008
FXUS10 KWNH 121645
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1243 PM EDT SUN APR 12 2020
VALID APR 12/1200 UTC THRU APR 16/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SOUTHERN STREAM SHORTWAVE LEADING TO INTENSE SURFACE LOW OVER
GREAT LAKES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC DETERMINISTIC BLEND
CONFIDENCE: MODERATE-HIGH
THE STRONG SOUTHERN STREAM TROUGH AND SHORTWAVE CURRENTLY OVER THE
SOUTHERN PLAINS WILL RAPIDLY TRACK NORTHEASTWARD ACROSS THE
ARKLATEX REGION THROUGH THIS EVENING, AND THEN REACH THE OHIO
VALLEY AND NORTHEAST U.S. BY MONDAY NIGHT WHILE PHASING WITH A
NORTHERN STREAM DISTURBANCE OVER THE GREAT LAKES REGION. THIS
WILL LEAD THE WAY FOR A RAPIDLY INTENSIFYING SURFACE LOW TO LIFT
NORTHEASTWARD ACROSS THE OHIO VALLEY AND GREAT LAKES, ALONG WITH A
STRONG COLD FRONT REACHING THE EAST COAST BY MONDAY EVENING. IT
APPEARS LIKELY THAT A DUAL SURFACE LOW STRUCTURE DEVELOPS, AND
THEN EVOLVES INTO ONE MAIN POWERFUL AND OCCLUDED LOW BY MONDAY
AFTERNOON ACROSS THE NORTHERN GREAT LAKES. THE MODEL GUIDANCE HAS
CONSOLIDATED ON A GENERAL TRACK AND INTENSITY, WITH THE MAIN
DIFFERENCE BEING WITH THE 00Z CMC IN THAT IT IS WEAKER WITH THE
SHORTWAVE PERTURBATION AND NOT QUITE AS STRONG WITH THE
INTENSIFYING LOW OVER THE NORTHERN GREAT LAKES AND ONTARIO. THERE
ARE ALSO SOME LATITUDINAL DIFFERENCES NOTED ACROSS MICHIGAN AS THE
SURFACE LOW CONSOLIDATES, AND THOSE DIFFERENCES CAN BE RESOLVED
WITH A NON-CMC DETERMINISTIC BLEND ACROSS THAT REGION.
AMPLIFYING UPPER TROUGH OVER THE NORTHERN U.S. THROUGH MIDWEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND THROUGH 00Z WEDNESDAY, THEN 12Z
GFS/12Z NAM/00Z CMC
CONFIDENCE: MODERATE
THE MODELS BRING AMPLIFYING SHORTWAVE/JET ENERGY SOUTHEASTWARD
FROM SOUTHWEST CANADA AND OUT ACROSS THE NORTHERN ROCKIES AND
NORTHERN PLAINS BY MONDAY, REINFORCING THE LONGWAVE PATTERN AND
BROAD CYCLONIC FLOW ALOFT OVER MUCH OF THE CONTINENTAL U.S.
THROUGH THE MIDDLE OF THE WEEK, WITH MULTIPLE SHORTWAVES PIVOTING
THROUGH. OVERALL, THE MODELS ARE IN GOOD AGREEMENT WITH THE
DETAILS OF THE LONGWAVE TROUGH EVOLUTION, WITH THE EXCEPTIONS OF
THE 00Z UKMET THAT IS A BIT MORE AMPLIFIED ACROSS THE
INTERMOUNTAIN WEST ON TUESDAY, AND THE ECMWF BECOMES MORE
AMPLIFIED WITH THE MID-LEVEL SHORTWAVE SINKING SOUTH ACROSS THE
NORTHERN ROCKIES ON WEDNESDAY.
SHORTWAVE NEAR THE PACIFIC NORTHWEST BY MIDWEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECENS/00Z UKMET/12Z NAM
CONFIDENCE: LIMITED
A CLOSED LOW CURRENTLY NEAR 40N AND 155W OVER THE NORTH PACIFIC
WILL TRY TO UNDERCUT AN UPPER LEVEL RIDGE NEAR THE GULF OF ALASKA
THROUGH TUESDAY, AND THEN SINK SOUTHWARD NEAR THE WEST COAST OF
THE U.S. BY THE MIDDLE OF THE WEEK. THE MODELS BEGIN TO DIFFER ON
THEIR SOLUTIONS AS EARLY AS 18Z TUESDAY AS THEY HAVE DIFFICULTY
HANDLING THE INTERACTIONS WITH THE EXISTING RIDGE AXIS. THE
LATITUDINAL AND THUS SPEED DIFFERENCES ARE MORE APPARENT BY
WEDNESDAY, WITH BOTH THE 6Z AND 12Z VERSIONS OF THE GFS FASTER
WITH THE CLOSED LOW OFFSHORE. THE 00Z CMC IS ON THE SLOWER SIDE
OF THE GUIDANCE AND THE ECMWF IS A BIT FARTHER WEST WITH THE CORE
OF THE UPPER LOW. GIVEN THESE DIFFERENCES, AN ENSEMBLE MEAN
APPROACH WITH THE 00Z ECENS ALONG WITH SOME OF THE UKMET AND NAM
WOULD YIELD A DECENT COMPROMISE.
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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