008
FXUS10 KWNH 100624
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
124 AM EST FRI JAN 10 2020
VALID JAN 10/0000 UTC THRU JAN 13/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
EXCEPTION: NON-CMC OUT OF CENTRAL ROCKIES AFTER 12.12Z
NON-NAM IN PACIFIC NW (WESTERN CANADA AFTER 12.00Z)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
07Z UPDATE: THE WEAKENING TREND PICKED UP ON BY THE 00Z GFS, HAS
BEEN PICKED UP BY THE 00Z ECMWF AND CMC WHILE THE 00Z UKMET AND
GEFS MEAN REMAIN A BIT STRONGER AND SLOWER THROUGH THE GREAT LAKES
THE SPREAD IS STILL FAIRLY SMALL OVERALL AND AS SUCH A GENERAL
MODEL BLEND IS SUPPORTED BUT AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.
WITH SLIGHTLY FASTER DOWNSTREAM SYSTEM, THERE WAS EQUAL SHIFT
FASTER WITH THE SECOND SHORTWAVE THROUGH THE PLAINS INTO THE GREAT
LAKES BY MONDAY. HERE ONLY THE CMC REMAINS OUT OF PHASE BEING A
BIT STRONGER AND SOUTH LEADING TO LAG BEST CONSENSUS THAT SHIFTED
SLIGHTLY FASTER.
IN THE PACIFIC NW AT THE END OF DAY 3 (AS WELL AS WESTERN CANADA),
THE NAM REMAINS THE ONLY SYSTEM OUT OF AGREEMENT, AS THE CMC
TRENDED CLOSER TO THE CONSENSUS. SO A NON-NAM SOLUTION IS FAVORED
AFTER 12.00Z ACROSS THAT REGION.
---PRIOR DISCUSSION---
THE OVERALL PATTERN CONTINUES TO TIGHTEN INTO A COMMON SOLUTION
THROUGHOUT THE SHORT-TERM FORECAST PERIOD WITH THE SYSTEMS MOVING
THROUGH THE LARGER SCALE BROAD CYCLONIC PATTERN IN THE CONUS.
THE ONLY EXCEPTION TO THIS IS THE 12Z CMC WHICH REMAINS IN A
TYPICALLY NEGATIVE BIAS OF BEING A BIT SLOW THROUGH THE EVOLUTION
OF EACH SYSTEM. THIS IS PARTICULARLY THE CASE WITH THE CURRENT
DEEP MERIDIONAL TROF WITH THE BASE SHORTWAVE CURRENTLY ACROSS AZ,
EVOLVING INTO A DEEP SURFACE CYCLONE ACROSS THE MS RIVER VALLEY
INTO THE GREAT LAKES BY LATE SAT INTO SUNDAY. INTERESTINGLY, THE
00Z GFS SHOWED A SLIGHT SHIFT, TRENDING A BIT FASTER WITH THE
INITIAL SHORTWAVE PULSE THROUGH THE SOUTHWEST, ENHANCING THE 25H
JET A BIT STRONGER/FASTER LEADING IT TO BE GENERALLY WEAKER AND
THEREFORE FASTER AS THE CYCLONE CYCLES ACROSS THE GREAT LAKES. IT
IS NOT TERRIBLY OUT OF TOLERANCE COMPARED TO THE 00Z NAM, 12Z
ECMWF/UKMET OR ENSEMBLE GUIDANCE OF THE 18Z GEFS AND 12Z ECENS,
BUT JUST ENOUGH TO SUPPORT UTILIZING THE 18Z GFS OVER IT,
PARTICULARLY WITH THIS FIRST SYSTEM. EVENTUALLY, THE WAVE
STRETCHES EASTWARD IN THE STRONG INCREASINGLY CONFLUENT MID TO
UPPER LEVEL FLOW ACROSS THE LOWER GREAT LAKES INTO THE NORTHEAST,
EVEN THE WEAKER GFS REMAINS IN SOLID AGREEMENT TO HAVE SLIGHTLY
ABOVE TO ABOVE AVERAGE CONFIDENCE IN THE NON-CMC PREFERENCE.
UPSTREAM, GULF OF AK COMPACT SHORTWAVE/CLOSED LOW BROADENS/OPENS
UP ACROSS THE PACIFIC NW, UNDER STRONG MODEL CONGRUENCE. AS THE
WAVE BROADENS THE LARGE SCALE TROF THROUGH THE INTERMOUNTAIN WEST,
ONLY THE 12Z CMC CONTINUES TO LAG/SLOW, TO KEEP IT LESS FAVORABLE.
EVENTUALLY, THE SHORTWAVE REACHES THE SOUTHEAST SIDE OF THE
LARGER TROF AND SHARPENS WITH SOME NEGATIVE TILTING ACROSS THE
LOWER MO VALLEY BY 0Z MON, HERE THE 12Z UKMET IS A TAD SLOWER THAN
THE ECMWF/GFS/NAM SO WOULD SUGGEST A BIT LESS OF ITS INFLUENCE IN
THE PREFERENCE BUT OVERALL A NON-CMC BLEND REMAINS PREFERRED HERE
AS WELL.
---PACIFIC NW DAY 3---
THE NEXT SHORTWAVE SHARPENS ALONG THE EASTERN SIDE OF THE ALASKAN
OMEGA BLOCK DRAWING A PORTION OF THE POLAR VORTEX AND ASSOCIATED
COLD AIR INTO BC AND ALBERTA; THIS IS WHERE THE GREATEST
UNCERTAINTY REMAINS, AS THE 12Z CMC IS VERY COLD AND MUCH FURTHER
WEST WITH THE WAVE, BUT LOOKS BETTER WITHIN THE ENSEMBLE SUITE
(PARTICULARLY COMPARED TO ECMWF/ECENS SOLUTIONS) RELATIVE TO
ELSEWHERE IN THE CONUS. THE 00Z NAM, LIKE PRIOR RUNS SHOWS
GREATER PHASING AND STRONGER AMPLIFICATION OF THE WAVE DROPPING IT
INTO S BC AND THE NORTHERN ROCKIES BY 84HRS, WHICH SEEMS A BIT TOO
AGGRESSIVE, AND WHILE IT IS NOT TOO FAR OUT OF THE REALM OF
POSSIBILITY, IT IS LESS FAVORED AND LIKELY SHOULD BE REMOVED IN
THE PREFERENCE ACROSS THIS AREA BY THE END OF DAY 3. OTHERWISE,
THE GFS, UKMET AND ECWMF HAVE SOLID ENOUGH AGREEMENT BY THE END OF
DAY 3 IN A LOW TO MILD ENSEMBLE SPREAD REGIME TO HAVE HIGHER
CONFIDENCE IN THIS BLEND OVERALL.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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