MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 248 AM EDT MON MAY 22 2017 VALID MAY 22/0000 UTC THRU MAY 25/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z FINAL MODEL EVALUATION/PREFERENCES AND CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...CLOSED LOW OVER THE UPPER MS VALLEY AND GREAT LAKES TODAY... ...COLD FRONT MOVING ACROSS THE CENTRAL AND EASTERN U.S.... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT WITH THE EVOLUTION OF THIS LARGE SCALE SYNOPTIC SYSTEM. A GENERAL MODEL BLEND WILL BE PREFERRED TO RESOLVE ANY LINGERING SMALLER SCALE DIFFERENCES. FINAL UPDATE: NO CHANGES ...SHORTWAVE CROSSING THE GREAT BASIN/CENTRAL ROCKIES TODAY... ...EJECTING OUT INTO THE SOUTHERN PLAINS ON MON... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE OVERALL THERE REMAINS GOOD MODEL AGREEMENT WITH THIS FEATURE. FINAL UPDATE: NO CHANGES ...SHORTWAVE MOVING INTO MT EARLY MON AROUND THE BACKSIDE OF THE UPPER MS VALLEY AND SOUTHERN CANADA CLOSED LOW... ...ENERGY AMPLIFYING OVER THE MIDWEST AND MOVING TOWARDS THE EAST COAST THROUGH WED... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON NAM BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS CONTINUE TO ADVERTISE A WELL-DEFINED SHORTWAVE DIGGING SOUTHEAST TODAY ACROSS THE MT HIGH PLAINS AND THEN AROUND THE SOUTHWEST FLANK OF THE LARGER SCALE UPPER MS VALLEY/SOUTHERN CANADA CLOSED LOW BY TUES WITH THE ENERGY AMPLIFYING AS IT ARRIVES OVER THE MIDWEST. THIS ENERGY EVENTUALLY HELPS DIG THE TROUGH OVER THE CENTRAL PORTION OF THE COUNTRY BY TUES...WITH THE TROUGH MOVING TOWARDS THE EAST COAST BY LATER WED INTO THURS. THE 0Z NAM CONTINUES TO STAND OUT AS AN OUTLIER WITH THE EVOLUTION OF THIS TROUGH...BEING QUICKER IN CLOSING OFF A DEEP LAYER LOW AND SLOWER PROGRESSING THE TROUGH EASTWARD. THE 12Z UKMET/GEM ALSO HANDLE THE SHORTWAVE ENERGY WITHIN THE TROUGH IN WHAT APPEARS TO BE A LESS LIKELY WAY...WITH THE UKMET A LITTLE TOO SLOW WITH THE OVERALL PROGRESSION AND THE GEM TOO QUICK. WHILE DIFFERENCES DO EXIST BETWEEN THE GFS AND ECMWF SOLUTIONS...THERE OVERALL EVOLUTION ARE PROBABLY THE MOST SIMILAR AMONGST THE GUIDANCE...AND THUS FOR NOW WOULD PREFER TO STICK CLOSE TO A BLEND OF THE 0Z GFS AND 12Z ECMWF SOLUTIONS. FINAL UPDATE: OVERALL HAVE SEEN PRETTY GOOD MODEL CONVERGENCE WITH THE 0Z SUITE. THE 0Z NAM CONTINUES TO STAND OUT AS A BIT OF A SLOW OUTLIER...AND ALSO IS STRONGER WITH THE CLOSING OFF OF A LOW WED/THU. THE 0Z GEM IS A BIT MORE AMPLIFIED WITH THE LARGE SCALE TROUGH AS A WHOLE...BUT NOT REALLY A BIG ENOUGH OUTLIER TO BE DISREGARDED AT THIS TIME. THUS A NON NAM BLEND SHOULD SUFFICE WITH THIS FEATURE. ...SOUTHERN STREAM WAVE ARRIVING ACROSS SOUTHEAST TX ON MON... ...ADDITIONAL SHORTWAVE ENERGY MOVING ACROSS THE GULF COAST/SOUTHEAST MON/TUE... ...SURFACE LOWS TRAVERSING THE GULF COAST INTO THE SOUTHEAST TUES... