578  
FXUS10 KWNH 281852  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
151 PM EST WED FEB 28 2018  
 
VALID FEB 28/1200 UTC THRU MAR 04/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
   
..12Z MODEL EVALUATION ALONG WITH FINAL PREFERENCES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
 
 
...SHORTWAVE OVER THE SOUTHWEST, EJECTING EASTWARD INTO THE PLAINS  
TONIGHT AND REACHING THE EAST COAST LATE THURSDAY WHILE  
INTERACTING WITH A NORTHERN STREAM WAVE DROPPING SOUTH FROM THE  
UPPER MISSISSIPPI VALLEY...  
...RESULTANT SURFACE CYCLONE INTO THE OHIO VALLEY ON THURSDAY WITH  
SURFACE LOW REFORMING SOUTHEAST OF THE NEW ENGLAND COAST THROUGH  
FRIDAY MORNING...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM/GFS/ECMWF BLEND (EVEN WEIGHTING)  
CONFIDENCE: AVERAGE  
 
00Z GEFS/ECMWF/CMC ENSEMBLE SPAGHETTI HEIGHTS AT 534 DAM CONTINUE  
TO SHOW THE GEFS AND OLDER RUNS OF THE GFS AS STRONGER AND ON THE  
WESTERN EDGE OF THE AVAILABLE MEMBERS VALID FRIDAY ACROSS THE  
NORTHEAST. ENSEMBLE TRENDS IN THE HEIGHTS AND SURFACE LOW PLOTS  
HAVE SHOWN A WESTERN SHIFT VALID 12Z/02 OFFSHORE OF NEW ENGLAND  
WITH THE GEFS MEMBERS ON THE FAR NORTHWESTERN EDGE AND ECMWF  
MEMBERS THE SOUTHEASTERN EDGE OF THE ENVELOPE OF SOLUTIONS. THE  
PREFERENCE IS TO BE NEAR THE CENTROID OF THE AVAILABLE ENSEMBLE  
SCATTER LOW PLOT POSITIONS, CONSIDERING TRENDS, WHICH IS BETWEEN  
THE 00Z GEFS AND 00Z EC MEMBERS, OR NEAR THE 12Z NAM POSITION  
VALID 12Z/02.  
 
THE 12Z MODELS HAVE CONTINUED TO COME INTO BETTER AGREEMENT WITH  
THE 12Z GFS AND 12Z ECMWF CONVERGING TOWARD ONE ANOTHER, AND LYING  
A BIT EAST OF THE 12Z NAM. VALID 00Z/03, THE 12Z NAM ENDS UP ON  
THE WESTERN SIDE OF THE ENSEMBLE SPREAD, AND DESPITE TRENDS IN  
THAT DIRECTION FROM THE ENSEMBLES, BLENDING WITH THE FARTHER EAST  
12Z GFS AND 12Z ECMWF APPEARS PRUDENT WITH THE 12Z UKMET AND 12Z  
CMC ALSO DEPICTING A FARTHER EAST SOLUTION THAN THE 12Z NAM. THE  
12Z UKMET APPEAR A BIT STRONGER OR DISPLACED AWAY FROM IDEA  
CONCERNING THE ENSEMBLE SPREAD. WHILE SOME 12Z DETERMINISTIC  
GUIDANCE HAS SHOWN AN EASTWARD SHIFT VALID 12Z/02, TRENDS HAD BEEN  
WEST SO WE PREFER TO STAY GROUNDED TOWARD A MIDDLE ROAD APPROACH.  
REGARDING MASS FIELDS, THE 12Z NAM/GFS/ECMWF LOOK REASONABLY  
SIMILAR DESPITE TEMPERATURES IN THE LOWEST KILOMETER OR SO ABOVE  
GROUND LEVEL, WITH THE 12Z NAM COLDEST, 12Z GFS WARMEST AND 12Z  
ECMWF IN THE MIDDLE.  
 
 
...LARGE CLOSED LOW OFF OF THE PACIFIC NORTHWEST BY THURSDAY  
EVENING...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
SIMILAR TO YESTERDAY, THERE CONTINUES TO BE GOOD AGREEMENT WITH  
THIS SYSTEM. THERE HAVE BEEN SOME MODELS THAT HAVE TRENDED A BIT  
SLOWER COMPARED TO YESTERDAY'S RUNS, BUT ENSEMBLES CONTINUE TO  
SHOW RELATIVELY GOOD AGREEMENT, LED BY THE CONSISTENT ECMWF MEAN.  
THE 12Z UKMET BACKED OFF OF A STRONGER SURFACE LOW FROM ITS 00Z  
CYCLE WHICH WAS CONSIDERED UNLIKELY IN THE PRELIMINARY  
PREFERENCES, SO A GENERAL 12Z MODEL BLEND IS RECOMMENDED FOR THIS  
SYSTEM WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE GIVEN SMALL SPREAD  
AND LITTLE RUN TO RUN CHANGES.  
 
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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