145  
FXUS10 KWNH 221917  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
317 PM EDT TUE OCT 22 2019  
 
VALID OCT 22/1200 UTC THRU OCT 26/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z FINAL MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
CENTRAL U.S. CYCLONE; SECONDARY LOW FROM CAROLINAS TO NEW ENGLAND  
TODAY-WEDNESDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
19Z UPDATE: MODELS REMAIN IN FAIRLY GOOD AGREEMENT ACROSS THE  
CONUS DURING THE FIRST HALF OF THE FORECAST PERIOD. NO ADJUSTMENTS  
NEEDED TO THIS PORTION OF THE EVALUATION.  
 
PREVIOUS DISCUSSION: A SURFACE LOW WILL CONTINUE TO LIFT INTO  
ONTARIO THROUGH THE NEXT COUPLE OF DAYS WITH AN ASSOCIATED COLD  
FRONT TRAVERSING THE EAST COAST. THE TROUGH AXIS WILL PIVOT  
THROUGH NEW ENGLAND WEDNESDAY INTO EARLY THURSDAY. AS MUCH OF THE  
CONUS WILL BE UNDER TROUGHING, NORTHWEST FLOW ACROSS THE NORTHERN  
ROCKIES WILL ALLOW MID-LEVEL IMPULSES TO QUICKLY MOVE SOUTH AND  
EAST INTO THE NORTHERN PLAINS. HIGH PRESSURE WILL QUICKLY BUILD  
BEHIND THE APPARENT COLD FRONT ACROSS THE EAST THROUGH WEDNESDAY  
WITH RIDGING IN THE WEST.  
 
THE NCEP/NON-NCEP MODELS INCLUDING ENSEMBLE MEANS ARE IN GOOD  
AGREEMENT WITH THE TIMING AND INTENSITY DURING THIS TIME.  
 
STRONGER SHORTWAVE DROPPING THROUGH ROCKIES INTO THE SOUTHERN  
PLAINS WEDNESDAY PM-SATURDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z ECMWF/ECMWF MEAN/CMC/UKMET  
CONFIDENCE: BELOW AVERAGE  
 
19Z UPDATE: THERE IS NO CHANGE TO THE PRELIM PREFERENCES GIVEN THE  
MODEL DIFFERENCES CONTINUE. THE 12Z GFS/NAM IS STILL FASTER AND  
MORE AMPLIFIED WHILE THE EC/UK/CMC IS SLOWER AND DEEPER WITH THE  
CLOSED LOW IN THE SOUTHERN PLAINS. THE ENSEMBLES AND ALSO THE  
SLIGHT ADJUSTMENT TO A SLOWER SOLUTION FROM THE GFS (WHICH SHOWS  
SIGNS OF ENERGY BREAKING OFF THE MAIN TROUGH BY THE WEEKEND) HAS  
RESULTED IN A HIGHER LEVEL OF CONFIDENCE TOWARD THE NON-NCEP  
SOLUTIONS.  
 
PREVIOUS DISCUSSION: MODELS CONTINUE TO BE IN DISAGREEMENT WITH  
REGARDS TO THE PATTERN CHANGES SET FOR LATE WEDNESDAY INTO THE  
WEEKEND. THERE IS A CLEAR DICHOTOMY BETWEEN THE NCEP AND NON-NCEP  
MODELS THAT HAS LED TO VASTLY DIFFERENT SYNOPTIC FEATURES AND THUS  
QPF PLACEMENT AND INTENSITY.  
 
NCEP MODEL (GFS/NAM) OUTPUT CONTINUES TO PROGRESS A TROUGH EAST  
WITH MID-LEVEL VORTICITY CLEANLY ROUNDING THE TROUGH AXIS.  
MEANWHILE, THE NON-NCEP MODELS (EC/UKMET/CMC) CALVES OFF A  
SHORTWAVE FROM THE MAIN TROUGH AXIS WHICH IS GENERATING A  
MID-LEVEL LOW INTO THE DESERT SOUTHWEST. AS A RESULT, THE NCEP  
MODELS ARE PRODUCING A MORE AMPLIFIED TROUGH PATTERN THAT WILL  
GENERATE A MORE PROGRESSIVE COLD FRONT THROUGH THE CENTRAL US AND  
SURFACE LOW OFF THE GULF COAST REGION BY EARLY FRIDAY. CONVERSELY,  
THE NON-NCEP MEMBERS ARE DEVELOPING A STRONG SURFACE LOW ACROSS  
NM/TX WHICH IS SLOW TO PROGRESS EASTWARD THROUGH THE PERIOD. THIS  
PIECE OF ENERGY BREAKING OFF THE MAIN TROUGH WILL LEAD TO A  
QUICKER NORTHERN JET STREAM AND SURFACE FRONT THROUGH THE GREAT  
LAKES AND NORTHEAST DURING THE DAY FRIDAY.  
 
IN OBSERVING THE RUN-TO-RUN CONTINUITY AMONG THE MODELS, IT  
APPEARS THEY ARE ALL FAIRLY CONSISTENT. THIS IS MAKING IT A  
CHALLENGE IN DETERMINING WHICH MODEL MAY BE THE BEST CHOICE  
THROUGH DAY 3. HOWEVER, WHEN DIVING INTO THE ENSEMBLE MEANS, IT  
APPEARS THE 00Z/12Z GEFS ILLUSTRATES A TREND TOWARD THE NON-NCEP  
SOLUTIONS, SLOWING THE PROGRESSION OF THE TROUGH WITH A BIT MORE  
INTERACTION WITH THE MID-LEVEL IMPULSES. ALSO, THE 12Z GFS  
COMPARED TO THE 06Z SHOWS SOME SIGNS OF SLOWING AS WELL, WHICH HAS  
BEEN QUITE SUBTLE OVER THE PAST COUPLE OF RUNS. THE 12Z NAM ALSO  
SLOWED. BASED ON THIS AND THE FACT THE THE 00Z ECMWF HAS DEEPENED  
THE SURFACE/MID-LEVEL LOW OVER THE PAST COUPLE OF CYCLES, WITH THE  
EC MEAN STAYING VERY CONSISTENT, FEEL THERE IS NO EVIDENCE TO  
CHANGE THE BLEND AT THIS POINT.  
 
THE WPC PREFERENCE REMAINS FOR A HEAVY WEIGHT TOWARD THE NON-NCEP  
GUIDANCE, WITH MOST OF THE WEIGHT TOWARD THE ECENS MEAN WHICH IS A  
GOOD COMPROMISE UNTIL FORECAST CONFIDENCE INCREASES AND MODEL  
SPREAD LOWERS.  
 
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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