164  
FXUS10 KWNH 230529  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1228 AM EST THU JAN 23 2020  
 
VALID JAN 23/0000 UTC THRU JAN 26/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH PRELIMINARY PREFERENCES AND FORECAST  
CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~  
 
...SHORTWAVE TROUGH MOVING ONSHORE THE PACIFIC NORTHWEST THURSDAY  
NIGHT-FRIDAY, THEN INTO THE PLAINS SAT-SAT NIGHT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~~  
PREFERENCE: GENERAL MODEL CONSENSUS THROUGH DAY 2, THEN ECMWF WITH  
GEFS/ECENS MEAN BY DAY 3.  
CONFIDENCE: AVERAGE...THEN BELOW AVERAGE BY DAY 3.  
 
A PIECE OF ENERGY SHEDDING FROM A CLOSED LOW NEAR THE GULF OF  
ALASKA WILL EJECT EASTWARD INTO THE PACIFIC NORTHWEST ON FRIDAY,  
ACCOMPANIED BY AN INTENSIFYING, ALTHOUGH STILL MODEST, PACIFIC JET  
STREAK BRINGING HEAVY RAINFALL TO THE NORTHWEST.  
 
FAIRLY STARK MODEL DIFFERENCES EMERGE BY THE END OF DAY 2 INTO DAY  
3 -- BOTH WITH THE TIMING AND PHASING (OR LACK THEREOF) OF BOTH  
NORTHERN/SOUTHERN SHORTWAVES. THE GFS, NAM, CMC AND TO A LESSER  
EXTENT THE UKMET, ARE TOO AMPLIFIED AND SLOW WITH THE NORTHERN  
STREAM SHORTWAVE TROUGH AND DOWNSTREAM SHORTWAVE RIDGE WHEN  
COMPARED TO THE ECMWF AND GLOBAL ENSEMBLE MEANS. WHILE ANY OF  
THESE SOLUTIONS MAY CERTAINLY PAN OUT, GIVEN THE TIMING/AMPLITUDE  
DISPARITY OF THE OPERATIONAL GUIDANCE AS A WHOLE, AT THIS POINT  
(DAY 3 FORECAST) THE RECOMMENDATION WOULD BE TO OPT FOR THE  
FLATTER OPERATIONAL ECMWF ALONG WITH THE ECENS AND GEFS MEANS.  
 
...NEXT SHORTWAVE TROUGH MOVING ONSHORE THE WEST COAST BY EARLY  
SUNDAY (DAY 3)...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~~  
PREFERENCE: ECMWF WITH GEFS/ECENS MEAN  
CONFIDENCE: AVERAGE  
 
THE 00Z GFS IS ON THE FASTER EDGE OF THE MODEL SPREAD (INCLUDING  
GEFS/ECENS) WITH THE SHORTWAVE COMING ASHORE BY 12Z SUN, WHILE THE  
NAM, UKMET, AND CMC WERE A BIT MORE AMPLIFIED/SLOWER COMPARED TO  
THE ECMWF AND THE ECENS AND GEFS MEANS.  
 
...PHASING NORTHERN AND SOUTHERN STREAM TROUGHS AND EVENTUAL  
CLOSED UPPER LOW THURSDAY-SATURDAY NIGHT  
FROM THE PLAINS INTO THE OH VALLEY AND NORTHEAST...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~  
PREFERENCE: GENERAL MODEL CONSENSUS THROUGH DAY 2...ECMWF AND  
UKMET BLEND ON DAY 3  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
MANY DETAILS STILL NEED TO BE IRONED OUT WITH TWO MID-LEVEL  
IMPULSES MOVING THROUGH THE PLAINS TODAY INTO THURSDAY, AND HOW  
THEY WILL INTERACT THROUGH THE REST OF THE WEEK. MULTIPLE FEATURES  
INTERACTING CREATE LOWER THAN USUAL CONFIDENCE, BUT THE LEADING  
SHORTWAVE MOVING THROUGH THE NORTHERN ROCKIES SHOULD EVENTUALLY  
BECOME DOMINANT AND INTENSE, ESPECIALLY LATE ON FRIDAY NIGHT FROM  
THE MISSOURI VALLEY AND INTO THE OHIO VALLEY. THIS SHOULD LEAD TO  
STRONG CYCLOGENESIS ALONG A TRIPLE POINT ACROSS THE MID-ATLANTIC  
BY SATURDAY, WITH THIS TRIPLE POINT EXTENDING FROM A PRIMARY  
SURFACE LOW BENEATH THE TRAILING UPPER TROUGH OVER THE UPPER  
MIDWEST.  
 
GIVEN THE MINIMAL SPREAD, A GENERAL MODEL CONSENSUS WOULD APPEAR  
VIABLE THROUGH DAY 2. BY SATURDAY, THE GFS, NAM, AND TO A LESSER  
EXTENT THE CMC BEGIN TO OUTPACE THE OTHER GUIDANCE WITH THE  
PROGRESSION OF THE MID-LEVEL LOW ACROSS THE OH VALLEY AND INTO THE  
EASTERN GREAT LAKES REGION. AS A RESULT, THE GFS AND NAM ARE  
FASTER WITH THE SURFACE FROPA OFF THE MID ATLANTIC COAST SATURDAY  
MORNING, AND THUS QUICKER WITH THE LOW-MID LAYER COLD ADVECTION.  
THESE SOLUTIONS ARE ALSO FASTER WITH THE ABSORPTION OF THE GREAT  
LAKES SURFACE LOW. A BLEND OF THE ECMWF AND UKMET IS THEREFORE  
FAVORED, ESPECIALLY WHEN COMPARED TO THE GEFS AND ECENS, WHICH  
BOTH MAINTAIN A SURFACE LOW OVER THE GREAT LAKES (EASTERN LOWER  
MI) THROUGH 00Z SUN.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
HURLEY  
 

 
 
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