MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 305 PM EDT TUE JUL 26 2016 VALID JUL 26/1200 UTC THRU JUL 30/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z PRELIMINARY MODEL EVALUATION AND PREFERENCES ...MULTIPLE SHORTWAVES MOVING EAST OVER THE SOUTHWEST RIDGE...DROPPING SOUTHEAST INTO A DEVELOPING EAST COAST TROUGH... ...SHORTWAVE ENERGY MOVING NORTH OUT OF THE GULF OF MEXICO...ALSO BEING ABSORBED INTO THE EAST COAST TROUGH... PREFERENCE: CONSENSUS OF THE 12Z GFS/ECMWF/UKMET/GEM CONFIDENCE: SLIGHTLY BELOW AVERAGE COMPLEX PATTERN OVER THE CONUS FOR THE SHORT TERM PERIOD. FORECAST IS LARGELY DRIVEN BY SMALL SCALE CONVECTIVE FEATURES...WHICH ARE DIFFICULT TO TRACK AND FORECAST. IN THE LARGE SCALE THERE IS PRETTY GOOD AGREEMENT AMONGST THE MODELS...WITH A SOUTHWESTERN U.S. UPPER RIDGE...AND A DEVELOPING EAST COAST TROUGH. ALSO GOOD AGREEMENT THAT WE WILL SEE MULTIPLE SHORTWAVES RIDE UP AND OVER THE RIDGE INTO THE TROUGH...WITH ENERGY IN THE GULF OF MEXICO ALSO MOVING NORTH AND BEING ABSORBED INTO THE TROUGH. THE DISAGREEMENT COMES FROM THE TIMING/STRENGTH OF BOTH THE SHORTWAVES MOVING OVER THE RIDGE ACROSS THE PLAINS AND THE GULF OF MEXICO ENERGY...AND HOW THESE TWO END UP INTERACTING OVER THE EAST. THE GFS HAS CONSISTENTLY BEEN THE QUICKEST SOLUTION IN THE PROGRESSION OF THE TROUGH EASTWARD...WITH THE ECMWF THE SLOWEST. THINK THE GFS MAY BE ON TO SOMETHING WITH HOW IT IS INITIALLY HANDLING THE GULF OF MEXICO ENERGY...WITH THE ECMWF TAKING TOO LITTLE ENERGY INTO MS/LA TODAY AND TOMORROW. HOWEVER THINK THE GFS THEN ENDS UP SHEARING THINGS OFF TO THE NORTHEAST TOO QUICKLY. IN GENERAL THE 0Z UKMET/GEM ARE SOMEWHERE BETWEEN THE GFS AND ECMWF...SO THINK THE GFS AND ECMWF MOST LIKELY REPRESENT THE BOOKENDS OF POSSIBLE SOLUTIONS...WITH THE MOST PROBABLE OUTCOME IN BETWEEN...CLOSER TO EITHER THE 0Z UKMET OR GEM. THE 12Z NAM IS A DEEP AND NORTH OUTLIER...AND APPEARS TO FALL OUTSIDE THE BEST MODEL CLUSTERING...AND THUS WILL NOT BE PREFERRED AT THIS TIME. CONFIDENCE REMAINS LOW GIVEN THE MODEL SPREAD AND LACK OF SIGNAL IN THE ENSEMBLES...HOPEFULLY THE REMAINDER OF THE 12Z GUIDANCE WILL CONTINUE TO CONVERGE ON A SOLUTION. 19Z UPDATE: THE 12Z ECMWF DID INDEED TREND CLOSER TO THE GFS WITH ITS HANDLING OF THE SHORTWAVE ENERGY MOVING NORTH OUT OF THE GULF OF MEXICO...AND IN TURN IS ALSO QUICKER WITH THE TROUGH PROGRESSION ACROSS THE EAST. THE GFS REMAINS THE MOST PROGRESSIVE SOLUTION...BUT NOT BY MUCH. THE TREND HAS ALSO BEEN FOR A FURTHER NORTH WAVE AND SURFACE LOW TRACK THURSDAY INTO FRIDAY. THE NAM STILL APPEARS TOO STRONG WITH ENERGY ON THE NORTHERN EDGES OF THE TROUGH IN THE LOWER GREAT LAKES. THE 12Z UKMET IS THE SLOWEST SOLUTION...BUT STILL WITHIN THE RANGE OF PLAUSIBLE SOLUTIONS. THE GFS IS NOW THE FURTHEST SOUTH SOLUTION. THE 12Z GEFS MEAN IS A BIT NORTH AND SLOWER THAN THE DETERMINISTIC RUN...ABOUT HALFWAY BETWEEN THE DETERMINISTIC 12Z ECMWF AND GFS WITH REGARDS TO TIMING AND CLOSER TO THE LATITUDE OF THE ECMWF. THUS STILL BELIEVE A CONSENSUS SOLUTION IS MOST LIKELY...WHICH IS PROBABLY BEST REPRESENTED BY THE 12Z ECMWF. ALTHOUGH SOME INCORPORATION OF THE 12Z GFS/GEM AND UKMET IS STILL PREFERRED AS WELL. CHENARD www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...