MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1238 AM EDT SAT APR 16 2016 VALID APR 16/0000 UTC THRU APR 19/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ UPPER LOW CURRENTLY OVER THE LOWER MISSISSIPPI VALLEY...SHIFTING EAST AS PART OF A REX BLOCK THROUGH SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE MODELS CONTINUE STRONG CONGRUENCE WITH THE REMAINING REMNANTS OF THE UPPER LOW SHEARING ACROSS THE SOUTHEAST INTO THE WESTERN ATLANTIC SAT/SUN WITH THE REMAINING TROF DROPPING SOUTHEAST ACROSS FLORIDA SUN/MON. AN OPERATIONAL MODEL BLEND IS PREFERRED AT ABOVE AVERAGE CONFIDENCE. TROUGH/FRONT MOVING INTO THE NORTHEAST ON LATE MON/TUES...SURFACE CYCLOGENESIS OFF SE NEW ENGLAND TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM BLEND CONFIDENCE: AVERAGE ENERGY LIFTING OUT OF THE NORTHERN PLAINS SHIFTS EASTWARD UNDER STRONG WESTERLY CANADIAN FLOW AND IS AHEAD OF A STRONGER NORTHERN STREAM SHORTWAVE THAT AMPLIFIES OVER NEW ENGLAND MONDAY NIGHT INTO TUESDAY. THE 00Z NAM IS A BIT SLOWER TO DRAW THE ENERGY OUT OF THE NORTHERN PLAINS AND THEREFORE IS MUCH CLOSER PROXIMITY TO THE DIGGING WAVE...HELPING TO DRAW IT FASTER EAST DIGGING THE OVERALL TROF EARLIER THAN MUCH OF THE GUIDANCE. OTHERWISE THE OPERATIONAL GUIDANCE IS FAIRLY WELL TIMED WITH THE UPPER TROF AND THEREFORE ALIGNED WITH THE SURFACE TROF AND PRESENTS A WEAK SURFACE CYCLOGENESIS SOUTHEAST OF NEW ENGLAND BY THE END OF THE FORECAST PERIOD WITH SOME MORE AGGRESSIVE THAN OTHERS (ECMWF). THE 00Z GFS IS A BIT LESS AMPLIFIED BY TUESDAY WITH THE WEAKEST SURFACE REFLECTION...BUT NOT OUT OF THE REALM OF POSSIBILITY BY DAY 3. AS SUCH WILL SUPPORT A NON-NAM BLEND AT AVERAGE CONFIDENCE. INTERMOUNTAIN WEST/PLAINS TROUGH AND CUTOFF UPPER LOW ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/12Z ECMWF BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE OVERALL THE MODELS MASS FIELDS CONTINUE TO BE IN VERY GOOD AGREEMENT IN THE LARGE SCALE PARTICULARITY THROUGH ABOUT 50-60HRS...BUT AS THE OVERALL CYCLONE LOSES STRENGTH...INTERNAL SHORTWAVES BEGIN TO DOMINATE THE MASS FIELDS DRIVEN ON SMALLER SCALE FEEDBACK FROM CONVECTIVE DEVELOPMENT THAT BECOMES PARTICULARLY DIFFICULT TO DIAGNOSE/FORECAST WITH SIGNIFICANT CONFIDENCE. THIS WILL SUPPORT UTILIZING THE ENSEMBLE MEANS MAINLY INTO DAY 3. THE 00Z NAM IS MOST OUT OF PHASE WITH THE EVOLUTION/SHAPE WITH A STRONGER TROUGHING/ELONGATION INTO THE NORTHERN PLAINS LIKELY DUE TO THE FASTER NORTHERN STREAM TROUGHING OVER NEW ENGLAND (LEADING TO STRONGER RIDGING OVER MANITOBA/ONTARIO) WHICH WAS NOT A FAVORED SOLUTION. THE 00Z GFS AND 12Z ECMWF BOTH INDICATE SOME OF THE AFOREMENTIONED INTERNAL WAVE DIFFERENCES BUT ON A WHOLE ARE GOOD REPRESENTATIONS OF THE 18Z GEFS MEAN/12Z ECENS MEAN AND 12Z CMCE. THE GFS/GEFS IS A BIT FASTER AND NORTH...WHILE THE ECMWF/ECENS MEAN ARE SLOWER/FURTHER SOUTH. THE 12Z UKMET IS PROBABLY THE CLOSEST TO THIS MIDDLE GROUND SOLUTION...BUT DOES HAVE ITS ISSUES AS WELL. AS SUCH WILL FAVOR A 00Z GFS/12Z ECMWF BLEND TO BEST REPRESENT THE 18Z GEFS/12Z CMCE/12Z ECENS MEANS. GIVEN THE SPREAD IS NOT TERRIBLY DIFFERENT...CONFIDENCE REMAINS SLIGHTLY ABOVE AVERAGE OVERALL. PLEASE NOTE: THESE MINOR DIFFERENCES IN THE PLACEMENT/MAGNITUDE OF INDIVIDUAL SHORTWAVE IMPULSES AND CONVECTIVE EVOLUTION DO CONTINUE TO RESULT IN SOME QPF DIFFERENCES. PLEASE REFER TO THE LATEST QPFPFD FOR MORE DETAILS AND SPECIFIC PREFERENCES. APPROACHING UPPER LOW OFF WEST COAST BY TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS AND 12Z UKMET/ECMWF BLEND CONFIDENCE: AVERAGE ENSEMBLE SPREAD CONTINUES TO REDUCE AND SUPPORT MAINTAINING A SMALL CUT-OFF LOW JUST WEST OF CA BY TUESDAY BEING FAIRLY CONSISTENT IN PLACEMENT OF THE WAVE OVERALL FOR THE LAST FEW CYCLES. THE 00Z NAM IS WELL SOUTH OF THE BETTER CLUSTER WHILE THE 12Z CMC IS FASTER AND HAS OPENED BACK UP. OTHERWISE...THE 00Z GFS AND 12Z ECMWF/UKMET ALL PRESENT THE ENSEMBLE MEANS WELL AND WILL SUPPORT THEM AS THE BLEND AT AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA