138  
FXUS10 KWNH 031700  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1200 PM EST SAT FEB 03 2018  
 
VALID FEB 03/1200 UTC THRU FEB 07/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
   
..12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...SHORTWAVE TRACKING FROM THE ROCKIES THIS MORNING AND  
DISSIPATING EAST OF THE MISSISSIPPI RIVER EARLY SUNDAY...  
...SURFACE LOW NEAR THE LOWER MISSISSIPPI VALLEY EARLY ON SUNDAY  
MORNING, REACHING THE MID-ATLANTIC COAST SUNDAY EVENING...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM/12Z GFS/00Z ECMWF BLEND  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
THE 12Z NAM/GFS ARE QUICKER THAN THE 00Z ECMWF/UKMET/CMC REGARDING  
THE SURFACE LOW CROSSING THE LOWER MISSISSIPPI VALLEY INTO THE  
SOUTHEASTERN U.S. WHILE THE LATEST ENSEMBLE SCATTER LOW PLOTS SHOW  
GOOD AGREEMENT TOWARD THE 00Z GUIDANCE, THE NEWER 12Z NAM/GFS MAY  
BE PICKING UP ON NEWER INFORMATION AND WILL BE INCORPORATED AS A  
BLEND WITH THE 00Z ECMWF GIVEN THE ECMWF IS BETTER TIED TO THE  
PREVIOUS CONSENSUS.  
 
...SHORTWAVE TRACKING ACROSS THE GREAT LAKES/OHIO VALLEY ON  
SUNDAY, EAST COAST ON MONDAY...  
...SURFACE LOW TRACKING ACROSS THE GREAT LAKES EARLY SUNDAY  
MORNING, REACHING SOUTHERN QUEBEC EARLY MONDAY MORNING WITH  
TRAILING COLD FRONT...  
...CONSOLIDATING SURFACE LOW IN THE VICINITY OF NEW ENGLAND SUNDAY  
NIGHT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM/12Z GFS/00Z ECMWF BLEND  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
THERE ARE SOME DIFFERENCES REGARDING THE CONSOLIDATION OF TWO  
SURFACE LOWS, ONE IS DESCRIBED IN THE PRECEDING SECTION AND THE  
OTHER IS A REFLECTION OF A NORTHERN STREAM CROSSING THE GREAT  
LAKES LATE SUNDAY. AS DESCRIBED IN THE PRECEDING SECTION, THE  
NEWER 12Z NAM/GFS MAY BE PICKING UP ON NEWER INFORMATION AND  
SHOULD BE GIVEN MORE WEIGHT WITH LESSER INCLUSION OF THE 00Z  
ECMWF. ENSEMBLE SPREAD IS RATHER LARGE GIVEN THE COMPLEX EVOLUTION  
OF THIS SYSTEM. THERE ARE MINOR TIMING DIFFERENCES WORTH NOTING AS  
WELL WITH THE 12Z GFS SLIGHTLY FASTER THAN THE REMAINING GUIDANCE,  
BUT WHEN BLENDING TOGETHER WITH THE 12Z NAM AND 00Z ECMWF, AN  
ACCEPTABLE TIMING/STRENGTH IS REACHED.  
 
...WEAK 700 MB SHORTWAVE TRACKING ACROSS THE CENTRAL PLAINS INTO  
THE MIDWEST MONDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: AVERAGE  
 
THE 00Z ECMWF IS SLIGHTLY FASTER WITH THIS FEATURE AND THE 00Z  
UKMET SLIGHTLY FARTHER SOUTH, BUT ALL-IN-ALL, THE DETERMINISTIC  
MODELS SHOW DECENT AGREEMENT WITH THIS SYSTEM.  
 
...ONSHORE FLOW INTO THE PACIFIC NORTHWEST WITH LOW AMPLITUDE  
SHORTWAVE MOVING INLAND SUNDAY NIGHT AND NEARING THE FOUR CORNERS  
REGION TUESDAY EVENING...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM / 00Z UKMET BLEND  
CONFIDENCE: AVERAGE  
 
THERE IS GOOD AGREEMENT HERE UNTIL AROUND 00Z/06 WHEN THE 12Z GFS  
AND 00Z CMC BEGIN TO SPEED UP RELATIVE TO THE AGREEABLE ENSEMBLE  
MEANS. THE 00Z ECMWF IS SLOWEST OF THE DETERMINISTIC GUIDANCE. THE  
12Z NAM AND 00Z UKMET ARE IN THE MIDDLE OF THE DETERMINISTIC AND  
ENSEMBLE SPREAD, WHICH WILL BE LEANED UPON FOR THE PREFERENCE AT  
THIS TIME. OVERALL ENSEMBLE TRENDS HAVE BEEN SLIGHTLY SLOWER OVER  
THE PAST 4 CYCLES.  
 
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
 
OTTO  
 

 
 
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