575  
FXUS10 KWNH 241640  
PMDHMD  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1139 AM EST SUN NOV 24 2019  
 
VALID NOV 24/1200 UTC THRU NOV 28/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...MID-ATLANTIC/NORTHEAST SHORTWAVE(S) AND ASSOCIATED SURFACE  
LOW...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE LAST VESTIGES OF THE NOR'EASTER ACROSS NEW ENGLAND OCCUR  
THROUGH THE REST OF SUNDAY. THE CMC IS A BIT WEAKER INITIALLY,  
BUT OVERALL ITS SLOWER DEVELOPMENT REACHES THE LEVEL OF THE OTHER  
GUIDANCE WITHIN 3 TO 6 HOURS BY EARLY MONDAY, THAT IS NOT A MAJOR  
DIFFERENCE. SO A GENERAL MODEL BLEND CAN BE SUPPORTED AT ABOVE  
AVERAGE CONFIDENCE FOR ITS REMAINDER IN THE CONUS.  
 
...SHORTWAVE RACING THROUGH CANADIAN ROCKIES SUNDAY BEFORE  
SUPPORTING NORTHERN TIER SURFACE WAVE MONDAY AND SHEARING OUT  
ALONG THE GREAT LAKES/SW QUEBEC BY TUES...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
GOES-W WV STARING TO SHOW THE AMPLIFICATION OF THE NORTHERN STREAM  
SHORTWAVE OVER BC AT THIS TIME IN PREPARATION FOR CROSSING THE  
CANADIAN ROCKIES. THE GUIDANCE SUITE HAS TIGHTENED OVER THE LAST  
24HRS THOUGH THERE REMAINS A SMALL LATITUDE DIFFERENCE IN THE QPF  
SWATH WITH THE NCEP GUIDANCE A BIT NORTH AND THE UKMET/CMC/ECMWF  
SUITE A TAD SOUTH (ALONG/JUST SOUTH OF THE BORDER MON INTO EARLY  
TUES). THIS IS FAIRLY MINOR AND IN LINE WITH TYPICAL BIASES...TO  
SUPPORT AN EQUAL BLEND OF THE GUIDANCE TO SPLIT THE DIFFERENCE,  
ESPECIALLY AS THE GUIDANCE REMAINS AGREEABLE THROUGH THE SHEARING  
PHASE THROUGH THE GREAT LAKES INTO QUEBEC. CONFIDENCE IN A  
GENERAL MODEL BLEND IS SLIGHTLY ABOVE AVERAGE.  
 
...LEAD SHORTWAVE IN DEVELOPING GLOBAL-SCALE TROF IN FOUR CORNERS  
BY 00Z TUESDAY...  
...DEVELOPMENT OF STRONG/BROAD SURFACE LOW IN PLAINS TUESDAY AND  
GREAT LAKES BY WED...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z GFS/00Z ECMWF BLEND  
CONFIDENCE: AVERAGE  
 
