MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 151 AM EST SUN JAN 12 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 CMC/UKMET/ECMWF ALONG WITH FINAL 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... FINAL 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... FINAL PREFERENCE: GENERAL MODEL COMPROMISE 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. THIS SHORTWAVE ENERGY DOES BEGIN TO SHEAR OUT AS IT RISES TOWARD THE LOWER TN VALLEY AHEAD OF THE NEXT AMPLIFIED TROF. THE TIMING OF THIS APPROACHING SYSTEM WILL INFLUENCE THE PATH THE SHEARING SHORTWAVE WILL TAKE. WHILE THERE ARE DIFFERENCES...IT IS DIFFICULT TO CHOOSE ONE MODEL OVER ANOTHER SO WILL FAVOR A GENERAL MODEL COMPROMISE. ...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... FINAL PREFERENCE: BLEND OF THE 00Z ECMWF/UKMET 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 21Z SREF MEAN. THE 21Z SREF MEAN SUGGESTS A RATHER FAST SURFACE FRONTAL PROGRESSION IN THIS CASE. 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 00Z ECMWF/UKMET 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 00Z GEFS/21Z SREF MEANS SHOWING LITTLE TO NO DEVELOPMENT. MEANWHILE...THE GFS SOLUTIONS CONTINUE TO BE MORE SUPPRESSED WITH DEVELOPMENT OCCURRING FURTHER OFFSHORE. WILL CONTINUE TO STICK WITH THE ECMWF IDEA WHILE INCORPORATING THE 12Z ECMWF ENSEMBLE MEAN TO ACCOUNT FOR THE UNCERTAINTY. ...SECONDARY SYSTEM ARRIVING INTO THE GREAT LAKES BY 15/1200Z... FINAL PREFERENCE: 00Z ECMWF 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 00Z UKMET BEING ONE OF THE SLOWER PIECES OF GUIDANCE OUT THERE. THE 00Z ECMWF HAS SLOWED RELATIVE TO ITS PREVIOUS RUN WHILE ALSO NOT DEPICTING THE CLOSED LOW CENTER IT HAD EARLIER ADVERTISED. GIVEN THE IDEA OF FOLLOWING THE SLOWER SOLUTION FOR THIS LONGWAVE TROF...WILL LEAN HEAVILY ON THE 00Z ECMWF HERE TO BE CONSISTENT WITH THE FEATURE DOWNSTREAM. CHOOSE NOT TO INCORPORATE ITS ENSEMBLE MEAN AS EXPECT THE NEW MEAN TO SLOW TO MATCH CLOSER TO ITS OWN DETERMINISTIC MODEL. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER