578   
FXUS10 KWNH 120426  
PMDHMD  
  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1225 AM EDT SAT OCT 12 2019  
  
VALID OCT 12/0000 UTC THRU OCT 15/1200 UTC  
  
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
  
00Z INITIAL MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  
SUBTROPICAL STORM MELISSA  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
  
SUBTROPICAL STORM MELISSA IS NOW BEGINNING TO ACCELERATE TOWARDS  
THE EAST-NORTHEAST AFTER REMAINING NEARLY STATIONARY WELL TO THE  
SOUTH OF CAPE COD, MASSACHUSETTS.  THE UPPER LEVEL RIDGE THAT HAD  
BLOCKED THE STORM IS NOW MOVING OUT OF THE WAY AND THE LARGE SCALE  
CIRCULATION AROUND THE UPPER MIDWEST LOW IS INCREASING THE  
STEERING FLOW AND CAUSING IT TO GAIN FORWARD SPEED.  SIMILAR TO  
THE 12Z GUIDANCE ON FRIDAY, THE LATEST GUIDANCE SHOWS GOOD  
AGREEMENT WITH THE EVOLUTION AND TIMING OF THIS SYSTEM AND THUS A  
GENERAL MODEL BLEND IS PREFERRED.  
  
DEEP PLAINS/UPPER MIDWEST CYCLONE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND THROUGH SUNDAY NIGHT, THEN  
GFS/ECMWF  
CONFIDENCE: ABOVE AVERAGE  
  
AN IMPRESSIVE DEEP LAYER CYCLONE OVER THE NORTH-CENTRAL U.S. HAS  
REACHED MAXIMUM INTENSITY AS OF FRIDAY NIGHT, AND IS NOW FORECAST  
TO GRADUALLY WEAKEN AFTER REMAINING NEARLY STATIONARY ON SATURDAY.  
 IT SHOULD THEN TRACK IN A GENERAL EASTWARD DIRECTION ACROSS LAKE  
SUPERIOR AND THEN NORTHEASTWARD ACROSS ONTARIO.  THE COLD FRONT  
TRAILING FROM THE PARENT SURFACE LOW WILL CROSS THE APPALACHIANS  
SATURDAY MORNING AND THEN EXIT THE EAST COAST BY SATURDAY NIGHT,  
ALBEIT NOT NEARLY AS STRONG AS IT WAS OVER THE PLAINS.  A  
SECONDARY COLD FRONT ASSOCIATED WITH THE STORM SYSTEM WILL LIKELY  
DEVELOP AND CROSS THE MIDWEST ON SUNDAY AND THEN MOVE TOWARD THE  
EAST COAST ON MONDAY.  THE MODELS REMAIN WELL CLUSTERED WITH THE  
MASS FIELD EVOLUTION OF THIS SYSTEM THROUGH SUNDAY NIGHT.  BY  
MONDAY MORNING, THE 12Z CMC HAS ITS CLOSED LOW AND MID LEVEL  
HEIGHT FIELDS SLIGHTLY FARTHER SOUTH THAN THE OTHER MODELS AS THE  
ENERGY CROSSES INTO SOUTHEAST CANADA.  THEREFORE, A GENERAL MODEL  
BLEND IS BEST THROUGH 60 HOURS, FOLLOWED BY A GFS/ECMWF BLEND.  
  
PACIFIC NORTHWEST TO THE NORTHERN PLAINS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NAM/GFS/ECMWF  
CONFIDENCE: ABOVE AVERAGE  
  
THE NEXT FEATURE OF INTEREST TO AFFECT THE WESTERN U.S. WILL BE A  
PROGRESSIVE UPPER-LEVEL TROUGH AND ASSOCIATED COLD FRONT THAT  
SHOULD REACH THE WEST COAST BY EARLY SUNDAY, AND THEN ADVANCE  
INLAND ACROSS THE NORTHERN ROCKIES ON MONDAY.  BY MONDAY NIGHT,  
THE HEIGHT FALLS START ARRIVING ACROSS THE HIGH PLAINS AND INDUCES  
LEE-SIDE CYCLOGENESIS OVER THE CENTRAL PLAINS TO UPPER MIDWEST.   
THE MAIN DIFFERENCE NOTED WITH THE MODELS IS THAT THE 12Z UKMET IS  
LESS AMPLIFIED THAN THE MODEL CONSENSUS WITH THE 500MB HEIGHTS,  
AND IS SLOWER WITH THE FRONT THAT DEVELOPS ACROSS THE PLAINS.   
THERE IS ENOUGH AGREEMENT AMONG THE NAM, GFS, AND ECMWF TO MERIT A  
BLEND OF THESE MODELS.  
  
SOUTHWESTERN U.S.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: ECMWF/UKMET/EC MEAN  
CONFIDENCE: NEAR AVERAGE  
  
A SOUTHERN STREAM SHORTWAVE PERTURBATION IS PROGGED TO REACH  
CALIFORNIA SUNDAY NIGHT AND SEPARATES FROM THE NORTHERN STREAM  
TROUGH MENTIONED ABOVE.  THE CMC APPEARS SLIGHTLY MORE AMPLIFIED  
IN THE MID TO UPPER LEVELS AND THE GFS BECOMES FASTER AS THE  
SYSTEM CROSSES THE DESERT SOUTHWEST BY MONDAY.  THE ECMWF AND  
UKMET APPEAR TO FIT THE PATTERN BEST AND HAVE SUPPORT FROM THE EC  
MEAN.  
  
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
  
HAMRICK  
  
  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.


The Nexlab HPC Page

Main Text Page