423  
FXUS10 KWNH 211624  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1223 PM EDT MON OCT 21 2019  
 
VALID OCT 21/1200 UTC THRU OCT 25/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
CENTRAL U.S. CYCLONE; SECONDARY LOW FROM CAROLINAS TO NEW ENGLAND  
TUE-WED.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE LOW OVER THE UPPER MS VALLEY WILL LIFT NORTHWARD INTO CANADA  
OVER THE NEXT COUPLE DAYS. SLIGHT STRENGTHENING OF THE LOW WILL  
CONTINUE TODAY, HOWEVER BY TONIGHT THE SYSTEM WILL BECOME STACKED  
AND FILL IN AS IT LIFTS NORTHWARD. A SECONDARY LOW WILL FORM OVER  
THE MID ATLANTIC TUESDAY AND LIFT NORTHEASTWARD INTO NEW ENGLAND  
THROUGH WEDNESDAY. OVERALL GUIDANCE IS IN GOOD AGREEMENT WITH THE  
EVOLUTION OF THIS SYSTEM. THE 0Z ECMWF IS PROBABLY A TAD SLOW WITH  
THE FRONT MOVING ACROSS NEW ENGLAND TUESDAY NIGHT INTO WEDNESDAY,  
OTHERWISE A GENERAL MODEL BLEND SHOULD SUFFICE FOR THIS SYSTEM.  
 
STRONGER SHORTWAVE DROPPING THROUGH ROCKIES INTO THE SOUTHERN  
PLAINS EARLY TO MID WEEK  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON NCEP BLEND (ECWMF,ECMWF MEAN, UKMET, CMC)  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
MODELS ARE IN PRETTY GOOD AGREEMENT THOUGH 12Z WED (23RD) WITH THE  
SHORTWAVE ENERGY DROPPING SOUTHWARD THROUGH THE CANADIAN ROCKIES  
AND INTO THE NORTHERN PLAINS. THEREAFTER SPREAD INCREASES  
SIGNIFICANTLY. THE NON NCEP GUIDANCE (ECMWF/UKMET/CMC/EC MEAN) ALL  
SHOW A STRONGER WAVE AND A TROUGH DIGGING DEEPER TO THE SOUTHWEST  
ACROSS THE ROCKIES AND PLAINS...EVENTUALLY RESULTING IN THE  
DEVELOPMENT OF A CUTOFF LOW. THE 12Z GFS AND NAM SHOW A WEAKER AND  
MORE PROGRESSIVE SYSTEM.  
 
THE LAST SEVERAL RUNS OF THE ECMWF HAVE BEEN VERY CONSISTENT WITH  
THE DEEPER AND SLOWER TROUGH...AND WITH THE OTHER NON NCEP MODELS  
TRENDING IN THIS DIRECTION AS WELL...IT WOULD APPEAR THIS  
SLOWER/DEEPER SOLUTION IS BECOMING INCREASINGLY LIKELY. THUS WPC  
WILL CONTINUE TO PREFER A NON NCEP MODEL BLEND FOR THIS SYSTEM  
AFTER 12Z WED. CONFIDENCE HAS INCREASED SOME, BUT IS STILL  
SLIGHTLY BELOW AVERAGE GIVEN THE SPREAD...HOWEVER IF THE NEW 12Z  
NON NCEP MODELS REMAIN CONSISTENT WITH THEIR DEEPER/SLOWER  
SOLUTIONS, THEN CONFIDENCE WOULD INCREASE TOWARDS AVERAGE FOR THIS  
SYSTEM.  
 
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
CHENARD  
 

 
 
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