528
FXUS10 KWNH 091843
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 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 MODEL EVALUATION WITH FINAL PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CLOSED LOW CROSSING ONTARIO THROUGH SAT
..ASSOCIATED COLD FRONT CROSSING THE GREAT LAKES FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/12Z UKMET BLEND
CONFIDENCE: SLIGHTLY BELOW 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.
BOTH THE 12Z ECMWF/UKMET HAVE BECOME STRONGER WITH THE MID LEVEL
SYSTEM, CLOSING IT OFF AT VARIOUS POINTS ACROSS THE EASTERN OH
VALLEY INTO WESTERN NY STATE IN RESPONSE TO SHORT WAVE ENERGY
DROPPING INTO IT FROM EASTERN ONTARIO. THOUGH THE STRENGTH OF THE
MID LEVEL SYSTEM AS CHANGED, THE TIMING IS BASICALLY THE SAME, SO
THIS PAIR REMAINS THE PREFERRED SOLUTION. HOWEVER, DUE TO THE
CHANGE IN STRENGTH, FORECAST CONFIDENCE HAS BEEN DROPPED TO
SLIGHTLY BELOW AVERAGE.
...LOW PRESSURE MOVING NORTHEAST ALONG EASTERN SEABOARD INTO THIS
WEEKEND...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/12Z UKMET/12Z CMC BLEND
CONFIDENCE: SLIGHTLY BELOW 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.
THOUGH THE TREND IN THE 12Z NON-NCEP GUIDANCE HAS BEEN TO BRING
THE TRACK OF THE SURFACE LOW BACK WEST, IT IS STILL SLOWER AND
FURTHER EAST THAN THE 12Z NCEP GUIDANCE. THE CHANGE IN THE 12Z
ECMWF SURFACE LOW TRACK SEEMS TO BE TIED TO HOW THE MID LEVEL
SYSTEMS ARE INTERACTING, AS THE 12Z ECMWF HAS CLOSED OFF A MID
LEVEL SYSTEM OVER THE EASTERN OH VALLEY. WHILE THE CHANGE IN THE
12Z ECMWF IS CONCERNING, IT SEEMS TO HAVE EMBRACED THE GENERAL
WESTWARD SHIFT ALL OF THE 12Z GUIDANCE.
IN THE END, THE PREFERENCE HAS NOT CHANGE, DESPITE THE RATHER
LARGE CHANGE IN THE 12Z ECMWF. HOWEVER, SINCE IT IS NOT CLEAR HOW
THE MID LEVEL INTERACTIONS WILL ULTIMATELY IMPACT THE SURFACE LOW
TRACK, FORECAST CONFIDENCE IS DROPPED TO SLIGHTLY BELOW AVERAGE.
...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: NON 12Z NAM 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. AFTER INGESTING THE NON-NCEP
GUIDANCE, IT NOW APPEARS AS THOUGH THE 12Z NAM IS THE WESTERNMOST
OUTLIER WITH RESPECT TO THE SPEED OF THE SHORT WAVE AS IT
APPROACHES THE OH VALLEY, IT HAS BEEN DROPPED FROM THE 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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