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 0Z ECMWF/NAM BLEND CONFIDENCE: AVERAGE THE MODELS REMAIN IN AGREEMENT IN BRINGING A SOUTHERN STREAM WAVE ACROSS NORTHERN MEXICO AND EASTWARD INTO TX BY EARLY MON. AS THIS ENERGY...ALONG WITH ADDITIONAL ENERGY DROPPING SOUTHEAST AROUND THE BASE OF THE CENTRAL U.S. TROUGH... INTERACTS WITH A STALLED FRONT NEAR THE SOUTHEAST TX COAST...ONE OR MORE WAVES OF LOW PRESSURE SHOULD DEVELOP ALONG THIS FRONT AND THEN ADVANCE EAST-NORTHEAST...MOVING JUST INLAND ACROSS THE CENTRAL GULF COAST BEFORE THEN LIFTING NORTHEAST UP ACROSS THE INTERIOR SOUTHEAST U.S. AND MID-ATLANTIC IN AN ELONGATED FASHION THROUGH LATE TUES INTO WED. HAVE GENERALLY SEEN SOME CONVERGENCE AMONGST RECENT GFS/ECMWF RUNS...WITH THE GFS TRENDING A BIT SLOWER AND WEAKER WITH THE LEAD WAVE...AND THE ECMWF TRENDING A LITTLE QUICKER. HOWEVER STILL THINK THE GFS IS PROBABLY PUTTING TOO MUCH EMPHASIS ON THE LEAD WAVE AND LOW. APPEARS TO BE SOME CONVECTIVE FEEDBACK ISSUES IN THE GFS TODAY ACROSS THE LOWER MS VALLEY AND SOUTHEAST THAT COULD BE EXACERBATING THIS PROBLEM. FOR NOW WOULD CONTINUE TO PREFER A SOLUTION CLOSER TO THE MORE CONSISTENT ECMWF/UKMET. THE 0Z NAM IS MORE SIMILAR TO THE GFS...AND THE 12Z GEM IS OVERALL STRONGER AND FURTHER INLAND WITH THE SYSTEM AND DOES NOT HAVE MUCH SUPPORT AT THIS TIME. FINAL UPDATE: THE GENERAL TREND HAS BEEN FOR A SLIGHTLY QUICKER LEAD WAVE TODAY INTO TUESDAY...SIMILAR TO WHAT THE GFS HAD BEEN ADVERTISING. HOWEVER STILL THINK CONVECTIVE FEEDBACK ISSUES IN THE GFS ARE RESULTING IN TOO MUCH EMPHASIS BEING PLACED ON THIS LEAD WAVE. THINK THE 0Z UKMET MAY BE A BIT SLOW EJECTING THE TRAILING ENERGY EASTWARD...WITH THE 0Z GEM A TAD TO AMPLIFIED WITH THE TROUGH ALLOWING FOR A FURTHER INLAND TRACK. PREFER TO STICK WITH A SOLUTION CLOSER TO THE 0Z ECMWF/NAM WITH THE HANDLING OF THE STRUNG OUT AREA OF LOW PRESSURES MOVING ACROSS THE SOUTHEAST AND OFF THE MID ATLANTIC (ALTHOUGH THE ECMWF MAY VERY WELL BE A TAD TOO FAR INLAND WITH THE LOW). AS MENTIONED ABOVE THE NAM FALLS OUT OF PREFERENCE BY LATER WEDNESDAY AS THE LONGWAVE TROUGH BEGINS TO MOVE TOWARDS THE EAST COAST. ...UPPER TROUGH MOVING ACROSS THE PACIFIC NORTHWEST ON TUES... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE A RATHER STRONG UPPER TROUGH IS EXPECTED TO BE DIGGING SOUTHEAST TOWARD THE PACIFIC NORTHWEST ON TUES FROM THE GULF OF AK. THIS ENERGY WILL ADVANCE INLAND AND CROSS THE NORTHERN ROCKIES ON WED. MODEL CLUSTERING IS GOOD ENOUGH WITH THIS SYSTEM TO RECOMMEND A GENERAL MODEL BLEND FOR THE TIME BEING. FINAL UPDATE: NO CHANGES WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/ WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/ CHENARD