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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