892
FXUS10 KWNH 121709
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
109 PM EDT WED AUG 12 2020
VALID AUG 12/1200 UTC THRU AUG 16/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
LONGWAVE TROUGH OVER THE NORTHWEST TO THE NORTHERN PLAINS THROUGH
FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NAM/CMC/ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
A BROAD UPPER LEVEL TROUGH, IN CONJUNCTION WITH A CLOSED LOW OVER
SOUTHWESTERN CANADA AND A CLOSED MID- AND UPPER-LEVEL HIGH ALONG
155W, WILL BE IN PLACE ACROSS THE NORTHWESTERN U.S. THROUGH THE
MIDDLE OF THE WEEK. OVERALL, THE MODELS ARE IN AGREEMENT WITH THE
IDEA THAT THE TROUGH GRADUALLY SHIFTS EASTWARD AND BE IN PLACE
ACROSS THE NORTHERN PLAINS BY THE WEEKEND. THIS WILL SUSTAIN A
COLD FRONT TRACKING FROM THE NORTHERN ROCKIES TO THE DAKOTAS. THE
12/12Z GFS BECOMES FASTER AND MORE AMPLIFIED WITH THIS TROUGH BY
12Z FRIDAY ACROSS THE DAKOTAS THAN THE 12/00Z RUNS OF THE UKMET
AND ECMWF WHICH IS A TYPICAL BIAS OF THE GFS. WILL CONTINUE TO
FAVOR A BLEND OF THE 12/12Z NAM AND 12/00Z CMC/ECMWF PREFERENCE.
NORTHEASTERN U.S. UPPER TROUGH
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: ECMWF/CMC BLEND
CONFIDENCE: AVERAGE
AN UPPER LEVEL TROUGH AXIS GRADUALLY BUILDS IN ACROSS NEW ENGLAND
AND EASTERN CANADA BY THE END OF THE WEEK, DOWNSTREAM OF A
BUILDING RIDGE AXIS ACROSS ONTARIO AND WESTERN QUEBEC. THE LATEST
NAM WAS THE STRONGEST WITH THE TROUGH, WHILE THE GFS WAS SLIGHTLY
EAST OF THE MODEL CONSENSUS. BLENDING THE ECMWF AND CMC WOULD
STILL YIELD A SUITABLE STARTING POINT IN THE PROCESS PROCESS.
SOUTHEASTERN U.S. UPPER TROUGH
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12/00Z ECMWF
CONFIDENCE: BELOW AVERAGE
A WEAK CLOSED LOW CURRENTLY OVER MISSOURI WILL SLOWLY TRACK
EASTWARD AND EVOLVE INTO AN OPEN TROUGH AS IT REACHES THE OHIO
VALLEY AND SOUTHERN APPALACHIANS BY THIS WEEKEND. THE MODELS HAVE
A BETTER HANDLE ON THE EVOLUTION OF THE FLOW PATTERN ALOFT BUT
SOME RATHER LARGE DIFFERENCES DEVELOP AT 850 MB AND...TO A LESSER
EXTENT...AT 700 MB WITH RESPECT TO WHERE A CLOSED LOW FORMS. THE
ECMWF FAVORED A LOW OVER ALABAMA WHILE THE GFS WAS NORTH OF THE
OHIO RIVER BY SATURDAY MORNING. GIVEN THE RANGE OF SOLUTIONS WILL
TEND TO PREFER THE ECMWF SOLUTION OVERALL BUT WITH BELOW AVERAGE
CONFIDENCE.
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.
BANN
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