368  
FXUS10 KWNH 270827  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
326 AM EST FRI DEC 27 2019  
 
VALID DEC 27/0000 UTC THRU DEC 30/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE INTERVALS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
OVERALL PATTERN ACROSS THE CONUS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: ECENS/ECMWF BLEND WITH SOME GFS/UKMET  
CONFIDENCE: AVERAGE  
 
08Z UPDATE: NO MAJOR DIFFERENCES SEEN IN THE REST OF THE 00Z  
GUIDANCE (ECMWF/CMC/UKMET) COMPARED TO THE GFS/NAM AND EARLIER  
ANALYSIS. THE 00Z NAM REMAINS A BIT OF AN OUTLIER WITH THE MIDWEST  
SYSTEM BY DAY 3. BUT OVERALL THERE IS GOOD CLUSTERING WITH THE LOW  
TRACKS WITH THE SYSTEM TO CONTINUE WITH THE PRIOR PREFERENCE.  
 
---PREVIOUS DISCUSSION---  
RELATIVELY AMPLIFIED SYNOPTIC PATTERN EXPECTED TO EVOLVE OVER THE  
CONUS THROUGH THE NEXT 3 DAYS. LATEST WATER VAPOR IMAGERY SHOWS  
WELL DEFINED CLOSED LOW OVER SOUTHERN CALIFORNIA WITH ANOTHER  
SHORTWAVE TROUGH ACROSS SOUTHERN INTERIOR CANADA. DOWNSTREAM  
RIDGING EXISTS ACROSS THE SOUTHEAST AND MID-ATLANTIC US. THE  
CLOSED LOW WILL SLOWLY MOVE EASTWARD AND SPRAWL OUT OVER THE  
CENTRAL U.S. THROUGH THE WEEKEND WITH A DEEPENING SURFACE LOW  
EXPECTED TO DEVELOP BY SATURDAY MORNING THAT THEN TRACKS TOWARD  
MSP BY SUNDAY. THE 00Z GFS IS ON THE NORTHERN SPREAD OF THE MODEL  
SPREAD AND A TOUCH DEEPER ON SATURDAY COMPARED TO THE REST OF THE  
MODELS. THE 12Z UKMET HOWEVER IS FASTER AND STRONGER WITH THE  
500/250 MB FLOW AND ITS SURFACE LOW IS ON THE EASTERN PERIPHERY OF  
THE SPREAD. COMPARED TO THE PREVIOUS CYCLES, THERE IS TIGHTENING  
OF THE MODEL SOLUTIONS WITH BETTER AGREEMENT SEEN IN THE ENSEMBLE  
LOW TRACK SPREAD, PARTICULARLY BY DAY 2/3. THE ECMWF/ECENS IS THE  
MOST FAVORED CONSENSUS APPROACH, BUT THE CMC/UKMET/GFS OFFER SOME  
UTILITY IN THE DAY 1/2 PERIOD. THE 00Z NAM BECOMES LESS USABLE  
TOWARD DAY 3, AS ITS LOW TRACKS FURTHER TO THE NORTHWEST, WRAPPED  
UP IN THE DEEPER AND FURTHER NORTH MID/UPPER LEVEL LOW. THE WPC  
PREFERENCE IS FOR A BLEND OF THE ECMWF/ECENS MEAN WITH SOME  
COMPONENTS OF THE GFS/UKMET.  
 
FOR THE REST OF THE CONUS, THERE IS ABOVE AVERAGE AGREEMENT,  
ESPECIALLY ACROSS THE EASTERN US WHERE PRIMARILY RIDGING ALOFT AND  
SOUTHERLY FLOW WILL DOMINATE. ANOTHER ANOMALOUSLY STRONG CLOSED  
LOW APPROACHES THE PACIFIC NORTHWEST SUNDAY/MONDAY AND HERE THERE  
IS VERY GOOD AGREEMENT WITH THE MASS FIELDS. THE 12Z CMC IS A  
TOUCH FAST WITH THE APPROACH OF THE SYSTEM BUT OVERALL A GENERAL  
MODEL BLEND CAN BE USED.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
TAYLOR  
 

 
 
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