GULF OF MEXICO WILL GRADUALLY REACH THE NORTHEASTERN TIP OF MEXICO/SOUTH TX BY LATER TONIGHT. OVERALL THE MODELS AGREE WITH THE EXISTENCE OF THIS FEATURE WITH SUBTLE TIMING DIFFERENCES. THE 00Z NAM BECOMES MORE AGGRESSIVE WITH THE STRENGTH OF THIS WAVE WHILE THE 12Z CMC/UKMET CARRY ADDITIONAL MID-LEVEL ENERGY FROM THE YUCATAN PENINSULA TOWARD SOUTH TX ON SATURDAY. THERE IS SOME SIGNATURE OF THIS SOLUTION IN OTHER MODELS BUT NOT TO SUCH A DEGREE AS THE 12Z CMC/UKMET. GIVEN THE UNCERTAINTY...WILL LEAN ON THE MORE CONSERVATIVE SOLUTIONS LIKE THE 12Z ECMWF ALONG WITH THE ENSEMBLE MEANS. ...WEAK EASTERLY WAVE NEARING SOUTH FL BY SATURDAY... PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF FORECAST CONFIDENCE: AVERAGE ANOTHER EASTERLY WAVE IS IN THE FORECAST WITH THE ENERGY AFFECTING SOUTH FL THIS WEEKEND. THE 12Z CMC/UKMET ARE THE MOST ROBUST WITH THE SYSTEM CONTOURING A 588-DM LOW OVER THE REGION. DO NOT HAVE ENOUGH CONFIDENCE IN THESE SOLUTIONS SO WILL STAY A LITTLE MORE CONSERVATIVE FAVORING THE 00Z GFS/12Z ECMWF. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER