844
FXUS10 KWNH 041928
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
327 PM EDT MON MAY 04 2020
VALID MAY 04/1200 UTC THRU MAY 08/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z FINAL MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SERIES OF IMPULSES ON A PAIR OF MID-LEVEL SHORTWAVES TRACKING
ACROSS THE NORTHERN/CENTRAL GREAT PLAINS AND THE OHIO VALLEY
THROUGH TUESDAY NIGHT...
...THESE WAVES CONSOLIDATE OVER THE MID-ATLANTIC WEDNESDAY AND
TRACK OFF NEW ENGLAND THURSDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM GENERAL MODEL BLEND...LESS WEIGHT FOR 12Z GFS
ON DAY 2 AND THE 12Z ECMWF ON DAY 3
CONFIDENCE: AVERAGE
CONVECTIVE COMPLEXES OVER MISSOURI ARE AHEAD OF A MID-LEVEL WAVE
OVER THE CENTRAL GREAT PLAINS WHICH WILL BE REINFORCED BY ENERGY
COMING FROM A LOW OVER THE WESTERN CANADIAN PRAIRIES AS THE
FEATURES SHIFT TO THE OHIO VALLEY THROUGH TUESDAY NIGHT. A SURFACE
LOW WILL DEVELOP FROM THE MISSOURI COMPLEX OVER THE MID-SOUTH
TONIGHT AND TRACK EAST SOUTHERN APPALACHIANS TUESDAY BEFORE A
COASTAL LOW DEVELOPS ALONG THE CAROLINA COAST TUESDAY NIGHT. THE
OVERALL PATTERN OF THE SURFACE LOW TRACK AND COASTAL DEVELOPMENT
IS IN DECENT AGREEMENT AND A GENERAL MODEL BLEND IS PREFERRED
THROUGH TUESDAY/DAY 1.
AS A SURFACE LOW DEVELOPS AND SHIFTS NORTH OFF THE MID-ATLANTIC
WEDNESDAY DIFFERENCES IN TRACK ARISE. THE 12Z ECMWF REMAINS
FARTHEST EAST, PARTICULARLY WEDNESDAY NIGHT AND ON WHILE THE 12Z
UKMET/CMC SHIFTED WEST AND ARE A GOOD COMPROMISE BETWEEN THE ECMWF
AND THE FARTHER WEST 12Z GFS. THE 12Z GFS IS THE QUICKEST TO
DEVELOP, CLOSING OFF AT 500MB TUESDAY NIGHT WHICH ALLOWS A FARTHER
NORTH TRACK THAT COMES INTO BETTER ALIGNMENT BY WEDNESDAY NIGHT.
THE 12Z NAM, HOWEVER, TRACKS FARTHER SOUTH FROM THE CAROLINAS AND
IS SLOWER TO DEVELOP/WEAKER AND IS ENOUGH OF AN OUTLIER TO BE
DISMISSED FROM THE PREFERENCE.
..SHORTWAVE TROUGH BRUSHING PACIFIC NORTHWEST COAST TONIGHT
...MID-LEVEL SHORTWAVE MOVING FROM PACIFIC NORTHWEST COAST TUESDAY
NIGHT ACROSS THE NORTHERN ROCKIES WEDNESDAY NIGHT AND THE NORTHERN
PLAINS THURSDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF/UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
A SHORTWAVE TROUGH WILL PIVOT AROUND A BROAD UPPER LEVEL GYRE OVER
THE GULF OF ALASKA AND CLIP THE PACIFIC NORTHWEST COAST TONIGHT.
THERE ARE NO OUTLIERS WITH THIS FEATURE.
THE NEXT SHORTWAVE TROUGH IS MUCH STRONGER/AMPLIFIED AS IT CROSSES
THE WA/OR COAST TUESDAY NIGHT AND THE ID/MT ROCKIES WEDNESDAY
NIGHT. THERE IS LITTLE DIFFERENCE AMONG GUIDANCE HERE AS THE
TROUGH TAKES ON A NEGATIVE TILT AND CLOSES OFF INTO A LOW OVER MT.
THE 12Z ECMWF/GFS ARE IN EXCELLENT AGREEMENT (ALONG WITH THEIR DAY
2/3 QPF), SO THEY ARE PREFERRED. THE 12Z UKMET INCHED NORTH AND
INTO AGREEMENT WITH THE ECMWF/GFS. THE 12Z NAM IS SLIGHTLY SOUTH
AND THE 12Z CMC REMAINS EVEN FARTHER SOUTH. THE 12Z UKMET REMAINS
SLIGHTLY WEAKER WITH LESS OF A CLOSED LOW, BUT THE TRACK AGREEMENT
WARRANTS ITS INCLUSION IN THE PREFERENCE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
JACKSON
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