700  
FXUS10 KWNH 271848  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
248 PM EDT SUN OCT 27 2019  
 
VALID OCT 27/1200 UTC THRU OCT 31/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...DEPARTING MID-LEVEL TROUGH CURRENTLY OVER SOUTHERN  
ONTARIO/QUEBEC...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE LATEST MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE TRACK OF  
THE NEGATIVELY TILTED SHORTWAVE OVER THE GREAT LAKES REGION ON 12Z  
SUNDAY AND IT'S ASSOCIATED PARENT SURFACE LOW WEAKENING INTO  
CANADA AS A SECONDARY LOW DEVELOPS NEAR THE COAST OF NEW ENGLAND  
SUNDAY NIGHT. A GENERAL MODEL BLEND WILL BE PREFERRED. NO  
SIGNIFICANT CHANGES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC  
COMPARED TO THEIR PREVIOUS 00Z RUNS.  
 
   
..MID-LEVEL TROUGH EJECTING INTO THE CENTRAL PLAINS ON MONDAY
 
   
..SURFACE COLD FRONT OVER THE LOWER/MID MS VALLEY BY TUESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
ALTHOUGH THERE REMAIN SOME MINOR TIMING DIFFERENCES WITH A  
SHORTWAVE REACHING THE CENTRAL PLAINS FROM THE GREAT BASIN ON  
MONDAY, THERE IS ENOUGH AGREEMENT TO SUPPORT A GENERAL MODEL  
BLEND. OVERALL SPREAD IN THE DETERMINISTIC/ENSEMBLE GUIDANCE HAS  
REDUCED ENOUGH TO WHERE ANY FUTURE ADJUSTMENTS SHOULD BE MINOR AND  
WITHIN THE NOISE OF MODEL RUN TO RUN VARIABILITY. NO SIGNIFICANT  
CHANGES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC COMPARED TO THEIR  
PREVIOUS 00Z RUNS.  
 
   
..SHORTWAVE/CLIPPER LOW OVER MT/ND BY MONDAY EVENING
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
NO SIGNIFICANT DIFFERENCES EXIST WITH THIS SYSTEM AND RUN TO RUN  
CONTINUITY HAS BEEN GOOD SO ABOVE AVERAGE CONFIDENCE EXISTS FOR A  
GENERAL MODEL BLEND.  
 
...POWERFUL CLOSED LOW IN THE INTERMOUNTAIN WEST TUESDAY INTO  
WEDNESDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON 12Z GFS BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
ENSEMBLE SPAGHETTI 552 DAM HEIGHTS AT 500 MB SHOW SHRINKING SPREAD  
VALID WEDNESDAY OVER THEIR PAST 4 CYCLES (12Z/00Z ONLY). THE 12Z  
GFS HOWEVER, JUMPED SIGNIFICANTLY EAST/FASTER WITH THIS SYSTEM AND  
IS AN OUTLIER OUTSIDE OF THE LATEST ENSEMBLE ENVELOPE. NON 12Z GFS  
SOLUTIONS ARE IN RELATIVELY GOOD AGREEMENT BUT THE 12Z  
ECMWF/UKMET/CMC ALL NUDGED EAST TO SOME DEGREE VALID WEDNESDAY.  
THIS MAKES THE 12Z NAM LIE A BIT TOWARD THE WESTERN SIDE OF THE  
LATEST MODEL CLUSTERING. THE DEGREE OF SEPARATION BETWEEN THE  
CLOSED LOW AND A NORTHERN STREAM PORTION NEAR HTE U.S.-CANADIAN  
BORDER MAKES THE DIFFERENCE. AT THIS TIME, A 12Z ECMWF/UKMET/CMC  
BLEND IN THE MIDDLE OF THE LATEST SPREAD WILL BE PREFERRED, WITH  
THE 12Z NAM REMOVED.  
 
   
..POTENTIAL DISTURBANCE IN THE GULF OF MEXICO EARLY NEXT WEEK
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
THERE IS CURRENTLY AN AREA OF DISTURBED WEATHER JUST EAST OF THE  
YUCATAN PENINSULA WHICH SOME OF THE MODELS TRACK AROUND THE  
WESTERN SIDE OF THE SUBTROPICAL ATLANTIC RIDGE AND INTO THE GULF  
OF MEXICO. THE LATEST MODELS ARE IN SUFFICIENTLY GOOD ENOUGH  
AGREEMENT HERE TO SUPPORT A GENERAL MODEL BLEND. NO SIGNIFICANT  
CHANGES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC COMPARED TO THEIR  
PREVIOUS 00Z RUNS.  
 
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
OTTO  
 

 
 
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