017
FXUS10 KWNH 120749
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
348 AM EDT MON AUG 12 2019
VALID AUG 12/0000 UTC THRU AUG 15/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z FINAL MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12 ECENS/00 GEFS
CONFIDENCE: BELOW AVERAGE
07Z UPDATE: LOTS OF SMALL SCALE DETAILS TO IRON OUT AS THE PATTERN
EVOLVES THROUGH MID-WEEK. THE BIGGEST CHANGE TO THE PREVIOUS BLEND
WAS TO REMOVE THE DETERMINISTIC ECMWF DUE TO ITS HANDLING OF
SHORTWAVE ENERGY AND QPF IN THE CENTRAL PLAINS ON MONDAY, AS IT IS
A ROBUST OUTLIER AND HAS BEEN OVERDONE RECENTLY. THE LACK OF
RUN-TO-RUN CONTINUITY BY DAY 3 IN THE DETERMINISTIC SUITE IS
LOWERING CONFIDENCE IN THE EVOLUTION BY THAT TIME RANGE,
ESPECIALLY WITH RESPECT TO THE FRONT IN THE MID-ATLANTIC, AND ANY
WAVES THAT DEVELOP TO ENHANCE QPF ALONG IT. TO SMOOTH OUT SOME OF
THE FINER DETAILS, AND TO MAINTAIN SOME CONSISTENCY, HAVE OPTED
FOR AN APPROACH THAT WEIGHS HEAVILY ON THE ENSEMBLE MEANS FOR THE
PREFERRED BLEND.
PREVIOUS DISCUSSION:
THE SYNOPTIC EVOLUTION THROUGH THE FORECAST PERIOD IS WELL AGREED
UPON BY THE GLOBAL SUITE, BUT SMALL SCALE FEATURES CREATE
DISCREPANCIES IN THE SENSIBLE WEATHER AND SYNOPTIC EVOLUTION
LEADING TO A LOWER THAN AVERAGE CONFIDENCE FORECAST.
THE UKMET CONTINUES TO BE A STRONG OUTLIER WITH ITS RIDGE ON D1,
AND MAINTAINS ABOVE CONSENSUS HEIGHTS THROUGHOUT MUCH OF THE CONUS
THROUGH DAY 3, EVEN AS TROUGHING DEVELOPS IN THE EAST. THIS SHUNTS
MOST OF THE WEATHER FEATURES TOO FAR NORTH COMPARED TO THE GLOBAL
MEAN. THIS HAS BEEN A COMMON TREND IN THE UKMET, AND WITH LITTLE
SUPPORT ELSEWHERE IS NOT USED IN THE PREFERRED BLEND. THE 00Z NAM
CONTINUES TO BE THE FURTHEST NORTH WITH A SHORTWAVE MOVING ACROSS
MT/ND/SASKATCHEWAN D1, AND IS ALSO LIKELY TOO ROBUST AND TOO FAR
NORTH WITH QPF ALONG THE FRONT SAGGING INTO THE MID-ATLANTIC
TUESDAY INTO WEDNESDAY. ALTHOUGH THE CMC HAS A REASONABLE
EVOLUTION WHEN COMPARED TO THE PREFERRED GUIDANCE, IT IS USUALLY A
DEGREE OR TWO LONGITUDE TOO FAR EAST /FAST/ WITH MOST OF ITS
SHORTWAVES ROTATING INTO THE AMPLIFYING TROUGH ACROSS THE EAST.
THIS LEAVES THE GFS AND THE ECMWF. BOTH OF THESE DETERMINISTIC
MODELS HAVE SIMILAR EVOLUTION OF THE RIDGE BLOSSOMING IN THE WEST
LEADING TO DOWNSTREAM TROUGHING IN THE EAST. HOWEVER, THERE REMAIN
CONSIDERABLY SPATIAL DISCREPANCIES IN THE QPF FIELDS AND
FRONTAL/LOW POSITIONS. THE ECMWF HAS BEEN THE MOST CONSISTENT AND
REMAINS THE PREFERRED OF THE DETERMINISTIC MODELS. WITH SUCH
SPREAD IN FRONTAL POSITIONS BY DAY 3 AS IT LAGS ACROSS THE
MID-ATLANTIC, USE OF THE MEANS IS SUGGESTED TO ELIMINATE SOME OF
THE RUN TO RUN VARIABILITY EXHIBITED IN THE GFS.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
WEISS
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