552   
FXUS10 KWNH 261853  
PMDHMD  
  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
152 PM EST SUN JAN 26 2020  
  
VALID JAN 26/1200 UTC THRU JAN 30/0000 UTC  
  
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
  
12Z MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..SHORTWAVES CROSSING THE GREAT LAKES/OH VALLEY THROUGH TUESDAY  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
  
A SHORTWAVE CURRENTLY DIGGING SOUTHEAST OVER THE MIDWEST WILL RACE  
ACROSS THE OH VALLEY BY LATE MONDAY. IT WILL THEN REACH THE  
MID-ATLANTIC COAST MONDAY NIGHT. IN ITS WAKE, A SECOND SHORTWAVE  
WILL ALSO BE DROPPING DOWN FROM THE GREAT LAKES REGION WHICH WILL  
CROSS THE OH VALLEY THROUGH TUESDAY. THE 12Z NAM OCCASIONALLY  
APPEARS TO BE PERHAPS A TAD TOO STRONG, BUT THE OVERALL MODEL  
SPREAD IS QUITE MINIMAL, SO A GENERAL MODEL BLEND WILL BE  
PREFERRED.  
  
   
..SPLIT FLOW TROUGH CROSSING THE WEST COAST TODAY  
   
..ENERGY EJECTING THROUGH THE SOUTHWEST AND PLAINS BY TUESDAY  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z ECMWF/GEFS AND 00Z ECENS MEAN  
CONFIDENCE: BELOW AVERAGE  
  
THE MODELS ALL TAKE A PROGRESSIVE SPLIT-FLOW TROUGH ACROSS THE  
WEST TODAY, WITH A SOUTHERN STREAM PORTION OF THE ENERGY THEN  
DROPPING DOWN ACROSS THE SOUTHWEST AND AMPLIFYING INTO A CLOSED  
LOW AS IT APPROACHES THE SOUTHERN HIGH PLAINS BY EARLY TUESDAY.  
MEANWHILE, THE NORTHERN STREAM COMPONENT OF THE TROUGH WILL BE  
OVER THE NORTHERN HIGH PLAINS BY EARLY TUESDAY. ON WEDNESDAY,  
PORTIONS OF THE NORTHERN STREAM ENERGY WILL BE ATTEMPT TO DIG AND  
INTERACT WITH THE SOUTHERN STREAM ENERGY AS IT CROSSES THE GULF  
COAST STATES.  
  
THE 12Z NAM FOR A PERIOD OF TIME FROM 36 TO 60 HOURS IS SOMEWHAT  
OF A STRONGER OUTLIER WITH RESPECT TO THE SOUTHERN STREAM ENERGY.  
HOWEVER, THEREAFTER, THE 12Z CMC AND 12Z GFS BECOME THE STRONGEST  
SOLUTIONS, BUT WITH THE CMC SLOWER AND THE GFS FASTER. THE 12Z  
UKMET BECOMES A PROGRESSIVE/FLATTER OUTLIER. THE 12Z ECMWF THOUGH  
ACTUALLY IS VERY CLOSE TO THE OVERALL MODEL CONSENSUS AND SPLITS  
THE DIFFERENCE BETWEEN SLOWER/FASTER SOLUTIONS AND THE RESPECTIVE  
DEEPER/FLATTER CAMPS. INTERESTINGLY, THE 12Z GEFS MEAN HAS COME IN  
DEEPER AND SLOWER THAN ITS PREVIOUS CYCLE, AND SUGGESTS THAT  
VIRTUALLY ALL OF THE GLOBAL MODELS ARE TOO PROGRESSIVE BY THE END  
OF THE PERIOD. THE DIFFERENCES WITH THE NORTHERN STREAM ENERGY ARE  
NOT AS VAST, BUT THE NAM MAY BE TOO AMPLIFIED AND TOO FAR NORTH  
WITH THIS ENERGY. GIVEN THE DETERMINISTIC MODEL SPREAD WITH  
TIMING/DEPTH OF THE ENERGY CROSSING ESPECIALLY THE SOUTHERN U.S.,  
CONFIDENCE IS LIMITED, BUT THE PREFERENCE WILL BE TO BLEND THE 12Z  
ECMWF WITH THE 12Z GEFS AND 00Z ECENS MEAN FOR THE TIME BEING  
WHICH AT LEAST ADDRESSES THE IDEA OF THE GFS/UKMET SOLUTIONS BEING  
TOO PROGRESSIVE AND THE NAM TOO SLOW ACROSS THE SOUTH, AND IN THE  
CASE OF THE UKMET, TOO FLAT/WEAK.  
  
   
..PROGRESSIVE UPPER TROUGH OVER THE PACIFIC NORTHWEST TUESDAY  
   
..AMPLIFYING INTO THE WEST ON WEDNESDAY  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-NAM BLEND  
CONFIDENCE: AVERAGE  
  
YET ANOTHER IN A SERIES OF PACIFIC SHORTWAVE TROUGHS WILL ARRIVE  
ON TUESDAY ACROSS THE PACIFIC NORTHWEST, AND THEN DIG INTO THE  
WEST ON WEDNESDAY, WITH THE GRADUAL DEVELOPMENT OF A CLOSED LOW  
OVER THE SOUTHWEST LATE WEDNESDAY. THE 12Z NAM MAY BE A TAD TOO  
WEAK AND FAST AS THE ENERGY INITIALLY COMES INTO THE PACIFIC  
NORTHWEST, BUT THEN BY LATE WEDNESDAY APPEARS TO BE A LITTLE TOO  
SLOW WITH ITS HEIGHT FALLS PIVOTING TOWARD THE SOUTHWEST. THE  
GLOBAL MODELS ARE OVERALL IN PRETTY GOOD AGREEMENT WITH THE LARGER  
SCALE MASS FIELD EVOLUTION, BUT THE ECMWF MAY BE POSSIBLY DROPPING  
ITS CLOSED LOW A LITTLE TOO FAR SOUTH AT THE END OF THE PERIOD  
GIVEN WHERE THE GEFS/ECENS SUITES SUGGEST IT WOULD BE. REGARDLESS,  
WILL KEEP THE PRIOR RECOMMENDATION OF A NON-NAM BLEND FOR NOW.  
  
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
  
ORRISON  
  
  
 
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