169  
FXUS10 KWNH 251903  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
202 PM EST SUN FEB 25 2018  
 
VALID FEB 25/1200 UTC THRU MAR 01/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...WITH LATEST MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..DEEP SURFACE LOW LIFTING NORTHEAST ACROSS ONTARIO TODAY
 
   
..TRAILING COLD FRONT SWEEPING THROUGH THE EASTERN U.S
 
   
..SURFACE WAVE DEVELOPING JUST OFFSHORE SOUTHERN NEW ENGLAND
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS TAKE A DEEP SURFACE LOW AWAY FROM THE UPPER GREAT LAKES  
REGION TODAY AND UP ACROSS ONTARIO. THIS LOW WILL ADVANCE UP  
ACROSS QUEBEC TONIGHT THROUGH EARLY MONDAY. A TRAILING COLD FRONT  
MEANWHILE WILL BE SWEEPING ACROSS THE EASTERN U.S., ALTHOUGH THE  
GUIDANCE AGREES IN HANGING UP THE FRONT A BIT ALONG THE CENTRAL  
AND WESTERN GULF COAST REGION. ADDITIONALLY, THERE WILL A WAVE OF  
LOW PRESSURE DEVELOPING JUST OFFSHORE SOUTHERN NEW ENGLAND LATER  
TODAY THAT WILL LIFT NORTHEAST UP TOWARD THE CANADIAN MARITIMES ON  
MONDAY. ALL OF THE MODELS SHOW GOOD AGREEMENT GENERALLY WITH THE  
MASS FIELD EVOLUTION OF THESE FEATURES AND SO A GENERAL MODEL  
BLEND WILL BE PREFERRED.  
 
   
..SHORTWAVE EJECTING ACROSS THE FOUR CORNERS/HIGH PLAINS
 
   
..EJECTING EAST ACROSS THE MISSISSIPPI/OHIO VALLEYS ON MONDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
A SHORTWAVE WILL CROSS THE FOUR CORNERS REGION TODAY AND THEN  
RAPIDLY EJECT EAST TOWARD THE MISSISSIPPI VALLEY AND OHIO VALLEY  
ON MONDAY. THE ENERGY WILL THEN CROSS PARTS OF THE MID-ATLANTIC  
AND NORTHEAST BY MONDAY NIGHT. THE MODELS ARE IN GOOD AGREEMENT  
WITH THEIR MASS FIELD DETAILS OF THIS SYSTEM AND AS A RESULT A  
GENERAL MODEL BLEND WILL BE PREFERRED.  
 
   
..SHORTWAVE ARRIVING OVER THE PACIFIC NORTHWEST TODAY
 
   
..CLOSED LOW EVOLUTION OVER THE SOUTHWEST BY MONDAY
 
   
..ADVANCING EAST TOWARD THE SOUTHERN HIGH PLAINS BY WEDNESDAY
 
   
..SURFACE LOW DEVELOPMENT OVER THE CENTRAL PLAINS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF  
CONFIDENCE: AVERAGE  
 
THE NEXT IN A SERIES OF WESTERN NORTH AMERICAN SHORTWAVES WILL DIG  
INTO THE PACIFIC NORTHWEST TODAY ALONG WITH A PROGRESSIVE COLD  
FRONT. THE GUIDANCE IS IN GOOD AGREEMENT WITH THIS ENERGY DIGGING  
SHARPLY SOUTH DOWN ACROSS CALIFORNIA ON MONDAY WHICH WILL LEAD TO  
THE DEVELOPMENT OF A COMPACT AND RATHER ROBUST MID LEVEL LOW  
CENTER THAT DROPS DOWN ALONG THE COAST OF CENTRAL AND SOUTHERN  
CALIFORNIA BEFORE THEN PIVOTING EAST OVER AREAS OF THE DESERT  
SOUTHWEST BY TUESDAY. THE GUIDANCE IS IN GOOD AGREEMENT ON THE  
MASS FIELD EVOLUTION OF THIS SYSTEM THROUGH MONDAY, BUT THEN  
BEGINS TO SHOW SPREAD THEREAFTER OVER BROADER AREAS OF THE  
SOUTHWEST AND TOWARD THE SOUTHERN HIGH PLAINS. THE 12Z NAM BECOMES  
A SLOWER AND DEEPER OUTLIER AS THE HEIGHT FALLS CROSS ESPECIALLY  
SOUTHERN CALIFORNIA AND AREAS FARTHER EAST THROUGH TUESDAY AND  
WEDNESDAY REACHING TOWARD THE SOUTHERN HIGH PLAINS. THE 12Z GFS IS  
THE MOST PROGRESSIVE SOLUTION, BUT ALSO NOW HAS STRONG SUPPORT  
FROM THE 12Z ECMWF WHICH TRENDED FASTER WITH THIS CYCLE. THE 12Z  
UKMET AND 12Z CMC ARE JUST A LITTLE SLOWER THAN THE GFS AND ECMWF,  
BUT IT WAS NOTED THAT THE CMC ALSO BECOMES RATHER WEAK AND FLAT AS  
THE ENERGY REACHES THE SOUTHERN PLAINS WHICH RESULTS IN A MORE  
PROGRESSIVE SURFACE WAVE EVOLUTION. AS THE ENERGY APPROACHES THE  
SOUTHERN HIGH PLAINS, ALL OF THE GUIDANCE AGREES ON DEVELOPING LOW  
PRESSURE OVER THE CENTRAL PLAINS ALONG A FRONT. BASED ON THE  
LATEST MODEL TRENDS AND CLUSTERING, A BLEND OF THE GFS AND ECMWF  
WILL BE PREFERRED SURFACE AND ALOFT WHICH HAS GOOD SUPPORT FROM  
THE LATEST GEFS MEAN.  
 
   
..SHORTWAVES OVER THE NORTHERN ROCKIES/PLAINS THROUGH WEDNESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS BRING ANOTHER NORTHERN STREAM SHORTWAVE DOWN FROM  
WESTERN CANADA AND ACROSS THE NORTHERN ROCKIES MONDAY AND TUESDAY,  
FOLLOWED BY ANOTHER ONE THROUGH WEDNESDAY WITH ALL OF THE ENERGY  
ULTIMATELY EJECTING EAST OUT ACROSS THE NORTHERN PLAINS. SPREAD  
WITH THE INITIAL SHORTWAVE IS QUITE MINIMAL, BUT THERE IS SOME  
MODEST SPREAD MAINLY WITH THE DEPTH OF THE SECOND SHORTWAVE BY  
WEDNESDAY AS IT TRAVERSES THE NORTHERN PLAINS. WILL PREFER A  
GENERAL MODEL BLEND AT THIS TIME WITH BOTH SHORTWAVES.  
 
   
..STRONG UPPER TROUGH OFFSHORE THE PACIFIC NORTHWEST WEDNESDAY
 
   
..STRENGTHENING SURFACE LOW APPROACHING VANCOUVER ISLAND
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: BLEND OF THE 12Z GFS, 12Z UKMET AND 12Z ECMWF  
CONFIDENCE: AVERAGE  
 
THE GUIDANCE AGREES IN DROPPING ANOTHER SHORTWAVE TROUGH SOUTH  
FROM THE GULF OF ALASKA ON TUESDAY WHICH AMPLIFIES SHARPLY INTO A  
STRONG AND LARGER SCALE TROUGH NEAR BRITISH COLUMBIA AND  
APPROACHING THE PACIFIC NORTHWEST BY WEDNESDAY. A DEEPENING  
SURFACE LOW WILL BE APPROACHING VANCOUVER ISLAND WITH A TRAILING  
COLD FOCUSED OFFSHORE THE WASHINGTON AND OREGON COASTAL RANGES BY  
THE END OF THE PERIOD. THE STRONGER MODEL CLUSTERING AT THIS POINT  
RESIDES WITH THE 12Z GFS, 12Z UKMET AND 12Z ECMWF WHICH HAVE  
BETTER ENSEMBLE SUPPORT AS WELL. THE 12Z NAM TENDS TO BE LESS  
ROBUST WITH THE HEIGHT FALLS/SURFACE LOW DEEPENING, AND THE 12Z  
CMC NOW APPEARS TO BE THE MODEL THAT IS A BIT TOO SLOW. WILL  
PREFER A GFS/UKMET/ECMWF BLEND.  
 
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ORRISON  
 

 
 
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