MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1251 PM EDT SUN MAR 09 2014 VALID MAR 09/1200 UTC THRU MAR 13/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...CLOSED LOW INITIALLY BARRELING THROUGH MEXICO... ...SURFACE WAVE DEVELOPING IN THE WESTERN GULF EARLY TUESDAY... PRELIMINARY PREFERENCE: A NON-12Z NAM/09Z SREF MEAN SOLUTION FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE A CUT-OFF LOW SEEN ON WATER VAPOR IMAGERY SPINNING ACROSS NORTHWESTERN MEXICO WILL NOSE TOWARD THE SOUTH AND EAST BEFORE ACCELERATING TOWARD THE WESTERN GULF COAST. MODELS VARY IN DEPICTING WHETHER THIS SYSTEM WILL REMAIN CLOSED IN NATURE OR BECOME MORE OF AN OPEN WAVE. WITH REGARD TO TIMING...THE 12Z NAM/09Z SREF MEAN IS A HAIR SLOWER EJECTING THIS UPPER CYCLONE WHICH RESULTS IN A SLIGHTLY MORE WESTERN POSITION OF THE SURFACE WAVE OFFSHORE OF THE SOUTHEAST TX COAST BY 11/1200Z. THE SYSTEM IS FORECAST TO SLOWLY SHEAR APART AND BECOME LESS DEFINED WHEN REACHING THE EASTERN GULF COAST BY THE FOLLOWING MORNING. WHILE THE 12Z GFS AND 00Z CMC/UKMET/ECMWF AGREE WITH THE TIMING OF THE SHORTWAVE...THE TRACK SOMEWHAT VARIES WITH THE 12Z GFS/00Z CMC BEING TO THE NORTH WHILE THE 00Z ECMWF/UKMET IS JUST OFF TO THE SOUTH. SEEMS FAIR THAT EITHER OF THESE MODELS WILL SUFFICE SO WILL RECOMMEND A BLEND OF THESE OR MORE SIMPLY A NON-12Z NAM/09Z SREF MEAN SOLUTION. ...PAIR OF NORTHERN STREAM SYSTEMS CROSSING THE NORTHEAST ON SUNDAY/MONDAY... ...STRONG SURFACE LOW MOVING THROUGH SOUTHERN QUEBEC... PRELIMINARY PREFERENCE: BLEND OF THE 12Z NAM/GFS FORECAST CONFIDENCE: AVERAGE THE ACTIVE NORTHERN STREAM OF THE JET WILL ALLOW A SERIES OF SHORTWAVES TO TRACK ACROSS SOUTHERN CANADA AND EVENTUALLY INTO THE NORTHEASTERN STATES. THE INITIAL SYSTEM WITHIN THE LONG CHAIN IS CURRENTLY EXITING COASTAL NEW ENGLAND WITH THE NEXT WAVE REACHING THE INTERIOR NORTHEAST BY 10/0600Z. DIFFERENCES ON AVERAGE ARE SMALL BUT THERE IS A TAD MORE UNCERTAINTY WITH THE NEXT IMPULSE WHICH CURRENTLY IS MOVING THROUGH WESTERN CANADA AS OF THIS MORNING. THE PROGRESSIVE SHORTWAVE SHOULD GRAZE THE GREAT LAKES REGION MONDAY AFTERNOON BEFORE ARRIVING INTO NEW ENGLAND BY THAT NIGHT. THE 12Z NAM/GFS AND 06Z GEFS MEAN ARE A FEW OF THE FASTER SOLUTIONS WHILE THE 00Z CMC/UKMET/ECMWF ARE THE WESTERN SIDE OF THE SMALL AMOUNT OF SPREAD. GIVEN THE PROGRESSIVE FLOW IN PLACE...WOULD LIKE TO REMAIN ON THE FASTER SIDE OF THE ENVELOPE. THE WPC PREFERENCE WILL BE A COMBINATION OF THE 12Z NAM/GFS. ...UPPER TROF REACHING THE WEST COAST BY 10/1200Z... ...EVENTUAL PHASING WITH THE NORTHERN STREAM OVER THE GREAT LAKES REGION... ...WELL-DEFINED SURFACE CYCLONE CROSSING THE CENTRAL APPALACHIANS BY MIDDAY WEDNESDAY... PRELIMINARY PREFERENCE: THROUGH 12/0000Z: BLEND OF THE 12Z GFS/00Z ECMWF...THEREAFTER...COMBINATION OF THE 06Z GEFS/00Z ECMWF ENSEMBLE MEANS WITH THE 00Z UKMET FORECAST CONFIDENCE: INITIALLY AVERAGE...THEN BECOMING BELOW AVERAGE A STRONG UPPER TROF ARRIVING INTO THE WESTERN U.S. LATE TONIGHT IS IN REASONABLE AGREEMENT THROUGH 10/1200Z. SUBTLE DIFFERENCES BECOME EVIDENT AS THE SHORTWAVE ENERGY SLIDES THROUGH THE CENTRAL GREAT BASIN WITH THE 00Z ECMWF/ECMWF ENSEMBLE MEAN BEING ON THE FASTER SIDE