051
FXUS10 KWNH 210647
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
147 AM EST SAT DEC 21 2019
VALID DEC 21/0000 UTC THRU DEC 24/1200 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
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS, 00Z ECMWF, 00Z CMC
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
---06Z UPDATE---
THE 00Z CMC IS NOW INCLUDED IN THE PREFERENCE AS IT HAS TRENDED
CLOSER TO THE GFS AND ECMWF WITH TIMING OF THE LOW IN THE
SOUTHEAST. THE 00Z UKMET IS NOW ON THE FAST SIDE WITH THAT LOW,
AND STILL DIGS A SHORTWAVE FURTHER SOUTH INTO THE BASE OF THE WEST
COAST TROUGH.
---PREVIOUS DISCUSSION---
MODELS HAVE CONTINUED TO GRADUALLY CONVERGE ON THEIR MASS FIELD
FORECASTS OVER THE NEXT FEW DAYS AS AN AMPLIFIED SYNOPTIC PATTERN
SETS UP. FOR INSTANCE, THE DETERMINISTIC MODELS PLACE THE SURFACE
LOW ALONG THE GULF COAST AND SOUTHEAST ATLANTIC COAST GENERALLY
WITHIN 150 MILES OF EACH OTHER. THIS HAS LED TO MORE SIMILAR QPF
FROM THE MODELS, AND A SLIGHT INCREASE IN FORECAST CONFIDENCE.
THE MOST SIGNIFICANT DIFFERENCES APPEAR TO BE FROM THE 00Z NAM AND
12Z UKMET WITH THE TROUGH APPROACHING THE WEST COAST. BOTH MODELS
DIG A SHORTWAVE MUCH FURTHER SOUTH INTO THE BASE OF THE TROUGH,
LEADING TO A SLOWER PROGRESSION OF THE OVERALL TROUGH AXIS THROUGH
THE SOUTHWEST, AND SOME VARIATION IN THE QPF ACROSS THE REGION.
THE 00Z GFS CONTINUES TO PROGRESS THE TROUGH SLIGHTLY FASTER TO
THE EAST, WHICH IS A TYPICAL BIAS, BUT THERE IS INCREASING OVERLAP
WITH SOME OF THE FASTER ECMWF ENSEMBLE MEMBERS AND THEREFORE A
BLEND OF THE GFS, ECMWF AND CMC APPEARS REASONABLE.
FOR THE CLOSED LOW IN THE SOUTHEAST, THE 12Z CMC CONTINUES TO SHOW
A FASTER PROGRESSION THAN THE OTHER MODELS. IT IS ALSO NOTEWORTHY
THAT THE ECMWF AND GFS ARE FASTER THAN THEIR ENSEMBLE MEANS,
SUGGESTING THE LOW MAY SLOW DOWN FURTHER IN FUTURE MODEL RUNS.
THEREFORE, THE CMC IS NOT PREFERRED FOR ITS HANDLING OF THIS
SYSTEM.
OVERALL, A BLEND OF THE GFS AND ECMWF SHOULD OFFER A FORECAST WITH
MORE SUBSTANTIAL ENSEMBLE SUPPORT, AND A COMPROMISE IN THE TIMING
OF THE TROUGH IS PREFERRED THROUGH THE WEST.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
LAMERS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page