MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1244 AM EDT TUE OCT 21 2014 VALID OCT 21/0000 UTC THRU OCT 24/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...SHEARING MID-LEVEL ENERGY OVER SOUTHERN NM/FAR WEST TX... PRELIMINARY PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH A BATCH OF VORTICITY SLIDING ACROSS NORTH-CENTRAL MX WILL CONTINUE TO SHEAR AS IT NEARS THE RIO GRANDE. ALL MODELS AGREE ON THIS OCCURRING DURING THE NEXT 12 TO 24 HOURS SO WILL RECOMMEND A GENERAL MODEL CONSENSUS GIVEN THE AGREEMENT. ...SHORTWAVES CROSSING THE GREAT LAKES REGION EARLY ON... ...COASTAL STORM AFFECTING THE NORTHEASTERN U.S. COAST WEDNESDAY THROUGH FRIDAY... PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE WATER VAPOR IMAGERY SHOWED A PAIR OF IMPULSES MOVING THROUGH THE CENTRAL APPALACHIANS AND LOWER GREAT LAKES...RESPECTIVELY. EVENTUALLY THE SYSTEM BECOMES BETTER ORGANIZED AS IT CLOSES ALOFT FORMING A CLOSED LOW OVER THE MID-ATLANTIC BY TUESDAY EVENING. THROUGH 36 HOURS/WEDNESDAY MORNING...MODELS SHOW SUFFICIENT AGREEMENT BEFORE DIFFERENCES EMERGE WITH THE COASTAL DEVELOPMENT. THE ENSEMBLE SURFACE LOW PLOT BY 22/1200Z SHOWS THE 12Z GEFS MEMBERS BEING WEST OF THE 12Z ECMWF/CMC ENSEMBLE MEMBERS. THIS SEPARATION HAS BEEN NOTED IN THE 3 OF THE PAST 4 PLOTS DATING BACK TO MODELS RUN 36 HOURS AGO. HOWEVER...BY 23/0000Z...THE 12Z ECMWF ENSEMBLE MEMBERS ARE CLOSER TO THE COAST. THROUGHOUT THE EVOLUTION OF THIS COASTAL LOW...THE 18Z GEFS/21Z SREF/12Z ECMWF ENSEMBLE MEANS ARE FAIRLY IN LINE WITH ANOTHER. THE 00Z GFS/12Z ECMWF APPEAR TO FOLLOW THIS CONSOLIDATED SOLUTION MOST READILY. AT TIMES THE 12Z UKMET APPEARED REASONABLE BUT THEN ALLOWS THE COASTAL LOW TO LINGER NEAR LONG ISLAND MUCH LONGER. WILL SUGGEST A BLEND OF THE 00Z GFS/12Z ECMWF WITH SOMEWHAT COMPROMISED CONFIDENCE. ...STRONG SHORTWAVE CURRENTLY MOVING INTO NORTHERN CA... ...EVENTUAL SPLIT FLOW OVER THE CENTRAL U.S. BY MID-WEEK.... PRELIMINARY PREFERENCE: THROUGH 23/1200Z: BLEND OF THE 00Z GFS/12Z ECMWF...THEREAFTER: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: BELOW AVERAGE A PRONOUNCED SHORTWAVE CURRENTLY PUSHING INTO NORTHERN CA WILL QUICKLY LIFT NORTHEASTWARD TOWARD THE NORTHERN GREAT BASIN DURING THE NEXT 24 HOURS. AGREEMENT IS MUCH BETTER THAN RECENT DAYS WHERE SOME OF THE GUIDANCE TRIED TO ALLOW SHORTWAVE ENERGY TO SINK SOUTHWARD TOWARD THE FOUR CORNERS REGION. THE FORECAST BECOMES MORE UNCERTAIN THEREAFTER AS SOME OF THE MID-LEVEL VORTICITY LIFTS INTO CENTRAL CANADA WHILE THE REMAINING ENERGY TRACKS ALONG THE NORTHERN TIER MID-WEEK. THE 00Z NAM AND 12Z CMC/UKMET SHOW MORE OF THE SYSTEM MIGRATING INTO MANITOBA WHICH LEAVES A WEAKER SYSTEM ACROSS THE NORTHERN PLAINS. THIS LEAVES A RATHER MESSY FORECAST IN PLACE FOR THE CENTRAL U.S. AND EVENTUALLY INTO THE MS RIVER VALLEY. THE 576-DM SPAGHETTI PLOT SHOWS THE UNCERTAINTY QUITE WELL WITH A SLEW OF SOLUTIONS PORTRAYED BY THE INDIVIDUAL ENSEMBLE MEMBERS. THROUGH 60 HOURS/THURSDAY MORNING...WILL LEAN ON THE CLUSTER OF THE 00Z GFS/12Z ECMWF WHICH SUPPORT A MORE ROBUST SYSTEM IN THE NORTHERN TIER STATES. THEREAFTER...HAVE TO PUSH AWAY FROM THE DETERMINISTIC MODELS GIVEN THE GROWING SPREAD AND UTILIZE A 18Z GEFS/12Z ECMWF ENSEMBLE MEANS BLEND THROUGH 24/1200Z. ...BROAD CYCLONIC FLOW ACROSS THE NORTHEASTERN PACIFIC WEDNESDAY THROUGH FRIDAY... PRELIMINARY PREFERENCE: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: BELOW AVERAGE IN THE WAKE OF THE INITIAL SYSTEM MOVING INTO THE INTERMOUNTAIN WEST...THE MID-LATITUDE FLOW SEE THE AMPLITUDE DECREASE AND BECOME A BIT MORE ZONAL IN NATURE. WITH LOWER HEIGHTS CENTERED OVER THE NORTHEASTERN PACIFIC....A MYRIAD OF PROGRESSIVE SHORTWAVES WILL BOMBARD THE PACIFIC NORTHWEST WITH ENHANCED ONSHORE FLOW ACCOMPANYING EACH WAVE. THE MODELS INITIALLY HAVE A DECENT HANDLE ON THE PATTERN BEFORE UNCERTAINTY INCREASES. MORE SPECIFICALLY...THE GUIDANCE BEGINS TO STRUGGLE WITH THE TIMING OF THE NEXT ROUND OF HEIGHT FALLS APPROACHING THE NORTHWESTERN U.S. LATE IN THE WORK WEEK. THE 552-DM SPAGHETTI PLOT SHOWS THE 12Z GEFS MEMBERS BEING EAST OF THE SLOWER 12Z ECMWF ENSEMBLE MEMBERS. THE SPREAD BETWEEN THESE TWO ENSEMBLE MEANS HAS DECREASED RECENTLY...PARTICULARLY COMPARED TO THE 00Z MODEL CYCLE THE PREVIOUS DAY. WILL SPLIT THE DIFFERENCE BETWEEN THESE TWO ENSEMBLE MEANS FOR NOW. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER