MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1157 PM EST SUN JAN 12 2014 VALID JAN 13/0000 UTC THRU JAN 16/1200 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 CROSSING THE WESTERN GULF COAST EARLY MONDAY BEFORE GRADUALLY SHEARING... PRELIMINARY PREFERENCE: MODEL COMPROMISE BETWEEN THE 00Z GFS/12Z ECMWF FORECAST CONFIDENCE: ABOVE AVERAGE A SHORTWAVE SEEN ON WATER VAPOR IMAGERY CROSSING THE SOUTHERN EXTENT OF THE RIO GRANDE WILL CONTINUE TO PROGRESS NORTH AND EAST AHEAD OF AN AMPLIFIED LONGWAVE TROF. THE 500-MB ENERGY ASSOCIATED WITH THIS IMPULSE SHOULD GRADUALLY SHEAR AS MOVES UP THROUGH THE MID-ATLANTIC BY 14/0000Z. DIFFERENCES ARE FOR THE MOST PART SMALL WITH THE 00Z NAM/GFS AND 12Z CMC JUST OFF TO THE WEST WHILE THE 12Z ECMWF/UKMET ARE SLIGHTLY EASTWARD. WILL JUST TAKE A SPLIT BETWEEN THESE TWO CAMPS WITH A PREFERENCE OF THE 00Z GFS/12Z ECMWF. ...PROGRESSIVE SYSTEM MOVING THROUGH THE TN/OH VALLEYS BY LATE MONDAY NIGHT... ...SURFACE LOW TRACKING ALONG THE EASTERN SEABOARD... PRELIMINARY PREFERENCE: BLEND OF THE 12Z CMC/ECMWF WITH THE 12Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE A QUICK MOVING UPPER TROF WILL RACE FROM THE CENTRAL U.S. INTO THE MS RIVER VALLEY BY ROUGHLY 14/0000Z. THERE ARE SOME SMALL DIFFERENCES INITIALLY WITH THE 12Z CMC/UKMET BEING A BIT SLOWER THAN THE REMAINDER OF THE PACK. BY 14/1800Z...THE 00Z GFS BECOMES SLIGHTLY FASTER THAN THE CONSENSUS AS THE IMPULSE LIFTS THROUGH THE CAROLINAS. WHILE A MAJORITY OF THE MODELS ARE IN DECENT AGREEMENT WITH THE SURFACE LOW EVOLUTION ACROSS THE SOUTHEASTERN U.S...THE 00Z NAM/21Z SREF MEAN APPEAR TO BE OUTLIERS WITH THE LOW DEVELOPMENT DIFFERING IN TIMING/PLACEMENT. WILL REMOVE THESE MODELS FROM CONSIDERATION GIVEN THE OUTLYING NATURE OF ITS SURFACE FIELD. WITH REGARD TO THE 500-MB TROF TIMING...THE PAST FOUR SPAGHETTI PLOTS HAVE SHOWN A TREND IN THE SLOWER DIRECTION WITH THESE DIAGRAMS DATING BACK TO 48 HOURS AGO. THIS MULTI-DAY TREND WILL BE UTILIZED HERE AND FAVOR THE SLOWER IDEA PORTRAYED BY THE 12Z CMC/ECMWF/ECMWF ENSEMBLE MEAN. THIS COMBINATION ALSO ALLOW FOR A SOMEWHAT MORE COASTAL SURFACE LOW TRACK VERSUS THE OFFSHORE 12Z UKMET. ...SECONDARY DISTURBANCE AMPLIFYING OVER THE SOUTHEASTERN U.S. BY 16/0000Z... ...POTENTIAL COASTAL LOW DEVELOPMENT... PRELIMINARY PREFERENCE: BLEND OF THE 12Z UKMET/ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE ON THE WINGS OF THE INITIAL SYSTEM CROSSING THE EASTERN SEABOARD...A SECONDARY DISTURBANCE DROPPING THROUGH THE UPPER GREAT LAKES EARLY TUESDAY WILL EVENTUALLY DIG SOUTHWARD TOWARD THE TN VALLEY/SOUTHEASTERN U.S. BY THE END OF THE PERIOD. AS EXPECTED...SIMILAR TIMING DIFFERENCES AS NOTED DOWNSTREAM OCCUR WITH THIS SYSTEM AS THE 00Z NAM/GFS AND 18Z GEFS MEAN ARE ON THE FASTER SIDE OF THE GUIDANCE. WILL DEFINITELY BE LEANING TOWARD THE SLOWER SOLUTIONS TO BE CONSISTENT WITH THE PREVIOUS EASTERN U.S. SYSTEM AND FOLLOW THE SUGGESTED MULTI-DAY TRENDS IN THE SPAGHETTI PLOTS. THE 12Z ECMWF ACTUALLY BECOMES SLOWER THAN ITS OWN ENSEMBLE MEAN BY THE TIME THE SYSTEM REALLY BEGINS TO DIG INTO THE SOUTHEASTERN U.S. BY LATE WEDNESDAY/EARLY THURSDAY. GIVEN THE UNCERTAINTY IN THE FORECAST...WILL STICK CLOSER TO THE 12Z ECMWF ENSEMBLE MEAN WHICH IS PRETTY CONSISTENT ALOFT WITH ITS PREVIOUS RUN. THE 12Z UKMET APPEARS TO BE THE BEST MATCH TO THIS ENSEMBLE MEAN SO WILL COMBINE THE TWO IN THIS PREFERENCE. CONFIDENCE WILL BE ON THE LOWER SIDE GIVEN THE LACK OF AGREEMENT IN THE MODELS ALONG WITH THE FACT DETERMINISTIC SOLUTIONS ARE EVEN DISAGREEING WITH THEIR OWN ENSEMBLE MEANS. ...UPPER TROF DIGGING INTO THE NORTHERN PLAINS/UPPER MIDWEST BY WEDNESDAY EVENING... PRELIMINARY PREFERENCE: BLEND OF THE 00Z NAM WITH THE 12Z ECMWF/ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE WITH AN EXPANSIVE UPPER RIDGE HOLDING STRONG ACROSS THE WESTERN U.S...YET ANOTHER SYSTEM IS EXPECTED TO DROP DOWN THE EASTERN EXTENT OF THE RIDGE INTO THE NORTHERN PLAINS/UPPER MIDWEST BY MID-WEEK. AS OF RIGHT NOW...THE 00Z GFS/12Z CMC ARE TWO OF THE MORE PROGRESSIVE SOLUTIONS WITH THIS UPPER TROF WHILE THE 21Z SREF MEAN IS BY FAR THE SLOWEST PIECE OF GUIDANCE AVAILABLE. THE FASTER SOLUTIONS INCLUDING THE 00Z GFS/12Z CMC AS WELL AS THE 12Z UKMET LATER IN THE PERIOD END UP BRINGING A SIGNIFICANT SURFACE LOW INTO THE UPPER GREAT LAKES BY 16/1200Z. WILL END UP STAYING CONSISTENT WITH THE SLOWER PROGRESSION OF THE LONGWAVE TROF WHICH BODES WELL FOR THE 00Z NAM AND 12Z ECMWF/ECMWF ENSEMBLE MEAN. UNTIL ADDITIONAL 00Z GUIDANCE ARRIVES...WILL ADVERTISE A COMBINATION OF THE 00Z NAM WITH THE 12Z ECWMF/ECMWF ENSEMBLE MEAN. DECIDED TO KEEP THE ECMWF ENSEMBLE MEAN IN THERE TO ACCOUNT FOR THE UNCERTAINTY IN THIS FORECAST. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER