789
FXUS10 KWNH 151643
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1242 PM EDT WED APR 15 2020
VALID APR 15/1200 UTC THRU APR 19/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...LAST SHORTWAVE IN LARGER SCALE GLOBAL TROF EXITING NEW ENGLAND
BY FRIDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND (THROUGH NEW ENGLAND)
OFFSHORE (FRI):12Z NAM AND 00Z ECMWF/UKMET (06Z GEFS/00Z ECENS)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
GOES-WV DENOTES A SUBTLE SHORTWAVE CROSSING THE GREAT LAKES WITH
ANOTHER UPSTREAM SHORTWAVE OVER NW ONTARIO. THE COMBINATION OF
THESE FEATURES APPEARS THE BE THE LAST VESTIGES OF THE LARGER
GLOBAL TROF THAT HAS DOMINATED THE EASTERN PORTION OF THE
CONTINENT OVER THE LAST HALF-WEEK. THE GREAT LAKES WAVE WILL
SHARPEN A BIT AS IT SLIDES THROUGH THE NORTHEAST WITH THE UPSTREAM
CANADIAN WAVE KICKING IT OUT BY EARLY FRIDAY. THE SPREAD THROUGH
THE NORTHEAST IS SMALL ENOUGH THAT A GENERAL MODEL BLEND CAN BE
AFFORDED, THOUGH MARINE INTERESTS NEAR THE CANADIAN MARITIME MAY
BE BEST SUITED BY A 12Z NAM AND 00Z ECMWF/UKMET BLEND THAT DEPICT
A MORE AMPLIFIED (BUT NOT TOO AMPLIFIED WAVE) AND SUPPORTS SOLID
CLUSTERING OF THE SURFACE LOW WITHIN THE HIGHEST CONCENTRATED
AREAS WITHIN THE ENSEMBLE CLUSTER. CONFIDENCE IS SLIGHTLY ABOVE
AVERAGE FOR THIS BLEND.
...NORTHERN SHORTWAVE DROPPING THROUGH ROCKIES AND MOVING ACROSS
MIDWEST/OHIO VALLEY FRI/SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 17.00Z
00Z ECENS/UKMET BLEND WITH 00Z CMC/ECMWF AT LOWER WEIGHTING
AFTER
CONFIDENCE: SLIGHTLY BELOW AVERAGE
GOES-WV SUITE SHOWS A SHARPENING SHORTWAVE ACROSS (JUST WEST OF)
THE ROCKIES. THIS WAVE'S BASE WILL SETTLE ACROSS THE UT/CO
ROCKIES BY 00Z FRIDAY THOUGH THE TOP/LEAD EDGE WILL SHEAR/ELONGATE
INTO THE CENTRAL PLAINS AND SUPPORT A SURFACE TROF THAT WILL
EVENTUALLY BREAK INTO A SURFACE WAVE THROUGH THE MID-MS VALLEY
INTO THE OHIO/S GREAT LAKES BY MIDDAY FRI. THE SPREAD IN GUIDANCE
WILL ALREADY START BY THIS TIME, WITH THE 12Z NAM AND GFS BOTH
TRENDING FAST, WITH THE NAM IN A TYPICAL STRONGER BIAS, BOTH
TRACKING WELL NORTH OF THE REMAINING GUIDANCE, INCLUDING THE 06Z
GEFS/09Z SREF SOLUTIONS. GIVEN THIS IS A TYPICAL NEGATIVE BIAS,
WILL CONTINUE TO REMOVE BOTH SOLUTIONS FROM THE BLEND. THE 00Z
ECMWF INTERESTINGLY, TRENDED SLOWER AND THEREFORE MORE COMPACT
EMERGING OUT OF THE ROCKIES, EVEN COMPARED TO THE MAJORITY OF
ECENS MEMBERS; AGAIN LIKE THE GFS/NAM...TYPICAL OF A NEGATIVE BIAS
AND SHOULD BE REDUCED IN PREFERENCE COMPARED TO ITS MEAN, BUT NOT
FULLY REJECTED AS IT HAS BEEN LEADING THE LONGER-TERM TREND
SIGNAL.
THE 00Z UKMET HAS BEEN CONSISTENT, AND WHILE INITIALLY
STRONGER/MORE STRUNG OUT THROUGH THE OHIO VALLEY, IT TRENDS NICELY
WITH THE ENSEMBLE TRENDS OVER THE LAST FEW CYCLES. THIS IS TRUE
OF THE 00Z CMC AS WELL; AND WHILE IT REMAINS ELONGATED AS IT
EMERGES OFF THE EAST COAST PRESENTING A WEAKER SURFACE REFLECTION
THAT SLIDES TO THE EAST OF THE BEST CLUSTERING. COULD AFFORD SOME
INCREASED INCLUSION OF THAT MODEL. SO WHILE DAY 1-2 ACROSS THE
ROCKIES IS FAIRLY SOLID AND A GENERAL MODEL BLEND IS
PREFERRED...WILL TREND TO A ECENS MEAN/UKMET AND CMC BLEND
THEREAFTER...WITH LOWER WEIGHTING TO THE CMC TOWARD THE END OF DAY
3 ALONG THE EAST COAST. GIVEN THE OVERALL TRENDS AND INCREASING
SPREAD/UNCERTAINTY THROUGH THE OHIO VALLEY THROUGH THE EAST COAST,
CONFIDENCE IS SLIGHTLY BELOW AVERAGE.
...SHORTWAVE(S) ALONG WEST COAST THROUGH FRI AND ACROSS THE
SOUTHWEST SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THRU 18.00Z
06Z GEFS AND 00Z ECMWF/UKMET/CMC/ECENS BLEND THEREAFTER
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
CLOSED LOW APPEARS TO BE MOVING THROUGH THE APEX OF A STATIONARY
LARGE SCALE RIDGE, WITH THE MAIN BODY STILL SOLIDLY INTACT.
GUIDANCE IS IN SOLID WITH THE TIMING AND GENERAL STRENGTH OF THE
LEAD SHORTWAVE/CLOSED LOW AS IT DESCENDS ALONG THE CA COAST ENOUGH
TO SUPPORT A GENERAL MODEL BLEND...THE UNCERTAINTY REMAINS AS IT
ENTERS THE TERRAIN OF THE SOUTHWEST BY EARLY SAT. THE 12Z NAM AND
GFS BOTH CONTINUE TO BE COMPACT/STRONGER, THOUGH DIFFERING ON THE
TRACK. THE NAM SHIFTS NORTH AND FASTER, TRENDING WITH THE
WEAKENING ECMWF/UKMET/CMC IN TIMING; WHILE THE GFS SLOWS/SHARPENS
ACROSS NM AT THE END OF THE FORECAST PERIOD. SO WOULD PREFER A
NON-NAM SOLUTION THROUGH THE FORECAST PERIOD, MASS-WISE, BUT THE
MOISTURE RETURN/QPF SIGNAL BY THE END OF DAY 3, SUGGESTS KEEPING
IT FROM THE PREFERENCE ON DAY 3. THE 06Z GEFS, HOWEVER, IS MORE
COMPARABLE AND WOULD SERVE AS A GOOD REPLACEMENT. AS SUCH A
GENERAL MODEL BLEND IS SUPPORTED THROUGH 18.00Z BECOMING A 06Z
GEFS AND 00Z ECMWF/UKMET/CMC/ECENS MEAN BLEND THEREAFTER.
CONFIDENCE IS SLIGHTLY ABOVE AVERAGE IN THIS SOLUTION.
...SOUTH-CENTRAL CANADA SHORTWAVE SAT, WITH ATTENDANT COLD FRONT
ACROSS THE NORTHERN PLAINS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF BLEND
CONFIDENCE: AVERAGE
STRONG NORTHWESTERLY FLOW WILL DOMINATE NW CANADA EARLY IN THE
FORECAST PERIOD, THOUGH WITH BROAD CYCLONIC FLOW AND AN ELONGATED
TROF ACROSS THE CENTRAL US, THE PATTERN WILL FOLD LEADING TO
INCREASED RIDGING THEN TROF AS STRONGER JET ENERGY SLIDES THROUGH
NORTHERN AK FRIDAY. SO IN RESPONSE, INITIAL COLD AIR WILL SPILL
SOUTHWARD ACROSS CENTRAL CANADA AND SUPPORTS A COLD FRONT TO REACH
THE NORTHERN TIER AT THE END OF DAY 3, WITH A STRONGER SURFACE
CYCLONE ACROSS N ONTARIO. THE UKMET/CMC SEND THE ENERGY EASTWARD
AND FASTER THAN THE OTHERWISE CLUSTERING SOLUTIONS, AND WHILE THE
DIFFERENCE ACROSS THE CONUS IS SMALLER...THESE SOLUTIONS WOULD NOT
BE FAVORED AT THIS TIME. THE 00Z ECMWF AND ECENS MEAN CONTINUE TO
HAVE SOLID CONTINUITY BUT SLIGHTLY OUTPACE THE GFS/GEFS SOLUTIONS,
WHICH IS ATYPICAL, BUT STILL A GOOD AGREEMENT OVERALL. THE 12Z
NAM IS INITIALLY CLUSTERED WELL HERE, BUT BY THE END OF DAY 3,
LIKELY DUE TO HIGHER RESOLVED COLDER AIR, IT SLOWS AND SHOWS
GREATER CYCLOGENESIS AND DELAYS THE COLD FRONT JUST A BIT TOO
MUCH. AS SUCH A 12Z GFS/00Z ECMWF BLEND IS PREFERRED BUT ONLY AT
AVERAGE CONFIDENCE; WHILE THE CLUSTERING IS GOOD, THE IMPORTANCE
OF THE DOWNSTREAM EFFECTIVE BLOCKING PATTERN AND STRENGTH/DEPTH OF
THE COLD AIR LEAVES THE PREDICTABILITY OF THE ENVIRONMENT A BIT
TOO HIGH FOR HIGHER CONFIDENCE AT THIS TIME. I
...SUBTLE SHORTWAVE AMPLIFYING ALONG BC COAST INTO PACNW LATE
SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS AND 00Z UKMET/ECMWF BLEND
CONFIDENCE: AVERAGE
THE STATIC RIDGE OVER THE EASTERN PACIFIC WILL MAINTAIN NORTHWARD
ACROSS THE GULF OF AK EVEN AS THE SHORTWAVE (TWO SECTIONS ABOVE)
CUTS THROUGH IT TODAY. AS SUCH STRONG JET/SHORTWAVE ENERGY IS
DIRECTED NORTH ACROSS AK. AT THE TAIL END OF A TROF OVER-TOPPING
THE RIDGE ON THURSDAY, FAVORABLE CONDITIONS ON THE NORTHEAST SIDE
OF THE RIDGE WILL ALLOW FOR AMPLIFICATION AS IT TRACKS,
SEMI-PHASED, WITH THE MAIN TROF ACROSS CANADA. HOWEVER, THE
CANADIAN ROCKIES WILL SEPARATE THE WAVE AND EVENTUALLY BECOME A
COMPACT VORTICITY CENTER ALONG VANCOUVER ISLAND, ABLE TO TAP SOME
LIMITED MOISTURE FOR SOME QPF ON SAT. BY THIS TIME, THE 00Z CMC
AND 12Z NAM ARE SLOWER/DEEPER THAN A MORE PROGRESSIVE
ECMWF/GFS/UKMET, WHICH CONTINUE TO MATCH THE ENSEMBLE SUITE WELL.
THIS GENERALLY JIVES WITH THE PREFERENCE OF THE PHASED NORTHERN
STREAM PORTION TO GIVE SOME CONFIDENCE IN THIS BLEND. STILL, THIS
IS A LOW PREDICTABILITY SITUATION GIVEN THE POSITION TO THE RIDGE
AND AFFECTS OF THE ROCKIES ON SEVERING THIS CONNECTION FULLY. AS
SUCH, THERE IS AVERAGE CONFIDENCE IN A 12Z GFS AND 00Z UKMET/ECMWF
BLEND.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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