MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1209 PM EST TUE FEB 23 2016 VALID FEB 23/1200 UTC THRU FEB 27/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DEVELOPING CLOSED UPPER LOW NEAR ARKLATEX TODAY AND ASSOCIATED SURFACE REFLECTION LIFTING INTO THE EASTERN GREAT LAKES THUR AND ST. LAWRENCE SEAWAY BY FRI NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC WEIGHTED TOWARD 12Z NAM/00Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE THE LEADING EDGE OF HEIGHT FALLS ALONG THE NOSE OF A 125 KNOT PACIFIC JET HAS SPAWNED A BROAD AREA OF SHOWERS/THUNDERSTORMS CENTRAL TX. THIS SYSTEM IS FORECAST TO QUICKLY EVOLVE INTO A CLOSED UPPER LOW ALONG THE RED RIVER BY AROUND 23/18Z WITH AN EVENTUAL TRACK FROM THE LOWER MS VALLEY UP TO THE LOWER GREAT LAKES THROUGH 25/12Z. THIS UPPER LEVEL CYCLONE IS FURTHER REINFORCED BY NORTHERN STREAM TROF ENERGY CURRENTLY SEEN IN WV OVER MINN THAT WILL SHEAR INTO AND FURTHER DEEPEN THE CYCLONE AND SOUTHERN EXTENSION TROF INTO THE SOUTHEAST THROUGH 25/12Z. OVERALL TIMING/PLACEMENT OF THE DEVELOPING CLOSED LOW AND SURFACE REFLECTION ARE IN FAIRLY GOOD AGREEMENT...HOWEVER INTERNAL SMALLER SCALE WAVE INTERACTIONS ARE LENDING TOWARD A LARGE SPREAD IN THE FINER SCALE DETAILS THAT MAKE SUCH A DIFFERENCE IN THE SENSIBLE WEATHER PATTERN. LARGEST SPREAD REMAINS TIED MAINLY TO THE INTENSITY OF THE SURFACE LOW...WITH THE 00Z ECMWF/UKMET AND 12Z GFS FAVORING AN INITIALLY STRONG REFLECTION WHILE THE 12Z NAM TRENDED TOWARD A WEAKER BROADER REFLECTION THAT EVENTUALLY IS STRONGER THROUGH THE OHIO VALLEY WITH BEST AGREEMENT WITH THE 00Z ECMWF... WHILE THE UKMET/GFS TRENDED TOWARD THE WEST/NORTHWEST OF THE GUIDANCE SUITE...AND WHILE THIS IS AWAY FROM EARLIER PREFERENCE AND ON THE PERIPHERY OF THE ENSEMBLE SUITE IT SHOULD NOT BE FULLY DISCOUNTED GIVEN THAT A STRONGER SURFACE REFLECTION GENERALLY TRENDS TOWARD THE WEST. THOUGH THIS WESTWARD SHIFT COULD BE UNDER THE INFLUENCE OF A EASTWARD TRACK OF THE UPSTREAM SHORTWAVE (SEE SECTION BELOW) OVER THE DAKOTAS. THE 00Z CMC IS MUCH WEAKER THAN THE BULK OF THE GUIDANCE SUITE AND GIVEN THE DYNAMICS INVOLVED EVEN CURRENTLY...SEEMS A BIT LESS LIKELY. OVERALL THIS SUPPORTS A NON-CMC BLEND BUT IN KEEPING WITH CONTINUITY AS WELL AS KEEPING TOWARD THE TRENDS NOTED IN THE ENSEMBLE SUITE...WILL CONTINUE TO FAVOR THE EASTERN TRACK AND WEIGHT MORE HEAVILY TOWARD THE 00Z ECMWF/12Z NAM WITHIN THE BLEND. GIVEN ALL THE EXTERNAL INFLUENCES (SHORTWAVE INTERACTIONS) AS WELL AS THE HIGHLY VARIABLE RUN TO RUN INTERNAL WAVE DIFFERENCES... CONFIDENCE IN THIS BLEND OVERALL IS SLIGHTLY BELOW AVERAGE. ROBUST SHORTWAVE DIGGING THROUGH THE DAKOTAS BY 24/1800Z...REINFORCING THE BASE OF LARGE SCALE TROF IN THE MID-MS RIVER VALLEY THURS AND SWEEPING THROUGH MID-ATLANTIC/CAROLINAS FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE A ROBUST SHORTWAVE IS CURRENTLY OBSERVED IN WV OVER ALBERTA BECOMING A BIT MORE AMPLIFIED WITH TIME ENTERING THE DAKOTAS TOMORROW MORNING (WED) SHORTENING THE SPACING FROM THE DEVELOPING UPPER LOW AND SUPPORTING ITS LIFT TOWARD THE NORTHEAST OVER THE NEXT FEW DAYS. EVENTUALLY AS THE PRECEDING UPPER LOW LIFTS...THE SHORTWAVE SHEARS/ELONGATES SOUTH OF ITS PREDECESSOR AND EVENTUALLY REINFORCING THE BASE OF THE TROF AND ACCELERATE EAST THROUGH THE SOUTH TOWARD THE CAROLINA COAST BY FRIDAY. AS NOTED IN THE ABOVE SECTION... THE 12Z GFS/NAM ARE A SHADE MORE CONSOLIDATED AND EAST COMPARED TO THE FURTHEST WEST 00Z ECMWF. THE 00Z UKMET IS TRUE TO BIAS...A BIT FASTER (AND NORTH LIKE THE NAM/GFS) WHILE ALSO RETAINING ENERGY UPSTREAM IN THE BASE OF THE TROF LIKE THE 00Z ECMWF/CMC; AS SUCH SPLITTING THE DIFFERENCES BECOMING THE MOST ELONGATED/SHEARED OF THE DETERMINISTIC MODELS...BUT ALSO STICKING OUT OF THE FAIRLY WELL AGREED UPON SHAPE WITHIN THE ENSEMBLE SPAGHETTI DIAGRAM. AS SUCH THE ECENS MEAN AND GEFS ARE FAIRLY GOOD AGREEMENT AND THEREFORE A NON-UKMET BLEND. SHORTWAVE ENERGY JUST OFFSHORE OR/CA TODAY LIFTING OVER THE LARGE SCALE MEAN RIDGE IN THE ROCKIES...EVENTUALLY TRACKING INTO UPPER/MID MO RIVER VALLEY FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/06Z GEFS CONFIDENCE: SLIGHTLY BELOW AVERAGE THE BASE OF A SHEARING OUT TROF IS LIFTING NORTH ALONG THE WESTERN EDGE OF A WELL ESTABLISHED LARGE SCALE RIDGE LOCKED OVER THE WESTERN U.S. THIS WAVE WILL PROVIDE A GLANCING BLOW TO WESTERN WA TODAY AND CONTINUE TO LIFT INTO CENTRAL BC. EVENTUALLY THE WAVE OVER-TOPS THE RIDGE THURSDAY AND DESCENDS IN THE DAKOTAS...FILLING THE VOID VACATED BY THE EXITING LARGER SCALE TROF. THE AMPLIFICATION OF THIS WAVE BECOMES GREATER INTO SATURDAY...BUT THERE REMAINS A BIT OF SPREAD IN TIMING/DEPTH OF THE WAVE ACROSS THE GREAT PLAINS FRIDAY. THE NON-NCEP MODELS FAVOR A SLIGHTLY FASTER SOLUTION THOUGH PLACE THE ENERGY/AMPLIFICATION OF THE WAVE IN DIFFERENT FLOW REGIMES... THE 00Z UKMET FAVORS EAST INTO MO WHILE THE 00Z ECMWF FAVORS WEST INTO W KS BY THE END OF THE PERIOD. THE ECENS MEAN SUPPORTS THE FASTER SOLUTION BUT CLOSER TO THE UKMET/CMC. THE ENSEMBLE SPAGHETTI PLOTS CONTINUE TO TREND TOWARD THE SLOWER SOLUTION THAT HAS BEEN BEST REPRESENTED BY THE GFS. THE 12Z GFS CONTINUED IN THIS CONSISTENCY SUPPORTED BY ITS 06Z GEFS MEAN AND A BIT BY THE 00Z NAM BUT IT APPEARS A BIT STRONGER/AMPLIFIED AS IT IS APT TO DO. THIS PROVIDES SOME CONFIDENCE IN THIS SCENARIO BUT WILL ONLY FAVOR 12Z GFS/06Z GEFS AT SLIGHTLY BEL0W AVERAGE CONFIDENCE GIVEN THE LARGE SPREAD IN TIMING. SHORTWAVE TROF APPROACHING NORTHERN WEST COAST BY FRIDAY EVENING INTO SAT. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/UKMET AND 00Z CMC BLEND CONFIDENCE: AVERAGE ENSEMBLES SHOW A MUCH STRONGER PACKING AND SUGGESTION OF A NARROW AMPLIFIED WAVE APPROACHING THE WEST COAST AT THE END OF THE PERIOD. THE 12Z GFS LEADS THE CLUSTER BUT IS NOT SUPPORTED BY MANY 00Z GEFS MEMBERS THOUGH IT DID SLOW A BIT FROM THE 00Z RUN...MAKING IT CLOSER TO THE MIDDLE SOLUTIONS. THE 12Z NAM SUPPORTS THE GFS AND IS A BIT MORE AMPLIFIED THE 00Z ECMWF ENSEMBLE SUPPORTED MANY MORE MEMBERS WITH AN AMPLIFICATION...PROVIDING CONFIDENCE TO THE SOLUTION BUT THE TIMING OF THE WAVES REMAINS QUITE SPREAD; THE 00Z ECMWF OPERATIONAL THOUGH WAS ON THE FASTER EDGE OF THIS PACKING. THE 00Z UKMET/CMC ARE MOST CENTRAL TO ALL SOLUTIONS IN FAIRLY GOOD AGREEMENT IN SHAPE/TIMING/STRENGTH OF THE WAVE TO EACH OTHER...THE 12Z UKMET DID TREND EVEN FURTHER EAST...TO SUPPORT INCORPORATING MORE OF THE 12Z GFS. AS SUCH WILL SUPPORT A 12Z GFS/UKMET AND 00Z CMC BLEND AT AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA