MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 151 PM EST WED JAN 29 2014 VALID JAN 29/1200 UTC THRU FEB 02/0000 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. ...LINGERING UPPER TROF ACROSS THE NORTHEASTERN U.S. EXITING BY THURSDAY AFTERNOON... ...ASSOCIATED FRONTAL ZONE INITIALLY STALLED OVER SOUTH FL... FINAL PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH A LONGWAVE TROF INITIALLY EXTENDING FROM THE LOWER TN VALLEY UP INTO THE NORTHEASTERN U.S. WILL GRADUALLY SHIFT EASTWARD DURING THE NEXT 24 TO 30 HOURS. A TRAILING BATCH OF ENERGY IS FORECAST TO CROSS THE LOWER MID-ATLANTIC EARLY THURSDAY MORNING BEFORE EXITING TO THE OFFSHORE WATERS. A GENERAL CONSENSUS IS FORMED DURING THIS PERIOD OF TIME WITH THE 12Z CMC NOW JOINING THIS WELL CLUSTERED SOLUTION. WPC WILL THUS FAVOR A GENERAL MODEL CONSENSUS SOLUTION WHICH ALSO HANDLES THE STALLED BOUNDARY QUITE WELL. ...SHORTWAVE CROSSING THE GULF OF MEXICO ON THURSDAY... FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE SHORTWAVE ENERGY SLIDING EASTWARD INTO THE WESTERN GULF OF MEXICO WILL EVENTUALLY GAIN STRENGTH AS UPSTREAM ENERGY HELPS CARVE OUT A MORE DEFINED SYSTEM OVER THE CENTRAL GULF BY MIDDAY THURSDAY. THE MID-LEVEL ENERGY GRADUALLY BEGINS TO SLOW IN ITS FORWARD PROGRESSION AS IT REMAINS CUT-OFF FROM THE STRONGER BELT OF WESTERLIES TO THE NORTH. THE 12Z ECMWF/00Z ECMWF ENSEMBLE MEAN INSIST ON THE SHORTWAVE NEARLY STALLING WEST OF FL BY 01/0000Z. IN FACT...THE ECMWF SUITE SHOWED THAT TO A LESSER EXTENT IN THEIR PREVIOUS RUN AS WELL. GIVEN THIS RELATIVE CONSISTENCY...WILL THROW THE 12Z ECMWF INTO THE MIX WHILE ALSO INCORPORATING A DOWNSTREAM SOLUTION. A BLEND OF THE 12Z ECMWF/UKMET WILL BE PREFERRED IN THIS CASE. ...CLOSED LOW STRENGTHENING OVER WESTERN ONTARIO BY 30/0600Z... ...COLD FRONT EVENTUALLY BECOMING ILL-DEFINED OVER THE LOWER GREAT LAKES... FINAL PREFERENCE: A NON-12Z GFS/GEFS MEAN SOLUTION FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE A COMPACT UPPER LOW IS FORECAST TO DROP TOWARD THE SOUTH AND EAST FROM SASKATCHEWAN AND SHOULD GATHER ADDITIONAL STRENGTH WHEN CROSSING INTO THE WESTERN ONTARIO BY LATE WEDNESDAY NIGHT. ALTHOUGH THERE ARE SOME SUBTLE DIFFERENCES WITH THE TRACK OF THIS UPPER LOW...THEY ARE DEFINITELY NOT SIGNIFICANT ENOUGH TO AFFECT THE FORECAST. HOWEVER...AT THE SURFACE...THERE ARE AGAIN SOME DIFFERENCES WITH THE TIMING OF THE COLD FRONT WHICH HELPS REINFORCE THE MODIFIED ARCTIC AIR IN PLACE. LIKE YESTERDAY...THE GFS SUITE INCLUDING ITS ENSEMBLES HAVE FAVORED A SLIGHTLY FASTER SOLUTION. THE PAST FOUR SPAGHETTI PLOTS GOING BACK TO 48 HOURS AGO SUGGEST A TREND IN THE SLOWER DIRECTION. WILL THUS LEAN AWAY FROM THIS PROGRESSIVE IDEA AND FAVOR A CONSENSUS OF THE OTHER GUIDANCE. ...SERIES OF SHORTWAVES MOVING THROUGH THE WESTERN U.S. EVENTUALLY REACHING THE MIDDLE OF THE CONUS... ...SURFACE LOW TRACKING TOWARD THE OH VALLEY LATE IN THE PERIOD... FINAL PREFERENCE: BLEND OF THE 12Z GFS/ECMWF WITH THE 00Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE THE UPPER RIDGE WHICH HAS REMAINED A MAINSTAY FEATURE FOR SEEMINGLY WEEKS ACROSS THE WESTERN U.S. WILL FINALLY BEGIN TO FLATTEN OUT AS A MYRIAD OF SHORTWAVES SLIDE EASTWARD HELPING CARVE OUT AN ELONGATED TROF OVER THE WEST. WITH REGARD TO THE INITIAL BATCH OF ENERGY CROSSING NORTHERN/CENTRAL CA ON THURSDAY AFTERNOON...THE 12Z NAM/09Z SREF MEAN ARE QUICKER THAN A LARGE MAJORITY OF THE SOLUTIONS. THE 00Z ECMWF ENSEMBLE MEMBERS ON THE 552-DM SPAGHETTI PLOT DOES SHOW AN EVOLUTION MORE REPRESENTATIVE OF THE NON-12Z NAM/09Z SREF MEAN GUIDANCE WITH EVEN A HAND FULL OF SOLUTIONS BEING EVEN SLOWER THAN THE DETERMINISTIC/ENSEMBLE IDEAS. THE 00Z ECMWF ENSEMBLE MEAN HAS SHOWN REASONABLE STABILITY AS INDICATED IN THE RECENT SPAGHETTI PLOTS. THE PREFERENCE IN THIS CASE WILL FOLLOW THE 12Z GFS/ECMWF AS THEY SEEM TO FAVOR THE SOLUTION PROVIDED BY THE 00Z ECMWF ENSEMBLE MEAN. AS THE ENERGY SLIDES INTO THE MIDDLE OF THE COUNTRY...A WAVY FRONTAL SYSTEM SETS UP FROM THE SOUTHERN HIGH PLAINS INTO THE ARKLATEX AND UP THROUGH THE WESTERN TN/OH VALLEYS. BY 01/1200Z...THE 12Z/00Z CMC DEPICTS A WELL-DEFINED SURFACE LOW NEARING LOWER MI WHICH CURRENTLY HAS HALF DECENT SUPPORT FROM THE 12Z NAM/UKMET. THERE ARE STILL OTHER MODELS WHICH ARE WEAKER WHICH INCLUDES THE GFS/ECMWF SUITE OF SOLUTIONS. WILL REMAIN MORE ON THE CONSERVATIVE SIDE WITH THIS LOW DEVELOPMENT AND CONTINUE THE PREFERENCE FROM OUT WEST. SUCH AN IDEA TENDS TO AVERAGE OUT THE DIFFERENCES WITH THE FRONTAL PLACEMENT ACROSS THE UPPER GREAT LAKES WITH THE 12Z ECMWF TRENDING SLIGHTLY SLOWER THAN ITS PREVIOUS RUN. ...NEXT UPPER TROF EXPECTED TO DIVE THROUGH THE NORTHERN TIER OF THE NATION BY THE WEEKEND... FINAL PREFERENCE: BLEND OF THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: LOW WITH BROAD CYCLONIC FLOW ANCHORING CENTRAL/EASTERN CANADA...ANOTHER AXIS OF HEIGHT FALLS WILL SLIDE DOWN THE WESTERN EDGE OF THE VORTEX REACHING THE NORTH-CENTRAL STATES BY THE WEEKEND. THIS FORECAST IS NEBULOUS AT BEST GIVEN THE HIGH AMOUNT OF SPREAD SEEN IN THE GUIDANCE ALONG WITH THE FACT THE CURRENT SOLUTIONS DISAGREE WITH THEIR PREVIOUS CYCLES. ONE NOTABLE TREND ARE THE 12Z GEFS/09Z SREF/00Z ECMWF ENSEMBLE MEANS ALL SHIFTED TO A SLOWER SOLUTION. UNFORTUNATELY THE SIMPLEST WAY TO GO ABOUT THIS IS FOLLOWING THE LEAD OF THE ENSEMBLE MEANS. AT THE MINIMUM...THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS HAVE DECENT AGREEMENT WITH TIMING. THUS...WPC WILL GO WITH AN EVEN BLEND OF THE TWO WITH TOO MUCH UNCERTAINTY TO INCORPORATE ANY DETERMINISTIC RUNS. ...AREA OF HEIGHT FALLS SLIDING THROUGH THE DESERT SOUTHWEST ON SATURDAY... FINAL PREFERENCE: BLEND OF THE 12Z GFS/GEFS MEAN/ECMWF...WEIGHTED SLIGHTLY MORE TOWARD THE 12Z ECMWF FORECAST CONFIDENCE: BELOW AVERAGE AS THE UPPER FLOW BEGINS TO SPLIT OVER THE WESTERN U.S...A SYSTEM WITHIN THE SOUTHERN STREAM MAY CARVE OUT A RATHER POTENT UPPER TROF ACROSS THE DESERT SOUTHWEST BY LATE IN THE WEEKEND. THE 12Z NAM/CMC/UKMET ARE MUCH FLATTER AND PROGRESSIVE WITH THIS WAVE WITH DISAGREES WITH THE ENSEMBLE MEANS WHICH HINT AT ADDITIONAL AMPLIFICATION...PARTICULARLY THE 12Z GEFS MEAN. AT LEAST THE 12Z GFS/00Z ECMWF SUPPORTS THIS MORE AMPLIFIED IDEA AS DOES THE MOST RECENT 564-DM SPAGHETTI PLOT. THE 12Z GFS ACTUALLY SHOWS THIS SOLUTION IN THE MOST AGGRESSIVE FASHION. THIS RECENT SPAGHETTI PLOT IS DEFINITELY IN CONTRAST WITH THE FLATTER SOLUTIONS SEEN IN PREVIOUS SPAGHETTI PLOTS IN RECENT MODEL CYCLES. THE PREFERENCE WILL FAVOR THE 12Z GFS/ECMWF AND ADD THE 12Z GEFS MEAN TO ACCOUNT FOR THE HIGH AMOUNT OF UNCERTAINTY. WILL LEAN A BIT MORE TOWARD THE ECMWF GIVEN THE MORE EXTREME NATURE OF THE GFS HERE. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER