043
FXUS10 KWNH 071835
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
135 PM EST SAT DEC 07 2019
VALID DEC 07/1200 UTC THRU DEC 11/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
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PREFERENCE: 12Z ECMWF; 00Z ECMWF ENSEMBLE MEAN
CONFIDENCE: AVERAGE
---18Z UPDATE---
WHILE THE 12Z UKMET REMAINED RELATIVELY CONSISTENT WITH ITS 00Z
RUN, THERE WERE IMPORTANT TRENDS ON THE CMC AND ECMWF. THE 12Z
ECMWF SLOWED DOWN TO BE MORE COMPARABLE WITH THE GFS, WHILE THE
12Z CMC SPED UP CONSIDERABLY AND IS NOW A REASONABLY GOOD MATCH TO
THE ECMWF WITH THE SOUTHERN STREAM WAVE DIGGING THROUGH THE
SOUTHWEST AND INTO THE SOUTHERN PLAINS. THE PREFERENCE HAS BEEN
SHIFTED TO INCLUDE THE SLOWER 12Z ECMWF SCENARIO, BUT STILL
BLENDED WITH THE 00Z ECMWF ENSEMBLE MEAN TO INCORPORATE THE PRIOR
CONSENSUS. IT MAY TAKE ANOTHER MODEL CYCLE OR TWO TO DETERMINE
WHETHER THE SLOWER TREND WILL CONTINUE OR NOT.
---PREVIOUS DISCUSSION---
MODELS ARE SHOWING SOME MORE SUBSTANTIAL DIFFERENCES BEYOND 09.06Z
(SUNDAY NIGHT), PARTICULARLY WITH HOW THEY HANDLE A SOUTHERN
STREAM WAVE DIGGING THROUGH THE SOUTHWEST, AND HOW THAT EVENTUALLY
PHASES WITH A LARGER, AMPLIFYING TROUGH OVER THE CENTRAL U.S. THIS
IS MOST NOTABLE IN A RELATIVELY LARGE SPREAD IN TIMING CENTERED
AROUND 10.00Z (MONDAY EVENING) OVER THE SOUTHWEST. OVER THE PAST
FEW MODEL CYCLES, THE ECMWF AND ECMWF ENSEMBLE MEAN HAVE GRADUALLY
CONVERGED AROUND THEIR POSITIONS DEPICTED ON THE 00Z RUNS. OTHER
MODELS HAVE BEEN LESS CONSISTENT, WITH THE UKMET TRENDING FASTER
AND LESS AMPLIFIED, AND THE GFS TRENDING SLOWER.
THE PREFERENCE WILL BE TO LEAN TOWARD THE 00Z ECMWF AND 00Z ECMWF
ENSEMBLE MEAN, GIVEN THE MULTI-RUN CONSISTENCY THEY HAVE SHOWN,
AND THE 00Z GFS GIVEN ITS RELATIVELY GOOD ALIGNMENT WITH THE ECMWF
ENSEMBLE ENVELOPE. CONCEPTUALLY, THE ECMWF ALSO MAKES SENSE AS THE
SOUTHERN STREAM WAVE MAY HAVE A TENDENCY TO DEAMPLIFY AND
ACCELERATE AS IT IS OVERWHELMED BY LARGER HEIGHT FALLS FROM THE
LONGWAVE TROUGH EXPANDING OVER THE CENTRAL U.S. THE 00Z CMC AND
MANY 00Z NAEFS MEMBERS HANG THE SOUTHERN STREAM WAVE BACK MORE
OVER THE SOUTHWEST, AND THE 12Z GFS HAS JOINED THAT CLUSTER. THIS
CAN'T BE COMPLETELY DISCOUNTED, BUT THERE IS A LACK OF SUPPORT
FROM OTHER GLOBAL MODELS.
FINALLY, A PREFERENCE CENTERED AROUND THE 00Z GFS AND ECMWF WILL
PROVIDE CONSISTENCY WITH THE PREVIOUS FORECAST, AS THAT WAS THE
PREFERRED MODEL BLEND OVERNIGHT AS WELL.
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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