095  
FXUS10 KWNH 120652  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
252 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 FINAL MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
SUBTROPICAL STORM MELISSA  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND AND NHC FORECAST TRACK  
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 NIGHT, THE 00Z CMC HAS ITS MID LEVEL HEIGHT FIELDS SLIGHTLY  
FARTHER SOUTH THAN THE OTHER MODELS AS THE ENERGY CROSSES THE  
NORTHEAST U.S., BUT CLOSER TO THE CONSENSUS COMPARED TO ITS 12Z  
RUN. THEREFORE, A GENERAL MODEL BLEND IS BEST THROUGH 60 HOURS,  
FOLLOWED BY A GFS/ECMWF BLEND.  
 
PACIFIC NORTHWEST TO THE NORTHERN PLAINS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
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 00Z UKMET HAS TRENDED CLOSER TO THE CONSENSUS COMPARED TO ITS  
12Z RUN REGARDING THE LEVEL OF AMPLIFICATION. BY THE END OF THE  
FORECAST PERIOD TUESDAY MORNING, THE 00Z GFS IS SLIGHTLY AHEAD  
WITH THE TROUGH AXIS OVER THE UPPER MIDWEST AND THE ECMWF SLIGHTLY  
SLOWER, BUT CLOSE ENOUGH TO STILL BE INCLUDED IN THE FORECAST  
BLEND. THERE IS EXCELLENT AGREEMENT ON THE TIMING OF THE COLD  
FRONT ACROSS THE MIDWEST ON TUESDAY MORNING, AND A GENERAL MODEL  
BLEND CAN BE INCORPORATED.  
 
SOUTHWESTERN U.S.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: ECMWF/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 AND UKMET APPEAR SLIGHTLY MORE  
AMPLIFIED IN THE MID TO UPPER LEVELS AND THE GFS AND NAM BECOME  
FASTER AS THE SYSTEM CROSSES THE DESERT SOUTHWEST BY MONDAY. THE  
ECMWF APPEARS TO SPLIT THE DIFFERENCE BEST AND HAS 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  
 

 
 
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