MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 232 PM EDT THU JUL 24 2014 VALID JUL 24/1200 UTC THRU JUL 28/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 12Z CMC/UKMET/ECMWF ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...SHEARING UPPER LOW ACROSS SOUTHEASTERN LA... FINAL PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH THE LATEST WATER VAPOR IMAGERY DEPICTED CONTINUAL WEAKENING OF AN UPPER LOW SWIRLING IN THE VICINITY OF SOUTHEASTERN LA. GUIDANCE AS A WHOLE SUGGEST THIS TREND WILL CONTINUE WHICH SUPPORTS A GENERAL MODEL CONSENSUS WITH THIS SYSTEM. ...SURFACE LOW CROSSING THE NORTHERN PLAINS THIS EVENING... FINAL PREFERENCE: A NON-12Z/00Z CMC MODEL COMPROMISE FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE MID-LEVEL ENERGY SLIDING EASTWARD ABOVE A BROAD RIDGE SITTING ACROSS THE FOUR CORNERS REGION/SOUTHERN PLAINS WILL ALLOW AN AREA OF LOW PRESSURE TO DEVELOP OVER THE NORTHERN PLAINS LATER THIS AFTERNOON/EVENING. THROUGH 25/1200Z...THE ENSEMBLE LOW SCATTER PLOTS DID NOT SHOW MUCH SPREAD WITH DECENT AGREEMENT NOTED IN THE PAST FEW MODEL CYCLES. THE SURFACE WAVE SHOULD GRADUALLY WEAKEN BY FRIDAY EVENING AS THE MID-LEVEL IMPULSE CONTINUES RACING TOWARD THE EAST. WITH THE EXCEPTION OF THE 12Z/00Z CMC...THE MODELS ARE WITHIN TOLERANCE OF THE SCATTER DEPICTED BY THE AFOREMENTIONED ENSEMBLE LOW PLOT. WILL RECOMMEND A NON-12Z/00Z CMC MODEL COMPROMISE GIVEN THIS ASSESSMENT. ...STRONG CLOSED LOW MOVING FROM THE PACIFIC NORTHWEST TOWARD SOUTHERN SASKATCHEWAN... FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/GEFS MEAN FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE AN ANOMALOUS UPPER LOW LIFTING OUT OF THE PACIFIC NORTHWEST TOWARD SOUTHERN ALBERTA WILL MAINTAIN VERY LOW HEIGHTS FOR LATE JULY WITH THE GUIDANCE SUGGESTING 500-MB HEIGHT DEPARTURES IN EXCESS OF 2 STANDARDIZED ANOMALIES. AS THE CLOSED SYSTEM MOVES ACROSS SOUTHERN SASKATCHEWAN ON FRIDAY...THE FORWARD MOTION SHOULD BRIEFLY HALT WHICH IS INDICATED BY ALL OF THE AVAILABLE GUIDANCE. SOME UNCERTAINTY IS NOTED THEREAFTER WITH HOW QUICKLY THE SYSTEM OPENS UP AND ACCELERATES DOWN TOWARD THE UPPER MIDWEST/GREAT LAKES. THE 09Z SREF MEAN IS DEFINITELY THE QUICKEST AMONG THE DETERMINISTIC/ENSEMBLE GUIDANCE AND STRAYS FROM THE BETTER CLUSTERING IN SPAGHETTI PLOTS. THE 12Z GEFS MEAN HAS TRENDED A BIT FASTER BUT SEEMS TO MATCH THE SHIFT EASTWARD NOTED IN THE LATEST 12Z ECMWF. FROM THE PREVIOUS ISSUANCE...THE 12Z GFS WAS NOTED TO BE TOO QUICK WHICH CONTINUES TO BE THE CASE AFTER EVALUATING THE LATEST GUIDANCE. WILL GO AHEAD AND FAVOR THIS TREND AND REMOVE THE 00Z ECMWF ENSEMBLE MEAN AS IT NOW APPEARS TOO SLOW. THE SUGGESTED BLEND IS A MIX OF THE 12Z ECMWF/GEFS MEAN. ...MEAN UPPER TROF ANCHORING THE NORTHEASTERN SECTOR OF NORTH AMERICA... FINAL PREFERENCE: A NON-12Z/00Z CMC MODEL COMPROMISE FORECAST CONFIDENCE: AVERAGE A MEAN TROF WILL MAINTAIN A POSITION ACROSS THE EASTERN THIRD OF THE COUNTRY FOR MUCH OF THE PERIOD WITH THE SYNOPTIC PATTERN BEING REINFORCED BY THE WEEKEND AS THE UPPER TROF DIGS THROUGH THE UPPER GREAT LAKES. THE MODELS ARE IN CLOSE AGREEMENT AS ONE BATCH OF ENERGY SLIDES OFFSHORE WITH ADDITIONAL SHORTWAVES SPILLING IN UPSTREAM. THE PREVIOUSLY MENTIONED IMPULSE TRACKING FROM THE NORTHERN TIER INTO THE MIDDLE MS VALLEY/UPPER GREAT LAKES EVENTUALLY HAS IMPACTS ON THE POSITION OF THE UPPER TROF. GIVEN THE 12Z/00Z CMC DISAGREED WITH THE CONSENSUS IN THAT CASE...WILL NOT INCLUDE THEM IN THE PREFERENCE FOR THIS SYSTEM EITHER. ...SHORTWAVE APPROACHING NORTHERN CA BY 28/0000Z... FINAL PREFERENCE: BLEND OF THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: AVERAGE TOWARD THE END OF THE PERIOD...A SHORTWAVE IS EXPECTED TO REACH THE NORTHERN CA COAST. THE GUIDANCE AGREE WITH THE IDEA OF THIS FEATURE BUT VARY WITH PLACEMENT. ADDITIONALLY...RUN-TO-RUN CONTINUITY HAS NOT BEEN GREAT OVERALL. WITH THIS BEING THE CASE...WILL UTILIZE THE ENSEMBLE MEANS GIVEN SUCH VARIABILITY. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER