MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 246 PM EDT MON APR 03 2017 VALID APR 03/1200 UTC THRU APR 07/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/CMC AND ECMWF ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...LOW PRESSURE CROSSING THE GREAT LAKES/NORTHEAST TUES/WED... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS AGREE IN LIFTING THE MAIN SURFACE LOW ASSOCIATED WITH THE MID MS VALLEY CLOSED LOW OFF TO THE NORTHEAST INTO THE GREAT LAKES REGION LATER TONIGHT AND ON TUES...WITH SECONDARY REDEVELOPMENT EXPECTED FARTHER EAST NEAR SOUTHERN NEW ENGLAND BY LATE TUES. THE GUIDANCE AGREES IN ALLOWING THE COASTAL LOW CENTER BECOMING THE DOMINANT LOW BY WED NEAR THE GULF OF MAINE BEFORE IT THEN ADVANCES EAST AND OUT TO SEA. THE 12Z UKMET TENDS TO TAKE ITS SECONDARY LOW PRESSURE WAVE A TAD FARTHER NORTH THAN ANY OTHER MODEL THROUGH THE PERIOD...WITH THE REMAINING MODELS STILL WELL CLUSTERED WITH LOW PRESSURE FOCUSING A TAD FARTHER SOUTH BY COMPARISON. THE LATEST GEFS MEAN AND ECENS MEAN SOLUTIONS FAVOR A NON-UKMET CONSENSUS. ...SHORTWAVE TROUGH SPLITTING OVER THE INTERMOUNTAIN WEST... ...SURFACE LOW OVER THE SOUTHERN PLAINS/MID MS VALLEY TUES/WED... ...LIFTING INTO THE OH VALLEY THROUGH THURS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF CONFIDENCE: AVERAGE THE MODELS CONTINUE TO ADVERTISE A SPLITTING UPPER TROUGH OVER THE INTERMOUNTAIN WEST THAT WILL LEAD TO A MORE DOMINANT SOUTHERN STREAM CLOSED LOW OVER THE CENTRAL/SOUTHERN PLAINS BY LATE TUES AND A WEAKER NORTHERN STREAM COMPONENT OVER THE NORTHERN PLAINS/UPPER MIDWEST. BY WED NIGHT AND THURS...THERE IS GENERAL AGREEMENT THAT A SEPARATE NORTHERN STREAM TROUGH WILL DIG SOUTHEAST ACROSS THE MIDWEST AND THEN PHASE WITH THE SOUTHERN STREAM ENERGY THAT WILL LEAD THE WAY FOR A LARGE AND STRONG CLOSED LOW OVER THE OH VALLEY AND CENTRAL APPALACHIANS THROUGH THURS. THIS WILL DRIVE SURFACE LOW PRESSURE UP ACROSS THE OH VALLEY...WITH SECONDARY REDEVELOPMENT OVER THE CENTRAL MID-ATLANTIC REGION THROUGH THURS. THE 12Z NAM GRADUALLY BECOMES A BIT STRONGER THAN THE MODEL CONSENSUS ALOFT AS THE HEIGHT FALLS MOVE INTO THE OH VALLEY...WHICH MAY BE TIED INTO IT HAVING A SOMEWHAT STRONGER INTRUSION OF NORTHERN STREAM ENERGY. THE REMAINING GUIDANCE IS PRETTY WELL CLUSTERED WITH TIMING AND DEPTH...HOWEVER THERE ARE SOME DIFFERENCES NOTED AT THE SURFACE. THE 12Z NAM/GFS AND THE 12Z CMC BOTH TEND TO HAVE A BIT MORE LOW PRESSURE ELONGATED NORTHWESTWARD BACK ACROSS THE LOWER GREAT LAKES REGION...WITH THE 12Z ECMWF AND 12Z UKMET FOCUSED A TAD FARTHER SOUTH AND EAST BY COMPARISON. THE GEFS MEMBERS OVERALL FAVOR THE GFS-LED CAMP...WITH THE 12Z GFS ALSO IS NOTED TO BE A TAD SLOWER THAN THE ECMWF/UKMET CAMP. FOR NOW...WILL RECOMMEND A COMPROMISE BETWEEN THE SLOWER/NORTHWEST TRACKING CAMP OF THE NAM/GFS/CMC VERSUS THE FASTER ECMWF/UKMET. ...LONGWAVE TROUGH/FRONTAL ZONE OFFSHORE THE NORTHWEST BY WED... ...SURFACE LOW APPROACHING NORTHERN CA/OR BY THURS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z NAM/12Z UKMET/12Z ECMWF...LEAD WAVE 12Z ECMWF...UPSTREAM TROUGH CONFIDENCE: AVERAGE THE LATEST GUIDANCE CONTINUES TO INDICATE A LONGWAVE TROUGH EVOLVING OFFSHORE THE WEST COAST BY WED ALONG WITH A LEAD AREA OF LOW PRESSURE THAT IS EXPECTED TO LIFT NORTHEAST UP ALONG THE WEST COAST BY THURS IMPACTING NORTHERN CA AND COASTAL AREAS OF OR. THE 12Z ECMWF IS A BIT FASTER WITH THE LEAD LOW PRESSURE WAVE...WITH THE 12Z GFS THE SLOWEST. THE 12Z NAM...12Z CMC AND 12Z UKMET ARE CLUSTERED IN BETWEEN...WITH THE CMC APPEARING TO BE A WEAK OUTLIER. GIVEN THE FASTER DEEP LAYER SOUTHWEST FLOW AHEAD OF THE LARGER SCALE UPSTREAM TROUGH...A SOMEWHAT MORE PROGRESSIVE SOLUTION WILL BE PREFERRED. THE BETTER MODEL CLUSTERING IN SUPPORT OF THIS FASTER PROGRESSION WOULD BE WITH THE NAM/UKMET AND ECMWF AT THIS POINT...AND SO A BLEND OF THESE WILL BE PREFERRED WITH THE LEAD WAVE. THE 12Z GFS DOES NOT SHOW AS MUCH OF A CLOSED MID LEVEL CENTER UPSTREAM OVER THE EASTERN PACIFIC BY LATE THURS...COMPARED TO THE 12Z UKMET/CMC AND ECMWF. THE 12Z UKMET THOUGH IS IS LIKELY A TAD TOO DEEP WITH ITS MID LEVEL CENTER. THE 12Z NAM APPEARS TO BE TOO PROGRESSIVE...AND CONSEQUENTLY IS ALSO MORE PROGRESSIVE WITH THE NEXT SURFACE LOW OFFSHORE. THE 12Z ECMWF IS CLOSEST TO THE MODEL CONSENSUS WITH THE NEXT UPSTREAM TROUGH AND ALSO HAS SUPPORT FROM THE LATEST GEFS MEAN AND ECENS MEAN...AND SO A SOLUTION TOWARD THE ECMWF WILL BE PREFERRED WITH THE UPSTREAM ENERGY. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON