MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 141 PM EST FRI MAR 04 2016 VALID MAR 04/1200 UTC THRU MAR 08/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DEEPENING LOW CENTER OFF THE EAST COAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z NAM/UKMET/ECMWF CONFIDENCE: AVERAGE FURTHER TIGHTENING OF THE SURFACE LOW CLUSTERING OCCURS NOW THAT THE 12Z NAM HAS SHIFTED RIGHT AND THOUGH IT IS A HAIR LEFT OF BEST CLUSTERED 00Z ECMWF/UKMET/CMC AND 00Z ECENS MEAN IT IS CLOSE ENOUGH TO INCLUDE. THE GEFS MEMBERS ALONG WITH THE 00Z/06Z GFS ARE GENERALLY FASTER THAN THE REMAINING GUIDANCE...THE 12Z GFS DID TREND A BIT SLOWER TOWARD BETTER CLUSTER BUT REMAINS AN OUTLIER PARTICULARLY AFTER 05/12Z INTO SE CANADA . THE 12Z CMC FOLLOWED THE 12Z GFS BEING A BIT FASTER OUTPACING THE OTHERWISE CLUSTERED 12Z NAM AND NEW 12Z UKMET/ECMWF. THIS BRINGS A BIT OF QUESTION TO THE SPREAD OVERALL AND WITH CONSISTENT RUN TO RUN CONSISTENCY OF THE GFS AND 12Z GEFS FROM THE 06Z...BUT WILL CONTINUE TO FAVOR THE EARLIER TRACK PREFERENCE OF THE 12Z NAM/UKMET/ECMWF BUT REDUCED CONFIDENCE TO AVERAGE IN THIS PRECISE TRACK/POSITION/STRENGTH. SHORTWAVE/CLIPPER LOW DIGGING ACROSS THE UPPER MIDWEST INTO OH VALLEY SAT CROSSING MID-ATLANTIC/OFF SHORE ON SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM BLEND CONFIDENCE: ABOVE AVERAGE UP TO 06/06Z... AVERAGE AFTERWARD ALL MODELS ARE GENERALLY WELL AGREED UPON THROUGH THE UPPER MIDWEST/GREAT LAKES UNTIL SAT EVENING WHEN MODELS START TO INCREASE SPREAD. THE 00Z CMC BECOMES FASTER AND FLATTER OVERALL...WHILE THE OPPOSITE SIDE THE 12Z NAM REMAINS A BIT SLOWER AND STRONGER WITH A SURFACE LOW CROSSING THE MID-ATLANTIC AND NEAR COASTAL ZONES BEFORE TRANSFERRING TOWARD THE SURFACE CYCLOGENESIS NORTH OF BERMUDA 07/00Z. THE 12Z GFS AND 00Z ECMWF/UKMET REMAIN CLOSELY TIED THOUGH THE UKMET IS GENERALLY BROADER WITH THE TROF AND WEAKER WITH THE SURFACE REFLECTION AFTER SUNDAY...BUT THIS IS MINOR TO SUPPORT A 12Z GFS AND 00Z ECMWF/UKMET BLEND AT ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: THE 12Z NON-NCEP MODELS CONTINUED A TREND OF SLOWING AND AMPLIFYING THE TROF THROUGH THE MID-ATLANTIC AND OFFSHORE...WITH LARGEST DIFFERENCES OCCURRING MONDAY MORNING. THE 12Z ECMWF/CMC ARE A BIT DEEPER WHILE THE ECMWF/UKMET ARE A BIT SLOWER THAN THEIR PRIOR RUNS. THIS LEADS TO SURFACE CYCLOGENESIS SPLIT WITH THE UKMET/GFS NORTH AND CMC/ECMWF SOUTH THOUGH MERIDIONALLY AGREEABLE WITH THE NAM NOT SUPPORTING MUCH REFLECTION. OVERALL A NON-NAM BLEND OVER THE CONTINENT WOULD SUPPORT ABOVE AVERAGE CONFIDENCE BUT AFTERWARD TOWARD BERMUDA AND SURFACE CYCLOGENESIS WOULD BE CLOSER TO AVERAGE CONFIDENCE IN NON-NAM BLEND. SERIES OF WEAKER PACIFIC WAVES/IMPULSES AIMED INTO THE PACIFIC NORTHWEST U.S FRI/SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE PARADE OF SHORTWAVES CONTINUES AFTER THE LEADING WAVE IS ENTERING THE FAR PAC NW CURRENTLY...WITH ONE MORE SIGNIFICANT WAVE ADVANCING TOWARD THE NORTHWEST FRI NIGHT/SAT MORNING. THIS WAVE IS CURRENTLY SEEN IN WV AMPLIFYING NEAR 40N140W...THE 00Z UKMET IS MUCH MORE AMPLIFIED BUT MORE IMPORTANTLY MUCH FURTHER EAST TOWARD VANCOUVER ISLAND BY 05/12Z...WITH A STRONG SURFACE REFLECTION WELL EAST OF THE BETTER CLUSTER. THE 00Z CMC ALSO APPEARS A BIT OF OUT PHASE WITH THE OTHERWISE BETTER CLUSTERED 12Z NAM/GFS/00Z ECMWF AS WELL AS THE 00Z ECENS MEAN/06Z GEFS MEAN...AS IT IS A BIT MORE AMPLIFIED/WRAPPED WITH A CLOSED 7H LOW...UP BUT ITS PROXIMITY TO THE BETTER GFS/NAM/ECMWF CLUSTER IS CLOSER TO THAN THE UKMET. AS SUCH WILL FAVOR A 12Z NAM/GFS AND 00Z ECMWF BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 19Z UPDATE: A MUCH STRONGER CLUSTERING EXISTS WITH WEAKER SHIFT OF THE 12Z CMC AND 12Z UKMET THOUGH THE UKMET REMAINS A BIT MORE AMPLIFIED WITH A DEEPER WAVE AND SURFACE REFLECTION ON SAT MORNING. CONSISTENCY IN THE 12Z ECMWF KEEPS CONFIDENCE UP IN A NON-UKMET BLEND. DEEPER PACIFIC TROF ENTERING WESTERN U.S. SUN AND SHIFTING INTO THE ROCKIES MONDAY ALONG WITH ASSOCIATED DEVELOPING LOW PRESSURE OVER THE NORTHERN HIGH PLAINS SUN/MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ PREFERENCE: 12Z GFS/ECMWF/CMC BLEND CONFIDENCE: AVERAGE AS THE NEXT WAVE AMPLIFIED WHILE APPROACHING THE WEST COAST...THE NORTHERN PORTION OF THE WAVE UNDER INFLUENCE OF THE WEAKENING AND SOUTHEASTWARD SHIFTING CENTROID OF THE NORTHERN PACIFIC GYRE SHEARS THE WAVE NORTHWARD WRAPPING THE INNER CORE RAPIDLY JUST OFFSHORE OF THE OR/WA/VANCOUVER ISLAND COAST SUNDAY MORNING. THE REMAINING TROF/COLD FRONT PROGRESSES ASHORE INTO THE GREAT BASIN LEADING TO HEIGHT FALLS ACROSS THE GREAT PLAINS AND LEE CYCLOGENESIS THAT SHIFTS SOUTHWARD WITH TIME ON MONDAY. MODELS ARE GENERALLY IN GOOD AGREEMENT WITH THE TIMING AND SYNOPTIC EVOLUTION OF THIS SCENARIO....HOWEVER INTERNAL DIFFERENCES/AGREEMENTS DENOTE MORE CENTRAL/AVERAGE SOLUTION THAT CONTINUE TO HAVE FAIR CONTINUITY. THE 00Z UKMET IS THE MOST WRAPPED UP OF THE DETERMINISTIC MODELS ON SUNDAY WITH A VERY STRONG AND THEREFORE SLOWER SURFACE REFLECTION. ON THE OPPOSITE SIDE...THE 12Z NAM REMAINS GENERALLY WEAKER AND WEST WITH RESPECT TO THE SAME FEATURE THAN THE BEST CLUSTERED 00Z CMC/ECMWF AND 12Z GFS WHICH ARE SUPPORTED BY THE RECENT ENSEMBLE SUITE INCLUDING THE 09Z SREF. DOWNSTREAM...THE SOUTHERN PORTION OF THE TROF IS WELL AGREED UPON BY THE GUIDANCE THOUGH THE 00Z UKMET IS A BIT STRONGER/DEEPER WITH THE UPPER WAVE IN E CO AND ACROSS SASKATCHEWAN BY THE END OF THE PERIOD...AND THE 12Z GFS TRENDED A BIT STRONGER AND FASTER AT 08/00Z BUT NOT OUT OF LINE TOO MUCH YET. AS SUCH A NON-UKMET BLEND IS FINE ACROSS THE GREAT BASIN/PLAINS INCLUDING THE SURFACE DEVELOPMENT...BUT QUESTIONS WITH THE NAM IN THE PACIFIC SUPPORT A 12Z GFS AND 00Z ECMWF/CMC BLEND AT AVERAGE CONFIDENCE. 19Z UPDATE: LITTLE CHANGES IN THE 12Z NON-NCEP SUITE KEEPS GOOD AGREEMENT WITH THE CMC/GFS/ECMWF THOUGH THERE IS A LITTLE BIT OF INCREASED SPREAD AT THE VERY END OF THE PERIOD WITH THE DEEPER/FASTER GFS AT 08/00Z...WHILE THE ECMWF IS MUCH WEAKER AND WASHED OUT AND FAVORS ITS SLOWER BIAS. THE 12Z CMC SUPPORTS BOTH...BY BEING FASTER LIKE THE GFS BUT WEAKER LIKE THE ECMWF...WHICH HAS ALSO BEEN THE TREND...STILL OVERALL THIS REMAINS MINOR TO KEEP AN AVERAGE CONFIDENCE IN A 12Z ECMWF/GFS/CMC BLEND. THE 12Z UKMET REMAINS STRONGER WITH THE DEEPENING TRIPLE POINT OFF THE WA/OR COAST AND TRANSLATES THIS ENERGY TOWARD A DEEPER AMPLIFICATION ACROSS S CANADA BY THE END OF THE PERIOD...KEEPING IT CONSISTENT WITH ITS 00Z RUN BUT ALSO OUT OF FAVOR. PACIFIC ENERGY APPROACHING WEST COAST MONDAY AND DIGGING OUT THE START OF A CUT-OFF LOW IN S CA/NW MEXICO BY 00Z TUES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~ PREFERENCE: NON-NAM BLEND CONFIDENCE: AVERAGE IN THE WAKE OF THE DEEPER PACIFIC TROF ENTERING THE PERSISTENT MEAN RIDGE IN THE ROCKIES...STRONG WESTERLY FLOW/JET ENERGY APPROACHES THE BLOCK AND STARTS TO CARVE OUT A DEEPER TROF EVOLVING INTO A CUT-OFF LOW NEAR SOUTHERN CALIFORNIA/NW MEXICO AT THE END OF THE FORECAST PERIOD INTO DAY 4. MODELS CONTINUE TO BE FAIRLY CONSISTENT WITH THIS DEVELOPMENT PARTICULARLY THE ECENS MEAN/GEFS MEAN...WHICH CONTINUE WITH THIS CYCLE. THE 12Z GFS TRENDED A BIT MORE CUT-OFF AND WEAKER OVERALL BY A FEW DECAMETERS BUT WITH GOOD AGREEMENT IN TIMING/PLACEMENT AND STRENGTH WITH THE 00Z ECMWF AND THE ENSEMBLE MEANS...FEEL FAIRLY CONFIDENT IN THE LARGER SCALE...THOUGH THE INTERNAL DETAILS MAY CONTINUE TO WAVER FOR AN OVERALL AVERAGE CONFIDENCE IN TOTALITY WITH THIS WAVE AT THIS POINT. THOUGH THE OVERALL TIMING OF THE WAVE IT SUPPORTED BY THE REMAINING GUIDANCE THERE REMAINS SOME CONCERNS IN THEIR EVOLUTIONARY PATHS TO INCLUDE THEM IN THE BLEND. THE 12Z NAM IS QUITE STRONG WITH A DEEP COAST HUGGING SURFACE REFLECTION THAT SEEM WELL OUT OF PLACE. WHILE THE 00Z UKMET/CMC BOTH FAVOR A STRONGER LEAD PORTION OF THE WAVE ENTERING THE OR/CA COASTLINE SHEDDING MORE ENERGY NORTHWARD THAN THE GFS/ECMWF...AS REFLECTED WELL BY THE WEAK SURFACE LOW NEARING THE COAST SUNDAY NIGHT/MONDAY MORNING. THE 00Z CMC IS ALSO SLOW TO INJECT ENERGY INTO THE BASE OF THE DIGGING TROF WHILE THE 00Z UKMET HAS A MUCH NARROWER WAVELENGTH. AS SUCH WILL FAVOR THE 12Z GFS/00Z ECMWF BLEND AT AVERAGE CONFIDENCE. 19Z UPDATE: 12Z NON-NCEP MODELS FURTHER SUPPORT THE EVOLUTION OF THE 00Z ECMWF/12Z GFS THOUGH A BIT FURTHER EAST THE TIMING SHAPE ARE IN GOOD ENOUGH AGREEMENT TO SUPPORT THEM OVERALL. THERE REMAIN SOME DIFFERENCE ON HANDLING A WEAK SURFACE WAVE NEARING CA/OR...THE 12Z ECMWF IS A BIT MORE AMPLIFIED TO SUPPORT A FASTER WEAK WAVE SIMILAR TO THE 12Z UKMET WHILE THE 12Z CMC IS A BIT MORE AMPLIFIED BUT SLOWER AND TRACKS TOWARD THE GFS. THERE IS QUITE A BIT OF SPREAD ON THIS AREA AROUND 07/00-12Z NEAR THE CA/OR COASTLINE...AND IT APPEARS TO BE A NARROW WINDOW/SPACE THAT TEETERS IT NORTH OR SOUTH...BUT GIVEN THE OVERALL AGREEMENT WILL SUPPORT GOOD CONFIDENCE IN THE LARGE SCALE SYNOPTIC EVOLUTION BUT THE INNER DETAILS LIKE THIS SURFACE WAVE AND IMPACTS TO QPF KEEP CONFIDENCE POOR WITH THIS SCALE. AS GIVEN THE ENSEMBLE MEANS WILL SUPPORT A NON-NAM BLEND AT AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA