248
FXUS10 KWNH 030640
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
239 AM EDT FRI JUL 3 2020
VALID JUL 3/0000 UTC THRU JUL 6/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z FINAL MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
6Z UPDATE: THE CMC AND UKMET BOTH TRENDED SLOWER WITH THE
SHORTWAVE ENTERING THE PACIFIC NORTHWEST ON DAY 3, AND THE ECMWF
TRENDED STRONGER. THE NAM REMAINS THE MOST AMPLIFIED WITH THE
FIRST SHORTWAVE ACROSS WASHINGTON AND BRITISH COLUMBIA THROUGH
SATURDAY NIGHT. THE UKMET IS STILL WEAKER WITH THE GULF COAST
UPPER TROUGH COMPARED TO THE MODEL CONSENSUS, WITH NO OVERALL
CHANGE IN THE MODEL PREFERENCE.
TROUGH OVER THE NORTHEAST U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF BLEND
CONFIDENCE: MODERATE
THE UPPER LOW THAT IS DEPARTING THE NORTHEAST U.S. FRIDAY MORNING
WILL BE FOLLOWED BY ANOTHER ROUND OF HEIGHT FALLS BY SUNDAY ACROSS
NEW ENGLAND, AS A SHORTWAVE ROTATES AROUND A BROAD UPPER LEVEL
TROUGH OVER EASTERN CANADA. AT THE SURFACE WILL BE A WEAK
BACK-DOOR COLD FRONT THAT SINKS SOUTH ALONG THE EAST COAST, AND A
SECOND COLD FRONT CROSSING NEW ENGLAND BY MONDAY MORNING. THE
MODELS ARE IN DECENT AGREEMENT ON THE TIMING OF THE FIRST FRONT.
FOR THE NEXT TROUGH OVER THE NORTHEAST, THE NAM IS A BIT MORE
AMPLIFIED BY SUNDAY MORNING, WITH THE CMC ALSO ON THE STRONGER
SIDE OF THE GUIDANCE. THE 12Z UKMET IS INDICATING A SLOWER
PASSAGE OF THE TROUGH AXIS, WITH A STRONGER RIDGE AXIS ACROSS THE
GREAT LAKES AND ONTARIO. A BLEND OF THE GFS/ECMWF SHOULD WORK
WELL AS A STARTING POINT.
TROUGH OVER THE GULF COAST REGION
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/NAM/ECMWF
CONFIDENCE: LIMITED-MODERATE
ALONG THE GULF COAST, A BROAD TROUGH WILL DEVELOP BENEATH THE
RIDGE EXPANDING FROM THE PLAINS TO THE OHIO VALLEY ON FRIDAY.
THIS TROUGH WILL THEN BE AMPLIFIED BY MID-LEVEL IMPULSES ROTATING
ATOP THE RIDGE AND ACROSS THE GULF COAST. WHILE DISCREPANCIES
EXIST IN THE TIMING, INTENSITY, AND PLACEMENT OF THESE SMALLER
SCALE SHORTWAVES/MCVS, THE END RESULT IS A BROAD AND MODEST TROUGH
THAT BECOMES ANCHORED ALONG THE GULF COAST AND TOWARDS THE
SOUTHEAST U.S. THE MODELS GENERALLY AGREE THAT THE TROUGH WILL
PERSIST THROUGH THE WEEKEND BUT UNLIKELY TO CLOSE OFF. THE UKMET
IS WEAKER WITH THIS FEATURE OWING TO A STRONGER CENTRAL U.S. RIDGE
COMPARED TO THE OTHER GUIDANCE. HOWEVER, IS SHOULD BE NOTED THAT
CONFIDENCE DROPS BY SUNDAY DUE TO INTERACTIONS WITH THE SMALLER
SCALE SHORTWAVES, AND POSSIBLE SURFACE LOW DEVELOPMENT BENEATH
THIS TROUGH.
DEEP UPPER TROUGH/CLOSED LOW ACROSS THE PACIFIC NORTHWEST AND
WESTERN CANADA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z CMC/ECMWF/EC MEAN
CONFIDENCE: MODERATE
A LARGE CLOSED LOW PIVOTING ACROSS THE PACIFIC NORTHWEST AND INTO
WESTERN CANADA WILL REMAIN NEARLY IN PLACE AS SEVERAL VORT
IMPULSES ROTATE CYCLONICALLY AROUND EACH OTHER TO REINFORCE THE
TROUGH. THROUGH SATURDAY MORNING, THE GUIDANCE IS IN VERY GOOD
AGREEMENT WITH THE POSITION AND AMPLITUDE OF THIS FEATURE. BY
SATURDAY AFTERNOON, THE UKMET IS QUICKER TO LIFT OUT THE TROUGH
ACROSS THE PACIFIC NORTHWEST, AND THE NAM/GFS ARE STRONGER WITH
THIS TROUGH ACROSS BRITISH COLUMBIA AND ALBERTA ON SUNDAY. THE
NEXT DISTURBANCE DROPS SOUTHEAST ALONG THE COAST BY MONDAY
MORNING, AND THE NAM IS A STRONGER SOLUTION WITH THAT SHORTWAVE
AND A BIT MORE PROGRESSIVE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
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