838  
FXUS10 KWNH 051906  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
205 PM EST MON MAR 05 2018  
 
VALID MAR 05/1200 UTC THRU MAR 09/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...ALONG WITH MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..CENTRAL PLAINS/MIDWEST STORM SYSTEM TODAY
 
   
..PASSING OFF TO DEVELOPING EAST COAST NOR'EASTER BY WEDNESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS/12Z UKMET AND 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS TAKE THE NEGATIVELY TILTING TROUGH AND EVOLVING DEEP  
LAYER CLOSED LOW EJECTING OUT ACROSS THE CENTRAL/NORTHERN PLAINS  
OFF TO THE EAST THROUGH THE MIDWEST ON TUESDAY. AS THIS OCCURS,  
THERE WILL BE AN INCREASING DEGREE OF BINARY INTERACTION WITH A  
CLOSED LOW OVER ONTARIO WITH THIS SEPARATE CLOSED LOW FEATURE  
BEGINNING TO ROTATE AROUND THE NORTH SIDE OF THE MIDWEST STORM.  
THE MODELS SHOWS VERY GOOD AGREEMENT THROUGH TUESDAY IN TAKING A  
SIZABLE PORTION OF ENERGY/HEIGHT FALLS WITH THE MIDWEST SYSTEM OFF  
TO THE EAST AND TOWARD THE OHIO VALLEY. BY TUESDAY NIGHT, THE  
UPPER TROUGH SHOULD TAKE ON A NEGATIVE TILT ACROSS THE OHIO VALLEY  
AND THEN THE CENTRAL APPALACHIANS AS A 130+KT 250 MB JET MAX  
ROUNDS THE BASE OF THE TROUGH THROUGH THE TENNESSEE VALLEY. THIS  
WILL ULTIMATELY ALLOW THE SYSTEM TO DEEPEN FURTHER AND ALL OF THE  
MODELS SHOW A CLOSED LOW CROSSING THE MID-ATLANTIC REGION ON  
WEDNESDAY BEFORE THEN LIFTING UP ACROSS OR VERY NEAR SOUTHERN NEW  
ENGLAND. THE RESULT WILL BE SURFACE LOW EVOLUTION THAT INITIALLY  
FOCUSES OVER THE UPPER MIDWEST BUT THEN EVOLVES EAST-SOUTHEAST  
ACROSS THE OHIO VALLEY THROUGH TUESDAY. ON TUESDAY NIGHT, THE OHIO  
VALLEY LOW WILL WEAKEN AND SECONDARY LOW PRESSURE DEVELOPING OVER  
THE SOUTHEAST COASTAL PLAIN WILL LIFT UP OFF THE VIRGINIA CAPES BY  
EARLY WEDNESDAY AND BECOME THE DOMINANT LOW CENTER. THE LOW WILL  
DEEPEN FURTHER THROUGH WEDNESDAY AND WEDNESDAY NIGHT AS THE LOW  
LIFTS JUST OFFSHORE NEW JERSEY, LONG ISLAND AND ADJACENT AREAS OF  
SOUTHERN NEW ENGLAND. ON THURSDAY, THE SYSTEM WILL LIFT UP ACROSS  
THE GULF OF MAINE.  
 
MODEL SPREAD WITH THE ENTIRE SYSTEM IS MOSTLY CENTERED ON THE EAST  
COAST/NOR'EASTER EVOLUTION. THE 12Z GUIDANCE HAS GENERALLY BEEN  
SHIFTING THE LOW TRACK FARTHER WEST. THE 12Z NAM WHICH HAD BEEN ON  
THE WEST SIDE OF THE MODEL CONSENSUS, HAS GAINED AGREEMENT FROM  
THE 12Z UKMET IN A SOLUTION THAT IS FARTHER WEST AND ESPECIALLY AS  
IT RELATES TO COASTAL AREAS OF THE NORTHERN MID-ATLANTIC AND NEW  
ENGLAND. HOWEVER, ONE CONCERN RIGHT NOW WITH THE NAM IS THAT IT  
IS A BIT STRONGER ALOFT THAN ANY OTHER MODEL BY WEDNESDAY EVENING  
AND THROUGH THURSDAY WITH THE NOR'EASTER EVOLUTION. THIS RESULTS  
IN A VERY STRONG DEFORMATION ZONE WRAPPING FARTHER BACK TO THE  
WEST OVER THE NORTHEAST. THE 12Z GFS AT THE SURFACE IS A LITTLE  
EAST OF THE NAM/UKMET CLUSTER. THE 12Z CMC HAS ALSO TRENDED A BIT  
FARTHER WEST, BUT IS STILL GENERALLY A LITTLE EAST OF THE MODEL  
CONSENSUS, WITH THE 00Z ECMWF THE FARTHEST EAST SOLUTION. UPDATE:  
THE 12Z ECMWF HAS TRENDED IN TANDEM WITH THE OTHER DETERMINISTIC  
WITH A NOTABLE WESTWARD TREND IN THE LOW TRACK, AND IS VERY CLOSE  
TO THE MODEL CONSENSUS.  
 
THE WESTWARD SHIFT IN THE GUIDANCE HAS BEEN NOTED IN CONSECUTIVE  
CYCLES OF THE GEFS ENSEMBLE MEMBERS WITH STRONGER CLUSTERING THAT  
IS MORE SUPPORTIVE OF THE NAM/UKMET CAMP. THIS IS LIKELY RELATED  
TO THE DETAILS OF A PERSISTENT AND RELATIVELY STRONG BLOCKING  
RIDGE OVER EASTERN CANADA. IT IS FEASIBLE THAT SOME ADDITIONAL  
WESTWARD SHIFTING OF THE GUIDANCE MAY OCCUR, AND ESPECIALLY AS IT  
RELATES TO THE LOW TRACK RELATIVE TO NEW ENGLAND SINCE THE  
GUIDANCE MAINTAINS THIS BLOCKING PATTERN. ALSO, THE GUIDANCE TAKES  
THE CLOSED LOW FEATURE DROPPING SOUTH OVER ONTARIO DOWN TO THE  
SOUTHEAST TOWARD THE OHIO VALLEY BY THURSDAY WHICH MAY HELP TO  
BACK THE LARGE SCALE FLOW ENOUGH FOR THE NEW ENGLAND CLOSED  
LOW/NOR'EASTER TO TRACK FARTHER LEFT. OVERALL, WPC WILL FAVOR A  
GENERAL MODEL BLEND THROUGH THE PERIOD GIVEN THE IMPROVED MODEL  
CLUSTERING ALONG THE EAST COAST, BUT WITH THE GREATEST WEIGHTING  
TOWARD A BLEND OF THE GFS, UKMET AND ECMWF AS THERE ARE CONCERNS  
THAT THE NAM IS TOO STRONG ALOFT.  
 
   
..WEST COAST/NORTHWEST U.S.
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE LARGE SCALE FLOW PATTERN WILL CONSIST A DEEP CLOSED LOW NEAR  
38.5N 142.0W INITIALLY THAT ADVANCES OFF TO THE EAST AND  
APPROACHES THE WEST COAST BY LATE WEDNESDAY AND THEN MOVES INLAND  
ACROSS THE NORTHWEST U.S. THROUGH THURSDAY. SURFACE LOW WILL  
ARRIVE ACROSS COASTAL OREGON ON THURSDAY ALONG WITH A WELL-DEFINED  
COLD FRONT SWEEPING IN ACROSS THE COASTAL RANGES. THE 12Z NAM AND  
12Z CMC ARE A BIT STRONGER WITH THE ARRIVAL OF THE SYSTEM AS  
COMPARED TO THE 12Z GFS AND 12Z ECMWF. THE 12Z UKMET APPEARS  
OVERALL TO BE TAD TOO WEAK. THE GFS/ECMWF SOLUTIONS ARE VERY WELL  
CLUSTERED AND HAS VERY GOOD ENSEMBLE SUPPORT AND SO WILL PREFER A  
BLEND OF THE GFS AND ECMWF AT THIS TIME.  
 
PREVIOUS MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
PREVIOUS 500 MB FORECASTS AT  
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ORRISON  
 

 
 
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