Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
234 AM EDT Sun Aug 12 2018

Valid Aug 12/0000 UTC thru Aug 15/1200 UTC

...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...

00Z model evaluation with final preferences
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...Overall Synoptic Pattern across the CONUS...
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Preference: 00Z GFS/ECMWF/UKMET blend
Confidence: Average

07Z update:

The biggest change in the 00Z ECMWF/UKMET/CMC compared to their
12Z cycles is across the Northeast with the 00Z UKMET speeding up
with the 500 mb trough axis, nearer to the consensus. Still some
minor timing differences with the 00Z GFS fastest and 00Z ECMWF
slowest, although spread is relatively small.

Elsewhere, minor fluctuations were seen in the guidance but the
00Z UKMET is now close enough to the preferred CONUS model
evolution to include it as part of the preferred blend. The 00Z
GFS is considered a bit too fast with a shortwave nearing the
northern High Plains Wednesday morning, with more weight toward
the 00Z ECMWF/UKMET preferred.


Previous discussion follows:

With a closed low over the northern Mid-Atlantic region, timing
differences appear by Tuesday/Wednesday. The 00Z GFS begins to
nudge faster while the 12Z UKMET is significantly slower. a middle
ground away from the 12Z UKMET is best with this system.

Over the Northwest, a closed low will deamplify as it tracks
east-northeastward with only the 00Z NAM showing significantly
different (slower) than the remaining model consensus, although
the 00Z GFS is a bit faster (typical bias). Greater differences
appear with the trailing mid-level vort axis across Montana and
the northern High Plains with large ensemble spread. Smaller scale
differences also show up with the northeastward movement of a
relatively broad shortwave trough over the southern/central Plains
Tuesday into Wednesday. With these features a blend is preferred
with a greater weight on the 00Z GFS/12Z ECMWF given better
placement within the greater ensemble clustering..

Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

Otto