Prognostic Meteorological Discussion
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000 FXUS10 KWNH 210638 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 238 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 ALL 00Z MODEL GUIDANCE ALONG WITH FINAL 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... FINAL 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... FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF FORECAST CONFIDENCE: 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 OFF 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. IN SPITE OF THIS SEPARATION...THE CURRENT ENSEMBLE MEANS...00Z GEFS/21Z SREF/12Z ECMWF ARE FAIRLY IN LINE WITH ANOTHER. THE 00Z GFS/ECMWF AGREE REASONABLY WITH THIS WHILE THE 00Z CMC/UKMET ARE DISPLACED TO THE NORTH AND EAST. SUCH A SOLUTION APPEARS TO HOLD STEADY THROUGHOUT THE REMAINDER OF THE SHORT RANGE PERIOD. WILL CONTINUE WITH THE PREVIOUS SOLUTION AND RAISE THE CONFIDENCE UP TO AVERAGE NOW. ...STRONG SHORTWAVE CURRENTLY MOVING INTO NORTHERN CA... ...EVENTUAL SPLIT FLOW OVER THE CENTRAL U.S. BY MID-WEEK.... FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF/CMC (WEIGHTED MORE TOWARD THE GFS/ECMWF) 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 CMC/UKMET APPEAR TO HAVE CHANGED GEARS AND SHIFTED AWAY FROM THEIR PREVIOUS SOLUTIONS. BOTH OF THESE MODELS ALLOW MORE ENERGY TO CROSS THE NORTHERN TIER OF THE CONUS. TO VARYING DEGREES THE 00Z GFS/ECMWF/CMC SHOW REASONABLE AGREEMENT WITH ONE ANOTHER. THE 00Z UKMET INITIALLY IS AMONG THIS CLUSTERING BUT IT EVENTUALLY CARRIES A CLOSED LOW ACROSS THE LOWER MO VALLEY BY EARLY FRIDAY WHICH HAS LITTLE SUPPORT IN THE ENSEMBLES. OVERALL UNCERTAINTY STILL REMAINS ON THE HIGHER SIDE BY ONE LOOK AT THE 576-DM SPAGHETTI PLOT. RUN-TO-RUN CONTINUITY HAS NOT BEEN THE GREATEST SO WILL KEEP THE CONFIDENCE BELOW AVERAGE WITH THIS SYSTEM. WPC WILL FAVOR A COMBINATION OF THE 00Z GFS/ECMWF/CMC WITH MORE WEIGHTING ON THE GFS/ECMWF AS THEY AT LEAST WERE SOMEWHAT CONSISTENT WITH THEIR 12Z RUNS. ...BROAD CYCLONIC FLOW ACROSS THE NORTHEASTERN PACIFIC WEDNESDAY THROUGH FRIDAY... FINAL PREFERENCE: BLEND OF THE 00Z 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 SEES 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 UNTIL THE SPREAD DIMINISHES. ...MODEL TREND GRAPHICS AT www.wpc.ncep.noaa.gov/html/model2.shtml... ...500 MB FORECASTS AT www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER $$

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