832  
FXUS10 KWNH 251646  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1145 AM 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
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: GENERAL MODEL BLEND...THROUGH 36 HOURS  
00Z ECMWF...AFTER 36 HOURS  
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. IN GENERAL, THE 12Z  
NAM APPEARS TO BE A SLOWER AND DEEPER OUTLIER AS THE HEIGHT FALLS  
CROSS ESPECIALLY SOUTHERN CALIFORNIA AND AREAS FARTHER EAST THOUGH  
TUESDAY AND WEDNESDAY REACHING TOWARD THE SOUTHERN HIGH PLAINS.  
GRADUALLY THE 00Z UKMET BECOMES QUITE SLOW LIKE THE NAM AS WELL,  
BUT NOT AS DEEP. BY THE END OF THE PERIOD, THE 12Z GFS AND 00Z CMC  
ARE THE MOST PROGRESSIVE WITH ENERGY EJECTING OUT ACROSS THE  
SOUTHERN PLAINS. THE 00Z ECMWF SPLITS THE DIFFERENCE, BUT IS  
SUPPORTED BY THE BROADER ECENS SUITE AND SOME GEFS MEMBERS,  
ALTHOUGH THE MAJORITY OF THE GEFS ARE FASTER LIKE THE OPERATIONAL  
GFS. WILL PREFER A GENERAL MODEL BLEND THROUGH 36 HOURS, AND THEN  
LEAN TOWARD THE 00Z ECMWF THEREAFTER AS A COMPROMISE BETWEEN  
FASTER AND SLOWER CAMPS.  
 
 
...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 AND 00Z 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 AND 00Z ECMWF WHICH HAVE BETTER ENSEMBLE  
SUPPORT AS WELL. THE 12Z NAM AND 00Z CMC TENDED TO BE LESS ROBUST  
WITH THE HEIGHT FALLS/SURFACE LOW DEEPENING, AND THE 00Z UKMET  
APPEARS TO BE TOO SLOW. WILL PREFER A BLEND OF THE GFS AND ECMWF  
AT THIS TIME AS A RESULT.  
 
 
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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