MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1152 PM EST SAT JAN 11 2014 VALID JAN 12/0000 UTC THRU JAN 15/1200 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... THE 00Z GFS SEEMED TO INITIALIZE THE EASTERN EDGE OF THE GREAT LAKES TROF A BIT TOO DEEP WITH THE 500-MB HEIGHTS BEING 2 TO 3 DM LOWER IN THE GFS VERSUS OBSERVATIONS ACROSS THE NORTHEASTERN U.S. MEANWHILE...NO DEFINABLE ISSUES WITH THE 00Z NAM. ...AMPLIFIED TROF EXITING THE EASTERN SEABOARD BY MIDDAY SUNDAY... ...DEPARTING SURFACE COLD FRONT... PRELIMINARY PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH A MERIDIONALLY ORIENTED UPPER TROF CURRENTLY RACING THROUGH THE LOWER GREAT LAKES AND DOWN INTO THE OH/TN VALLEYS WILL QUICKLY WORK ITS WAY OFFSHORE OF THE EAST COAST BY MIDDAY SUNDAY. THIS WILL USHER THE SURFACE BOUNDARY OFFSHORE AS COLD AIR ADVECTION ENSUES ALONG THE EASTERN SEABOARD. GIVEN THE FACT THIS SYSTEM ONLY IMPACTS THE CONUS FOR APPROXIMATELY 12 TO 18 HOURS...ITS DIFFERENCES ARE RELATIVELY SMALL SO A GENERAL MODEL CONSENSUS WILL BE RECOMMENDED HERE. ...CLOSED LOW OVER SOUTHERN GULF OF BAJA CA/SEA OF CORTEZ REACHING SOUTH TX BY 13/0600Z... PRELIMINARY PREFERENCE: BLEND OF THE 00Z NAM/GFS WITH THE 12Z ECMWF FORECAST CONFIDENCE: AVERAGE A CLOSED 576-DM LOW INITIALLY OVER THE SOUTHERN TIP OF BAJA CA WILL EVENTUALLY TRANSITION INTO MORE OF AN OPEN WAVE WHILE MIGRATING NORTHEASTWARD TOWARD THE SOUTHERN EXTENT OF TX. THROUGH THE FIRST DAY OR SO...THE 12Z CMC SEEMS TO BE A TAD SLOWER IN EJECTING THIS SYSTEM TOWARD THE SOUTHERN PLAINS. THIS SHORTWAVE ENERGY DOES BEGIN TO SHEAR OUT AS RISES TOWARD THE LOWER TN VALLEY AHEAD OF THE NEXT AMPLIFIED TROF. THE 12Z UKMET TENDS TO CARRY THIS ENERGY MORE QUICKLY AND AHEAD OF THE BETTER CONSENSUS. THE 00Z NAM/GFS AND 12Z ECMWF FORM A REASONABLE SOLUTION AND WILL BE RELIED ON AS THE PREFERENCE. ...PROGRESSIVE UPPER TROF SWINGING FROM THE PACIFIC NORTHWEST TO THE GREAT LAKES THROUGH MONDAY... ...POTENTIAL SURFACE LOW TRACKING UP THE EASTERN SEABOARD BY EARLY TUESDAY... PRELIMINARY PREFERENCE: BLEND OF THE 12Z CMC/ECWMF WITH THE 12Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE A LONGWAVE TROF WITHIN EMBEDDED SHORTWAVES IS CURRENTLY AFFECTING THE PACIFIC NORTHWEST AND NORTHERN ROCKIES WITH WIDESPREAD PRECIPITATION. ACCOMPANYING A STRONG UPPER JET...THIS SYSTEM IS FORECAST TO QUICKLY RACE OFF TO THE EAST WITH SOME GAIN IN AMPLITUDE AS IT CROSSES THE MIDDLE OF THE COUNTRY BY 13/0000Z. THE MULTI-CYCLE SPAGHETTI PLOTS SHOW FAIRLY GOOD CONSISTENCY DATING BACK A COUPLE OF DAYS. THE MODELS BEGIN TO DIVERGE A BIT THEREAFTER WITH THE 00Z NAM BEING ON THE QUICKER SIDE WHICH AGREES WITH THE 18Z GEFS/21Z SREF MEANS. THESE LATTER TWO ENSEMBLE MEANS SUGGEST A RATHER FAST SURFACE FRONTAL PROGRESSION. AS IN PREVIOUS DAYS...THE GUIDANCE IS AT ODDS WITH THE PROGRESSION OF THIS SHORTWAVE WITH THE 12Z ECMWF ENSEMBLE MEMBERS CONTINUING TO ADVERTISE A SLOWER/DEEPER SOLUTION RELATIVE TO THE FLATTER/MORE PROGRESSIVE 12Z GEFS MEMBERS. GIVEN ITS PERSISTENCE WITH THIS IDEA...WILL FAVOR THE SLOWER SOLUTION WHICH INCLUDES THE 12Z ECMWF/CMC ALONG WITH THE 12Z ECMWF ENSEMBLE MEAN. THE SURFACE LOW TRACK WHICH CARRIES A LOW FROM THE SOUTHEASTERN U.S. UP ALONG THE GULF STREAM IS QUITE NEBULOUS AT THIS TIME WITH THE 00Z NAM AND 18Z GEFS/21Z SREF MEANS SHOWING LITTLE TO NO DEVELOPMENT. MEANWHILE...THE GFS SOLUTIONS CONTINUE TO BE MORE SUPPRESSED WITH DEVELOPMENT OCCURRING FURTHER OFFSHORE. WHILE THE 12Z CMC/ECMWF/ECMWF ENSEMBLE MEAN AGREE REASONABLY ALOFT...SURFACE DIFFERENCES WILL STILL COME INTO PLAY THUS LEAVING THE PREFERENCE AT A LOWER THAN AVERAGE CONFIDENCE. ...SECONDARY SYSTEM ARRIVING INTO THE GREAT LAKES BY 15/1200Z... PRELIMINARY PREFERENCE: BLEND OF THE 00Z NAM/12Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE ON THE WINGS OF THE INITIAL AMPLIFIED SHORTWAVE MARCHING THROUGH THE TN VALLEY WILL BE ANOTHER SYSTEM EXPECTED TO REACH THE GREAT LAKES BY EARLY WEDNESDAY. AS EXPECTED THIS FAR INTO THE SHORT RANGE PERIOD...MODEL DIFFERENCES ARE EVIDENT WITH THE 12Z CMC BEING MUCH MORE PROGRESSIVE WHILE ON THE OTHER EXTREME IS THE 12Z UKMET WHICH IS QUITE SLOW. THE OTHER EXTREME SOLUTION AT THIS TIME IS THE 12Z ECMWF WHICH CARRIES A STRONG CLOSED LOW INTO THE UPPER OH VALLEY BY 15/1200Z. UNTIL FURTHER GUIDANCE ARRIVES...WPC WILL STAY ON THE MORE CONSERVATIVE SIDE FAVORING THE 12Z ECMWF ENSEMBLE MEAN WITH THE 00Z NAM BEING ADDED AS IT LOOKS FAIRLY SIMILAR ALOFT. PLUS THIS WILL ALLOW FOR DETAILS NECESSARY ACROSS THE GREAT LAKES AND LOCAL TERRAIN. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER