MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 209 AM EST THU FEB 04 2016 VALID FEB 04/0000 UTC THRU FEB 07/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SURFACE LOW LIFTING AWAY FROM THE GREAT LAKES ATTENDANT COLD FRONT SWEEPING OFF THE EASTERN SEABOARD BY EARLY THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE MODELS ARE IN SOLID AGREEMENT WITH ENSEMBLE MEANS IN PLACEMENT/TIMING AND STRENGTH OF THE SURFACE CYCLONE MOVING INTO QUEBEC AND AS WELL AS ASSOCIATED SLOW MOVING FRONTAL ZONE ACROSS THE EASTERN SEABOARD TONIGHT AND ACROSS NEW ENGLAND THROUGHOUT THE DAY...TO SUPPORT AN OPERATIONAL MODEL BLEND AT ABOVE AVERAGE CONFIDENCE. SHARPENING BASE OF LARGE SCALE TROF INTO CAROLINAS BY FRIDAY MORNING WITH ASSOCIATED LOW PRESSURE OFF THE OUTER BANKS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z ECMWF/GFS BLEND PRIOR TO 05/18Z 00Z ECMWF/CMC AFTER CONFIDENCE: AVERAGE PRIOR TO 05/18Z SLIGHTLY BELOW AVERAGE AFTER WARMING NOTED IN RECENT WV ACROSS N MEXICO IS THE ENERGY REINFORCING THE BASE OF THE LARGE SCALE TROF...WITH TIME THE BREADTH OF THE LARGE SCALE TROF REDUCES AND OVERALL THE BASE SHARPENS ACROSS THE SOUTHERN U.S BEFORE LIFTING THRU THE CAROLINAS AS A STRONGER WAVE THAT LEADS TO SURFACE CYCLOGENESIS ALONG THE LINGERING FRONTAL ZONE NEAR/OFF THE CAROLINA COAST FRIDAY MORNING. TWO FACTORS LEAD TO LARGE SPREAD WITH RESPECT OF THIS SURFACE WAVE...THE POSITION OF THE FRONTAL ZONE AND THE TIMING/STRENGTH OF THE WAVE. THE ENSEMBLE TREND SUPPORTS A SLIGHTLY SLOWER AND THEREFORE DEEPER WAVE WHICH FAVORS THE 12Z ECMWF/UKMET AND 12Z ECENS MEAN. THE 21Z SREF IS THE SLOWEST AND APPEARS WELL OUT OF PHASE WITH OTHER ENSEMBLE MEANS/MEMBERS INCLUDING ITS OPERATIONAL 00Z NAM. THE 12Z GFS/GEFS HAS TRENDED SLOWER AND DEEPER TO SUPPORT THIS SOLUTION...WHILE THE CMC AND CMCE REMAIN PROGRESSIVE OUT OF PHASE WITH THE TREND. THE GEFS/GFS WERE DO REMAIN FURTHER EAST WITH THE FRONTAL ZONE...THIS ALLOWS FOR THE SPREAD WITHIN THE ENSEMBLE SURFACE CLUSTER TO BE QUITE LARGE STRETCHING FROM OFF CAPE FEAR TO SE OF CAPE COD AT 05/12Z...WITH GEFS MEMBERS FURTHER EAST AND SOUTH...THE CMCE MEMBERS WELL NORTH ALMOST ALONE AND ECENS MEMBERS ON PAR LATITUDINALLY WITH THE GEFS CAMP THOUGH WEST CLOSER TO THE COAST; OVERALL THE GEFS/ECENS MEMBERS ARE MUCH BETTER CLUSTERED THAN PRIOR DAYS...GIVING BETTER CONFIDENCE IN THE GEFS/ECENS MEANS...BUT THE ECENS CONSISTENCY FAVORS IT MORE THAN THAN THE GEFS. THE 00Z NAM IS A BIT FASTER/NORTH WITH THE WAVE; CLOSER TO THE UNFAVORED 12Z CMC/CMCE. THE 00Z GFS IS A BIT FURTHER NORTH AND STRONGER THAN ITS 12Z/18Z RUNS MAKING IT IN LINE WITH THE ECENS MEAN UNTIL IT SLOWS/STRENGTHENS AND SHIFTS EAST FRIDAY EVENING/SAT MORNING WHEN IT IS WELL OUT OF PHASE . THE 12Z UKMET LOOKS QUITE FAVORABLE ALOFT BUT IS MUCH STRONGER AND THEREFORE AMPLIFIES A VERY STRONG AND VERY NEAR COASTAL SURFACE WAVE THAT APPEARS MUCH TOO DEEP AND WEST GIVEN THE REST OF THE ENSEMBLE SUITE. WITH BETTER PLACEMENT TIMING TOWARD THE ECENS MEAN...A BLEND OF THE 00Z GFS AND 12Z ECMWF WILL BEST REPRESENT THE MOST PREFERRED AND CENTRAL 12Z ECENS MEAN. CONFIDENCE IS AVERAGE IN THIS BLEND WITHIN THIS LARGE OVERALL SPREAD. 07Z UPDATE: THE 00Z ECMWF AND UKMET BOTH TRENDED FASTER ALOFT AS WELL AS AT THE SURFACE...AND THE 00Z CMC SLOWED TO BE IN BETTER ALIGNMENT WITH THE 00Z NAM/UKMET...THOUGH THE UKMET IS STILL VERY CLOSE TO THE COAST...CMC CENTRAL AND NAM EAST. HOWEVER...ALL OUTPACE THE ECMWF INITIALLY AND WELL OUTPACE THE 00Z GFS (WHICH IS LOOKING MORE AND MORE LIKE AN SIGNIFICANT OUTLIER IN MASS FIELDS PARTICULARLY AFTER 05/18Z). THE TIMING OF THE ECMWF/CMC BECOME BETTER ALIGNED WITH A SLOWING OF THE CMC AS THE SURFACE LOW APPROACHES NOVA SCOTIA...WHILE THE UKMET AND NAM DO AS WELL BUT REMAIN WEST AND EAST RESPECTFULLY. AS SUCH WILL FAVOR A 00Z ECMWF/GFS BLEND (TO REPRESENT THE 12Z ECENS MEAN) THROUGH 05/18Z AT AVERAGE CONFIDENCE AND 00Z ECMWF/CMC BLEND AFTERWARD...AT SLIGHTLY BELOW AVERAGE CONFIDENCE. SYSTEM ENTERING THE PAC NW TODAY DIGGING INTO THE CENTRAL ROCKIES FRI...SOUTHERN PLAINS SAT INTO THE SOUTHEAST SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z ECMWF/CMC BLEND CONFIDENCE: AVERAGE PROGRESSIVE PACIFIC FLOW CARRY SHORTWAVE ENERGY ENTERING THE PACIFIC NORTHWEST (AND WEAKER TROF IN SOUTHERN STREAM) ACROSS THE INTERMOUNTAIN WEST BEFORE LEADING TO SPLIT FLOW ALLOWING MUCH OF THE ENERGY TO CONSOLIDATE INTO A WEAK CUT-OFF SYSTEM ACROSS SOUTHERN PLAINS SAT BEFORE ADVANCING INTO THE SOUTHEAST BY THE END OF THE FORECAST PERIOD...DRAWING SOME DEEPER TROPICAL MOISTURE NORTHWARD. THE 00Z NAM IS GENERALLY FAST AND 12Z UKMET IS UNCHARACTERISTICALLY SLOW. THE 18Z GFS AND ECMWF REPRESENTED THEIR ENSEMBLE MEANS IN TIMING WITH THE 18Z GEFS/GFS SLIGHTLY OUTPACING THE ECENS MEAN/ECMWF THIS INCLUDES GOOD AGREEMENT IN THE PLACEMENT OF SURFACE CYCLOGENESIS EAST OF FL ON SUNDAY MORNING. THE 00Z GFS TRENDED MUCH FASTER ACROSS THE SOUTHEAST BY DAY 3 ALMOST AS FAST AS THE 00Z NAM. THE NAM/GFS MAY BE ONTO A TREND...HOWEVER RUN TO RUN ENSEMBLES SUPPORT THE SLOWER/CENTRAL SPEED OF THE ECMWF/ECENS MEAN/18Z GEFS. THOUGH THE 12Z CMC IS A BIT SLOWER AND DEEPER THAN THE ECMWF IT IS ALSO IS WELL CLUSTERED ALOFT AND WITH THE SURFACE REFLECTION TO INCLUDE INTO A BLEND. AS SUCH A 12Z CMC/ECMWF BLEND IS PREFERRED AT AVERAGE CONFIDENCE BEST REPRESENTING THE ENSEMBLE SPREAD INCLUDING THE 12Z/18Z GEFS. 07Z UPDATE: THE 00Z ECMWF/CMC CONTINUE GOOD CONTINUITY THOUGH THE ECMWF IS A FURTHER SOUTH THAN THE 12Z RUN AND A BIT WEAKER WITH THE SURFACE REFLECTION; WHILE THE 12Z UKMET REMAINS SLOW BUT ALSO A BIT FURTHER SOUTH...PROVIDING SOME CONFIDENCE IN THE CMC/ECMWF BLEND. NORTHERN STREAM CYCLONE DIPPING INTO GREAT LAKES SAT AND NEW ENGLAND SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z ECMWF/CMC BLEND CONFIDENCE: AVERAGE MODELS SHOW A LOBE OF THE ARCTIC CYCLONE CURRENTLY OVER CONTINENTAL NUNAVUT TO DROP SOUTH INTO THE NORTHERN SIDE OF THE SPLIT FLOW AMPLIFYING OVER THE GREAT LAKES LATE SAT AND SHIFTING INTO NEW ENGLAND BY SUNDAY. THE 12Z UKMET IS CLEARLY OUT OF PHASE MUCH SHALLOWER AND PROGRESSIVE THAN MUCH OF THE OUTER THE GUIDANCE...WHILE THE 00Z NAM IS ON THE OTHER SIDE BEING A BIT AGGRESSIVE/STRONG BUT SLOW. THE 00Z GFS JUST LIKE IN THE SOUTHERN STREAM...TRENDED TOWARD THE 00Z NAM...BEING A BIT SLOWER AND MORE PHASED TOWARD THE SOUTHERN STREAM ACROSS NEW YORK AND THE MID-ATLANTIC ALOFT. JUST LIKE IN THE SOUTHERN STREAM THE NAM/GFS MAY BE ONTO A PROPER TREND BUT GIVEN IT IS A BREAK EVEN FROM THE 12Z/18Z GEFS AND OTHER ENSEMBLE GUIDANCE...WILL RESERVE THE ABILITY TO SHIFT IF FURTHER SUPPORT COMES FROM THE 00Z ECMWF/UKMET AND CMC. THE 00Z CMC AND ECMWF DID NOT FOLLOW THIS INCREASED PHASING/DEEPER INFLECTION IN THE TROF SUGGESTED BY THE NAM/GFS...STAYING MORE IN LINE WITH PRIOR CONTINUITY IF NOT A SHADE SLOWER IN TIMING. THE 00Z UKMET IS EVEN TRENDING FLATTER AND FASTER THAN THE 12Z RUN...WHICH SEEMS LESS LIKELY GIVEN ALL OTHER MODELS TRENDS TOWARD SLOWER OR DEEPER. AS SUCH WILL RETAIN A 00Z ECMWF/CMC BLEND AT AVERAGE CONFIDENCE. FAST MOVING PACIFIC SHORTWAVE RACING THE NORTHWEST SAT AMPLIFYING ACROSS THE DAKOTAS INTO THE GREAT LAKES BY SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/GFS BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE A BROAD BUT ALSO QUITE PROGRESSIVE WAVE BOLTS THROUGH THE NORTHERN PACIFIC APPROACHING THE NORTHWEST PACIFIC BY FRIDAY EVENING INTO SAT MORNING IN FAIRLY GOOD AGREEMENT IN TIMING OF THE WAVE WITH THE TYPICAL ARRANGEMENT...THE NAM/GFS/UKMET SLIGHTLY OUTPACING THE ECMWF AND THEN THE CMC. DIFFERENCES EXIST IN THE DEPTH/STRENGTH OF THE WAVE WITH THE ECMWF BEING GENERALLY FLATTER OVERALL THOUGH THE NAM/GFS HAVE TRENDED DEEPER WITH THE 00Z RUN. GIVEN THE PROGRESSIVE FLOW AND DOWNSTREAM SPLIT FLOW (MORE OR LESSER SO BASED ON MODEL SPECIFICS)...EVENTUALLY AS THE WAVE ENTERS THE NORTHERN US ROCKIES IT BEGINS TO AMPLIFY ACROSS THE NORTHERN PLAINS. THE ECMWF ENTERED FLATTER AND SO ACCELERATED INTO THE BLOCKING DOWNSTREAM TROF...BECOMING FASTER AND STRONGER THAN THE REST OF THE GUIDANCE INCLUDING A SURFACE REFLECTION NEARLY 8MB DEEPER THAN OTHER GUIDANCE AS WELL AS MANY OF ITS 12Z ENSEMBLE MEMBERS. AS SUCH THE ECENS MEAN IS A SLOWER BUT DOES REFLECT THE DEEPENING TROF IN A FAVORABLE WAY...MUCH LIKE THE 12Z/18Z GEFS (THOUGH THEY ARE A BIT SLOWER IN TIMING AND DEEPER). THE 12Z UKMET WAS STRONG BUT DUE TO DOWNSTREAM PROGRESSION DOES NOT DIG FURTHER SOUTH BUT STRADDLES THE US/CANADA BORDER...WHICH IS APPEARING LESS LIKELY GIVEN THE DOWNSTREAM TRENDS. THE 00Z CMC REMAINS SLOW AND LESS CONSOLIDATED WITH THE WAVE COMPARED TO THE ENSEMBLE MEANS AND ALL OTHER GUIDANCE. AS SUCH WILL CONTINUE TO FAVOR THE ENSEMBLE MEANS WHICH ARE BEST REPRESENTED BY A BLEND OF THE 00Z NAM/GFS...THOUGH NOT GREATLY SO...SO CONFIDENCE REMAINS SLIGHTLY BELOW AVERAGE. (IF POSSIBLE TO BLEND 18Z GEFS AND 12Z ECENS MEANS WITH THE NAM/GFS IT MAY BE PRUDENT TO DO SO TO BOLSTER CONFIDENCE OVERALL). 07Z UPDATE: THE 00Z UKMET AND CMC BOTH MADE DRAMATIC CHANGES WITH THE WAVE EVOLUTION AFTER LANDFALL IN THE PACIFIC NORTHWEST. THE 00Z UKMET IS VERY SIMILAR IN STRENGTH AND POSITION AS THE 00Z ECMWF WHICH SHOWED LITTLE DIFFERENCE IN TIMING BUT WAS A BIT FURTHER NORTH/LESS DEEP ACROSS THE NORTHERN TIER PARTICULARLY WITH THE SURFACE LOW. THE 00Z CMC FAVORS THE NAM/GFS SOLUTION BUT MAKE BE A BIT TOO FAST DIGGING INTO THE UPPER MISSISSIPPI RIVER VALLEY AT THE END OF DAY 3 TO FEEL CONFIDENT IN ITS INCLUSION. OVERALL THE POSITIONING OF THE SURFACE WAVE AND MUCH OF THE SENSIBLE WX FIELDS LOOK QUITE AGREEABLE THROUGH THIS TIME TO POTENTIALLY SUGGEST AN OPERATIONAL BLEND...BUT MASS FIELD SHAPE/DIFFERENCES REMAIN LARGE ENOUGH IN EVOLUTION PARTICULARLY ALOFT TO SUPPORT EITHER THE GFS/NAM OR UKMET/ECMWF. THOUGH THE ECMWF IS BEEN CONSISTENT THE LAST TWO RUNS FAVORING THAT CAMP...ENSEMBLE MEAN TROF SUPPORT THE GFS/NAM AS WELL AS YESTERDAY'S 00Z ECMWF LOOKS REMARKABLY SIMILAR TO TODAY'S 00Z GFS/NAM. AS SUCH WILL PREFER THE GFS/NAM SLIGHTLY OVER THE ECMWF/UKMET. CONFIDENCE IN THE GFS/NAM BLEND IS SLIGHTLY BELOW AVERAGE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA