665  
FXUS10 KWNH 231904  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
304 PM EDT WED OCT 23 2019  
 
VALID OCT 23/1200 UTC THRU OCT 27/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
19Z UPDATE: NO CHANGES TO THE MODEL PREFERENCES AS THE 12Z EC HAS  
ONLY SUBTLE DIFFERENCES FROM ITS PREVIOUS RUN. THE 12Z CMC IS NOT  
AS SLOW WITH THE CLOSED LOW ACROSS THE SOUTHERN PLAINS AND IS WELL  
CLUSTERED WITH THE REST OF THE MODEL GUIDANCE. HOWEVER, IT IS  
STILL THE SLOWEST DETERMINISTIC SOLUTION AND THUS WILL NOT BE  
ADDED TO THE BLEND AT THIS TIME.  
 
CENTRAL U.S. CYCLONE THROUGH EARLY THURSDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
A POSITIVELY TILTED TROUGH DIGGING SOUTH FROM THE UPPER MID-WEST  
INTO THE CENTRAL ROCKIES IS IN GOOD AGREEMENT AMONG THE MODELS.  
IN RESPONSE, MID-LEVEL IMPULSES ROUNDING THE TROUGH WITH INTERACT  
WITH SURFACE FEATURES THAT WILL CONTINUE TO PRODUCE PRECIPITATION  
FROM THE NORTHERN ROCKIES ACROSS THE NORTHERN PLAINS. MEANWHILE,  
AN ASSOCIATED COLD FRONT WILL CONTINUE TO TREK NORTHEAST OFF OF  
MAINE.  
 
AS A SHORTWAVE DIVES SOUTH FROM THE CENTRAL ROCKIES OVERNIGHT INTO  
THE SOUTHERN PLAINS, CYCLOGENESIS WILL DEVELOP. IT WAS AT THIS  
POINT WHERE MODELS STRUGGLED TO DETERMINE THE EVOLUTION OF THIS  
PIECE OF ENERGY WITH THE GFS TOO FAST. HOWEVER, THE LATEST 12Z  
GFS IS COMING INTO BETTER AGREEMENT, THUS FEEL A GENERAL MODEL  
BLEND ACROSS THE CONUS WILL SUFFICE.  
 
STRONGER SHORTWAVE DROPPING THROUGH ROCKIES; CLOSING OFF ACROSS  
THE SOUTHERN PLAINS THROUGH SATURDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z ECMWF, ECENS MEAN, UKMET, GEFS (LESSER WEIGHT)  
BLEND  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
THE AFOREMENTIONED SHORTWAVE WILL CALVE OFF THE MAIN TROUGH,  
SPLITTING FROM THE NORTHERN STREAM. NOW ALL MODELS ARE  
ILLUSTRATING A CLOSED MID-LEVEL LOW DROPPING SOUTH INTO THE  
SOUTHERN PLAINS. THOUGH THE DIFFERENCES AMONG THE MODELS CONTINUE  
WITH POSITION, TIMING AND INTENSITY. THE 12Z GFS TRENDED SLOWER  
AND IS COMING MORE IN LINE WITH THE MODEL DIAGNOSTIC PREFERENCES  
OVER THE PAST SEVERAL DAYS: EC/EC MEAN/UKMET. THE 00Z CMC  
CONTINUES TO BE THE SLOWEST SOLUTION, ALONG WITH THE LATEST SREF  
MEAN; THUS WILL NOT USE WITHIN THE BLEND. A LOT DEPENDS ON THE  
SHORTWAVE INTERACTION WITH BOTH THE DEPARTING TROUGH AXIS MOVING  
EAST FRIDAY AND ALSO THE APPROACHING TROUGH IN THE WEST. THE  
PREVIOUS RUNS OF THE GFS HAD THE SHORTWAVE BEING CARRIED BY THE  
DEPARTING TROUGH, WHILE THE NON-NCEP MEMBERS HAD THE APPROACHING  
TROUGH CARRY THE EXISTING SHORTWAVE/CLOSED LOW NORTHEAST. IT WOULD  
SEEM THAT A SLOWER SOLUTION WITH RESPECT TO THE CLOSED LOW IS MOST  
FITTING GIVEN THE ANOMALOUSLY HIGH HEIGHTS INTO ALASKA (RIDGING BY  
LATE IN THE PERIOD) AND THE COOLER TEMPERATURE DIVING INTO THE  
ROCKIES. IN ADDITION, THE STRENGTHENING JET AXIS TO THE NORTH ALSO  
FAVORS A SLOWER PROGRESSION. SO WITH THE GFS COMING INTO BETTER  
AGREEMENT WITH THE EC/EC MEAN/UKMET, COULD FEASIBLY INCORPORATE  
THIS MODEL INTO THE BLEND. HOWEVER, FOR NOW, SINCE THE GFS IS  
STILL TOO FAST, WILL USE THE GEFS MEAN. AGAIN, THE POSITION AND  
TIMING OF THE SHORTWAVE AND HOW IT INTERACTS WITH THE APPROACHING  
TROUGH WILL ULTIMATELY DETERMINE THE TRACK/INTENSITY OF THE  
SURFACE LOW.  
 
SHORTWAVE TROUGHING ACROSS PACIFIC NORTHWEST FRIDAY-SATURDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
THE ANOMALOUS RIDGE OVER THE EASTERN PACIFIC AND WESTERN U.S. MID  
TO LATE WEEK WILL BE SHUNTED AND BROKEN DOWN SOME AS ANOTHER  
STRONG SHORTWAVE TROUGH APPROACHES FROM THE GULF OF ALASKA. WHILE  
THE PREVIOUS MODEL RUNS SHOWED A BIT BETTER AGREEMENT AMONG THE  
GFS/EC WITH THIS FEATURE, THE EC/ECMEAN AND NOW THE THE 12Z GFS IS  
SHOWING A SHARPENING OF THE TROUGH AS IT MOVES THROUGH THE  
NORTHERN ROCKIES. THIS DIFFERS FROM THE REST OF THE MODEL  
GUIDANCE. REGARDLESS OF THIS VARIABILITY, THE QPF DIFFERENCES ARE  
NEGLIGIBLE. THUS WITH A GENERAL MODEL BLEND, THIS SHOULD TAKE  
CARE OF ANY SUBTLE DIFFERENCE THAT EXIST WITHIN THE MASS FIELDS  
THIS LATE IN THE FORECAST PERIOD.  
 
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
PAGANO  
 

 
 
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