520  
FXUS10 KWNH 061848  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
148 PM EST MON NOV 06 2017  
 
VALID NOV 06/1200 UTC THRU NOV 10/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH FINAL PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...COLD FRONT MOVING THROUGH THE NORTHEAST TODAY BUT STALLING OVER  
THE SOUTH TUE/WED...   
..FRONTAL LOW OVER THE TN VALLEY ON TUE
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
GOOD MODEL AGREEMENT EXISTS WITH THE COLD FRONTAL PASSAGE ACROSS  
THE EAST COAST BUT SOME DIFFERENCES CONTINUE REGARDING A FRONTAL  
WAVE IN THE TN VALLEY BY TUE MORNING. THE 12Z NAM REMAINS THE  
STRONGEST OF THE DETERMINISTIC MODELS WHILE THE 12Z UKMET IS A BIT  
WEAKER THAN THE CONSENSUS. ENSEMBLE SCATTER LOW PLOTS HAVE BEEN  
RELATIVELY CONSISTENT WITH A PLACEMENT IN E-CNTRL TN FOR 12Z/TUE  
THOUGH MOST OF THE ECMWF MEMBERS ARE NOW A BIT FURTHER EAST THAN  
CONSENSUS. A BLEND OF THE 12Z GFS AND 00Z ECMWF APPEARS BEST FOR  
THIS SYSTEM THROUGH WEDNESDAY NIGHT AS THE LOW WEAKENS TOWARD THE  
EAST.  
 
UPDATE: BETTER AGREEMENT WITH THE SURFACE LOW POSITION ACROSS  
CENTRAL TENNESSEE BY TOMORROW MORNING WITH THE 12Z GUIDANCE. FINAL  
PREFERENCE WILL BE A GENERAL MODEL BLEND  
 
...POSITIVELY TILTED TROUGH TRANSLATING FROM THE PACIFIC NORTHWEST  
TODAY TO THE PLAINS BY WEDNESDAY...SOUTHEAST BY THURSDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z GFS / 12Z ECMWF  
CONFIDENCE: AVERAGE  
 
THE 12Z NAM AND TO A CERTAIN EXTENT THE 12Z GFS HAVE TRENDED  
TOWARD A LESS AMPLIFIED SOLUTION WITH THIS TROUGH. THE 00Z CMC IS  
FAST WITH THE PROGRESSION AND THE 00Z UKMET IS FLATTER COMPARED TO  
A MODEL CLUSTER OF THE 12Z NAM/GFS AND 00Z ECMWF. ENSEMBLE  
SPAGHETTI PLOTS SHOW THAT A FAIR BIT OF SPREAD...WITH THE ECMWF  
AND GEFS MEMBERS SHOW A MUCH MORE AMPLIFIED SCENARIO ACROSS THE  
PLAINS BY WEDNESDAY MORNING. PREFER A BLEND OF THE 12Z GFS/00Z  
ECMWF AT THIS TIME.  
 
UPDATE: THE 12Z ECMWF IS A BIT SHARPER/DEEPER WITH THE TROUGH OVER  
THE GREAT BASIN/ROCKIES INTO WEDNESDAY MORNING. THIS IS A TREND  
TOWARD WHAT THE ENSEMBLES WERE SHOWING WITH A MORE AMPLIFIED  
PATTERN SO WHILE ITS A BIT OF AN OUTLIER COMPARED TO THE REST OF  
THE GUIDANCE IT SEEMS REASONABLE TO INCLUDE. THE 12Z CMC IS A BIT  
FLATTER/FASTER AS THE TROUGH ENTERS THE PLAINS ON WEDNESDAY.  
SPREAD INCREASES AS THE SHORTWAVE TROUGH PUSHES INTO THE SOUTHEAST  
DUE TO INTERACTS WITH THE DEEP LONGWAVE TROUGH OVER THE NORTH  
CENTRAL U.S. FINAL PREFERENCE IS TO BLEND THE 12Z GFS/ECMWF.  
 
