288  
FXUS10 KWNH 031842  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
141 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 MODEL EVALUATION WITH FINAL 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/12Z ECMWF BLEND  
CONFIDENCE: AVERAGE  
 
THE 12Z ECMWF/UKMET/CMC HAVE SPED UP SOME TO MATCH THE FASTER 12Z  
NAM/GFS 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  
TRENDS IN THE NEWER 12Z GUIDANCE CAN NOT BE IGNORED. A 12Z  
NAM/GFS/ECMWF BLEND IS PREFERRED GIVEN A BLEND OF THESE THREE  
MODELS REPRESENT THE NEW MIDDLE GROUND SHOWN IN THE LATEST  
GUIDANCE.  
 
...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: GENERAL MODEL BLEND  
CONFIDENCE: 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 12Z  
GUIDANCE HAS PICKED UP ON NEWER INFORMATION AND SHOULD BE GIVEN  
MORE WEIGHT WITH LESSER INCLUSION OF THE 00Z ECMWF/UKMET/CMC.  
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 REMAINING 12Z GUIDANCE, 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.  
 
19Z UPDATE: THE 12Z ECMWF/UKMET/CMC CONTINUE TO SHOW BROAD  
CONVERGENCE TOWARD A COMMON TIMING/LATITUDE WITH THIS FEATURE SO A  
GENERAL MODEL COMPROMISE CONTINUES TO BE PREFERRED.  
 
...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 / 12Z ECMWF / 00Z UKMET BLEND  
CONFIDENCE: AVERAGE  
 
THERE IS GOOD AGREEMENT HERE UNTIL AROUND 00Z/06 WHEN THE 12Z GFS  
AND 12Z UKMET BEGIN TO SPEED UP RELATIVE TO THE AGREEABLE ENSEMBLE  
MEANS. THE 00Z ECMWF WAS SLOWEST OF THE DETERMINISTIC GUIDANCE BUT  
THE 12Z ECMWF HAS SPED UP TO THE PREVIOUS PREFERENCE.THE 12Z CMC  
IS MOSTLY UNCHANGED FROM ITS PREVIOUS RUN SO IT IS STILL  
CONSIDERED A BIT TOO FAST WITH THE SHORTWAVE BY 00Z/07. OVERALL  
ENSEMBLE TRENDS HAVE BEEN SLIGHTLY SLOWER OVER THE PAST 4 CYCLES,  
BUT THE BETTER CLUSTERING IS NEAR THE 12Z NAM, 12Z ECMWF AND 00Z  
UKMET.  
 
 
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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