MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 235 PM EDT SUN JUN 19 2016 VALID JUN 19/1200 UTC THRU JUN 23/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/CMC/ECMWF AND MODEL PREFERENCES ...SHORTWAVE MOVING FROM THE NORTHERN PLAINS TO THE UPPER MIDWEST TODAY... ...LARGER SCALE TROUGH DIGGING TOWARD THE GREAT LAKES AND NORTHEAST ON TUES... ...COLD FRONT ADVANCING TOWARD THE GREAT LAKES ON MON AND THE EAST COAST ON TUES... PREFERENCE: GFS/ECMWF BLEND CONFIDENCE: AVERAGE MODEL AGREEMENT WITH RESPECT TO THE SHORTWAVE IS GOOD INITIALLY AS IT SKIRTS THE NORTHERN PLAINS AND UPPER MIDWEST THROUGH THIS EVENING. AS THE WAVE MOVES NORTHEAST TOWARD JAMES BAY TONIGHT, THE NAM APPEARS TO WEAKEN IT TOO MUCH AND BECOMES UNDER AMPLIFIED WITH THE WAVE INTO MONDAY. THIS APPEARS TO TRANSLATE INTO A SLOWER TIMING FOR THE SURFACE COLD FRONT ON MONDAY ACROSS THE GREAT LAKES IN THE NAM RELATIVE TO THE GFS, WHICH IS SIMILAR TO THE ECMWF. BY LATE MONDAY THE PROGRESSION OF THIS COLD FRONT WILL BECOME GOVERNED MORE BY THE LARGE SCALE TROUGH DIGGING SOUTH OF HUDSON BAY INTO THE GREAT LAKES. THE NAM IS SLIGHTLY MORE AMPLIFIED WITH THIS TROUGH, WHICH SEEMS TO CAUSE ITS SURFACE COLD FRONT OVER THE OHIO VALLEY TO CATCH UP SOMEWHAT TO THE GFS/ECMWF/UKMET IN TERMS OF TIMING. WILL PREFER A BLEND OF THE GFS AND ECMWF THROUGH 00Z TUES. AS THE TROUGH CONTINUES TO AMPLIFY ACROSS THE GREAT LAKES/NORTHEAST INTO TUESDAY, THE GFS APPEARS A BIT TOO FAST, BUT HAS BEEN JOINED BY THE UKMET AND CMC IN ITS FASTER SOLUTION. THE NAM AND ECMWF CONTINUE TO SHOW A SOMEWHAT SLOWER SOLUTION, WHICH IS LENT SOME SUPPORT BY THE 12 GEFS MEAN WHICH IS SLIGHTLY SLOWER THAN THE DETERMINISTIC GFS. GIVEN THE FASTER TREND AMONG THE UKMET/CMC, DO NOT WANT TO DISCOUNT THIS FASTER SOLUTION, THUS WILL ADJUST THE PREFERENCE AFTER 00Z TUES TO ALSO BE A GFS/ECMWF BLEND. ...UPPER LOW DEVELOPING OFF THE EAST COAST ON SUN... PREFERENCE: GFS/NAM/UKMET BLEND CONFIDENCE: AVERAGE AN UPPER-LEVEL LOW IS FORECAST TO DEVELOP ON SUN BETWEEN THE U.S. EAST COAST AND BERMUDA AS A RESULT OF SHORTWAVE ENERGY DIGGING SOUTH AND AMPLIFYING. THIS WILL HELP TO CONSOLIDATE AN ELONGATED AREA OF SURFACE LOW PRESSURE NEAR AND TO THE SOUTHWEST OF BERMUDA...AND GRADUALLY DRIVE IT NORTH AND EVENTUALLY NORTHEAST AHEAD OF STRONGER HEIGHT FALLS MOVING INTO THE NORTHEAST U.S. THE NAM AND GFS ARE IN GOOD AGREEMENT WITH THE MODEL CONSENSUS AS THE UPPER LOW DEVELOPS AND MOVES WESTWARD AND THEN NORTHWARD. AS THE UPPER LOW COMES UNDER THE INFLUENCE OF THE DEVELOPING TROUGH OVER THE GREAT LAKES/NORTHEAST BY TUESDAY, THE NAM AND GFS ARE A BIT SLOWER TO OPEN THE LOW INTO A WAVE AND MOVE IT NORTH, RELATIVE TO THE ECMWF, WHICH CONTINUES TO MOVE THE WAVE NORTHWARD MORE QUICKLY THAN ANY OTHER DETERMINISTIC SOLUTION. THE UKMET AND CMC CONTINUE TO SUPPORT THE SLOWER SOLUTION. THIS, WILL STICK WITH A GFS/NAM/UKMET PREFERENCE. ...UPPER-LEVEL LOW OFF THE NORTHWEST ON SUN/MON... ...ENERGY ADVANCING DOWNSTREAM TO THE NORTHERN PLAINS TUES/WED... PREFERENCE: GFS/ECMWF BLEND CONFIDENCE: AVERAGE A VORTICITY MAX LEFT BEHIND WHEN THE INITIAL UPPER LOW LIFTS EAST WILL INTERACT WITH A SHORTWAVE MOVING SOUTH FROM THE GULF OF ALASKA TO FORM A BROAD AND ELONGATED UPPER TROUGH WITH TWO DISTINCT UPPER LOW CENTERS OFF THE WEST COAST TODAY INTO MON. ONE CENTER FOCUSED JUST OFF THE PACIFIC NORTHWEST SUN NIGHT WILL EVENTUALLY OPEN INTO A SHORTWAVE AND MOVE EAST MON ACROSS THE PACIFIC NORTHWEST AND THEN QUICKLY DOWNSTREAM ACROSS THE NORTHERN ROCKIES AND INTO THE NORTHERN PLAINS TUES AND WED IN RESPONSE TO STRONGER UPSTREAM HEIGHT FALLS ENCROACHING ON THE AREA. THE EJECTING SHORTWAVE WILL FOCUS LOW PRESSURE ONCE AGAIN OUT ACROSS THE PLAINS ALONG WITH A COLD FRONT. THE NAM AND UKMET ARE THE QUICKEST MODELS TO MOVE THE SHORTWAVE INTO THE PACIFIC NORTHWEST AND ACROSS THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS, WHILE THE GFS/ECMWF ARE SLOWER BUT IN GOOD AGREEMENT WITH EACH OTHER. THE 00Z ECMWF ENS MEAN/12Z GEFS MEAN ALSO SUPPORT THE SLOWER GFS/ECMWF SOLUTION. AS A SURFACE LOW DEVELOPS OVER EASTERN WYOMING TUES AFTERNOON IN RESPONSE TO THE SHORTWAVE, THE SAME TRENDS HOLD, WITH THE NAM MOVING THE LOW EAST INTO THE PLAINS MORE QUICKLY AND THE GFS/ECMWF REPRESENTING A SLOWER SOLUTION. WILL PREFER THE GFS/ECMWF AT THIS TIME. ....TROUGH/UPPER LOW OFF THE PACIFIC NORTHWEST COAST ON WED... PREFERENCE: ECMWF/GFS BLEND (MORE WEIGHT TOWARD THE ECMWF) CONFIDENCE: AVERAGE THE MODELS INDICATE A LARGER SCALE TROUGH AND ASSOCIATED UPPER LOW DIGGING SOUTHEAST OFFSHORE BRITISH COLUMBIA AND TOWARD THE NORTHWEST U.S. BY WED. THE NAM AND GFS APPEAR TO MOVE THE SYSTEM TOWARD THE COAST A LITTLE MORE QUICKLY RELATIVE TO THE ECMWF, WHILE THE UKMET HAS SPED UP SLIGHTLY FROM ITS PREVIOUS RUN, NOW SHOWING A TIMING SIMILAR TO THE GFS. THE CMC REMAINS THE SLOWEST SOLUTION. THE GEFS MEAN CONTINUES TO SUPPORT A SOLUTION SLIGHTLY SLOWER THAN THE DETERMINISTIC GFS. THUS WILL CONTINUE THE PREFERENCE FOR SOMETHING A BIT SLOWER THAN THE GFS -- WILL RECOMMEND A BLEND OF THE ECMWF/GFS, WITH MORE WEIGHT TOWARD THE ECMWF. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RYAN