075
FXUS10 KWNH 151946
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
345 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 FINAL MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..TROUGH EXITING NEW ENGLAND LATE THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
GOES-16 WV DENOTES SHORTWAVES OVER MI AND NW ONTARIO, WESTERN SIDE
OF THE REMAINING TROUGH THAT HAS SHIFTING EAST ACROSS NORTH
AMERICA OVER THE PAST FEW DAYS. 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 REMAINS SMALL (AS EXPECTED FOR DAY 1) AND A GENERAL
MODEL BLEND IS PREFERRED.
...NORTHERN SHORTWAVE DROPPING THROUGH ROCKIES AND MOVING ACROSS
MIDWEST/OHIO VALLEY FRI/SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/UKMET BLEND WITH SOME 12Z CMC/00Z ECENS AT
LOWER WEIGHTING
CONFIDENCE: SLIGHTLY BELOW AVERAGE
GOES-17 WV DENOTES POSITIVELY TILTED SHORTWAVE TROUGH ACROSS THE
NORTHERN ROCKIES TO THE NORTHERN GREAT BASIN. THE WAVE BASE WILL
SETTLE ACROSS THE UT/CO ROCKIES BY 00Z FRIDAY THOUGH THE TOP/LEAD
EDGE WILL SHEAR/ELONGATE INTO THE NORTH-CENTRAL PLAINS AND SUPPORT
A SURFACE TROUGH THAT WILL EVENTUALLY BREAK INTO A SURFACE WAVE
THROUGH THE MID-MS VALLEY INTO THE OHIO VALLEY BY MIDDAY FRIDAY.
DIVERGENCE 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 12Z GEFS/09Z SREF SOLUTIONS. GIVEN THIS IS A TYPICAL
NEGATIVE BIAS, WILL CONTINUE TO REMOVE BOTH SOLUTIONS FROM THE
BLEND. THE 12Z ECMWF SPED A BIT FROM THE 00Z RUN AND IS NOW IN
EXCELLENT AGREEMENT WITH THE 12Z UKMET FOR BOTH TIMING AND
LATITUDE OF THE LOW LEVEL FEATURES NOW THAT THE UKMET TOOK A BIT
OF A NORTH SHIFT.
THE 12Z CMC TOOK A GREATER NORTH SHIFT AND IS NOW BETWEEN THE NAM
AND UKMET/ECMWF, PARTICULARLY FOR THE NORTHERN EDGE OF THE DAY 2
QPF IN THE MIDWEST AND DAY 3 QPF IN THE NORTHERN MID-ATLANTIC TO
SOUTHERN NEW ENGLAND AND WILL THEREFORE REDUCE THE CMC IN THE
PREFERENCE. GIVEN THE OVERALL TRENDS AND CONTINUED
SPREAD/UNCERTAINTY THROUGH THE OHIO VALLEY THROUGH THE EAST COAST,
CONFIDENCE REMAINS SLIGHTLY BELOW AVERAGE.
...SHORTWAVE(S) ALONG WEST COAST THROUGH FRI AND ACROSS THE
SOUTHWEST SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/UKMET/CMC/ECENS BLEND
CONFIDENCE: AVERAGE
CLOSED LOW OFF THE OR COAST THIS AFTERNOON WILL REMAIN CLOSED AS
IT SWINGS SOUTH ALONG THE CA COAST THROUGH THURSDAY NIGHT, OPENING
INTO A WAVE AS IT EJECTS EAST ACROSS THE DESERT SW/FOUR CORNERS
FRIDAY THROUGH SATURDAY. TIMING DIFFERENCES BEGINNING ON DAY 3 ARE
TYPICAL WITH THE 12Z NAM AND GFS BOTH CONTINUE TO BE
COMPACT/STRONGER AND QUICKER, THOUGH DIFFERING ON THE TRACK. THE
NAM SHIFTS NORTH AND FASTER, WHILE THE GFS SLOWS/SHARPENS ACROSS
NM AT THE END OF THE FORECAST PERIOD. THE 12Z ECMWF/UKMET/CMC ALL
SLOWED COMPARED THE PREVIOUS RUN AND ARE IN AGREEMENT, SO
PREFERENCE GOES TO THEM. GIVEN THE SHIFTING, CONFIDENCE IS AVERAGE
IN THIS SOLUTION.
...SOUTH-CENTRAL CANADA SHORTWAVE SAT, WITH ATTENDANT COLD FRONT
ACROSS THE NORTHERN PLAINS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM 12Z GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
STRONG NORTHWESTERLY FLOW WILL DOMINATE NW CANADA EARLY IN THE
FORECAST PERIOD, THOUGH WITH BROAD CYCLONIC FLOW AND AN ELONGATED
TROUGH ACROSS THE CENTRAL US, THE PATTERN WILL FOLD LEADING TO
INCREASED RIDGING THEN TROUGH 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
PUSH ACROSS THE BREADTH OF THE NORTHERN PLAINS FRIDAY
NIGHT/SATURDAY 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 12Z ECMWF AND 00Z ECENS MEAN CONTINUE TO SLIGHTLY
OUTPACE THE GFS/GEFS SOLUTIONS, WHICH IS ATYPICAL, BUT STILL A
GOOD AGREEMENT OVERALL AND ARE IN AGREEMENT WITH THE 12Z
CMC/UKMET. 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 THE 12Z NAM IS NOT PREFERRED WITH THE
REMAINING CLUSTERING GOOD. THE DOWNSTREAM BLOCKING PATTERN AND
STRENGTH/DEPTH OF THE COLD AIR LEAVES THE PREDICTABILITY OF THE
ENVIRONMENT A BIT TOO LOW FOR HIGHER THAN AVERAGE CONFIDENCE AT
THIS TIME.
..SHORTWAVE AMPLIFYING FROM BC COAST INTO PACNW SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM 12Z GENERAL MODEL 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 TROUGH 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 TROUGH 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 SATURDAY. BY THIS TIME, THE 12Z
NAM IS FASTER/DEEPER THAN THE LESS PROGRESSIVE 12Z
ECMWF/GFS/UKMET/GFS, 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.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
JACKSON
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