511
FXUS10 KWNH 201658
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1157 AM EST MON JAN 20 2020
VALID JAN 20/1200 UTC THRU JAN 24/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PRELIMINARY PREFERENCES AND FORECAST
CONFIDENCE
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~~
..AMPLIFYING SHORTWAVE CROSSING THE MIDWEST THROUGH MONDAY
..CLOSED LOW EVOLUTION OVER THE SOUTHEAST BY TUESDAY
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~~
PREFERENCE: 12Z GFS/00Z ECMWF BLEND
CONFIDENCE: NEAR AVERAGE
A SHORTWAVE IMPULSE CURRENTLY OVER THE MIDWEST IS TRACKING
SOUTHEASTWARD ON THE EAST SIDE OF AN UPPER LEVEL RIDGE OVER THE
ROCKIES. THIS IS FORECAST TO EVOLVE INTO A CLOSED LOW NEAR THE
SOUTHEAST COAST BY TUESDAY MORNING AND THEN TRACK EASTWARD OUT TO
SEA. THIS WILL INDUCE SURFACE CYCLOGENESIS ALONG A FRONTAL
BOUNDARY SITUATED WELL OFFSHORE. EXCEPT FOR SOME LIGHT RAIN NEAR
COASTAL AREAS, THIS SHOULD MAINLY BE A MARINE IMPACT. THE 12Z NAM
AND TO A LESSER DEGREE THE 00Z UKMET ARE CONSIDERABLY FARTHER WEST
THAN THE ENSEMBLE MEANS, AND THE NAM IS A STRONG OUTLIER. THESE
DIFFERENCES BECOME APPARENT MAINLY AFTER TUESDAY AFTERNOON.
..SOUTHERN STREAM SHORTWAVE CROSSING CALIFORNIA BY MONDAY
..ENERGY CROSSING THE SOUTHWEST/PLAINS TUESDAY AND WEDNESDAY
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PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE 12Z GFS/NAM APPEAR SLIGHTLY MORE PROGRESSIVE WITH THE
SHORTWAVE TROUGH COMPARED TO THE NON-NCEP GUIDANCE AS IT CROSSES
THE SOUTHWEST THROUGH TUESDAY. THE 00Z CMC IS A LITTLE WEAKER AT
THE 700MB LEVEL WITH THE SHORTWAVE AND THE GFS SLIGHTLY STRONGER.
THERE IS NOW ENOUGH AGREEMENT AMONG THE GUIDANCE TO MERIT A
GENERAL BLEND OF THE DETERMINISTIC GUIDANCE WITH THIS SHORTWAVE
PERTURBATION.
..UPPER TROUGH/CLOSED LOW OVER THE PACIFIC NORTHWEST BY TUESDAY
...ENERGY EJECTING OUT ACROSS THE NORTHERN PLAINS WEDNESDAY
NIGHT...
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PREFERENCE: BLEND OF THE 00Z ECMWF/EC MEAN
CONFIDENCE: SLIGHTLY BELOW AVERAGE
SOME MINOR LATITUDE DIFFERENCES CONTINUE TO EXIST WITH THIS SYSTEM
AS IT APPROACHES THE PACIFIC NORTHWEST ON TUESDAY WITH THE 00Z
ECMWF/UKMET NORTH WITH THE CENTER OF THE CLOSED LOW WHILE THE 12Z
NAM IS SLIGHTLY SOUTH. AS THE UPPER LEVEL ENERGY EMERGES OVER THE
NORTHERN HIGH PLAINS, THE 12Z GFS BECOMES MORE AMPLIFIED.
...UPSTREAM MID-LEVEL TROUGH OFFSHORE OF THE PACIFIC NORTHWEST
EARLY THURSDAY ALONG WITH ACCOMPANYING SURFACE CYCLONE...
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PREFERENCE: 12Z GFS/00Z UKMET BLEND
CONFIDENCE: AVERAGE
TIMING DIFFERENCES APPEAR TO BE THE SIGNIFICANT REASON FOR MODEL
DIFFERENCES WITH AN UPSTREAM, SHALLOW AMPLITUDE LONGWAVE TROUGH TO
NEAR THE PACIFIC NORTHWEST WEDNESDAY NIGHT. THE NAM/ECMWF ARE
FASTEST AND 00Z CMC SLOWEST WITH THE LEADING SHORTWAVE. THERE ARE
MODEST DIFFERENCES REFLECTED IN THE ENSEMBLE SPREAD AND GIVEN THE
SOURCE REGION FOR THIS SYSTEM IS AN AREA OF HIGHER UNCERTAINTY,
WILL PREFER TO GO IN THE MIDDLE OF THE SPREAD TOWARD THE 12Z GFS
AND 00Z UKMET AT THIS TIME.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
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