368
FXUS10 KWNH 110626
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
126 AM EST SAT JAN 11 2020
VALID JAN 11/0000 UTC THRU JAN 14/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
EXCEPTION: 00Z ECMWF/CMC/GEFS BLEND ACROSS PACIFIC NW/SW CANADA
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
07Z UPDATE: LITTLE SIGNIFICANT CHANGES WERE NOTED IN THE 00Z RUNS
OF THE UKMET, CMC OR ECMWF, WITH EXCEPTION OF THE ECMWF/CMC
ADJUSTING A BIT FURTHER EAST WITH THE HUB OF COLD AIR/CLOSED LOW
IN ALBERTA. SIMILARLY THE 00Z GEFS IS A BIT CLOSER OVERALL TO THE
ECENS MEAN AND THE ECMWF/CMC TO SUGGEST KEEPING THE INITIAL
PREFERENCE SELECTIONS AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.
---PRIOR DISCUSSION---
CURRENT HIGH MERIDIONAL TROF ACROSS THE CENTRAL CONUS WILL
CONTINUE TO LIFT NORTHEAST AND WEAKEN ACROSS THE GREAT LAKES INTO
INCREASINGLY CONFLUENT FLOW. THE TRENDS HAVE BEEN TOWARD A
SLIGHTLY FASTER AND WEAKER SYSTEM, BREAKING DOWN THE SURFACE
CYCLONE A BIT FASTER THAN THE LAST FEW DAYS, THE ONLY REMAINING
STRONGER/COMPACT SOLUTIONS REMAIN THE UKMET (THOUGH IS FASTER)
THAN THE 00Z NAM. IT IS NOT A TREMENDOUS DIFFERENCE IN THE
SPREAD, BUT WOULD WEIGHT THOSE SOLUTIONS LESS OR EVEN REMOVE THEM
FROM THE REMAINDER OF THIS SYSTEM.
AFTER THIS WAVE, THE LARGE SCALE PATTERN BROADENS TOWARD A LARGE
SCALE TROF THAT DOMINATES THE NORTHWESTERN TWO-THIRDS OF OF NORTH
AMERICA WITH A CENTRAL HUB/LOBE OF THE POLAR VORTEX TAKING UP
RESIDENCE ACROSS N BC/ALBERTA BY MONDAY. ALONG THIS OUTER EDGE IN
THE DEEPER WESTERLIES, FAST MOVING SHORTWAVES WILL SWING THROUGH
THE ROCKIES ON THEIR WAY THROUGH THE CENTRAL PLAINS ON LATE SUNDAY
INTO MONDAY AND THEN AGAIN ON TUESDAY, WITH A THIRD POTENT PACIFIC
WAVE ENTERING OREGON TUESDAY REACHING THE GREAT BASIN BY THE END
OF THE FORECAST PERIOD. THE FIRST WAVE THAT STARTS THE BROADENING
OF THE LARGE SCALE TROF IS ALREADY A BIT TO COMPACT/STRONG IN THE
00Z CROSSING THE INTERMOUNTAIN WEST, AND WHILE IT IS NOT TERRIBLY
OUT OF PHASE WITH THE ENSEMBLE SUITE, IT IS A BIT STRONGER AND HAS
NEGATIVE EFFECTS ON THE BROAD RETURN FLOW OF THE GULF AND
INTERSECTION/OVERRUNNING. THE 00Z GFS, MUCH LIKE PRIOR RUNS,
SHOWS SOME TYPICAL FAST BIAS, BUT WHAT IS INTERESTING IS THE
PLACEMENT/STRENGTH OF THE RETURN MOISTURE STREAM OUT OF THE GULF
(TIGHTER 850-7H GRADIENT FURTHER EAST) THAN THE ECMWF/UKMET, WHILE
THE MASS FIELDS ARE NOT TOO BAD, THIS FAST BIAS WOULD SUGGEST THE
GFS MAY BE A BIT TOO FAR EAST, THOUGH THE ECMWF/UKMET MAY BE TOO
FAR WEST AND A COMPROMISE MAY BE BEST. THIS PATTERN CONTINUES
WITH THE NEXT BUT WEAKER SHORTWAVE COMING THROUGH TUESDAY, WITH
THE GFS WEAKER AND FURTHER EAST WHILE THE UKMET/ECMWF FURTHER
WEST, WITH THE CMC FAVORING THE SLOWER SOLUTIONS OVER THE GFS TOO.
AS THE LARGE SCALE VORTEX/COLD POOL ANCHORS ITSELF MONDAY, THE
INTERNAL WOBBLE/BINARY INTERACTIONS, SHOW THE GFS PULL THE COLD
AIR AND THEREFORE THE CENTROID FURTHER EAST, A BIT MORE THAN EVEN
THE 18Z GEFS SUGGESTS, SO WOULD BE A BIT LEERY OF THERMAL PROFILES
IN THE NORTHERN HIGH PLAINS BY LATE MON/TUESDAY, THOUGH THE
TIMING/TRACK OF THE SHORTWAVE EMERGING FROM THE PACIFIC/GULF OF AK
APPEARS TO BE CONGRUENT WITH THE ECMWF/CMC TO HAVE SOME
CONFIDENCE. THE 12Z UKMET IS ALSO GENERALLY EAST WITH THE CENTER
OF THE VORTEX BY THE END OF DAY 3, BUT UNLIKE MUCH OF THE OTHER
GUIDANCE IS MUCH TOO SLOW AND VERY WEAK WITH THE PACIFIC/GULF OF
AK WAVE THAT IT WOULD NOT BE IN THE PREFERENCE ACROSS THE PACIFIC
NW ON DAY 3.
SO OVERALL, A NON-NAM BLEND IS SUPPORTED THROUGHOUT THE FORECAST
PERIOD, BUT AFTER THE INITIAL MERIDIONAL TROF LIFTS THROUGH THE
NORTHEAST AND BROADER TROF DEVELOPS WITH EMBEDDED SHORTWAVES,
WOULD PREFER TO UTILIZE THE GEFS OVER THE GFS IN GENERAL IN THE
PREFERRED BLEND. CONFIDENCE REMAINS WELL ABOVE AVERAGE FOR THE
OVERALL PATTERN, BUT THE SMALLER SCALE BUT IMPORTANT
PLACEMENT/TIMING/DEPTH ISSUES IN THE 00Z GFS/NAM AND UKMET IN THE
PACIFIC NORTHWEST ON DAY 3 REDUCE OVERALL CONFIDENCE TO SLIGHTLY
ABOVE AVERAGE FOR THE ENTIRE BLEND.
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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