844
FXUS10 KWNH 041648
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1247 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 INITIAL MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SERIES OF IMPULSES ON A MID-LEVEL SHORTWAVE 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: GENERAL MODEL BLEND...LESS WEIGHT FOR 12Z GFS/NAM AND
00Z CMC DAYS 2/3
CONFIDENCE: AVERAGE
THE BROAD AREA OF CONVECTION DRIVEN BY MID-LEVEL IMPULSES (AS WELL
AS CREATING NEW ONES) ACROSS THE NORTH-CENTRAL PORTION OF THE
CONUS IS 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. A SURFACE LOW WILL DEVELOP OVER THE
MID-SOUTH TONIGHT AHEAD OF THE CENTRAL PLAINS TROUGH. GIVEN THE
CONVECTIVE NATURE THERE ARE INHERIT DIFFERENCES WITH THE GLOBAL
MODELS. HOWEVER, THE OVERALL PATTERN OF THE SURFACE LOW TRACK IS
IN DECENT AGREEMENT AMONG GLOBAL GUIDANCE ACROSS THE SOUTHERN
APPALACHIANS AND CAROLINAS AND A GENERAL MODEL BLEND IS PREFERRED
THROUGH TUESDAY/DAY 1.
AS A SURFACE LOW ORGANIZES OFF THE MID-ATLANTIC ON WEDNESDAY,
THERE ARE ESSENTIALLY TWO CAMPS; A FARTHER EAST 00Z UKMET/ECMWF
WHICH AGREE WITH THE 00Z ECENS MEAN, AND A FARTHER WEST FROM THE
12Z GFS/NAM AND 00Z CMC ALONG WITH THE 06Z GEFS MEAN. AS THE NAM
AND GFS HAVE TRENDED THIS WAY AND THE DIFFERENCE IS NOT TOO GREAT,
WILL INCLUDE THEM IN THE PREFERENCE FOR NOW AND SEE WHAT THE 12Z
CMC/UKMET/ECMWF DO IN TERMS OF SURFACE LOW TRACK. THE IMPACT IS TO
QPF IN SOUTHEAST NEW ENGLAND WHICH WOULD BE HEAVIER IN A FARTHER
WEST TRACK.
..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/00Z ECMWF
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 00Z ECMWF/ECENS MEAN AND THE 12Z GFS ARE IN EXCELLENT
AGREEMENT (ALONG WITH THEIR DAY 2/3 QPF), SO THEY ARE PREFERRED.
NOTES ABOUT THIS LOW EVOLUTION ARE THAT THE REST OF THE GUIDANCE
IS SOUTH, THE 12Z NAM AND 00Z UKMET ARE SLIGHTLY SOUTH AND THE 00Z
CMC IS FARTHER SOUTH. THE 00Z UKMET/CMC ALSO SLIGHTLY WEAKER WITH
LESS OF A CLOSED LOW.
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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