980  
FXUS10 KWNH 311940  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
339 PM EDT WED JUL 31 2019  
 
VALID JUL 31/1200 UTC THRU AUG 04/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z FINAL MODEL EVALUATION AND PREFERENCES/CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERVIEW OF THE CONUS FEATURES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-UKMET THROUGH DAY 2  
ECENS/GEFS/NAEFS MEAN WITH SOME 12Z NAM/GFS  
CONFIDENCE: ABOVE AVERAGE THROUGH DAY 2  
SLIGHTLY BELOW AVERAGE DAY 3  
 
19Z UPDATE: THE NON-NCEP GUIDANCE HAS TRENDED TOWARDS THE NCEP  
REGARDING THE DAY 3 SHORTWAVE/MCS PIVOTING AROUND THE RIDGE INTO  
MISSOURI. THIS SUGGESTS INCREASED WEIGHT ON THE NCEP (NAM/GFS) 12Z  
DETERMINISTIC GUIDANCE, BUT NOT ENOUGH CONFIDENCE TO REMOVE THE  
ENSEMBLE MEANS AS THE PRIMARY PREFERENCE TO WASH OUT SOME OF THE  
SMALL BUT SIGNIFICANT DIFFERENCES. OTHERWISE, NO CHANGES ARE  
REQUIRED TO THE PREVIOUS BLEND.  
 
PREVIOUS DISCUSSION  
GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH DAY 2 WITH A PERSISTENT  
MONSOON RIDGE CENTERED OVER NEW MEXICO ON DAY 1 SHIFTING SLOWLY  
WESTWARD WITH TIME THROUGH DAY 2 INTO THE WEEKEND. DOWNSTREAM OF  
THIS FEATURE, BROAD LONGWAVE TROUGHING WILL EXIST ACROSS THE  
EASTERN HALF OF THE CONUS. SIGNIFICANT SHORTWAVES LIFTING ONTO THE  
PACNW COAST DAY 2 AND APPROACHING NORTHERN NEW ENGLAND ON DAY 3  
WILL GENERALLY REMAIN NORTH OF THE INTERNATIONAL BORDER WITH  
CANADA. MORE SIGNIFICANT BUT SMALLER-SCALE IMPULSES WILL ROTATE  
AROUND THE MONSOON RIDGE THROUGH THE PERIOD BRINGING ROUNDS OF  
THUNDERSTORMS AND POTENTIAL MCS'S FROM THE SOUTHWEST THROUGH THE  
CENTRAL PLAINS AND INTO THE MISSISSIPPI VALLEY.  
 
THE UKMET CONTINUES TO BE A STRONG OUTLIER WITH ITS RIDGE STRENGTH  
NOTED BY HEIGHTS THAT ARE GENERALLY 2-4DM HIGHER THAN THE GLOBAL  
CONSENSUS ACROSS THE WEST. THIS HAS BEEN A TREND IN THE UKMET  
RECENTLY. ADDITIONALLY, THE UKMET IS QUICK TO SPIN UP WEAK  
IMPULSES IN THE GULF OF MEXICO INTO TWO STRONGER CLOSED FEATURES  
WITH SURFACE REFLECTION, WHICH IS NOT ECHOED BY ANY OTHER MODEL.  
FOR THESE IMPORTANT REASONS THE UKMET IS DISCOUNTED FROM THE BLEND.  
 
BY DAY 3, THE GUIDANCE SPLITS CONSIDERABLY WITH AN IMPORTANT  
FEATURE DROPPING AROUND THE PERIPHERY OF THE RIDGE INTO THE  
CENTRAL PLAINS AND MID-MISSISSIPPI VALLEY. THE GFS/NAM DRIVE THIS  
FEATURE MUCH FURTHER SW BOTH IN VORTICITY FIELDS AND QPF, WHILE  
THE NON-NCEP GUIDANCE KEEPS THE FEATURE MUCH FURTHER NORTH. THE  
SEPARATION IS SIGNIFICANT, SEVERAL DEGREES LATITUDE, AND AT THIS  
TIME THERE IS NO CLEAR PREFERRED SOLUTION. HOWEVER, THE  
SHORTWAVE/MCS ON DAY 2 MAY BREAK DOWN THE RIDGE ENOUGH TO SUPPORT  
THE FURTHER SOUTH NCEP SOLUTION, LENDING SOME CREDENCE TO THE  
NAM/GFS. DUE TO THE CONSIDERABLE SPREAD IN THE DETERMINISTIC  
GUIDANCE, AND A MUCH SMALLER SPATIAL ENVELOPE IN THE MEANS, THINK  
AN ENSEMBLE APPROACH IS BEST FOR NOW WITH THE NAEFS LYING  
SOMEWHERE IN BETWEEN THE ECENS AND GEFS MEAN.  
 
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
WEISS  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page