WHILE PLACED FURTHER TO THE WEST ARE THE 12Z GFS/00Z UKMET AND 06Z GEFS MEAN. EVEN THOUGH THE 00Z ECMWF SUITE IS FASTER...THERE ARE QUITE A FEW ENSEMBLE MEMBERS WITHIN THE 552-DM SPAGHETTI PLOT SUGGESTING SOMETHING SLOWER. INTERESTINGLY THE PAST FOUR SPAGHETTI PLOTS DATING BACK TO 36 HOURS AGO HAVE NOTED A TREND IN THE FASTER DIRECTION WITH THE SYSTEM. WHILE CROSSING THE ROCKY MOUNTAIN CHAIN...THE UPPER TROF IS EXPECTED TO SPLIT WITH THE LEAD ENERGY EVENTUALLY MERGING WITH THE NORTHERN STREAM BY TUESDAY. GIVEN THE COMPLEX INTERACTION...MODEL SPREAD DOES BEGIN TO INCREASE WITH THE 12Z GFS/00Z CMC AND 06Z GEFS/09Z SREF MEANS ON THE EASTERN SIDE OF THE UNCERTAINTY WHILE THE 12Z NAM IS QUITE SLOW AND PERHAPS OUTLYING. ALL OF THIS MODEL UNCERTAINTY LEADS TO QUITE A BIT OF SPREAD IN THE ENSEMBLE LOW PLOTS. AS EXPECTED...A MAJORITY OF THE 00Z ECMWF ENSEMBLE MEMBERS ARE IN THE MORE WESTERN/SLOWER CAMP WHILE THE 00Z GEFS MEMBERS ARE FASTER AND ALSO MORE SCATTERED ABOUT. THE FORMER SOLUTIONS ARE MUCH MORE TIGHTLY PACKED ACROSS THE LOWER OH VALLEY BY 12/1200Z. HAVE SOME CONCERNS USING THE 00Z ECMWF BEYOND DAY 2 AS ITS LOW POSITION IS AWAY FROM ITS OWN ENSEMBLE MEAN. WOULD PREFER TO UTILIZE MORE ENSEMBLE MEANS ON DAY 3 GIVEN THE INCREASING SPREAD ALTHOUGH FEEL THE 00Z UKMET COULD BE INCORPORATED A BIT AS ITS SURFACE LOW TRACK FOLLOWS THE MEANS CLOSE ENOUGH. ...ENERGY PEELING OFF OVER THE FOUR CORNERS REGION BY MID-WEEK... PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF WITH THE 06Z GEFS/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: LOW AS A CORE OF THE UPPER ENERGY SLIDES EASTWARD TO JOIN THE DEVELOPING LONGWAVE TROF ACROSS THE EASTERN U.S...SOME OF THE SYSTEM IS EXPECTED TO RETROGRADE BACK TOWARD THE SOUTHWESTERN CONUS. BY MID-WEEK...THE 12Z NAM/00Z UKMET ARE FURTHER TO THE SOUTH ACROSS THE DESERT SOUTHWEST WHILE THE 00Z CMC IS WELL OFF TO THE NORTH. UNFORTUNATELY A 570-DM SPAGHETTI PLOT IS NOT AVAILABLE FOR ANALYSIS BUT THE SPREAD APPEARS HIGH GIVEN THE VARIABILITY IN THE DETERMINISTIC/ENSEMBLE SOLUTIONS. THE PAST FOUR RUNS OF THE GUIDANCE DO NOT REALLY SHOW ANY CONSISTENT SOLUTION AT THIS TIME. GIVEN ALL OF THE ABOVE...FEEL IT IS BEST TO JUST STICK CLOSER TO THE CENTER OF THE SPREAD AND ADD SOME ENSEMBLE MEANS TO THE MIX. WILL FAVOR A BLEND OF THE 12Z GFS/00Z ECMWF WITH THE 06Z GEFS/00Z ECMWF ENSEMBLE MEANS. ...SHORTWAVE APPROACHING THE PACIFIC NORTHWEST BY 13/0000Z... PRELIMINARY PREFERENCE: NON-12Z GFS SOLUTION FORECAST CONFIDENCE: AVERAGE WITH A WEST-TO-EAST ORIENTED RIDGE SETTING UP ACROSS THE WESTERN U.S...A SHORTWAVE WILL TRACK ABOVE THIS DOME OF HIGH PRESSURE AND REACH THE UPPER PACIFIC NORTHWEST BY LATE IN THE PERIOD. GIVEN THE LOW-AMPLITUDE NATURE OF THE SYSTEM COMBINED WITH THE FACT IT REACHES THE COASTLINE APPROXIMATELY 78 TO 84 HOURS INTO THE FORECAST...THE ENSEMBLE MEANS SHOW LITTLE TO NO INDICATION OF THIS SHORTWAVE IN THEIR 500-MB HEIGHT FIELDS. THE 12Z GFS APPEARS TO BE THE FAST OUTLIER HERE SO FOR NOW WILL LEAN TOWARD A NON-12Z GFS MODEL SOLUTION. ULTIMATELY THE IMPACTS APPEAR LOW AS NO MEASURABLE PRECIPITATION REACHES THE PACIFIC NORTHWEST ON DAY 3. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER