611  
FXUS10 KWNH 161609  
PMDHMD  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1108 AM EST SUN FEB 16 2020  
 
VALID FEB 16/1200 UTC THRU FEB 20/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH PREFERENCES & CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..GREAT LAKES/GULF THROUGH EAST COAST SYSTEM(S)
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 06Z GFS AND 00Z ECMWF/CMC BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
BROAD GLOBAL CYCLONIC FLOW CURRENTLY EXIST ACROSS THE CONUS WITH A  
HIGHLY SHEARED SHORTWAVE MOVING THROUGH OLD MEXICO INTO THE GULF  
REGION SPARKING SOME DISTURBED WEATHER ACROSS THE GULF COAST THAT  
WILL SHIFT INTO THE SOUTHEAST BY MONDAY. GUIDANCE IS FAIRLY SOLID  
IN THE REMAINING EVOLUTION OF THIS PATTERN IN ADVANCE OF STILL  
BROAD BUT SHARPENING OF A TROF ACROSS THE NORTH CENTRAL PLAINS  
INTO THE SNAKE RIVER PLAIN BY MONDAY MORNING. THE LEADING EDGE OF  
THE HEIGHT-FALLS IN COMBINATION WITH A DIGGING ARCTIC SHORTWAVE  
WILL AMPLIFY THROUGH THE GREAT LAKES MONDAY INTO TUESDAY. THERE  
REMAINS MODEST MODEL SPREAD MAINLY IN THE SPACING AND TIMING OF  
THESE WAVES BETWEEN EACH OTHER. THE 00Z UKMET TRENDED MUCH WEAKER  
WITH THE LEAD PACIFIC ENERGY, WHILE THE NAM APPEARS TO GO TO THE  
OPPOSITE EXTREME THOUGH THE RESULTANT SURFACE WAVE IS CONGRUENT  
WITH THE REMAINING GUIDANCE/ENSEMBLE SUITE IT IS A BIT TOO STRONG  
WITH THE SURFACE WAVE AND MOISTURE FLUX INTO THE SYSTEM TO BE  
ACCEPTABLE IN A BLEND AT THIS TIME (THIS ALSO REDUCES  
CONVERGENCE/QPF ACROSS THE SOUTH AS A RESULT). THE 12Z GFS  
TRENDED A BIT FASTER WITH THE SHORTWAVE EMERGING OUT OF THE  
NORTHERN ROCKIES, WHICH TRACKS THE SURFACE WAVE A BIT TOO FAST  
THROUGH THE GREAT LAKES INTO THE NORTH-EAST. THE 06Z RUN IS MORE  
IN LINE WITH THE FLATTER CMC AND SLIGHTLY SLOWER ECMWF WHICH  
APPEAR TO BE THE NORMAL BIASES, ONCE BLENDED FIT NICELY TOWARD  
VERIFICATION...SO WILL SUPPORT A 06Z GFS/ECMWF/CMC BLEND WITH THIS  
SYSTEM CROSSING THE GREAT LAKES THROUGH THE SOUTH AND EAST COAST  
FROM LATE MONDAY THROUGH THE END OF THE FORECAST PERIOD.  
 
...DEVELOPING POSITIVE TILT WESTERN TROF WITH WINTER PRECIP IN  
SOUTHERN HIGH PLAINS WED...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z GFS AND 00Z CMC/UKMET BLEND  
CONFIDENCE: AVERAGE  
 
FURTHER WEST, AS THE TAIL END OF THE INITIAL SHORTWAVE SWINGS OUT  
OF THE ROCKIES INTO THE GREAT LAKES ON TUESDAY; REINFORCING  
SHORTWAVE ENERGY OVER-TOPS THE AMPLIFYING PACIFIC RIDGE DROPPING  
INTO THE DEVELOPING LARGER SCALE TROF OVER THE WEST BY WED. THIS  
WAVE, IN COMBINATION WITH EMERGING SHORTWAVE ENERGY OUT OF THE  
EAST-CENTRAL PACIFIC (UNDER THE PACIFIC RIDGE, AS WELL AS  
LINGERING FRONTAL ZONE ACROSS TX INTO THE SOUTHERN HIGH PLAINS  
WILL SET UP THE NEXT SYSTEM WITH THE POTENTIAL FOR WINTRY PROBLEMS  
BY LATE WED INTO THURSDAY. HERE, THERE IS MUCH MORE SUBSTANTIAL  
SPREAD, KEYING ON THE TIMING OF THE THE CENTRAL PACIFIC  
SHORTWAVE/MOISTURE TRANSPORT THROUGH THE DESERT SOUTHWEST INTO THE  
AREA OF CONCERN. HERE THE ECMWF SHOWS THE GREATEST TIMING  
DIFFERENCES BEING QUITE SLOW WITH THE WAVE, MAINLY AS IT LOST SOME  
ENERGY TO THE NORTHERN STREAM ALONG THE WESTERN SIDE OF THE  
DEVELOPING PACIFIC RIDGE, WHICH DELAYS THE ENERGY ADVANCING AS  
WELL AS DROPPING THE FOCUS FURTHER SOUTH. SO AS THE SHORTWAVE  
FROM THE NORTHERN STREAM DROPS, IT DOES NOT PHASE/AMPLIFY DELAYING  
ITS EJECTION INTO THE PLAINS. THE 12Z GFS AND 00Z CMC ARE MUCH  
FASTER WITH THIS SHORTWAVE CAPTURE AND START TO BREAK OUT  
INCREASED QPF ACROSS THE SOUTHERN HIGH PLAINS/TX BY 00Z THURSDAY.  
EVEN THOUGH IT IS TYPICAL OF THE GFS TO HAVE A FAST BIAS, THE  
SIMILARITY IN TIMING PRESENTED BY THE 00Z CMC AND UKMET SUGGEST  
LESS OR NO INFLUENCE OF THE ECMWF IN A PREFERRED BLEND AT THIS  
TIME. WHILE NOT FAVORED DUE TO TYPICAL DEEPER/OVER-AMPLIFIED  
SOLUTION THROUGH THE WEST; THE 12Z NAM IS ALSO FASTER LIKE THE  
GFS/CMC WITH THIS ENERGY, PROVIDING SOME CONFIDENCE, AS A STRONGER  
MORE AMPLIFIED SYSTEM SHOULD BE SLOWER. CONFIDENCE IN AVERAGE IN  
A 12Z GFS AND 00Z CMC/UKMET BLEND FOR THIS FEATURE.  
 
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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