MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 245 PM EDT SAT APR 25 2015 VALID APR 25/1200 UTC THRU APR 29/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DEEP TROUGH/CLOSED LOW DIGGING INTO SOUTHWEST U.S. THIS WEEKEND LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS BY MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z NAM...12Z ECMWF...12Z UKMET CONFIDENCE: SLIGHTLY ABOVE AVERAGE REGARDING THE 700 MB REFLECTION THAT MOVES INTO THE SRN PLAINS MONDAY MORNING...THE 12Z GFS IS NORTH OF THE LATEST DETERMINISTIC/ENSEMBLE CONSENSUS...AND THE 12Z GFS LIKELY HAS CONVECTIVE FEEDBACK OVER SERN TX ON MON. THE 12Z ECMWF ADJUSTED SLIGHTLY NORTH FROM ITS 00Z RUN AND THE 12Z UKMET REMAINS SIMILAR TO ITS PREVIOUS RUN...WITH THE NAM NEAR THE MIDDLE TO JUST NORTH OF THE CONSENSUS. GIVEN WOBBLES ARE LIKELY WITH FUTURE RUNS...THIS AGREEMENT IS PRETTY GOOD BUT IT SEEMS CLEAR TO RULE OUT THE 12Z GFS...IN FAVOR OF THE 12Z NAM/ECMWF/UKMET GIVEN THEIR BLENDED PLACEMENT CLOSE TO THE AGREEABLE ENSEMBLE MEANS 700-500 MB HEIGHT CENTROID THROUGH TUE. THIS MODEL AGREEMENT IS ALSO TRUE REGARDING LIKELY SURFACE LOW DEVELOPMENT NEAR THE CNTRL GULF COAST. SOUTHERN STREAM TROUGH TRAVELING FROM THE MISS VALLEY TO THE MID-ATLANTIC THROUGH TONIGHT ASSOCIATED SURFACE LOW CROSSING THE REGION ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THE SYNOPTIC SCALE DETAILS OF THIS SYSTEM WITH THE LATEST 12Z DETERMINISTIC MODELS COMING INTO AGREEMENT ON A WEAKER REMNANT SURFACE LOW NEAR THE SRN APPALACHIANS SUN MORNING AS SEEN WITH THE LATEST ENSEMBLE GUIDANCE. DEEP CLOSED LOW REMAINING ACROSS NEW ENGLAND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 12Z CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE OUTSIDE OF THE 12Z CMC...WHICH IS SLOWER MON NIGHT WITH A SHORTWAVE PINWHEELING AROUND THE SLOWLY DEPARTING CLOSED LOW CENTERED OFF OF NEW ENGLAND...THE MODELS SHOW REASONABLE AGREEMENT HERE. DETAIL DIFFERENCES WITH INDIVIDUAL SHORTWAVES ARE BEST BLENDED WITH A NON 12Z CMC MODEL CONSENSUS. TROUGH/FRONT CROSSING THE NORTHERN PLAINS THROUGH MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF CONFIDENCE: AVERAGE BLENDING THE GFS/ECMWF REPRESENTS THE MIDDLE OF THE LATEST MODEL SPREAD...FALLING CLOSE IN LINE WITH THE ENSEMBLE MEANS. THE 12Z NAM APPEARS FLATTEST/WEAKEST ALOFT WITH THIS FEATURE. TROUGH/FRONT APPROACHING THE PACIFIC NORTHWEST BY TUE MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 12Z UKMET BLEND CONFIDENCE: AVERAGE THE 12Z UKMET IS SIGNIFICANTLY SLOWER WITH A SHORTWAVE APPROACHING THE PACIFIC NORTHWEST EARLY ON TUE...WHILE THE REMAINING DETERMINISTIC MODELS AND ENSEMBLE MEANS ARE FASTER WITH REASONABLE AGREEMENT. THE 12Z ECMWF HAS BEEN WOBBLING ABOUT A SIMILAR TIMING OVER ITS PAST 4 RUNS...WITH THE MOST RECENT 12Z ECMWF TRENDING A BIT SLOWER...BUT NOT TO THE EXTENT OF THE UKMET. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO