MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 245 PM EDT SAT APR 12 2014 VALID APR 12/1200 UTC THRU APR 16/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF 12Z CMC/ECMWF/UKMET ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...INITIAL SURFACE WAVE MOVING THROUGH THE LOWER GREAT LAKES ON SUNDAY... ...ASSOCIATED WARM FRONT LIFTING INTO NEW ENGLAND... FINAL PREFERENCE: MODEL COMPROMISE BETWEEN THE 12Z GFS/ECMWF FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE BROAD MID-LEVEL SOUTHWESTERLY FLOW WILL HELP ESTABLISH PERSISTENT WARM ADVECTION AHEAD OF A MYRIAD OF MESOSCALE SHORTWAVES. MODELS ADVERTISE AN AREA OF LOW PRESSURE TRACKING FROM THE MIDDLE MS VALLEY INTO THE LOWER GREAT LAKES WHICH WILL ULTIMATELY CARRY A WARM FRONTAL ZONE NORTHWARD INTO NEW ENGLAND. THE 12Z/00Z CMC ARE A PAIR OF THE MORE PROGRESSIVE SOLUTIONS...PARTICULARLY BY MIDDAY SUNDAY AS THE LOW MOVES PAST LAKE HURON. WHILE THE 12Z GFS/ECMWF/UKMET AGREE REASONABLY WITH THE SURFACE LOW TRACK...THE 12Z/00Z UKMET ARE FURTHER NORTH WITH THE PLACEMENT OF THE WARM FRONT. THIS POSITION IS MORE NORTHWARD THAN ANY OF THE ENSEMBLE MEANS. GIVEN THIS...WILL TAKE THE 12Z UKMET OUT OF CONSIDERATION AND FAVOR A MODEL COMPROMISE BETWEEN THE 12Z GFS/ECMWF. ...MID-LEVEL IMPULSE TRACKING FROM THE DESERT SOUTHWEST TOWARD THE SOUTHERN PLAINS THROUGH SUNDAY... FINAL PREFERENCE: A NON-12Z CMC SOLUTION FORECAST CONFIDENCE: AVERAGE AN UPPER LOW WHICH HAD BEEN CLOSED OFF HAS EVOLVED INTO AN OPEN WAVE OVERNIGHT WITH THE REMNANT ENERGY CURRENTLY SLIDING THROUGH THE DESERT SOUTHWEST. THROUGH 13/1200Z...MODELS ARE IN DECENT AGREEMENT EXCEPT FOR THE 12Z/00Z CMC WHICH ARE A TAD NORTH WITH THE POSITION OF ITS SHORTWAVE. THIS PARTICULAR SYSTEM WILL BE THE FOCUS FOR SEVERE WEATHER WHERE A STRONG WAVE OF LOW PRESSURE WILL CONNECT A DRY LINE TO A SOUTHWARD DROPPING COLD FRONT. THIS SURFACE CYCLONE IS FORECAST TO LIFT WITH THE SHORTWAVE FROM OK UP INTO THE LOWER MO VALLEY ON SUNDAY. GIVEN THE 12Z/00Z CMC ARE NORTH OF THE CONSENSUS WITH THE UPPER TROF...THE LOW CENTER FOLLOWS SUIT BEING FASTER AND MORE TO THE NORTH MIDDAY SUNDAY. AS THE SYSTEM LIFTS NORTHEASTWARD AHEAD OF STRONGER UPSTREAM HEIGHT FALLS...IT BECOMES A BIT MORE DIFFICULT TO FOLLOW THE SHORTWAVE AS IT SHEARS WHILE TRACKING INTO THE UPPER GREAT LAKES LATE SUNDAY/EARLY MONDAY. GIVEN THE SUBTLE OUTLYING NATURE OF THE 12Z CMC...WILL FAVOR A NON-12Z CMC MODEL SOLUTION. ...UPPER TROF SLIDING FROM THE CENTRAL GREAT BASIN INTO THE ARKLATEX ON SUNDAY/MONDAY... ...NORTHERN STREAM ENERGY AFFECTING THE UPPER MIDWEST/GREAT LAKES REGION... ...STRONG BAROCLINIC ZONE/ASSOCIATED SURFACE WAVES... FINAL PREFERENCE: BLEND OF THE 12Z CMC/ECMWF/UKMET FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE ON EARLY SUNDAY...MODELS DEPICT A LONGWAVE TROF EXTENDING FROM THE INTERMOUNTAIN WEST OUT INTO THE GREAT PLAINS. A STRONG BATCH OF ENERGY DIVING SOUTH AND EAST THROUGH THE CENTRAL GREAT BASIN IS FORECAST TO REACH THE FOUR CORNERS REGION BY 14/0000Z. THE 12Z NAM IS CURRENTLY THE QUICKEST SOLUTION WHICH IS ALSO AHEAD OF THE ENSEMBLE MEANS. THE 12Z GFS HAS MADE A SHIFT IN THE EASTWARD DIRECTION TOWARD THE 12Z NAM BUT IS IN CONFLICT WITH THE SLOWER 12Z/06Z GEFS MEAN. THE OTHER 12Z GUIDANCE WHICH HAS ARRIVED...INCLUDING THE 12Z CMC/ECMWF/UKMET STILL AGREE MORE CLOSELY WITH THE 00Z ECMWF ENSEMBLE MEAN ALTHOUGH THIS MEAN IS NOW A HAIR SLOWER. AS THE UPPER TROF DIGS ACROSS THE RED RIVER VALLEY THE 12Z CMC/ECMWF/UKMET CONTINUE TO OFFER A REASONABLE SOLUTION RELATIVE TO THE QUICKER 12Z NAM/GFS. WHILE THE 12Z NAM IS QUICKER WITH THE SOUTHERN STREAM ENERGY...IT IS MUCH SLOWER WITH THE NORTHERN STREAM WHICH LEADS TO A SLOWER PROGRESSION OF THE COLD FRONT. OVERALL...WILL STICK WITH THE AFOREMENTIONED COMBINATION OF THE 12Z CMC/ECMWF/UKMET GIVEN THEIR REASONABLE CONTINUITY AND AGREEMENT WITH THE 00Z ECMWF ENSEMBLE MEAN. ...SHORTWAVE IMPACTING THE PACIFIC NORTHWEST/UPPER INTERMOUNTAIN WEST LATE IN THE PERIOD... FINAL PREFERENCE: BLEND OF THE 09Z SREF/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: LOW THE PROGRESSIVE MID-LATITUDE FLOW REGIME WILL HELP SHIFT A RIDGE ACROSS THE WESTERN U.S. INLAND AHEAD OF THE NEXT BATCH OF ENERGY EXPECTED TO AFFECT THE PACIFIC NORTHWEST/UPPER INTERMOUNTAIN WEST EARLY NEXT WEEK. WHILE THE SPREAD HAS DIMINISHED SINCE YESTERDAY...THERE IS STILL UNCERTAINTY IN THE FORECAST...PARTICULARLY AS THE PACIFIC SYSTEM ADVANCES INLAND. AS THE HEIGHT FALLS MOVE INLAND...THE 12Z NAM IS STILL CARRYING SHORTWAVE ENERGY INTO COASTAL WA/OR WHILE A MAJORITY OF THE OTHER MODELS ARE MUCH FURTHER INLAND. ON THE OTHER SIDE ARE THE 12Z ECMWF/UKMET WHICH ARE MUCH MORE PROGRESSIVE. MODEL CONTINUITY HAS BEEN RATHER POOR SO WILL STAY CONSERVATIVE WITH THE APPROACH OF THIS SYSTEM AND TAKE A BLEND OF ENSEMBLE MEANS UNTIL THE MODELS COME INTO BETTER AGREEMENT. THE WPC PREFERENCE WILL BE A BLEND OF THE 09Z SREF/00Z ECMWF ENSEMBLE MEANS. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER