MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 251 PM EDT THU APR 16 2015 VALID APR 16/1200 UTC THRU APR 20/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. KICKER SHORTWAVE REACHING THE N-CNTRL U.S. SAT NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z ECMWF/12Z GFS COMPROMISE CONFIDENCE: SLIGHTLY BELOW AVERAGE THE GFS HAS MAINTAINED GOOD RUN TO RUN CONTINUITY WITH THIS FEATURE THROUGH 00Z/20...BUT THE REMAINING DETERMINISTIC GUIDANCE HAS TRENDED A BIT DEEPER WITH THE ENSEMBLES FOLLOWING SUIT SINCE YESTERDAY. THE 12Z GFS/00Z ECMWF FORM A GOOD COMPROMISE...TOWARD THE MIDDLE TO DEEPER SIDE OF THE ENSEMBLE SPREAD WITH THE 12Z UKMET/CMC A BIT SLOWER/WEAKER WITH THE CORE OF THIS FEATURE. THE 12Z ECMWF HAS SPED UP A LITTLE AND IS A BIT STRONGER THAN PREFERRED WITH THE 850 MB LOW TRACKING ACROSS THE LOWER NRN PLAINS SAT NIGHT. CONFIDENCE IS REDUCED DUE TO ABOVE AVERAGE ENSEMBLE SPREAD AND ADJUSTMENTS MADE IN THE INDIVIDUAL MEMBER SPREAD SINCE YESTERDAY RESULTING IN SOME POSSIBLE INSTABILITY IN SOLUTIONS GOING FORWARD...BUT WILL STICK WITH THE PREVIOUS PREFERENCE AT THIS TIME. ENERGY ALOFT DROPPING DOWN THE CA COAST SAT/SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 12Z CMC COMPROMISE CONFIDENCE: AVERAGE THROUGH 00Z/20...THE MODELS SHOW SOME SLIGHTLY DIFFERENT EVOLUTIONS THROUGH TIME BUT END UP IN NEARLY THE SAME PLACE AND INTENSITY OFF OF THE CA COAST WITH THIS FEATURE. HOWEVER...THE 12Z CMC IS FAR ENOUGH OFFSHORE RELATIVE TO THE REMAINING GUIDANCE WITH ENERGY AT 500 HPA TO DROP SOUTHWARD AS RIDGING BUILDS NEAR VANCOUVER ISLAND. CLOSED LOW EMERGING INTO THE CNTRL PLAINS SAT/SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/ECMWF/CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE GUIDANCE GENERALLY GOOD AGREEMENT WITH THIS SYSTEM BUT THE 00Z ECMWF IS THE MOST CLOSELY MATCHED TO THE ENSEMBLE MEANS...TOWARD THE SRN END OF THE DETERMINISTIC MODEL SPREAD...WITH THE MAIN VORT MAX WEAKENING INTO THE CNTRL PLAINS THROUGH SUN. THE GFS IS THE NEXT CLOSEST MATCH. THE 12Z ECMWF ADJUSTED NORTH A BIT AS THE SYSTEM REACHES THE PLAINS...AND THE 12Z CMC APPEARS SIMILAR TO THE GFS/ECMWF. GIVEN THE GROWING CONSENSUS...THE PREFERENCE WILL BE REFLECT THIS SMALL ADJUSTMENT. DIFFERENCES WITH A KICKER SYSTEM TO THE NORTH START TO IMPACT THE REMNANT CLOSED LOW INTO THE PLAINS BY THE END OF THE WEEKEND...BUT OTHERWISE THERE IS NO SIGNIFICANT DIFFERENCE THROUGH 00Z/19. SHORTWAVE CROSSING NEW ENGLAND SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z NAM...12Z GFS...12Z ECMWF COMPROMISE CONFIDENCE: ABOVE AVERAGE THE NAM/GFS/ECMWF LINE UP WELL WITH EACH OTHER AND THE ENSEMBLE MEANS ALTHROUGH THE ECMWF IS SLIGHTLY LESS DEFINED WITH THE LOW LEVEL LOW COMPARED TO THE NAM & GFS. THE 12Z UKMET/CMC ARE A BIT DEEPER WITH THE SHORTWAVE TROUGH AND ARE LESS SUPPORTED BY THE ENSEMBLE MEANS AT THIS TIME. SHORTWAVE CROSSING NRN NEW ENGLAND FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE OUTSIDE OF MINOR TIMING/AMPLITUDE DIFFERENCES...THE GUIDANCE IS IN GOOD AGREEMENT WITH THESE FEATURES. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO