MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1250 PM EDT TUE JUN 03 2014 VALID JUN 03/1200 UTC THRU JUN 07/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ================================================== 12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES ================================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ================================================== ...EASTERN U.S... ...INCLUDING POTENT GREAT PLAINS SHORTWAVE EMERGING THIS EVENING... PREFERENCE: 12Z GFS...SUPPORTED BY 00Z UKMET/CANADIAN THE QUASI-PERMANENT TROUGH OVER THE NORTHEAST U.S. WILL SEE A MERGER OF TWO BROAD UPPER LOW CENTERS THROUGH THURSDAY. A LOW AMPLITUDE BUT POTENT SHORTWAVE WILL EJECT ACROSS THE CENTRAL PLAINS STATES TODAY AND ROUND THE BASE OF THE NORTHEASTERN TROUGH BY THURSDAY...PRODUCING A SURFACE LOW AND FRONTAL WAVE ALONG THE NEW ENGLAND COAST. THE OPERATIONAL MODELS HAVE BEEN A LITTLE UNSTEADY FROM RUN TO RUN...WITH FEEDBACK FROM CONVECTION OVER THE MIDWEST AND THE OHIO VALLEY REFLECTED IN THE MODEL SURFACE FORECASTS. THE 00Z ECMWF APPEARED TO SUFFER FROM FEEDBACK...AND PREDICTED A DEEPER SURFACE LOW MOVING ALONG MUCH MORE QUICKLY THAN CONSENSUS. ENSEMBLE SURFACE LOW PLOTS SHOW SOME CONVERGENCE TOWARD THE TRACK SEEN IN THE GFS...OR JUST SLIGHTLY NORTH. THE GFS HAS BEEN FAIRLY CONSISTENT AT THE SURFACE DATING BACK TO THE 02/12Z CYCLE...AND ITS UPPER LEVEL FORECAST SEEMS MORE REASONABLE NOW...HAVING SLOWED AND DEEPENED TO BETTER RESEMBLE THE ECMWF ENSEMBLE MEAN. THE GFS IS ALSO SUPPORTED RATHER WELL BY THE 00Z UKMET AND CANADIAN. THE NAM HAS DEMONSTRATED POOR RUN TO RUN CONTINUITY. ALTHOUGH THE SURFACE FORECAST APPEARS IMPROVED IN THE 12Z NAM...ITS UPPER LEVEL FORECAST FEATURES A NUMBER OF SHORTWAVE DEPTH AND TIMING AT ISSUES THAT EVENTUALLY LEAD TO A SLOWER AND DEEPER TROUGH IN THE NORTHEAST BY DAY 3. ...WESTERN SHORTWAVE REACHING THE CENTRAL/NORTHERN PLAINS THURSDAY MORNING... PREFERENCE: BLEND OF 12Z GFS WITH 00Z ECMWF/UKMET THIS TROUGH WAS ENTERING THE NORTHERN ROCKIES TODAY...AND WILL CONTINUE EASTWARD AS A RELATIVELY LOW AMPLITUDE WAVE...HELPING TO FOSTER CONVECTION AS IT GOES. THE NAM IS FLAT AND VERY FAST WITH THIS WAVE...AND IS DISCOUNTED BY 05/12Z. THE GLOBAL MODELS SHOW GENERAL AGREEMENT...THOUGH THE 00Z CANADIAN WAS SOMEWHAT SLOW AND DEEP RELATIVE TO THE OTHER THREE. ...TROUGHING OVER THE WEST THU/FRI... ...FRONT DROPPING INTO THE NORTHERN ROCKIES... PREFERENCE: BLEND OF 00Z ECMWF/UKMET THE NAM APPEARED TOO FAST IN THE NORTHERN STREAM...AND WAS TOO WEAK IN THE SOUTHWEST...INDICATING MUCH WARMER HEIGHTS THAN THE CONSENSUS FORECAST. THE GLOBAL MODELS SHOWED FAIR AGREEMENT...AND THE GFS IMPROVED UPON ITS 00Z RUN BY LOWERING HEIGHTS OVER THE SOUTHWEST. IN THE NORTHERN STREAM...THERE IS GENERAL AGREEMENT ALOFT...THOUGH THE 00Z CANADIAN WAS SOMEWHAT SLOWER. IN THE LOW LEVELS THE CANADIAN WAS SLOW...THE GFS FAST...AND THE ECMWF/UKMET BEST FIT THE ENSEMBLE CONSENSUS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BURKE