311
FXUS10 KWNH 091649
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1245 PM EDT THU JUL 09 2020
VALID JUL 09/1200 UTC THRU JUL 13/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CLOSED LOW CROSSING ONTARIO THROUGH SAT
..ASSOCIATED COLD FRONT CROSSING THE GREAT LAKES FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/UKMET/12Z ECMWF MEAN
CONFIDENCE: AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS TRACKING THE CLOSED MID
LEVEL LOW FROM ND INTO NORTHERN ONTARIO THIS AFTERNOON INTO SAT,
AND ARE INITIALLY CLOSE WITH SHORT WAVE ENERGY SOUTH OF IT
CROSSING THE UPPER GREAT LAKES (THROUGH ABOUT 11/00Z). AFTER THAT
TIME, THE 00Z NAM BECOMES FLATTER AND A BIT FASTER WITH THE SHORT
WAVE, AS IT APPEARS TO BE REACTING TO THE MID LEVEL TROUGH TO ITS
EAST. THE 12Z GFS IS CLOSER TO THE CONSENSUS AT THAT TIME, BUT
ALSO EVENTUALLY FLATTENS AS IT ENCOUNTERS THE SAME MID LEVEL
SYSTEM.
THE 00Z ECMWF/12Z ECMWF MEAN/00Z UKMET HAVE BEEN CONSISTENT WITH
THE TRACK OF THE SHORT WAVE AND ITS INTERACTION WITH THE MID LEVEL
SYSTEM DOWNSTREAM ACROSS NEW ENGLAND, AS WELL AS ITS ASSOCIATED
COLD FRONT. BASED ON THE CONSISTENCY, THE ABOVEMENTIONED MODEL
BLEND IS PREFERRED WITH THIS SYSTEM, BUT THE SPREAD IN THE NCEP
VERSUS NON-NCEP GUIDANCE RESULTS IN ONLY AVERAGE FORECAST
CONFIDENCE.
...LOW PRESSURE MOVING NORTHEAST ALONG EASTERN SEABOARD INTO THIS
WEEKEND...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/00Z UKMET/12Z ECMWF MEAN
CONFIDENCE: AVERAGE
THE 12Z NAM APPEARS TO BE TOO FAST WITH THE SURFACE LOW ALMOST
FROM INITIALIZATION, THOUGH IT TENDS TO SLOW A BIT TOWARD 11/00Z.
HOWEVER, BOTH THE 12Z NAM/GFS ARE FASTER WITH THE SURFACE LOW THAN
MUCH OF THE 00Z NON-NCEP GUIDANCE, AND REMAINS SO THROUGH 11/12Z.
THE 12Z NAM/GFS ARE GENERALLY WEAKER WITH THE SURFACE SYSTEM, AND
TEND TO DRAW IT BACK WESTWARD TOWARD THE BROAD LONG WAVE TROUGH
CROSSING THE MID ATLANTIC AND NEW ENGLAND THROUGH THE PERIOD.
IN CONTRAST, THE 00Z ECMWF/UKMET/12Z ECMWF MEAN KEEP A STRONGER
SURFACE LOW (DRIVEN MAINLY BY CONVECTIVE PROCESSES) AND TRACK IT
NORTHEAST ALONG WITH AND JUST AHEAD OF THE MID LEVEL SYSTEM. THESE
MODELS HAVE BEEN MORE CONSISTENT WITH THE TRACK OF THE SURFACE
LOW, THOUGH EACH AS BEEN FASTER WITH THE TRACK OVER THE PAST THREE
MODEL CYCLES.
AT THIS POINT, THE KEY TO THE TRACK OF THE SURFACE LOW WILL BE
WHETHER THE SYSTEM REMAINS STRONGER (FAVORING A TRACK FURTHER
EAST), OR REMAINS WEAKER AND IS PULLED MORE WESTWARD BY THE MID
LEVEL SYSTEM. BASED ON CONTINUITY, THE NON-NCEP GUIDANCE IS
PREFERRED WITH THE SURFACE TRACK. HOWEVER, BASED ON THE FAIR
AMOUNT SPREAD AND ITS IMPLICATIONS FOR THE QPF, FORECAST
CONFIDENCE IS AVERAGE AT BEST.
...TROUGH MOVING INTO THE PACIFIC NORTHWEST THURSDAY NIGHT,
CROSSING THE RIDGE AND MOVING ACROSS UPPER MIDWEST BY SAT, THEN
DIVING INTO THE OH VALLEY BY SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS WITH THE MID LEVEL
TROUGH COMING ASHORE ACROSS THE PACIFIC NORTHWEST THIS EVENING,
WHICH TRACKS ACROSS THE NORTHERN ROCKIES FRI MORNING, THEN REACHES
THE UPPER MS VALLEY SAT MORNING. THIS IS CLOSE TO THE MODEL
CONSENSUS WITH RESPECT TO TIMING AND STRENGTH, THOUGH THE NON-NCEP
GUIDANCE BECOMES A BIT FASTER AS THE SHORT WAVE MOVES ACROSS THE
OH VALLEY BY SUN.
HOWEVER, THE DIFFERENCES ARE NOT SUFFICIENT TO DEVIATE FROM A
GENERAL MODEL BLEND FOR A PREFERENCE.
..LONG WAVE TROUGH CLOSING OFF OVER WESTERN CANADA SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS TAKING A CLOSED MID
LEVEL LOW FROM THE SOUTHERN GULF OF ALASKA THIS AFTERNOON TO A
POSITION ALONG THE NORTHWEST BRITISH COLUMBIA COAST 12/00Z, AS A
LONG WAVE TROUGH EVOLVES TO ITS SOUTH. THE 12Z NAM/GFS SLOW A BIT
AS THEY CLOSE OFF ANOTHER MID LEVEL LOW OVER EASTERN BRITISH
COLUMBIA, WHEREAS THE NON-NCEP GUIDANCE IS A BIT FASTER, CLOSING
IT OFF OVER NORTHERN ALBERTA.
DESPITE THE DIFFERENCES WITH THE MID LEVEL CLOSED LOW, THE SHORT
WAVE ENERGY SOUTH OF THE CLOSED LOW IS IN REMARKABLY GOOD
AGREEMENT. BASED ON THIS, A GENERAL MODEL BLEND IS PREFERRED, BUT
BECAUSE OF THE DIFFERENCES IN THE PLACEMENT OF THE CLOSED MID
LEVEL LOW LATE OVER WESTERN CANADA, FORECAST CONFIDENCE IS
AVERAGE.
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 WITH THE 21Z ISSUANCE:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
HAYES
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