265
FXUS10 KWNH 230701
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
201 AM EST THU JAN 23 2020
VALID JAN 23/0000 UTC THRU JAN 26/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH FINAL PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SHORTWAVE TROUGH MOVING ONSHORE THE PACIFIC NORTHWEST THU
NIGHT-FRI, THEN INTO THE PLAINS SAT-SAT NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL CONSENSUS THROUGH DAY 2, THEN ECMWF WITH
GEFS/ECENS MEAN BY DAY 3.
CONFIDENCE: AVERAGE...THEN BELOW AVERAGE BY DAY 3.
A PIECE OF ENERGY SHEDDING FROM A CLOSED LOW NEAR THE GULF OF
ALASKA WILL EJECT EASTWARD INTO THE PACIFIC NORTHWEST ON FRIDAY,
ACCOMPANIED BY AN INTENSIFYING, ALTHOUGH STILL MODEST, PACIFIC JET
STREAK BRINGING HEAVY RAINFALL TO THE NORTHWEST.
FAIRLY STARK MODEL DIFFERENCES EMERGE BY THE END OF DAY 2 INTO DAY
3 -- BOTH WITH THE TIMING AND PHASING (OR LACK THEREOF) OF BOTH
NORTHERN/SOUTHERN SHORTWAVES. THE GFS, NAM, CMC AND TO A LESSER
EXTENT THE UKMET, ARE TOO AMPLIFIED AND SLOW WITH THE NORTHERN
STREAM SHORTWAVE TROUGH AND DOWNSTREAM SHORTWAVE RIDGE WHEN
COMPARED TO THE ECMWF AND GLOBAL ENSEMBLE MEANS. WHILE ANY OF
THESE SOLUTIONS MAY CERTAINLY PAN OUT, GIVEN THE TIMING/AMPLITUDE
DISPARITY OF THE OPERATIONAL GUIDANCE AS A WHOLE, AT THIS POINT
(DAY 3 FORECAST) THE RECOMMENDATION WOULD BE TO OPT FOR THE
FLATTER OPERATIONAL ECMWF ALONG WITH THE ECENS AND GEFS MEANS.
...NEXT SHORTWAVE TROUGH MOVING ONSHORE THE WEST COAST BY EARLY
SUN (DAY 3)...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: ECMWF WITH GEFS/ECENS MEAN
CONFIDENCE: AVERAGE
THE 00Z GFS IS ON THE FASTER EDGE OF THE MODEL SPREAD (INCLUDING
GEFS/ECENS) WITH THE SHORTWAVE COMING ASHORE BY 12Z SUN, WHILE THE
NAM, UKMET, AND CMC WERE A BIT MORE AMPLIFIED/SLOWER COMPARED TO
THE ECMWF AND THE ECENS AND GEFS MEANS.
...PHASING NORTHERN AND SOUTHERN STREAM TROUGHS AND EVENTUAL
CLOSED UPPER LOW THU THROUGH SAT NIGHT
FROM THE PLAINS INTO THE OH VALLEY AND NORTHEAST...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL CONSENSUS THROUGH DAY 2...ECMWF AND
UKMET BLEND ON DAY 3
CONFIDENCE: SLIGHTLY BELOW AVERAGE
MANY DETAILS STILL NEED TO BE IRONED OUT WITH TWO MID-LEVEL
IMPULSES MOVING THROUGH THE PLAINS TODAY INTO THURSDAY, AND HOW
THEY WILL INTERACT THROUGH THE REST OF THE WEEK. MULTIPLE FEATURES
INTERACTING CREATE LOWER THAN USUAL CONFIDENCE, BUT THE LEADING
SHORTWAVE MOVING THROUGH THE NORTHERN ROCKIES SHOULD EVENTUALLY
BECOME DOMINANT AND INTENSE, ESPECIALLY LATE ON FRIDAY NIGHT FROM
THE MISSOURI VALLEY AND INTO THE OHIO VALLEY. THIS SHOULD LEAD TO
STRONG CYCLOGENESIS ALONG A TRIPLE POINT ACROSS THE MID-ATLANTIC
BY SATURDAY, WITH THIS TRIPLE POINT EXTENDING FROM A PRIMARY
SURFACE LOW BENEATH THE TRAILING UPPER TROUGH OVER THE UPPER
MIDWEST.
GIVEN THE MINIMAL SPREAD, A GENERAL MODEL CONSENSUS WOULD APPEAR
VIABLE THROUGH DAY 2. BY SATURDAY, THE GFS, NAM, AND TO A LESSER
EXTENT THE CMC BEGIN TO OUTPACE THE OTHER GUIDANCE WITH THE
PROGRESSION OF THE MID-LEVEL LOW ACROSS THE OH VALLEY AND INTO THE
EASTERN GREAT LAKES REGION. AS A RESULT, THE GFS AND NAM ARE
FASTER WITH THE SURFACE FROPA OFF THE MID ATLANTIC COAST SATURDAY
MORNING, AND THUS QUICKER WITH THE LOW-MID LAYER COLD ADVECTION.
THESE SOLUTIONS ARE ALSO FASTER WITH THE ABSORPTION OF THE GREAT
LAKES SURFACE LOW. A BLEND OF THE ECMWF AND UKMET IS THEREFORE
FAVORED, ESPECIALLY WHEN COMPARED TO THE GEFS AND ECENS, WHICH
BOTH MAINTAIN A SURFACE LOW OVER THE GREAT LAKES (EASTERN LOWER
MI) THROUGH 00Z SUN.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HURLEY
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