000
FXUS10 KWNH 111648
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1247 PM EDT SAT JUL 11 2020
VALID JUL 11/1200 UTC THRU JUL 15/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..MID-LEVEL SHORTWAVE CROSSING THE NORTHEAST THROUGH SUN
..ASSOCIATED COLD FRONT CROSSING THE GREAT LAKES
PREFERENCE: 00Z ECMWF/12Z GFS/NAM MODEL BLEND
CONFIDENCE: AVERAGE
THE MODELS SHOW A 700 MB TROUGH MOVING SLOWLY ACROSS THE NORTHEAST
TONIGHT THROUGH SUNDAY, DRIVING A COLD FRONT ACROSS NY/NEW
ENGLAND. THE PRIOR RUNS OF THE UKMET HAD A HIGH AMPLITUDE 700 MB
TROUGH BUT THE 12Z RUN HAS BACKED OFF ON THE TROUGH AMPLITUDE AND
THE STRENGTH OF SFC LOW PRESSURE ACROSS THE BORDER IN SOUTHEAST
CANADA. GIVEN GOOD AND IMPROVING CLUSTERING OF SOLUTIONS, A
MULTI-MODEL BLEND WILL WORK WELL FOR THIS SYSTEM.
...MID-LEVEL SHORTWAVE TO CROSS THE MID-UPPER MS VALLEY TONIGHT,
OHIO VALLEY SUNDAY, GREAT LAKES TO THE APPALACHIANS/NORTHERN MID
ATLANTIC/NY/NEW ENGLAND MONDAY...
PREFERENCE: BLEND OF 12Z GFS/00Z UKMET/00Z CMC/00Z ECMWF MEAN/06Z
GEFS MEAN
CONFIDENCE: AVERAGE
THE MODELS NOW HAVE BETTER AGREEMENT WITH THE TIMING OF THE
700-500 MB TROUGH AS IT CROSSES THE OH VALLEY. THE 12Z NAM IS A
FEW HOURS FASTER, WITH 09Z SREF MEAN AND 06Z GEFS MEAN CLUSTERING
WELL WITH THE GFS/UKMET/ECMWF. THE 12Z GFS IS NOT AS AMPLIFIED AS
OTHER MODELS/06Z GEFS MEAN.
ONCE THE MID LEVEL TROUGH MOVES EAST OF THE CENTRAL APPALACHIANS,
LOW PRESSURE MAY DEVELOP ALONG THE FRONT AS IT CROSSES NJ/SOUTHERN
NY/NEW ENGLAND. TYPICAL RIMMING DIFFERENCES EXIST AMONG THE
UKMET/ECMWF/NAM, WITH THE UKMET SLOWEST OF ALL. A BLEND OF THE
00Z ECMWF/09 SREF MEAN/00Z ECMWF ENSEMBLE MEAN/00Z UKMET/12Z NAM
COULD BE USED TO MITIGATE THE DIFFERENCES.
...LONGWAVE TROUGH AXIS MOVING INTO WESTERN CANADA AND THE
NORTHWESTERN U.S. ON SUN...
PREFERENCE: BLEND OF 00Z ECMWF/12Z UKMET/12Z NAM
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MODELS SHOW A BROAD 500 MB TROUGH AND ASSOCIATED SURFACE COLD
FRONT MOVING ACROSS THE PACIFIC NORTHWEST AND NORTHERN ROCKIES
SUNDAY TO SUNDAY NIGHT AND NORTHERN PLAINS MONDAY. MAINLY MINOR
TIMING DIFFERENCES WERE NOTED IN THE LATEST GUIDANCE, WITH THE 12Z
GFS A FEW HOURS FASTER WITH THE MID LEVEL TROUGH THAN THE
NAM/UKMET/ECMWF/CANADIAN GLOBAL.
GIVEN THE LONG HISTORY OF A FAST BIAS IN THE GFS WITH LONGWAVE
TROUGHS, AND BLEND OF THE OTHER SOLUTIONS IS PREFERRED.
THERE IS A POSSIBILITY OF A SECONDARY LOW AMPLITUDE WAVE MOVING
EAST FROM WY/CO ACROSS KS/NE ON TUESDAY, WITH THE NAM A LITTLE
MORE AMPLIFIED THAN THE GFS/ECMWF. GIVEN THE CONFLUENT FLOW IN
THE MID-UPPER JET, A NEW WAVE DEVELOPING IS A DISTINCT
POSSIBILITY, SO BLENDING EQUALLY WEIGHTED SOLUTIONS IS PREFERRED
UNTIL A RESOLUTION DEVELOPS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
PETERSEN
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