987
FXUS10 KWNH 230657
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 AM EST MON DEC 23 2019
VALID DEC 23/0000 UTC THRU DEC 26/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCE AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
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PREFERENCE: BLEND OF 00Z GFS, 12Z CMC, 12Z UKMET
CONFIDENCE: SLIGHTLY BELOW AVERAGE
---06Z UPDATE---
THE 00Z ECMWF DID TREND SLIGHTLY CLOSER TO THE CONSENSUS OF THE
OTHER MODELS WITH THE DEVELOPING CLOSED LOW NEAR SOUTHERN
CALIFORNIA. THE PREFERENCE IS HELD THE SAME GIVEN THAT THE ECMWF
HAS TRENDED IN THAT DIRECTION AND THE GFS, CMC AND UKMET HAVE BEEN
RELATIVELY CONSISTENT.
---PREVIOUS DISCUSSION---
MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH TUESDAY NIGHT (AROUND
25.06Z) AND A GENERAL MODEL BLEND FOR THIS TIME PERIOD WOULD BE A
REASONABLE FORECAST PREFERENCE ACROSS MOST OF THE COUNTRY. AN
IMPORTANT DIVERGENCE IN MODEL GUIDANCE OCCURS WITH THE TROUGH
ALONG THE WEST COAST ON WEDNESDAY. A REINFORCING SHORTWAVE IS
FORECAST TO DIG SHARPLY SOUTHEAST FROM THE GULF OF ALASKA AND LEAD
TO CLOSED LOW DEVELOPMENT SOMEWHERE IN THE VICINITY OF CALIFORNIA.
THE 12Z ECMWF -- AND THE VAST MAJORITY OF ITS ENSEMBLE MEMBERS --
DIGS THE WAVE WITH MORE OF A SOUTHERLY COMPONENT RELATIVE TO MANY
OF THE OTHER MODELS. THIS EVENTUALLY LEADS TO A MID-UPPER LEVEL
CLOSED LOW FURTHER TO THE WEST BY 26.12Z, A SURFACE LOW FURTHER
OFFSHORE OF THE SOUTHERN CALIFORNIA COAST, AND HEIGHT FALLS ALOFT
CONSTRAINED CLOSER TO THE COAST. THE QPF IN THE INTERIOR WEST IS
ALSO LOWER.
MEANWHILE, THE 00Z GFS IS FASTER WITH SPREADING HEIGHT FALLS INTO
THE WEST AND HAS A SURFACE LOW CLOSER TO THE CALIFORNIA COAST. IT
IS JOINED BY THE 00Z NAM, 12Z CMC AND 12Z UKMET. NORMALLY AS AN
EVENT DRAWS NEARER IN TIME, DIFFERENT MODELS WILL BEGIN TO
CONVERGE ON A COMMON SCENARIO. IN THIS CASE, INDIVIDUAL ENSEMBLES
HAVE SEEN THEIR SPREAD NARROW, BUT THE GAP BETWEEN THE ECMWF, GEFS
AND CMC HAS NOT NARROWED SUBSTANTIALLY OVER THE PAST COUPLE MODEL
CYCLES.
IN THIS CASE, THE PREFERENCE IS TO LEAN TOWARD THE GFS, CMC AND
UKMET, GIVEN GREATER SUPPORT FROM A VARIETY OF DIFFERENT MODELS.
THIS ALSO ALIGNS MORE CLOSELY WITH THE WPC MEDIUM RANGE FORECAST
PREFERENCE, WHICH APPLIED SLIGHTLY GREATER WEIGHT TO THE GFS AND
UKMET AT THE BEGINNING OF THE MEDIUM RANGE PERIOD.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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