389  
FXUS10 KWNH 141846  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
143 PM EST WED FEB 14 2018  
 
VALID FEB 14/1200 UTC THRU FEB 18/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
   
..12Z MODEL EVALUATION WITH LATEST MODEL PREFERENCES/CONFIDENCE
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..CLOSED LOW INITIALLY OFFSHORE SOUTHERN CALIFORNIA
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS TAKE THE UPPER LOW OFFSHORE SOUTHERN CALIFORNIA  
GRADUALLY OFF TO THE EAST AND INLAND ACROSS THE DESERT SOUTHWEST  
OVER THE NEXT 12 TO 24 HOURS. AS THE ENERGY MOVES INLAND, IT WILL  
BE DEAMPLIFYING, AND IT IS EXPECTED TO SHEAR OUT ACROSS THE FOUR  
CORNERS REGION ON THURSDAY. THE LATEST GUIDANCE IS IN GOOD  
AGREEMENT ON THE DETAILS OF THIS, AND SO A GENERAL MODEL BLEND  
WILL BE PREFERRED AT THIS TIME.  
 
   
..SHORTWAVE DIGGING DOWN ACROSS THE PACIFIC NORTHWEST TODAY
 
   
..ENERGY DIGGING INTO THE SOUTHWEST BY THURSDAY
 
   
..EJECTING RAPIDLY EAST ACROSS THE SOUTHERN U.S FRIDAY.
 
   
..SOUTHERN STREAM SHORTWAVE OVER TENNESSEE VALLEY BY SATURDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS/12Z UKMET AND 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS ALLOW SHORTWAVE ENERGY CURRENTLY DIGGING SOUTH DOWN  
ACROSS THE PACIFIC NORTHWEST TO DROP DOWN INTO THE SOUTHWEST U.S.  
BY THURSDAY WHICH WILL EFFECTIVELY HELP KICK THE CURRENT ENERGY  
OVER THE SOUTHWEST DOWNSTREAM IN A SHEARED FASHION. THE NEW  
SHORTWAVE FOCUSING OVER THE SOUTHWEST WILL THEN TEND TO CAPTURE  
SOME OF THE SHORTWAVE/VORT ENERGY IN THE SUBTROPICAL STREAM TO THE  
WEST OF THE BAJA PENINSULA AND THEN BEGIN RAPIDLY EJECT DOWNSTREAM  
ACROSS THE SOUTHERN U.S. BY FRIDAY. A SOUTHERN STREAM SHORTWAVE  
REMNANT WILL THEN QUICKLY ARRIVE ACROSS THE LOWER MISSISSIPPI  
VALLEY AND TENNESSEE VALLEY REGION BY SATURDAY WHILE ATTEMPTING TO  
ALSO DEVELOP A WEAK SURFACE LOW. THE 12Z NAM IS MORE SHEARED AND A  
BIT WEAKER WITH THE SOUTHERN STREAM ENERGY AND TENDS TO PLACE MORE  
EMPHASIS ON NORTHERN STREAM ENERGY INSTEAD ACROSS THE MIDWEST. THE  
12Z GFS, 12Z ECMWF AND 12Z UKMET ARE BETTER DEFINED AND SUPPORT A  
PROGRESSIVE SYSTEM, BUT THE UKMET MAY BE A TAD TOO STRONG WITH ITS  
SURFACE LOW DEVELOPMENT AT THE END OF THE PERIOD OVER THE  
TENNESSEE VALLEY. THE UKMET ALSO IS SHOWING A BIT MORE  
NORTHERN/SOUTHERN STREAM INTERACTION BY SATURDAY UPSTREAM OVER THE  
THE MIDWEST WHICH THE ECMWF IS SHOWING AS WELL, BUT WITH THE UKMET  
A BIT SLOWER. BASED ON THE LATEST ENSEMBLE MEANS FROM THE GEFS AND  
ECENS, A COMPROMISE OF THE GFS, ECMWF AND UKMET SHOULD STILL  
SUFFICE, AND THIS CONSENSUS IS GENERALLY SUPPORTED BY THE LATEST  
CMC AS WELL.  
 
   
..SHORTWAVES CROSSING THE GREAT BASIN, MIDWEST AND GREAT LAKES
 
   
..STRONGER ENERGY OVER THE PACIFIC NORTHWEST BY SATURDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS/12Z UKMET AND 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
MULTIPLE NORTHERN STREAM SHORTWAVES ARE EXPECTED TO TRAVERSE THE  
NORTHERN U.S. OVER THE NEXT FEW DAYS. THE MODELS SHOW GOOD  
AGREEMENT WITH THE FIRST SHORTWAVE THAT CROSSES A PORTION OF THE  
NORTHWEST TODAY AND THEN QUICKLY EJECTS EAST ACROSS THE PLAINS AND  
MIDWEST THROUGH THURSDAY. THIS ENERGY THEN CROSSES THROUGH THE  
NORTHEAST BY FRIDAY. THEN A SECOND SHORTWAVE TRAVERSES THE  
NORTHWEST ON FRIDAY AND EJECTS OUT ACROSS THE MIDWEST ON SATURDAY.  
THE MODELS ARE IN GOOD AGREEMENT WITH THIS SECOND SHORTWAVE MINUS  
THE 12Z NAM WHICH IS A SOMEWHAT SLOWER AND MORE AMPLIFIED OUTLIER  
BY SATURDAY OVER THE MIDWEST.  
 
A THIRD AND STRONGER SHORTWAVE IMPULSE THEN DROPS SOUTH DOWN  
COASTAL AREAS OF BRITISH COLUMBIA ON FRIDAY AND INTO THE PACIFIC  
NORTHWEST ON SATURDAY. A WELL-DEFINED LOW CENTER WILL ACCOMPANY  
THIS NEXT SURGE OF ENERGY. THE 12Z NAM IS THE SLOWEST WITH THIS  
SYSTEM, WITH THE 12Z UKMET AND 12Z ECMWF THE FASTEST. THE 12Z GFS  
AND 12Z CMC SPLIT THE DIFFERENCE WITH TIMING BETWEEN CAMPS. WILL  
LEAN OVERALL TOWARD THE MORE PROGRESSIVE CONSENSUS WITH THE IDEA  
OF MORE VIGOROUSLY DIGGING ENERGY ARRIVING TOWARD THE PACIFIC  
NORTHWEST GIVEN THE STRENGTH OF THE MEAN LAYER RIDGE NOSING UP  
ACROSS THE GULF OF ALASKA BY SATURDAY. THUS, COLLECTIVELY A BLEND  
OF THE GFS, UKMET AND ECMWF WILL BE PREFERRED WITH THE NORTHERN  
STREAM SHORTWAVES.  
 
 
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