661  
FXUS10 KWNH 191901  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
200 PM EST FRI JAN 19 2018  
 
VALID JAN 19/1200 UTC THRU JAN 23/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...SOUTHERN STREAM WAVE EJECTING NORTHEAST FROM THE GULF OF  
MEXICO...  
 
PREFERENCE: NON-CMC CONSENSUS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS TAKE THE SOUTHERN STREAM CLOSED LOW/TROUGH OVER THE  
WESTERN GULF COAST REGION GRADUALLY OFF TO THE EAST THROUGH THE  
WEEKEND WHICH WILL ALLOW IT TO TRAVERSE THE REMAINDER OF THE GULF  
COAST STATES. THE SYSTEM WILL WEAKEN AND BEGIN TO DAMPEN OUT BY  
SUNDAY NIGHT AND MONDAY AS IT REACHES THE SOUTHEAST COAST AND  
PUSHES OFFSHORE. THE 12Z GUIDANCE HAS COME INTO BETTER AGREEMENT  
WITH THE ARRIVAL OF THE LATEST UKMET/CMC AND ECMWF SOLUTIONS. ALL  
OF THE NON-NCEP MODELS TRENDED A LITTLE SLOWER AND IN LINE WITH  
THE RELATIVELY SLOWER NAM AND GFS. HOWEVER...THE CMC SOLUTION DOES  
STILL APPEAR TO BE PERHAPS A TAD TOO WEAK AND PROGRESSIVE AS THE  
SYSTEM REACHES THE SOUTHEAST COAST AND THEN MOVES OFFSHORE AS  
COMPARED TO THE OTHER MODELS. THEREFORE WILL PREFER A NON-CMC  
CONSENSUS AT THIS TIME.  
 
   
..DEEPENING TROUGH MOVING INLAND ACROSS THE SOUTHWEST
 
   
..ENERGY EJECTING NORTHEAST ACROSS THE PLAINS/MIDWEST
 
   
..ATTENDANT SURFACE LOW LIFTING TOWARD THE GREAT LAKES
 
 
PREFERENCE: GENERAL MODEL BLEND...THROUGH 48 HOURS  
BLEND OF THE 12Z GFS/12Z UKMET...AFTER 48 HOURS  
CONFIDENCE: AVERAGE  
 
THE GUIDANCE AGREES IN TAKING A SOUTHERN STREAM TROUGH ACROSS CA  
AND THROUGH THE SOUTHERN GREAT BASIN AND ADJACENT AREAS OF THE  
SOUTHWEST U.S. THROUGH SATURDAY. THE SYSTEM IS THEN EXPECTED TO  
AMPLIFY AND CLOSE OFF IN THE MID LEVELS OVER THE FOUR CORNERS  
REGION SATURDAY NIGHT BEFORE EJECTING OUT ACROSS THE  
CENTRAL/SOUTHERN HIGH PLAINS ON SUNDAY. THE STRONG HEIGHT FALLS  
WILL DRIVE A WELL-ORGANIZED AREA OF LOW PRESSURE IN THE LEE OF THE  
ROCKIES INVOLVING SOUTHEAST CO WHICH SHOULD THEN ADVANCE EAST  
ACROSS SOUTHERN KS AND THEN LIFT NORTHEAST TOWARD THE GREAT LAKES  
REGION SUNDAY NIGHT THROUGH MONDAY. THE MODEL MASS FIELD SPREAD IS  
RATHER MINIMAL AS THE ENERGY TRAVERSES THE SOUTHWEST AND BROADER  
FOUR CORNERS REGION...BUT AS THE SYSTEM REACHES THE  
CENTRAL/SOUTHERN PLAINS...THE 12Z NAM BECOMES STRONGER THAN ANY  
OTHER MODELS WITH ITS 500/700 MB REFLECTION AND TENDS TO LEAN A  
BIT TOWARD THE FASTER SIDE OF THE GUIDANCE. THE 00Z ECMWF ALONG  
WITH THE LATEST 12Z ECMWF SOLUTION ARE GENERALLY SLOWEST WITH THE  
UPPER TROUGH/CLOSED LOW AND ALSO ARE A BIT SOUTH OF THE MODEL  
CONSENSUS WITH THE CLOSED LOW TRACK INVOLVING THE MIDWEST. THE 12Z  
GFS IS A BIT FASTER AND ONLY A LITTLE SLOWER THAN THE NAM. THE 12Z  
UKMET AND 12Z CMC ARE IN BETWEEN THE SLOWER ECMWF AND FASTER  
GFS...HOWEVER THE UKMET IS A LITTLE FARTHER SOUTH AND CLOSER TO  
THE ECMWF...WITH THE CMC FARTHER NORTH AND CLOSER TO THE GFS. THE  
00Z ECENS MEAN SUGGESTS THE ECMWF IS TOO SLOW BY THE END OF THE  
PERIOD...AND THE 12Z GEFS MEAN IS A LITTLE FASTER THAN THE  
OPERATIONAL GFS AND SUGGESTS THE RELATIVELY FASTER NAM IS WITHIN  
THE REALM OF POSSIBILITIES. BASED ON ALL OF THIS...WILL SUGGEST A  
GENERAL MODEL BLEND THROUGH 48 HOURS...FOLLOWED BY A SOLUTION THAT  
APPROXIMATES THE MODEL CONSENSUS...WHICH AFTER 48 HOURS WOULD TEND  
TO BE A BLEND OF THE GFS AND UKMET.  
 
   
..NORTHERN STREAM TROUGH CLIPPING THE NORTHERN PLAINS
 
 
PREFERENCE: BLEND OF THE 12Z GFS/12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
A WEAKER NORTHERN STREAM TROUGH COMING IN OFF THE PACIFIC OCEAN  
TODAY WILL CROSS THE PACIFIC NORTHWEST AND TRAVERSE THE NORTHERN  
PLAINS THROUGH SUNDAY. THE 12Z GFS AND 12Z ECMWF ARE REASONABLY  
WELL CLUSTERED AND HAVE DECENT SUPPORT FROM THE 12Z UKMET. THE 12Z  
NAM AND 12Z CMC ARE JUST A LITTLE SLOWER THAN THE GFS/UKMET/ECMWF  
CAMP. WILL CONTINUE TO FAVOR A BLEND OF THE GFS AND ECMWF AT THIS  
TIME BASED ON CLUSTERING AND ENSEMBLE SUPPORT.  
 
   
..UPPER TROUGH CROSSING INTO THE PACIFIC NORTHWEST BY SUNDAY
 
 
PREFERENCE: BLEND OF THE 12Z GFS/12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE NEXT UPPER TROUGH COMING ACROSS THE NORTHEAST PACIFIC WILL  
ARRIVE OVER THE NORTHWEST U.S. ON SUNDAY AND THEN BEGIN TO FLATTEN  
OUT BY MONDAY OVER THE GREAT BASIN AND NORTHERN ROCKIES. THE 12Z  
NAM TENDS TO BE THE STRONGEST OVERALL SOLUTION WITH THE TROUGH AND  
IS SOMEWHAT OF AN OUTLIER. MEANWHILE...THE 12Z UKMET HAS TRENDED  
FASTER AND IS CLOSE TO THE WELL-CLUSTERED 12Z GFS AND 12Z ECMWF.  
THIS COUPLED WITH FAVORABLE ENSEMBLE SUPPORT AGAIN SUGGESTS  
LEANING TOWARD OF A BLEND OF THE GFS/ECMWF SOLUTIONS.  
 
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ORRISON  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page