368  
FXUS10 KWNH 110626  
PMDHMD  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
126 AM EST SAT JAN 11 2020  
 
VALID JAN 11/0000 UTC THRU JAN 14/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-NAM BLEND  
EXCEPTION: 00Z ECMWF/CMC/GEFS BLEND ACROSS PACIFIC NW/SW CANADA  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
07Z UPDATE: LITTLE SIGNIFICANT CHANGES WERE NOTED IN THE 00Z RUNS  
OF THE UKMET, CMC OR ECMWF, WITH EXCEPTION OF THE ECMWF/CMC  
ADJUSTING A BIT FURTHER EAST WITH THE HUB OF COLD AIR/CLOSED LOW  
IN ALBERTA. SIMILARLY THE 00Z GEFS IS A BIT CLOSER OVERALL TO THE  
ECENS MEAN AND THE ECMWF/CMC TO SUGGEST KEEPING THE INITIAL  
PREFERENCE SELECTIONS AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.  
 
---PRIOR DISCUSSION---  
CURRENT HIGH MERIDIONAL TROF ACROSS THE CENTRAL CONUS WILL  
CONTINUE TO LIFT NORTHEAST AND WEAKEN ACROSS THE GREAT LAKES INTO  
INCREASINGLY CONFLUENT FLOW. THE TRENDS HAVE BEEN TOWARD A  
SLIGHTLY FASTER AND WEAKER SYSTEM, BREAKING DOWN THE SURFACE  
CYCLONE A BIT FASTER THAN THE LAST FEW DAYS, THE ONLY REMAINING  
STRONGER/COMPACT SOLUTIONS REMAIN THE UKMET (THOUGH IS FASTER)  
THAN THE 00Z NAM. IT IS NOT A TREMENDOUS DIFFERENCE IN THE  
SPREAD, BUT WOULD WEIGHT THOSE SOLUTIONS LESS OR EVEN REMOVE THEM  
FROM THE REMAINDER OF THIS SYSTEM.  
 
AFTER THIS WAVE, THE LARGE SCALE PATTERN BROADENS TOWARD A LARGE  
SCALE TROF THAT DOMINATES THE NORTHWESTERN TWO-THIRDS OF OF NORTH  
AMERICA WITH A CENTRAL HUB/LOBE OF THE POLAR VORTEX TAKING UP  
RESIDENCE ACROSS N BC/ALBERTA BY MONDAY. ALONG THIS OUTER EDGE IN  
THE DEEPER WESTERLIES, FAST MOVING SHORTWAVES WILL SWING THROUGH  
THE ROCKIES ON THEIR WAY THROUGH THE CENTRAL PLAINS ON LATE SUNDAY  
INTO MONDAY AND THEN AGAIN ON TUESDAY, WITH A THIRD POTENT PACIFIC  
WAVE ENTERING OREGON TUESDAY REACHING THE GREAT BASIN BY THE END  
OF THE FORECAST PERIOD. THE FIRST WAVE THAT STARTS THE BROADENING  
OF THE LARGE SCALE TROF IS ALREADY A BIT TO COMPACT/STRONG IN THE  
00Z CROSSING THE INTERMOUNTAIN WEST, AND WHILE IT IS NOT TERRIBLY  
OUT OF PHASE WITH THE ENSEMBLE SUITE, IT IS A BIT STRONGER AND HAS  
NEGATIVE EFFECTS ON THE BROAD RETURN FLOW OF THE GULF AND  
INTERSECTION/OVERRUNNING. THE 00Z GFS, MUCH LIKE PRIOR RUNS,  
SHOWS SOME TYPICAL FAST BIAS, BUT WHAT IS INTERESTING IS THE  
PLACEMENT/STRENGTH OF THE RETURN MOISTURE STREAM OUT OF THE GULF  
(TIGHTER 850-7H GRADIENT FURTHER EAST) THAN THE ECMWF/UKMET, WHILE  
THE MASS FIELDS ARE NOT TOO BAD, THIS FAST BIAS WOULD SUGGEST THE  
GFS MAY BE A BIT TOO FAR EAST, THOUGH THE ECMWF/UKMET MAY BE TOO  
FAR WEST AND A COMPROMISE MAY BE BEST. THIS PATTERN CONTINUES  
WITH THE NEXT BUT WEAKER SHORTWAVE COMING THROUGH TUESDAY, WITH  
THE GFS WEAKER AND FURTHER EAST WHILE THE UKMET/ECMWF FURTHER  
WEST, WITH THE CMC FAVORING THE SLOWER SOLUTIONS OVER THE GFS TOO.  
 
AS THE LARGE SCALE VORTEX/COLD POOL ANCHORS ITSELF MONDAY, THE  
INTERNAL WOBBLE/BINARY INTERACTIONS, SHOW THE GFS PULL THE COLD  
AIR AND THEREFORE THE CENTROID FURTHER EAST, A BIT MORE THAN EVEN  
THE 18Z GEFS SUGGESTS, SO WOULD BE A BIT LEERY OF THERMAL PROFILES  
IN THE NORTHERN HIGH PLAINS BY LATE MON/TUESDAY, THOUGH THE  
TIMING/TRACK OF THE SHORTWAVE EMERGING FROM THE PACIFIC/GULF OF AK  
APPEARS TO BE CONGRUENT WITH THE ECMWF/CMC TO HAVE SOME  
CONFIDENCE. THE 12Z UKMET IS ALSO GENERALLY EAST WITH THE CENTER  
OF THE VORTEX BY THE END OF DAY 3, BUT UNLIKE MUCH OF THE OTHER  
GUIDANCE IS MUCH TOO SLOW AND VERY WEAK WITH THE PACIFIC/GULF OF  
AK WAVE THAT IT WOULD NOT BE IN THE PREFERENCE ACROSS THE PACIFIC  
NW ON DAY 3.  
 
SO OVERALL, A NON-NAM BLEND IS SUPPORTED THROUGHOUT THE FORECAST  
PERIOD, BUT AFTER THE INITIAL MERIDIONAL TROF LIFTS THROUGH THE  
NORTHEAST AND BROADER TROF DEVELOPS WITH EMBEDDED SHORTWAVES,  
WOULD PREFER TO UTILIZE THE GEFS OVER THE GFS IN GENERAL IN THE  
PREFERRED BLEND. CONFIDENCE REMAINS WELL ABOVE AVERAGE FOR THE  
OVERALL PATTERN, BUT THE SMALLER SCALE BUT IMPORTANT  
PLACEMENT/TIMING/DEPTH ISSUES IN THE 00Z GFS/NAM AND UKMET IN THE  
PACIFIC NORTHWEST ON DAY 3 REDUCE OVERALL CONFIDENCE TO SLIGHTLY  
ABOVE AVERAGE FOR THE ENTIRE BLEND.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
GALLINA  
 

 
 
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