PATTERN CHANGING SHORTWAVE/JET SPEED MAX OVER-TOPPING THE CENTRAL  
PACIFIC RIDGE IS EXPECTED TO DIVE SOUTHEAST INTO THE GREAT BASIN  
BY 25.18Z. IN THE WEAK, BROAD CYCLONIC FLOW, THIS WAVE STARTS TO  
BUCKLE THROUGH THE CENTRAL ROCKIES AND START TO SPIN UP A BROAD  
SURFACE CYCLONE ACROSS THE CENTRAL HIGH PLAINS MONDAY INTO  
TUESDAY. THE ECMWF IS A BIT SLOWER WITH THIS AND SHOWS A BIT  
GREATER RIDGE AMPLIFICATION ACROSS THE ROCKIES INCREASING UPSLOPE  
MOISTURE FLOW. WHILE THE 12Z GFS IS IN A TYPICALLY SLIGHTLY  
FASTER TRANSITION MATCHING VERY CLOSELY THE CENTROID OF THE ECENS  
AND GEFS MEANS. WHILE THE 12Z NAM IS IN FAIRLY GOOD AGREEMENT,  
THERE IS GREATER DEPTH AND MORE CONCENTRIC APPEARANCE TO THE  
DEVELOPING CLOSED LOW BY WED AND IS ABOUT 40-60DM DEEPER THAN THE  
ECMWF/GFS. WHILE ON THE OPPOSITE SIDE, THE 00Z CMC IS VERY WEAK  
AND THE SURFACE WAVE IS A BIT SOUTH INITIALLY. THE 00Z UKMET  
WHILE ALSO FAIRLY AGREEABLE TO THE ECMWF, IS EVEN SLOWER WITH THE  
WAVE MOVING OUT OF THE ROCKIES (ATYPICAL) BUT THEN RAPIDLY  
ACCELERATES TO MATCH THE GFS BY THE END OF THE FORECAST PERIOD.  
OVERALL, THERE IS GROWING CONFIDENCE WITH THE EVOLUTION OF THE  
SYSTEM, BUT WITH IMPORTANCE OF TIMING AND ANGLE OF AMPLIFICATION  
TO THE ORIENTATION OF THE TERRAIN IN THE ROCKIES, WILL UTILIZE THE  
ENSEMBLE CENTROID AND SUGGEST A 12Z GFS/00Z ECMWF BLEND AS A BEST  
REPRESENTATION, THOUGH CONFIDENCE IS AVERAGE IN THIS BLEND.  
 
...STRONG SECONDARY SHORTWAVE SUPPORTING WITH VERY DEEP SURFACE  
LOW NEAR N CA TUES, EXPANDING  
ACROSS NORTHERN CA/N GREAT BASIN BY 00Z THURS...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-CMC BLEND (REDUCE/REMOVE NAM AFTER 27.00Z)  
CONFIDENCE: AVERAGE  
 
THE NEXT SHORTWAVE QUICK ON THE HEELS OF THE PRIOR, OVER-TOPS THE  
CENTRAL PACIFIC RIDGE BY 00Z TUES. HOWEVER, BEING A BIT STRONGER,  
IT TAMPS DOWN THE RIDGE, AND AS IT SLIDES SOUTHEAST ALONG THE  
EASTERN PORTION OF THE RIDGE, A SMALL FRACTION OF NORTHERN STREAM  
ENERGY AIDS IN A BROADER WAVE DEVELOPMENT EVENTUALLY TOWARD A  
CLOSED LOW. THE CMC IS THE ONLY GUIDANCE, THAT SUGGESTS GREATER  
INFLUENCE FROM THE NORTHERN STREAM WHICH LEADS TO IT BEING FURTHER  
EAST AND WEAKER OVERALL BY THE END OF THE FORECAST PERIOD, AND IS  
NOT PREFERRED IN THE PREFERENCE.  
 
THE REMAINING GUIDANCE, ALL NOW SUPPORT A VERY STRONG/COMPACT  
LEADING EDGE TO THE SHORTWAVE REACHING THE N CA COAST 00Z WED  
(LATE TUESDAY), WITH A VIGOROUSLY DEEPENING SURFACE CYCLONE.  
AFTER LANDFALL, THE UPPER LOW, BROADENS AND SLIDES SOUTH. THE  
GREATEST AGREEMENT EXISTS WITH THE 12Z GFS/00Z ECMWF BUT THE 12Z  
NAM AND 00Z UKMET ARE SOLID ENOUGH IN THE ENSEMBLE SUITE TO HAVE  
GOOD AGREEMENT TO INCORPORATE INTO A PREFERRED BLEND. THE NAM IS  
A BIT SLOW ON WED, THAT WOULD REDUCE/REMOVE THE WEIGHTING WITH  
TIME ON DAY 3. WHILE THERE IS GOOD ALIGNMENT OF THE WAVE  
DEVELOPMENT TO PROVIDE CONFIDENCE, ITS CURRENT LOCATION/SOURCE AND  
INFLUENCES OF THE RIDGE AND NORTHERN STREAM STILL PROVIDE SOME  
REDUCED ABSOLUTE CERTAINTY TO THIS BLEND. SO, WHILE THE  
CONFIDENCE HAS IMPROVED SUBSTANTIALLY SINCE YESTERDAY, IT IS STILL  
AVERAGE.  
 
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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