MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 251 PM EDT WED JUL 23 2014 VALID JUL 23/1200 UTC THRU JUL 27/0000 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. ...UPPER LOW SPINNING OVER SOUTHEASTERN LA... FINAL PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE BASED ON THE LATEST WATER IMAGERY...A MID/UPPER LOW WAS SEEN SPINNING IN THE VICINITY OF SOUTHEASTERN LA. IT HAS BECOME MORE ELONGATED IN NATURE COMPARED TO PREVIOUS DAYS BUT STILL REMAINS A FOCUS FOR CONVECTION...PRIMARILY DURING THE PEAK DIURNAL HEATING. THE GUIDANCE SHOWS THE SYSTEM CONTINUING TO SHEAR AS IT FEELS THE INFLUENCE OF A BROAD MID-LEVEL RIDGE ACROSS THE FOUR CORNERS REGION/SOUTHERN PLAINS. NOW THAT THE 12Z CMC HAS COME ON BOARD WITH THE OTHER MODELS IN TERMS OF PLACEMENT...A GENERAL MODEL COMPROMISE CAN BE RECOMMENDED. ...DEEP AND ANOMALOUS CLOSED LOW MOVING FROM THE PACIFIC NORTHWEST TO SOUTHERN SASKATCHEWAN... ...SURFACE LOW TRACKING THROUGH THE GREAT PLAINS ON THURSDAY/FRIDAY... FINAL PREFERENCE: BLEND OF THE 12Z GFS/ECMWF WITH THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE A RATHER STRONG UPPER LOW CURRENTLY APPROACHING THE PACIFIC NORTHWEST COAST WILL MOVE ONSHORE BY THIS AFTERNOON. THE 12Z NAM INDICATED THIS FEATURE IS AT LEAST 2 TO 2.5 STANDARDIZED ANOMALIES BELOW CLIMATOLOGY BASED ON 500-MB HEIGHTS. SUCH ANOMALIES ARE FORECAST TO PERSIST THROUGHOUT THE SHORT RANGE PERIOD EXTENDING THROUGH SATURDAY. SOLUTIONS VARY WITH THE SPEED OF THIS FEATURE WITH THE 12Z NAM BEING THE QUICKEST BY AS EARLY AS THURSDAY MORNING. THIS ARTIFACT OF THE FORECAST CONTINUES ONWARD WITH ENSEMBLE MEANS SUGGESTING A MUCH SLOWER EASTWARD PROGRESSION. GIVEN THE FORECAST INVOLVES A COMPACT CLOSED LOW...WOULD LIKE TO ERR ON THE WESTERN SIDE HERE. OVERALL...THE 12Z GFS/ECMWF CONTINUE TO BE BEST SUPPORTED BY THE ENSEMBLE MEANS. THE 576-DM SPAGHETTI PLOT SHOWS A RELATIVELY WELL BEHAVED PLOT WITH THE MODELS SUBTLY IN AGREEMENT. THE 00Z ECMWF ENSEMBLE MEMBERS DO SHOW HINTS AT A FASTER/MORE AMPLIFIED PROGRESSION BY SATURDAY ACROSS THE MIDDLE MS VALLEY/UPPER GREAT LAKES. IN SPITE OF THE SIMILARITY BETWEEN THE 12Z GFS/ECMWF WITH THE CORE OF THE LOWER HEIGHTS ACROSS SOUTHERN CANADA...THEY DIFFER WITH THE DETAILS OF JET ENERGY CROSSING THE NORTHERN TIER OF THE U.S. THIS HAS RAMIFICATIONS ON UNCERTAINTY WITH THE EVOLUTION OF THE SURFACE FEATURES...PARTICULARLY OVER THE REALM OF THE MESOSCALE. WILL MAINTAIN THE PREVIOUS SOLUTION BUT WILL INCORPORATE THE NEWER CYCLES OF THE ECMWF/GEFS MEAN. ...MEAN UPPER TROF OVER NORTHEASTERN NORTH AMERICA... ...ASSOCIATED COLD FRONT... FINAL PREFERENCE: A NON-12Z NAM SOLUTION FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE A PERSISTENT NEGATIVE HEIGHT ANOMALY ACROSS THE NORTHEASTERN SECTOR OF NORTH AMERICA WILL BE FEATURED DURING THE PERIOD. A SERIES OF IMPULSES TRAVERSING WITHIN THE CYCLONIC FLOW WILL MOVE THROUGH OH VALLEY AND MID-ATLANTIC/NEW ENGLAND. THROUGH 25/1200Z...THE MODELS ARE NOW IN GENERAL AGREEMENT WITH THE HEIGHT PATTERN ANCHORING THE EASTERN U.S. MORE UNCERTAINTY LOOMS UPSTREAM WITH A RATHER POTENT IMPULSE SLIDING THROUGH THE UPPER GREAT LAKES ON FRIDAY EVENING. THE GUIDANCE HAS TENDED TO WAVER WITH THE DETAILS AND ADDITIONALLY DO NOT SHOW MUCH AGREEMENT WITH ONE ANOTHER. THE 12Z NAM APPEARS TO BE THE OUTLIER BEING QUICKER OFF TOWARD THE SOUTHEAST BY 26/0000Z WHILE THE 12Z GFS/CMC/UKMET ARE IN THE VICINITY OF THE MI/IN BORDER. MEANWHILE...THE 12Z ECMWF HAS TRENDED TOWARD A MORE SUPPRESSED SOLUTION WHICH ENDS UP DIMINISHING THE QPF AMOUNTS RELATIVE TO ITS PREVIOUS CYCLE. WILL TEND TO STAY AWAY FROM THE 12Z NAM AND FAVOR SOME SORT OF COMPROMISE OF THE REMAINING DETERMINISTIC GUIDANCE UNTIL BETTER AGREEMENT ARISES. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER