MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 245 PM EDT SUN APR 13 2014 VALID APR 13/1200 UTC THRU APR 17/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 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. ...SURFACE WAVE CROSSING THE LOWER GREAT LAKES THIS AFTERNOON... ...WARM FRONTAL ZONE LIFTING INTO THE NEW ENGLAND... FINAL PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: HIGH A WEAK IMPULSE MOVING TOWARD THE LOWER GREAT LAKES THIS MORNING WILL LIFT A SUBTLE AREA OF LOW PRESSURE INTO SOUTHERN ONTARIO BY THIS EVENING. SOUTHWESTERLY FLOW ALOFT SHOULD ALLOW THE ASSOCIATED WARM FRONT TO RISE WELL INTO NEW ENGLAND AS WARM ADVECTION CONTINUES ACROSS THE EASTERN U.S. WATER VAPOR IMAGERY AT THIS HOUR SUGGESTS THE 00Z CMC MAY BE TOO QUICK WHICH SEEMS TO BE THE THEME OF THIS MODEL IN RECENT DAYS. HOWEVER...IT APPEARS TO HAVE RECOVERED OFF THIS AS THE 12Z CMC LOOKS MORE IN LINE WITH OTHER GUIDANCE. A GENERAL MODEL COMPROMISE WILL SUFFICE HERE. ...INITIAL HEIGHT FALLS MOVING INTO THE LOWER MO VALLEY TONIGHT... FINAL PREFERENCE: MODEL COMPROMISE BETWEEN THE 12Z CMC/ECMWF/UKMET FORECAST CONFIDENCE: AVERAGE A COMPLEX ARRAY OF SHORTWAVES MOVING THROUGH THE SOUTHERN/CENTRAL HIGH PLAINS THIS MORNING HAS HELPED SPREAD AN EXPANSIVE REGION OF PRECIPITATION TO THE CENTER OF THE CONUS. MODELS DISAGREE ON THE TIMING OF THIS SYSTEM VERY EARLY IN THE PERIOD WITH THE 12Z NAM/GFS AND 12Z GEFS/09Z SREF MEANS BEING QUICKER THAN THE REMAINING GUIDANCE. CURRENT RADAR AND WATER VAPOR TRENDS INDICATE THE NCEP GUIDANCE MAY BE A HAIR TOO FAST WITH THE EVOLUTION OF THIS SYSTEM SO WILL LEAN ON A 12Z CMC/ECMWF/UKMET MODEL COMPROMISE. ...NORTHERN/SOUTHERN STREAM SYSTEMS MOVING THROUGH THE MS RIVER VALLEY LATE MONDAY... ...ASSOCIATED COLD FRONT/FRONTAL WAVES... FINAL PREFERENCE: BLEND OF THE 12Z CMC/ECMWF FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE MODELS AGREE THAT A NORTHERN AND SOUTHERN STREAM SYSTEM WILL MIGRATE EASTWARD HELPING DRIVE A STRONG COLD FRONT EASTWARD REACHING THE EAST COAST BY TUESDAY. THE 12Z NAM CONTINUES TO BE THE SLOWEST MODEL EJECTING THE SYSTEM TOWARD THE EAST WHILE THE 12Z GFS/GEFS MEAN ARE A HAIR FASTER. BY 16/0000Z...THE 12Z UKMET BEGINS TO CATCH UP WITH THE 12Z GFS WITH THE SOUTHERN STREAM ENERGY ACROSS THE DEEP SOUTH WHICH NOW MAKES THE 12Z CMC/ECMWF SOME OF THE SLOWER MODELS. THE 12Z CMC/ECMWF CONTINUE TO AGREE WELL WITH THE ENSEMBLE MEANS INCLUDING THE 09Z SREF/00Z ECMWF ENSEMBLE MEANS. WILL FAVOR A COMBINATION OF THESE MODELS WITH THIS SYSTEM. ...MEAN TROF SETTING UP FROM THE PACIFIC NORTHWEST TO THE NORTH-CENTRAL CONUS EARLY/MID NEXT WEEK... FINAL PREFERENCE: BLEND OF THE 06Z GEFS/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: LOW THE PROGRESSIVE MID-LATITUDE PATTERN WILL CONTINUE AS ANOTHER PACIFIC SYSTEM MOVES INTO THE PACIFIC NORTHWEST/UPPER INTERMOUNTAIN WEST EARLY NEXT WEEK. THERE IS SPREAD WITH WHERE THE INITIAL ENERGY MOVES INLAND WITH THE 12Z UKMET/ECMWF/ECMWF ENSEMBLE MEAN BEING NORTH OF THE OTHER GUIDANCE. MODELS CONTINUE TO DIVERGE AS THE SYSTEM TRACKS INLAND AS THE 12Z GFS CARRIES MORE OF THE SHORTWAVE ENERGY TOWARD THE CENTRAL GREAT BASIN WHILE A MAJORITY OF THE OTHER GUIDANCE DEPICT A FLATTER SOLUTION. THE FORECAST CONTINUES TO BECOME MORE NEBULOUS AS A LOBE OF ENERGY FROM CENTRAL CANADA DROPS DOWN TOWARD THE NORTH-CENTRAL CONUS. SOLUTIONS SHOW A LOT OF VARIABILITY FROM RUN-TO-RUN WHICH MAKES THIS A LOW CONFIDENCE FORECAST. WILL FOLLOW THE ENSEMBLE MEANS HERE UTILIZING THE MORE NORTHWARD 00Z ECMWF ENSEMBLE MEAN AND COMBINING IT WITH THE SOUTHERN 12Z GEFS MEAN. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER