011  
FXUS10 KWNH 150628  
PMDHMD  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
128 AM EST WED JAN 15 2020  
 
VALID JAN 15/0000 UTC THRU JAN 18/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..SHORTWAVE CURRENTLY CROSSING NORTHERN ROCKIES
 
   
..CROSSING THE UPPER MIDWEST/NORTHEAST THROUGH WED/THURS
 
 
...DEEPENING SURFACE LOW THROUGH GULF OF MAINE/CANADIAN MARITIME  
BY LATE THURS INTO FRI...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
07Z UPDATE: THE 00Z UKMET TRENDED SUFFICIENTLY NORTH TO COMPLETE  
THE SOLID DETERMINISTIC AGREEMENT FOR THE EVOLUTION OF THE COASTAL  
LOW. SO A GENERAL MODEL BLEND CAN BE EMPLOYED AT ABOVE AVERAGE  
CONFIDENCE.  
 
---PRIOR DISCUSSION---  
INITIALLY THIS SYSTEM IS WELL BEHAVED IN THE GUIDANCE AS THE  
SHORTWAVE EMERGES FROM THE NORTHERN ROCKIES LATER TODAY SUPPORTING  
A FAST SURFACE WAVE FROM KS THROUGH THE GREAT LAKES BY 16.00Z  
THURS. THEREAFTER, STRONGER SHORTWAVE ENERGY STRETCHED FROM THE  
EASTERN PORTION OF THE OLD ARCTIC CLOSED LOW IN NW CANADA THROUGH  
LAST WEEKEND IS ADVECTED EASTWARD SHARPENING THE WESTERN SIDE OF  
THE TROF AND SUPPORTING FAVORABLE CYCLOGENESIS ACROSS THE  
NORTHEAST INTO THE GULF OF MAINE. TIMING AND MAGNITUDE  
DIFFERENCES IN THIS INTERACTION APPEAR TO LEAD TO THE DISPLACEMENT  
IN THE SURFACE CYCLONE AS WELL AS MOISTURE TRANSPORT/WARM CONVEYOR  
BELT. THE 12Z UKMET CONTINUES TO BE MOST OUTSIDE THE GROWING  
CONSENSUS BEING A BIT FASTER INITIALLY AND WINDING UP THE CYCLONE  
SOUTH AND EAST OF THE BEST CLUSTERING IN THE  
ENSEMBLE/DETERMINISTIC SUITE. THE CMC, IS NOT TERRIBLY OUT OF  
PHASE WITH THE TRACK/PLACEMENT BUT IS ON THE DEEPER SIDE OF THE  
ENSEMBLE SUITE, BUT STILL QUITE USEFUL TO ACCOUNT FOR THE  
SHRINKING PROBABILITIES. THE 00Z NAM TRENDED EVEN TIGHTER TO THE  
GEFS/ECENS MEANS AS WELL AS THE 12Z ECMWF. THE 00Z GFS LIKEWISE  
IS VERY SOLID, WITH LITTLE NOTABLE CHANGE FROM THE PRIOR RUNS. AS  
SUCH A NON-UKMET BLEND CAN BE SUPPORTED AT SLIGHTLY ABOVE TO ABOVE  
AVERAGE CONFIDENCE.  
 
   
..DEEP UPPER TROUGH CROSSING INTO THE WEST BY THURS
 
   
..EJECTING OUT ACROSS THE PLAINS/MIDWEST LATE FRI/EARLY SAT
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z ECMWF/GEFS AND 12Z ECENS MEAN W/SMALL UKMET WEIGHT  
(GENERAL MODEL BLEND BEFORE 17.00Z)  
CONFIDENCE: ABOVE AVERAGE THROUGH 48HRS; AVERAGE THEREAFTER  
 
07Z UPDATE: THE 00Z CMC KEPT IN LINE WITH THE FASTER/STRONGER  
SOLUTIONS THAT WERE SOUTH, BUT THE UKMET TRENDED MUCH SLOWER.  
WHILE IT IS STRONG COMPARED TO THE ECMWF, IT IS ALSO A TAD SLOWER  
BY THE END OF THE FORECAST PERIOD. THE 00Z GEFS REMAINED VERY  
SIMILAR TO THE 18Z GEFS AND GENERALLY BETWEEN THE GFS AND ECENS  
MEAN, BUT CLOSER TO THE ECENS MEAN. AS SUCH WILL NOT DEVIATE FROM  
INITIAL PREFERENCE AFTER 48HRS (WITH PERHAPS A BIT MORE INFLUENCE  
OF THE SLOWER UKMET WHICH HANDLES BETTER CONVECTIVE ENVIRONMENT  
ALONG THE TRAILING COLD FRONTAL ZONE IN THE SOUTHERN PLAINS INTO  
THE OZARKS RELATIVE TO EVEN THE SLIGHTLY WEAKER ECMWF.  
 
---PRIOR DISCUSSION---  
THE REMAINING CORE OF THE ARCTIC CLOSED LOW, WILL SHEAR THE BULK  
OF ENERGY WESTWARD TO FORM THE NORTHERN PORTION OF THE DEVELOPING  
DEEP/STRONG CLOSED LOW OFF OF VANCOUVER BY EARLY THURSDAY. THE  
REMAINING ENERGY IS COMING FROM A COMPACT SHORTWAVE/SURFACE  
CYCLONE THAT CONTINUES TO DEEPEN OVER THE SE PORTION OF THE GULF  
OF AK INTO THE NORTHEAST PACIFIC BASIN PER GOES-W WV SUITE. THIS  
RAPID CYCLOGENESIS HAS COME INTO MUCH STRONGER OVERALL AGREEMENT  
IN THE DETERMINISTIC AND ENSEMBLE SUITE TO HAVE ABOVE AVERAGE  
CONFIDENCE IN ITS EVOLUTION THROUGH 48HRS (17.00Z). THE  
UNCERTAINTY REMAINS IN THE PRECISE STRENGTH/TIMING OF THE UPPER  
LEVEL MERIDIONAL JET THE FORMS/AMPLIFIES THE TROF THROUGH MUCH OF  
CALIFORNIA BY 48HRS AS WELL. THE MAGNITUDE/PRECISE LATITUDE OF  
PEAK DEPTH REMAINS QUITE UNCERTAIN WHICH HAS LARGE DOWNSTREAM  
EVOLUTIONARY IMPACTS FOR THE SURFACE CYCLONE AND GULF MOISTURE  
RETURN ACROSS THE CENTRAL AND SOUTHERN PLAINS BY 18.00Z. ALSO,  
THE IMPORTANCE OF INTERACTION/AMPLIFICATION OF SHORTWAVE ENERGY  
EMERGING AHEAD OF THE TROF OUT OF THE SUBTROPICAL STREAM WILL PLAY  
A KEY ROLE AND SIGNIFICANTLY REDUCE CONFIDENCE IN THE SYSTEMS'  
EVOLUTION AND METEOROLOGICAL IMPACTS ACROSS THE PLAINS AND INTO  
THE UPPER MIDWEST.  
 
BOTH THE 12Z CMC/UKMET ARE VERY STRONG AND MUCH FURTHER SOUTH AT  
THE NOSE OF THE MERIDIONAL JET CROSSING THE FOUR CORNERS, BUT ALSO  
SHOW FASTER INJECTION OF THE SHORTWAVE OUT OF THE SUBTROPICS.  
THIS MAKES THE SOUTHERN SURFACE CYCLONE QUITE DOMINANT AND A BIT  
TOO FAST/SOUTH OVERALL. ON THE OPPOSITE SIDE, THE 00Z NAM AND  
LESSER SO 00Z GFS BOTH FAVOR A STRONG LEADING SHORTWAVE/VORT  
CENTER BUT FURTHER NORTH AND IN INTERACTION WITH THE SUBTROPICAL  
WAVE SHOWS GREATER BINARY INTERACTION AND QUICKER SNAPPING OF THE  
BASE OF THE TROF THROUGH THE CENTRAL PLAINS IN A NEUTRAL TO WEAKLY  
NEGATIVE TILT ORIENTATION. THIS MAKE THE 00Z GFS MUCH FASTER TOO,  
WHILE THE NAM MUCH STRONGER/COMPACT; BOTH IN LINE WITH TYPICAL  
NEGATIVE BIAS. THE INTERESTING POINT, IS THE OLD GFS-BASED GEFS  
MEAN SHOWS LOW TO MODERATE SPREAD BUT FAVORS A SLOWER MORE MIDDLE  
GROUND SOLUTION WITH THE 12Z ECENS AND 12Z ECWMF SOLUTION. THIS  
(12Z ECMWF/ECENS AND 18Z GEFS MEAN BLEND) WILL CONTINUE TO BE  
PREFERENCE AFTER 48HRS (GENERAL MODEL BLEND AT ABOVE AVERAGE  
CONFIDENCE PRIOR TO 48HRS). CONFIDENCE IS AVERAGE TO SLIGHTLY  
BELOW AVERAGE BY 84HRS.  
 
...COMPACT SHORTWAVE/DEEP SURFACE CYCLONE NEARING WEST COAST EARLY  
SAT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z ECMWF/GEFS AND 12Z ECENS BLEND W/SOME LOW 00Z  
UKMET WEIGHT  
CONFIDENCE: AVERAGE  
 
07Z UPDATE: THE UKMET AND LESSER SO, CMC SHOWED SIZABLE SLOWING OF  
THE CLOSED LOW WITH A TREND NEARING THE ECMWF/GEFS CENTROID. THE  
ECMWF SHOWED A SLOWER EVOLUTION OF THE TROF AND COLD FRONT PASSAGE  
BUT REMAINS CLOSEST OVERALL TO THE ENSEMBLE CENTER PROVIDING  
CONFIDENCE. THIS PLACES THE FASTER PRESS OF THE COLD FRONT IN THE  
OPERATIONAL GFS A BIT OUT OF TOLERANCE. AS SUCH WILL CONTINUE TO  
FAVOR A 00Z GEFS/ECMWF AND 12Z ECENS MEAN WITH SOME INCLUSION OF  
THE UKMET. CONFIDENCE IS A BIT BETTER WITH SOME POSITIVE  
TRENDING/REDUCTION IN OVERALL SPREAD.  
 
---PRIOR DISCUSSION---  
AS THE CLOSED LOW OVER VANCOUVER ISLAND RAPIDLY FILLS, A VERY  
STRONG MODERATELY BROAD BUT COMPACT SHORTWAVE APPROACHES ACROSS  
THE NORTHERN PACIFIC TO TAKE ITS PLACE FRIDAY INTO SAT. WHILE  
THERE IS VERY GOOD AGREEMENT IN THE SIZE AND STRENGTH OF THE  
SYSTEM, THERE ARE LARGE TIMING ISSUES AND THEREFORE EVOLUTIONARY  
PROBLEMS WITH THE INTERACTION WITH ENERGY FROM THE OLD SYSTEM.  
HERE THE UKMET/CMC ARE FASTER AND MORE MATURE THAN THE SLOWEST  
ECMWF AND LESSER SO NAM WITH THE GFS MORE IN THE MIDDLE. THE  
UKMET/CMC AS WELL AS THE ECMWF ALL SUGGEST A BROADER TRAILING TROF  
AND ASSOCIATED COLD FRONT APPROACHING THE ENTIRE WEST COAST, WHILE  
THE GFS ROUNDS OFF A BIT MORE FOCUSING FURTHER NORTH INTO THE  
PACIFIC NORTHWEST. THE GEFS AND ECENS MEANS SUPPORT SOMETHING  
CLOSER TO THE 12Z ECWMF AND EVEN THE 00Z NAM (IF JUST A BIT SOUTH  
AND EAST OF THE NAM). SO WILL FAVOR A 12Z ECMWF/ECENS MEAN WITH  
18Z GEFS WITH SOME SMALLER WEIGHTING TO THE 00Z NAM TO ACCOUNT FOR  
SOME NORTH-SOUTH VARIATION/INTERACTION WITH THE OLDER FILLING  
SYSTEM AND REMOVE THE CMC/UKMET FROM PREFERENCE/CONSIDERATION.  
CONFIDENCE IS SLIGHTLY BELOW AVERAGE DUE TO THE IMPORTANCE OF  
TIMING TO THE EVOLUTION/SPREAD DIFFERENCE.  
 
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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