882  
FXUS10 KWNH 190716  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
316 AM EDT FRI JUN 19 2020  
 
VALID JUN 19/0000 UTC THRU JUN 22/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
07Z UPDATE: NO SIGNIFICANT CHANGES NOTED WITH THE REST OF THE 00Z  
GUIDANCE AND NO MODEL BLEND PREFERENCE CHANGES NEEDED AS WELL.  
 
EASTERN U.S. CLOSED LOW AND COASTAL FRONT  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND DAY 1; LESS GFS BLEND FOR DAY 2/3  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
AN UPPER LEVEL LOW WILL REMAIN SPREAD OUT OVER THE CENTRAL  
APPALACHIANS, MID-ATLANTIC, AND NORTHEAST THROUGH THIS WEEKEND  
BEFORE GRADUALLY LIFTING NORTHEAST OFF THE EAST COAST.  
SYNOPTICALLY, THE LATEST GUIDANCE SHOWS ABOVE AVERAGE AGREEMENT  
AND CONSISTENCY FROM RUN TO RUN. THE MAIN DIFFERENCES LIE ON DAY 3  
WHERE THE 00Z NAM SHOWS A MUCH SLOWER EXIT OF THE COAST COMPARED  
TO THE GFS (WHICH IS A BIT FASTER THAN THE CONSENSUS) WHILE THE  
ECMWF LIES IN BETWEEN. AT THE SURFACE, SOME MODELS HINT AT A LOW  
DEVELOPING OFF THE NC COAST IN THE DAY 2/3 PERIOD, THOUGH THE GFS  
LACKS THIS FEATURE IN ITS DETERMINISTIC RUN AND MANY OF THE 18Z  
GEFS MEMBERS DO NOT SHOW A FEATURE AS WELL. MEANWHILE, THE ECMWF  
AND TO SOME DEGREE THE NAM/UKMET/CMC, OFFER A STRONGER LOW WITH  
MANY MORE ECENS MEMBERS DEVELOPING IT AFTER 60 HOURS. FROM A  
SENSIBLE WEATHER IMPACT, ONLY THE UKMET BRINGS MUCH HIGHER QPF TO  
EASTERN NC WITH THE OTHER MODELS WELL OFFSHORE. SO, A GENERAL  
MODEL BLEND IS PREFERRED FOR DAY 1 BUT THEN LESS WEIGHT IS  
PREFERRED TOWARD THE GFS FOR DAY 2/3.  
 
CLOSED LOW DEVELOPING OVER NORTHERN HIGH PLAINS AND PARADE OF  
SHORTWAVES ACROSS CENTRAL PLAINS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-GFS BLEND  
CONFIDENCE: AVERAGE  
 
A LARGE UPPER LOW OVER SASKATCHEWAN AND MANITOBA THAT WILL DEVELOP  
THROUGH THIS WEEKEND IS WELL AGREED UPON BY THE LATEST MODEL  
GUIDANCE. HOWEVER, INDIVIDUAL SHORTWAVES THAT WILL PARADE THE  
SOUTHERN PERIPHERY ACROSS THE CENTRAL PLAINS. THE FIRST SHORTWAVE  
COMES THROUGH LATE FRIDAY NIGHT INTO SATURDAY, WHERE THE GFS HAS  
BEEN CONSISTENTLY A BIT TOO DEEP/STRONG OVER KANSAS/MISSOURI AND  
THEN CONTINUES TO BE MORE AMPLIFIED AS IT LIFTS INTO THE UPPER  
MISSISSIPPI VALLEY. AS SUCH, ITS LOW TRACK IS TO THE WEST OF THE  
MODEL CONSENSUS,A BIT SLOWER, AND STRONGER. FOR D3, ANOTHER  
SHORTWAVE COMES OUT INTO THE CENTRAL PLAINS AND HERE THERE ARE  
MORE TIMING AND STRENGTH ISSUES. FOR NOW, THE PREFERENCE REMAINS  
TO EXCLUDE THE GFS AT THIS TIME AND LEAN TOWARD A ECMWF/UKMET/CMC  
BLEND.  
 
TROUGHS APPROACHING THE PACIFIC NORTHWEST THROUGH SUNDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
MULTIPLE SHORTWAVES ROTATING THROUGH THE BROAD GULF OF ALASKA GYRE  
WILL FUNNEL AN ACTIVE WEATHER PATTERN ACROSS THE REGION THROUGH  
THE WEEKEND. THE FIRST SHORTWAVE REACHES TH B.C. COAST LATE FRIDAY  
NIGHT. ASIDE FROM A SLIGHTLY FAST GFS SOLUTION STARTING LATE IN  
THE DAY 1 PERIOD AND CONTINUING THROUGH DAY 3, THE MODELS ARE IN  
AVERAGE TO ABOVE AVERAGE AGREEMENT SUCH THAT A GENERAL MODEL BLEND  
IS SUFFICIENT.  
 
TAYLOR  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 

 
 
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