...DEEP CYCLONE DROPPING FROM THE GULF OF ALASKA TO OFFSHORE OF  
THE PACIFIC NORTHWEST...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
THE MODELS ARE OVERALL IN FAIRLY GOOD AGREEMENT WITH THIS SYSTEM  
BUT SOME DIFFERENCES IN PLACEMENT AND STRENGTH OF THE LOW BEGIN TO  
EMERGE AFTER REACHING PEAK STRENGTH ON TUESDAY. ENSEMBLE SCATTER  
LOW PLOTS ARE FAIRLY WIDE RANGING BY THU MORNING OFF OF THE  
PACIFIC NORTHWEST. THERE DOES SEEM TO BE A TREND TOWARD A MORE  
CONSOLIDATED UPPER LOW. THE RESULT IS A LOW PRESSURE CENTER THAT  
MAINTAINS STRENGTH LONGER INTO THE FORECAST PERIOD AS SEEN IN THE  
12Z NAM/GFS. MUCH OF THE 00Z GUIDANCE SHOWED A SCENARIO WITH  
SEVERAL WEAKER SURFACE LOW CENTERS ROTATION AROUND EACH OTHER  
WHICH ACCELERATED THE WEAKENING OF THE OVERALL STORM. THE 00Z  
UKMET LOOKS LIKE A PRETTY BIG OUTLIER WITH THIS SYSTEM AS THE MAIN  
SURFACE LOW TRACK IS QUIT A BIT OFF FROM THE MODEL CONSENSUS.  
OUTSIDE OF THE UKMET...A BLEND OF THE 12Z GFS AND THE 00Z ECMWF IS  
PREFERRED AT THIS TIME TO ACCOUNT FOR THE NEW TREND.  
 
UPDATE: THE NON-NCEP 12Z GUIDANCE HAS BECOME FAIRLY WELL CLUSTERED  
WITH THE NCEP GUIDANCE. THE SURFACE LOW AND UPPER LEVEL LOWS ARE  
MORE CONSOLIDATED AND STRONGER. THE UKMET STILL SHOWS SEVERAL LOWS  
ROTATING AROUND BUT IT HAS COME CLOSER IN STRENGTH TO THE MODEL  
CONSENSUS. OVERALL THE TIMING OF THE SURFACE LOW HAS GOTTEN INTO A  
LOT BETTER AGREEMENT. A GENERAL MODEL BLEND IS THE FINAL MODEL  
PREFERENCE.  
 
...SOUTHERN END OF DEEP UPPER TROUGH LOCATED OVER THE N-CNTRL U.S.  
BY THU MORNING...   
..COLD FRONT SWEEPING THROUGH THE MS VALLEY WED/THU
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z GFS / 12Z ECMWF  
CONFIDENCE: AVERAGE  
 
A DEEP CLOSED UPPER LOW SLIDES OVER HUDSON BAY BY THURSDAY MORNING  
WITH A DEEP TROUGH AND COLD FRONT AFFECTING THE NORTH CENTRAL U.S.  
ENSEMBLES SHOW A FAIRLY LARGE SPREAD IN DEPTH AND TIMING OF THE  
TROUGH OVER THE GREAT LAKES. THE 00Z UKMET IS THE BIGGEST  
OUTLIER...MUCH FLATTER AND WEAKER WITH THE UPPER TROUGH AND LOW  
RESPECTIVELY. THE 00Z ECMWF AND 12Z NAM ARE A BIT FURTHER WEST  
WITH THE TROUGH AXIS AND SIMILAR WITH SHAPE/BROADNESS OF THE  
TROUGH. THE 00Z CMC IS FAIRLY CLOSE WITH THE TROUGH AXIS BUT IS A  
SHARPER TROUGH. THE 12Z GFS IS FASTER/FURTHER EAST. INITIAL  
PREFERENCE IS A BLEND OF THE 12Z GFS/00Z ECMWF.  
 
UPDATE: THE 12Z ECMWF GOT A LITTLE FASTER AND THE 12Z UKMET AND  
CMC GOT A LITTLE SLOWER. TIMING AND DEPTH ISSUES REMAIN SO FINAL  
PREFERENCE WILL BE A BLEND OF THE 12Z GFS/ECMWF WHICH IS CLOSE TO  
THE MODEL CONSENSUS.  
 
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