MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 238 PM EDT MON MAY 15 2017 VALID MAY 15/1200 UTC THRU MAY 19/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DEEP LOW TRACKING NORTHWARD NEAR THE NEW ENGLAND COAST THROUGH MONDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THERE IS SUFFICIENT AGREEMENT AND CONTINUITY TO HAVE HIGH CONFIDENCE IN A GENERAL MODEL BLEND IN THE REMAINDER OF ITS EVOLUTION THROUGH THE NORTHEAST CORRIDOR/SE CANADA. SHORTWAVE LIFTING OUT OF ROCKIES LATER TONIGHT/EARLY TUES PHASING WITH LINGERING TROF ENERGY OVER S CENT CANADA TUES SHIFTING INTO ONTARIO BY WED ASSOCIATED SURFACE WAVE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/ECMWF/UKMET BLEND CONFIDENCE: AVERAGE GOES-WV MOSAIC DENOTES FIRST INKLINGS OF THE NEXT SHORTWAVE EMERGING FROM SW FLOW OVER THE ROCKIES CURRENTLY OVER SE AZ TOWARD THE FOUR-CORNERS. SURFACE HAS ALREADY RESPONDED WITH A WAVE OVER E CO/NW KS. THIS SHORTWAVE WILL AMPLIFY IN THE LARGER SCALE UPPER LEVEL RIDGING ACROSS THE CENTRAL HIGH PLAINS TONIGHT AND EMERGE TOWARD THE DAKOTAS TOMORROW MORNING. TO BE EXPECTED THERE ARE MINOR DIFFERENCES WITH THE PLACEMENT/INTERACTION WITH THE PRECEDING WAVE AS WELL AS THE MAIN HEIGHT FALLS REMAINING UPSTREAM. ADDITIONALLY...LINGERING SHORTWAVE ENERGY FROM DECAYING UPPER LOW OVER SOUTH CENTRAL CANADA WILL ORIENT NE-SW AND ADVANCE EVENTUALLY PHASING WITH THE WAVE OVER NORTH DAKOTA INTO N MN LATE TUES INTO WED. THE MAIN DIFFERENCES IN THE GUIDANCE ARE RELATED TO THE INTERACTION OF THE CANADIAN WAVE AS WELL AS MAGNITUDE OF UPSCALE CONVECTIVE ENHANCEMENT MAINLY FROM THE 18Z-00Z TIME FROM ON TUES/WED. THE 00Z UKMET/ECMWF BOTH SUGGEST A SLIGHTLY FLATTER AND WEAKER UPSCALE DEVELOPMENT LIKELY DUE TO A SLIGHTLY FASTER/EASTWARD SHIFT OF THE CANADIAN TROF PLACEMENT...PLACING BOTH ON THE EASTWARD SIDE OF THE ENSEMBLE SOLUTION. THE 00Z CMC IS A DISTINCT OUTLIER SUGGESTING A MUCH SLOWER CANADIAN TROF ADVANCEMENT AND IS WELL ON THE NW SIDE OF THE ENSEMBLE CLUSTER. THE 12Z NAM HAS ONCE AGAIN SHIFTED BACK EAST FROM A DEEPER FURTHER NW SOLUTION CLOSER TOWARD THE 12Z UKMET/ECMWF THOUGH NOT AS FAR AS THE 12Z GFS. THE 12Z GFS HAS SHIFTED EASTWARD/FLATTER WITH THIS WAVE AND IS NOW WELL CLUSTERED WITH THE UKMET/ECMWF. AS SUCH WILL FAVOR A 12Z GFS AND 00Z ECMWF/UKMET BLEND WITH THIS SHORTWAVE. 19Z UPDATE: LITTLE CHANGE IN THE 12Z ECMWF/UKMET TO KEEP THEM CLUSTERED WELL WITH THE GFS. THE 12Z CMC WHILE TRENDING A BIT QUICKER; IT CONTINUES TO BE FURTHER NORTH AND WEST ENOUGH TO KEEP INITIAL PREFERENCE OF 12Z GFS/ECMWF/UKMET AT AVERAGE CONFIDENCE. CLOSED LOW OVER S CA SHIFTING ACROSS NM LATE TUES EJECTING CONSOLIDATING AND LIFTING NORTH THROUGH CENTRAL PLAINS WED INTO UPPER MIDWEST THURS WITH ASSOCIATED SURFACE LOW ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM BLEND UP TO 18/06Z 12Z ECMWF/UKMET BLEND AFTERWARD CONFIDENCE: SLIGHTLY ABOVE AVERAGE UP TO 18/06Z SLIGHTLY BELOW AVERAGE THEREAFTER GOES-WV MOSAIC INDICATES MAIN CORE OF MEAN TROF ENTERING S CA ATTM...THIS WAVE IS KICKED EASTWARD INTO THE CENTRAL PLAIN UNDER INFLUENCE OF STRONGER DIGGING CLOSED LOW (SEE SECTION BELOW) FROM THE NW. THIS ALSO SUPPORTS NEGATIVE TILT ORIENTATION OF THE TROF THROUGH THE CENTRAL/SOUTHERN PLAINS WITH A TYPICAL SETUP OF A SLOWER ECMWF/CMC AND FASTER GFS/NAM/UKMET IS NOTED IN THE EVOLUTION BUT PARTICULARLY THE SURFACE PATTERN EARLY WED. THIS SPREAD DOES NOT SEEM TO AFFECT THE LATTER TIME PERIODS AS IT LIFTS INTO THE UPPER MIDWEST WITH EXCEPTION OF THE 12Z NAM. THE 12Z NAM IS A BIT FASTER AND UNCHARACTERISTICALLY EARLY TO SHEAR THE UPPER LEVEL TROF INTO THE NORTHERN GREAT LAKES AND ONTARIO BY THURS. AFTER 18/00Z...THERE IS MILD SPREAD ASSOCIATED WITH THE INTERACTION/TIMING OF A KICKER TROF DIGGING THROUGH CENTRAL CANADA THURSDAY AS WELL. THE SPACING BETWEEN THESE WAVES IS SHORTEST IN SPACING WITH THE 00Z ECMWF AND GREATER IN THE 12Z GFS AND DRAMATICALLY SO IN THE 12Z UKMET. THIS SORT OF TIMING/SPACING DIFFERENCE IS MUCH MORE DIFFICULT TO DISCERN BY DAY 3 TO HAVE A TREMENDOUS AMOUNT OF CONFIDENCE LATE THURS TO 00Z FRI THOUGH THE AGREEMENT LEFT WITH THE 12Z GFS AND THE 00Z ECMWF/CMC IS A GOOD REPRESENTATION OF THE ENSEMBLES AND THE OVERALL TRENDS TO SUPPORT IT AS PREFERENCE (MAINLY AFTER 12Z THURS) AT AVERAGE CONFIDENCE (THOUGH SLIGHTLY ABOVE AVERAGE CONFIDENCE PRIOR TO 18/12Z WITH A NON-NAM BLEND). 19Z UPDATE: THE 12Z ECWMF/UKMET/CMC CONTINUE TO BE QUITE AGREEABLE WITH THE EVOLUTION TO THE 12Z GFS WITH RESPECT TO THE WAVE LIFTING THROUGH THE CENTRAL PLAINS INTO THE UPPER MIDWEST...ENOUGH TO KEEP THE NON-NAM BLEND PRIOR TO 18/06Z AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. HOWEVER...THE TIMING OF THE SHORTWAVE ACROSS S CANADA CONTINUES TO SPREAD WITH THE 12Z ECMWF TRENDING A BIT WEAKER BUT ALSO FASTER...AS SUCH SHEARING THE SOUTHERN STREAM WAVE ACROSS THE N GREAT LAKES THURS. THIS IS MATCHED BY THE 12Z UKMET HAVING SHIFTED FASTER WITH THE TIMING OF THE CANADIAN S/W. THE 12Z CMC PRESENTS A COMPROMISE OF THE ECMWF/GFS SOLUTIONS...BEING FASTER IN THE CANADIAN STREAM BUT WITH BEING A SLIGHT BIT MORE WOUND UP SOME OF THE ENERGY LINGERS IN THE DEFORMATION