431  
FXUS10 KWNH 300516  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
116 AM EDT THU JUL 30 2020  
 
VALID JUL 30/0000 UTC THRU AUG 02/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...MID-UPPER LEVEL TROUGHING OVER THE NORTHEAST TO THE OHIO VALLEY  
AND MID ATLANTIC...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF UKMET/NAM/CANADIAN GLOBAL  
CONFIDENCE: AVERAGE  
 
THE MODELS INDICATE A DEEP LAYER TROUGH DRIFTS EAST ACROSS NEW  
ENGLAND, WITH FAIRLY GOOD CLUSTERING OF SOLUTIONS, ALLOWING A  
CONSENSUS BASED APPROACH TO BE USED.  
DIFFERENCES EXIST AS THE WAVY FRONT IN THE OHIO VALLEY MOVES EAST  
ACROSS THE APPALACHIANS ACROSS THE MID ATLANTIC STATES.  
THE GFS LACKS WAVES ON THE FRONT NOTED IN THE  
NAM/UKMET/CANADIAN/ECMWF, SO THE GFS IS LEAST PREFERRED.  
THE NAM/ECMWF/UKMET/CANADIAN HAVE TIMING/PHASING DIFFERENCES. A  
BLEND OF THESE SOLUTIONS IS PREFERRED TO UTILIZE INTERMEDIATE  
TIMING UNTIL BETTER AGREEMENT DEVELOPS.  
 
...ENERGY ADVANCING SOUTH FROM THE PLAINS THURSDAY TO THE LOWER MS  
VALLEY FRI AND OHIO VALLEY SAT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 00Z NAM/UKMET/12Z ECMWF  
CONFIDENCE: AVERAGE  
 
MID-LEVEL ENERGY COMING OUT OF THE CENTRAL PLAINS SLOWLY SAGS  
SOUTHEASTWARD TOWARD THE OZARKS ON FRIDAY AND AMPLIFIES IN THE  
LARGER SCALE TROUGHING ALONG THE MS RIVER VALLEY THROUGH THE GREAT  
LAKES REGION BY SATURDAY MORNING. THE MODELS DEVELOP LOW PRESSURE  
IN THE LOWER MS RIVER VALLEY FRI NIGHT TO EARLY SAT. THE 00Z  
GFS/12Z CANADIAN WERE FASTER IN THE LOW PRESSURE PROGRESSION,  
WHICH ARE LEAST FAVORED AS USUALLY AMPLIFYING TROUGHS FAVOR SLOWER  
MOVING, MORE AMPLIFIED SYSTEMS.  
SO THE PREFERENCE HERE IS THE CLUSTER OF THE 12Z ECMWF/12Z UKMET  
AND 00Z NAM.  
 
...TROPICAL STORM ISAIAS PROXIMITY TO FL/ THE SOUTHEAST COAST THIS  
WEEKEND...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NHC ADVISORY  
CONFIDENCE: REFER TO NHC PRODUCTS  
 
THE MODELS HAVE SIGNIFICANT DIFFERENCES ON THE TRACK OF TROPICAL  
STORM ISAIAS, WITH THE 12Z ECMWF/00Z NAM OVERALL A BIT CLOSER TO  
THE NHC TRACK, WITH THE 12Z UKMET/00Z GFS/12Z CANADIAN GLOBAL WELL  
REMOVED FROM THE OFFICIAL TRACK. THE 00Z UKMET HAS A SIMILAR  
TRACK, BUT SLOWER TIMING. FOR THE LATEST INFORMATION ON TROPICAL  
STORM ISAIAS, PLEASE SEE THE LATEST NHC ADVISORY.  
 
...COLD FRONT MOVING THROUGH THE NORTH-CENTRAL U.S. FRIDAY AND  
SATURDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF ECMWF/GFS/NAM  
CONFIDENCE: AVERAGE  
 
THERE IS RELATIVELY GOOD AGREEMENT FOR THE TROUGH AXIS AND RELATED  
COLD FRONT IMPACTING THE NORTH-CENTRAL U.S. THROUGH SATURDAY.  
WHILE MINOR TIMING DIFFERENCES ARE EVIDENT, SUCH AS THE 12Z GFS  
AND 12Z CMC BEING SLOWER, THE DIFFERENCES ARE SMALL ENOUGH FOR A  
60 TO 84 HOUR FORECAST TO ALLOW FOR A GENERAL MODEL BLEND AT THIS  
TIME.  
 
   
..UPPER LOW/TROUGH APPROACHING THE PACIFIC NORTHWEST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF ECMWF/GFS/NAM  
CONFIDENCE: AVERAGE  
 
DUE TO THE HIGH AMPLITUDE DOWNSTREAM RIDGE OVER THE INTERIOR WEST,  
THE MID-UPPER TROUGH OVER THE EASTERN PACIFIC WILL BE SLOW TO MOVE  
EAST. THERE ARE NO SIGNIFICANT DIFFERENCES NOTED WITH THIS SYSTEM,  
WITH A LEAD SHORT AMPLITUDE PROGRESSIVE 700 MB WAVE MOVING NORTH  
ACROSS WA INCLUDED ON DAY 2.  
 
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  
 
PETERSEN  
 

 
 
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