894  
FXUS10 KWNH 060639  
PMDHMD  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
239 AM EDT SUN OCT 06 2019  
 
VALID OCT 06/0000 UTC THRU OCT 09/1200 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: GENERAL MODEL BLEND...WESTERN 2/3RDS OF CONUS  
12Z ECMWF/UKMET AND 00Z NAM (SOME GEFS...EASTERN CONUS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
AVERAGE IN EASTERN CONUS AFTER 09.00Z  
 
19Z UPDATE: THE 00Z ECMWF TRENDED A BIT WEAKER AND THEREFORE A BIT  
FASTER LIFTING THE LINGERING SHORTWAVE ENERGY OUT OF THE UPPER  
TN/OH VALLEY, LEAVING THE FOCUS FOR SURFACE CYCLOGENESIS FURTHER  
EAST LIKE THE PRIOR RUN AND INITIAL PREFERENCE AND CLOSE TO THE  
00Z NAM. THE 00Z UKMET, SHIFTED EVER SO MUCH CLOSER TO THE  
NAM/ECMWF WHILE THE CMC TRENDED STRONGER AND VERY CLOSELY PACKED  
TO THE GFS. THE 00Z GEFS CONTINUES TO DEPICT A SPLIT IN THE  
SOLUTIONS, HALF TOWARD THE OPERATIONAL GFS AND A FEW CLUSTERED  
TOWARD THE NAM/ECMWF/UKMET... STILL SUGGESTING THE NAM/ECMWF/UKMET  
BLEND IS STILL FAVORED OVER THIS SLOWER, MORE AMPLIFIED E TN/OH  
VALLEY SOLUTION WITH STRONGER WARM CONVEYOR BELT PUMPING MOISTURE  
BACK ACROSS THE MID-ATLANTIC. THIS WILL KEEP WITH INITIAL  
PREFERENCE AND CONFIDENCE STILL AT AVERAGE.  
 
ELSEWHERE, CONFIDENCE REMAINS SLIGHTLY ABOVE AVERAGE IN A GENERAL  
MODEL BLEND.  
 
---PRIOR DISCUSSION---  
THE NORTHERN STREAM FLOW PATTERN WILL SUPPORT A STRONG UPPER JET  
PROGRESSING THE LINGERING POSITIVE TILT TROUGH ENERGY ACROSS THE  
EASTERN THIRD OF THE CONUS, WITH EVENTUALLY STRONG COLD POOL  
DROPPING SOUTH OUT OF ARCTIC CANADA TO ENHANCE TROUGH DEVELOPMENT  
IN THE NORTHWEST/NORTHERN ROCKIES BY TUESDAY AND DIGGING INTO THE  
SNAKE RIVER/N GREAT BASIN BY THE END OF THE SHORT-RANGE FORECAST  
PERIOD. ADDITIONALLY, A TROPICAL WAVE WILL APPROACH THE BAHAMAS  
AND AMPLIFY IN FRONT OF THE ADVANCING EASTERN TROUGH, WITH LARGE  
MODEL VARIATION IN STRENGTH/PLACEMENT/EVOLUTION OF A GULF STREAM  
SURFACE WAVE AND ANY REMAINING SHORTWAVE ENERGY AT THE TAIL END OF  
THE NORTHERN STREAM TROF THROUGH THE CUMBERLAND PLATEAU INTO THE  
CENTRAL APPALACHIANS.  
 
AS FOR THE LEAD SHORTWAVE, THE TREND AS BEEN A BIT FASTER OVERALL  
IN THE ENSEMBLE SUITE/GUIDANCE, WITH THE 12Z ECMWF AND BULK OF  
MEMBERS ALONG WITH THE UKMET AND 00Z NAM PROGRESSING THE FRONTAL  
ZONE THROUGH THE UPPER TN/OH VALLEYS AND ACROSS THE  
MID-ATLANTIC/NORTHEAST. INTERESTINGLY, THE GFS HAS TRENDED AWAY  
FROM THIS EVOLUTION, SUPPORTING A SLOWER, MORE AMPLIFIED WAVE IN  
THE CUMBERLAND PLATEAU BY TUESDAY. THIS IS MOSTLY DUE TO A  
STRONGER, FASTER NORTHERN STREAM JET INITIALLY, TYPICAL OF A  
NEGATIVE BIAS. THIS IN TURN, SEVERS THE CONNECTION TO THE TAIL  
END OF THE TROF, WHICH MINUS THE VERY SLOW CMC IS FAIRLY ALONE,  
EVEN WITHIN THE 18Z GEFS MEMBER SOLUTIONS. ADDITIONALLY, THIS  
STRONGER CYCLONE AND FLATTER SURFACE FRONT ALONG THE  
MID-ATLANTIC/SOUTH OF NEW ENGLAND HELPS WITH THE TROPICAL WAVE  
LIFTING NORTH AND DRAWS A STRONGER EASTERLY FLOW JET NORTH OF THE  
BOUNDARY AND STRONGER WARM CONVEYOR, TO ADVECT MORE  
MOISTURE/INSTABILITY ACROSS THE BOUNDARY AND APPEARS LESS  
FAVORABLE EVEN IN THE CMC WHICH IS SLOW. AS SUCH WILL FAVOR A 12Z  
ECMWF/UKMET AND 00Z NAM BLEND FOR THE EASTERN US PARTICULARLY  
AFTER 09.00Z. GIVEN INCONSISTENCY IN THE GUIDANCE TRENDS AWAY  
FROM EACH OTHER AND THE IMPORTANCE OF SMALL TIMING/INTENSITY  
DIFFERENCES, CONFIDENCE IS AVERAGE IN THE BLEND, PARTICULARLY FOR  
DAY 3 WHEN THE TROPICALLY ORIGINATING WAVE LIFTS UP THE EAST  
COAST.  
 
IN THE WEST, THE GUIDANCE IS MUCH MORE AGREEABLE, WITH THE  
TIMING/ORIENTATION AND STRENGTH OF THE DIGGING TROF. THE 00Z NAM  
MAY BE A BIT OFF, GIVEN TYPICAL DAY 3 NEGATIVE BIAS OF BEING A BIT  
STRONGER; ALLOWING A STRONGER NORTHEAST SHORTWAVE OUT OF THE  
NORTHERN US ROCKIES INTO SE CANADIAN PRAIRIES LATE TUESDAY,  
RELATIVE TO THE OTHER GUIDANCE INCLUDING ECENS AND GEFS ENSEMBLE  
SUITES. STILL, THIS IS FAIRLY SMALL DIFFERENCES THAT ITS  
INCLUSION TO A BLEND IS FAIR, BUT PERHAPS AT LOWER WEIGHTING.  
THOUGH, THE 00Z NAM AND GFS MAY BE A BIT MORE FAVORABLE ABOUT THE  
SUBTLE SUBTROPICAL STREAM SHORTWAVE THAT SLIDES INTO THE SOUTHERN  
PLAINS IN ADVANCE OF THE TROF. BOTH ARE A BIT MORE AMPLIFIED AND  
SUPPORT A BIT NORTHWARD SHIFT IN LIGHT TO MODERATE QPF  
DEVELOPMENT. CONFIDENCE IS AVERAGE IN THIS GENERAL MODEL BLEND.  
 
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
GALLINA  
 

 
 
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