655  
FXUS10 KWNH 020653  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
253 AM EDT SUN AUG 02 2020  
 
VALID AUG 02/0000 UTC THRU AUG 05/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..MID-LEVEL TROUGH DIGGING ACROSS OH/TN VALLEYS
 
   
..SURFACE LOW CROSSING THE LOWER GREAT LAKES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
MID-LEVEL TROUGHING OVER THE OH/TN VALLEYS WILL LIFT NORTHEAST AND  
DRIVE A SURFACE LOW ACROSS THE LOWER GREAT LAKES REGION ON SUNDAY  
BEFORE THEN ADVANCING INTO SOUTHEAST CANADA. THE MODELS ARE IN  
GOOD AGREEMENT AND THUS A GENERAL MODEL BLEND WILL STILL BE  
PREFERRED.  
 
   
..HURRICANE ISAIAS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 03Z NHC ADVISORY PACKAGE  
BEST MODEL PROXY: GFS/CMC/UKMET/ECMWF BLEND  
 
THE 03Z NHC FORECAST TRACK OF HURRICANE ISAIAS IS OVERALL CLOSEST  
NOW TO A MULTI-MODEL BLEND CONSISTING OF THE 00Z GFS, 00Z UKMET,  
00Z CMC AND 00Z ECMWF. OF THESE SOLUTIONS, THE GFS AND CMC END UP  
GENERALLY A LITTLE FASTER THAN THE NHC TRACK, ESPECIALLY AFTER 48  
HOURS, AND WITH THE UKMET AND ECMWF A LITTLE SLOWER. THE ECMWF IS  
ALSO SEEN AS BEING A BIT LEFT OF THE NHC TRACK AS THE SYSTEM MAKES  
A LANDFALL ACROSS EASTERN SC AND SOUTHERN NC, AND THEN ADVANCES  
NORTHEASTWARD ACROSS THE REMAINDER OF THE MID-ATLANTIC COASTAL  
PLAIN GOING THROUGH 72 HOURS. THE 00Z NAM FOR ITS PART ENDS UP  
BEING THE SLOWEST AND FARTHEST WEST SOLUTION BY THE END OF THE  
PERIOD. HOWEVER, ALL OF THE MODELS SUPPORT THE SYSTEM RAPIDLY  
LIFTING THROUGH NEW ENGLAND BY THE END OF THE PERIOD. PLEASE  
CONSULT THE LATEST NHC FORECAST ADVISORY PACKAGE FOR MORE DETAILS.  
 
   
..NORTHERN STREAM TROUGH SETTING UP OVER THE GREAT LAKES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND...THROUGH 48 HOURS  
00Z GEFS/12Z ECENS BLEND...AFTER 48 HOURS  
CONFIDENCE: AVERAGE  
 
NORTHERN STREAM ENERGY WILL BE DIGGING DOWN ACROSS THE GREAT LAKES  
THROUGH SUNDAY WITH LIKELY DEVELOPMENT OF AN ELONGATED CLOSED LOW  
A BIT FARTHER NORTH OVER ONTARIO BY MONDAY AND TUESDAY. BY THE END  
OF THE PERIOD, THE 00Z GFS AND 00Z ECMWF SUGGEST A CLOSED LOW  
NORTH OF THE MODEL CONSENSUS OVER ONTARIO, WITH THE 00Z NAM  
FARTHER SOUTH. THE 00Z CMC AND 00Z UKMET SPLIT THE DIFFERENCE, BUT  
THE 00Z GEFS MEAN AND THE RECENT 12Z ECENS MEAN CLUSTER WELL AND  
APPROXIMATE THE MODEL CONSENSUS. THE GUIDANCE IS AT LEAST IN GOOD  
AGREEMENT THROUGH 48 HOURS, AND SO A GENERAL MODEL BLEND WILL BE  
PREFERRED TO THAT POINT, FOLLOWED THEREAFTER BY A BLEND OF THE 00Z  
GEFS MEAN AND YESTERDAY'S 12Z ECENS MEAN.  
 
   
..UPPER LOW/TROUGH CROSSING THE PACIFIC NORTHWEST
 
   
..ENERGY DROPPING DOWN OVER THE NORTHERN PLAINS/MIDWEST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 00Z NAM/GFS/CMC  
CONFIDENCE: AVERAGE  
 
AN UPPER TROUGH WILL CROSS IN THROUGH BRITISH COLUMBIA AND THE  
PACIFIC NORTHWEST LATE ON SUNDAY AND THEN WELL INLAND THROUGH  
MONDAY AND TUESDAY WITH THE MAIN FOCUS OF THE HEIGHT FALLS  
REMAINING ACROSS WESTERN AND CENTRAL CANADA. HOWEVER, THE GUIDANCE  
SUPPORTS SOME ENERGY IN THE BASE OF THE TROUGH SEPARATING OUT  
ACROSS THE FAR NORTHERN ROCKIES AND THEN ADVANCING SOUTHEAST BY  
WEDNESDAY ACROSS THE NORTHERN PLAINS AND MIDWEST. THE 00Z NAM AND  
00Z GFS ARE ON THE STRONGER SIDE OF THE GUIDANCE WITH THIS ENERGY  
OVER THE NORTHERN U.S. LATE IN THE PERIOD. THE 00Z ECMWF AND  
ESPECIALLY THE 00Z UKMET ARE NOTABLY WEAKER. HOWEVER, THE 00Z CMC  
HAS TRENDED TOWARD THE STRONGER NAM/GFS CAMP. IN FACT, THE NAM,  
GFS AND CMC WOULD ALL SUPPORT A MID-LEVEL CLOSED LOW FEATURE  
POTENTIALLY DROPPING SOUTHEAST ACROSS ND AT THE END OF THE PERIOD.  
THE PREFERENCE WILL BE TOWARD THE NAM/GFS/CMC CAMP FOR THE TIME  
BEING SINCE THERE IS A BIT OF A TREND TOWARD STRONGER ENERGY  
SEPARATING OUT FROM THE TROUGHING OVER CENTRAL CANADA.  
 
   
..SOUTHERN STREAM TROUGH MOVING INTO CA BY WEDNESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
A SOUTHERN STREAM TROUGH IS FORECAST BY THE MODELS TO MOVE IN OFF  
THE PACIFIC OCEAN BY EARLY WEDNESDAY AND CROSS MUCH OF CALIFORNIA.  
THE MODELS ARE IN VERY GOOD AGREEMENT WITH THE DETAILS OF THIS  
SYSTEM, SO A GENERAL MODEL BLEND WILL BE PREFERRED.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:  
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.  
PDF  
 
ORRISON  
 

 
 
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