ZONE ACROSS THE DAKOTAS TOWARD THE UPPER LOW OVER THE ROCKIES LIKE THE SLOWER TO SHEAR GFS. THIS LEADS TO REDUCTION OF CONFIDENCE AND TRADITIONALLY BEING SLOWER THAN THE ECMWF TENDS TO VERIFY NEGATIVELY...SO WHILE A SMALL ADJUSTMENT WILL SUPPORT A TREND TO THE FASTER CANADIAN STREAM AND SUPPORT A 12Z ECMWF/UKMET BLEND AT SLIGHTLY BELOW AVERAGE CONFIDENCE. CLOSED LOW ENTERING PAC NW TUES AND SETTLING IN ACROSS CENTRAL ROCKIES/UINTA WED INTO THURS WEAK SURFACE LOW ACROSS TX/OK PANHANDLES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM BLEND CONFIDENCE: ABOVE AVERAGE TO 18/00Z SLIGHTLY ABOVE AVERAGE AFTERWARD GOES-WV MOSAIC SHOWS AN ELONGATED UPPER LOW ALONG THE WESTERN COAST OF BC CURRENTLY THAT WILL BEGIN TO CONSOLIDATE AS IT DROPS INTO THE PACIFIC NORTHWEST TUES UNDER STRONG MODEL CONSENSUS. THIS CONTINUES THROUGH TO THE INTERMOUNTAIN WEST NEAR S ID/NE NV/N UT BY WED UNTIL THE INNER CORE/UPPER LOW HAS A BIT OF VORTEX BREAKDOWN SHEDDING ENERGY OUTWARD TOWARD AN OUTER RING OF VORTICITY THAT WITH TIME BECOMES A BIT MORE UNSTABLE WITH INCREASED WAVY PATTERN. THE 00Z ECMWF IS A BIT SLOWER TO THIS PROCESS WHICH IS TYPICAL EVEN WITHIN THE ECENS MEMBERS. IN THIS BREAK DOWN THE 12Z NAM IS VERY QUICK TO SHIFT EASTWARD AND EMERGE INTO THE GREAT PLAINS BY 00Z FRI...MUCH TOO QUICK WITH RESPECT TO THE ENSEMBLES AND THE OTHER GUIDANCE. THE REMAINING GUIDANCE SHOWS FAIRLY GOOD PLACEMENT/TIMING OF THE MEAN CENTER OF THE UPPER LOW BUT THE OVERALL ORIENTATION OF THE OUTER RING OF SHORTWAVES IS FAIRLY DRAMATIC WITH THE ECMWF MORE NW-SE BY 00Z FRI COMPARED TO THE W-E ORIENTATION OF THE GFS/CMC/UKMET. OVERALL ENSEMBLE SUITE FAVOR THE SLIGHTLY FASTER SOLUTIONS BUT THE ECMWF IS STILL PLAUSIBLE. AS SUCH A NON-NAM BLEND IS SUPPORTED AT AVERAGE CONFIDENCE (ABOVE AVERAGE PRIOR TO 18/00Z) THOUGH WEIGHTING AWAY FROM 00Z ECMWF BY 00Z FRIDAY. 19Z UPDATE: ISSUES WITH THE 00Z ECMWF HAVE TRENDED A BIT BETTER WITH THE 12Z CYCLE; AND WHILE IT REMAINS THE SLOWEST WITH THE SHORTWAVES AROUND THE INNER CORE OF THE UPPER LOW COMPARED TO OTHER PREFERRED MEMBERS...IT IS MUCH CLOSER TO THE 12Z GFS AND 12Z UKMET...WITH A MORE FAVORABLE ORIENTATION OF THE INNER CORE AFTER VORTEX BREAKDOWN. THE 12Z CMC WHILE UNCHARACTERISTICALLY QUICKER REMAINS WITHIN PROXIMITY/ENSEMBLE SUITE TO KEEP INITIAL PREFERENCE OF NON-NAM BLEND. CONFIDENCE REMAINS ABOVE AVERAGE UP TO 18/00Z BUT WITH THIS AGREEMENT IS INCREASED TO SLIGHTLY ABOVE AVERAGE AFTERWARD. WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/ WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/ GALLINA