111  
WTNT42 KNHC 142037  
TCDAT2  
 
HURRICANE OPHELIA DISCUSSION NUMBER 23  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL172017  
500 PM AST SAT OCT 14 2017  
 
OPHELIA CONTINUES TO HAVE AN IMPRESSIVE APPEARANCE IN SATELLITE  
IMAGERY. THE EYE HAS REMAINED CLEAR ALL AFTERNOON, SURROUNDED BY A  
VERY SYMMETRIC RING OF COLD CLOUD TOPS. SINCE THE CLOUD PATTERN HAS  
NOT CHANGED SIGNIFICANTLY OVER THE PAST FEW HOURS, THE INTENSITY HAS  
BEEN HELD AT 100 KT. MICROWAVE IMAGERY AND SCATTEROMETER RETRIEVALS  
INDICATE THAT BENEATH THE COLD CANOPY, OPHELIA'S STRUCTURE IS  
BEGINNING TO DETERIORATE, AT LEAST SLIGHTLY. A GMI OVERPASS AROUND  
1700 UTC INDICATED THAT THE VORTEX IS BEGINNING TO TILT TOWARD THE  
EAST WITH HEIGHT, PROBABLY A RESULT OF INCREASING SOUTHWESTERLY  
SHEAR ASSOCIATED WITH A LARGE UPPER-LEVEL TROUGH TO THE WEST.  
FURTHERMORE, A PAIR OF EARLIER ASCAT PASSES SUGGESTED THAT AN  
APPROACHING COLD FRONT IS ALREADY INFRINGING ON THE NW QUADRANT OF  
THE CIRCULATION, WITHIN ABOUT 80 N MI OF OPHELIA'S EYE. GIVEN THE  
CLOSE PROXIMITY OF THE COLD FRONT AND UPPER-LEVEL TROUGH,  
EXTRATROPICAL TRANSITION WILL LIKELY BEGIN WITHIN ABOUT 12 HOURS. A  
FAVORABLE BAROCLINIC ENVIRONMENT MAY ALLOW THE CYCLONE TO DEEPEN AS  
THE WIND FIELD INCREASES IN SIZE, SO ONLY A SLIGHT DECREASE OF THE  
MAXIMUM WIND IS EXPECTED THROUGH 36 HOURS. AFTER THAT TIME, THE  
POST-TROPICAL CYCLONE WILL LIKELY OCCLUDE AND INTERACT WITH LAND,  
CAUSING A FASTER RATE OF WEAKENING AND RESULTING IN THE EVENTUAL  
DISSIPATION OF THE SURFACE CIRCULATION IN ABOUT 96 HOURS.  
 
OPHELIA CONTINUES TO PICK UP FORWARD SPEED AND THE INITIAL MOTION  
ESTIMATE IS NOW 055/24 KT. THE HURRICANE REMAINS EMBEDDED WITHIN  
THE SOUTHWESTERLY FLOW AHEAD OF THE AFOREMENTIONED MID-LATITUDE  
TROUGH, AND THIS WILL KEEP OPHELIA ON A NORTHEAST OR NORTH-NORTHEAST  
HEADING THROUGH THE NEXT 72 HOURS. THE TRACK GUIDANCE REMAINS IN  
FAIRLY GOOD AGREEMENT, THOUGH IT HAS SHIFTED SOUTHWARD A LITTLE FOR  
THE FIRST 24 HOURS. THE NEW NHC TRACK FORECAST HAS BEEN ADJUSTED IN  
THAT DIRECTION, AND IS CLOSE TO THE GFS/ECMWF CONSENSUS THROUGHOUT  
THE FORECAST PERIOD.  
 
ALTHOUGH THE CENTER OF OPHELIA IS NOT FORECAST TO REACH IRELAND OR  
THE UK UNTIL MONDAY, WIND AND RAINS WILL ARRIVE WELL IN ADVANCE OF  
THE CYCLONE CENTER. INDIVIDUALS IN THOSE LOCATIONS SHOULD CONSULT  
PRODUCTS FROM THEIR LOCAL METEOROLOGICAL SERVICE FOR MORE  
INFORMATION ON LOCAL IMPACTS.  
 
TROPICAL-STORM-FORCE WINDS ARE POSSIBLE THROUGHOUT THE AZORES  
AFTER OPHELIA PASSES TO THE SOUTH AND EAST TONIGHT AS A COLD FRONT  
MOVES THROUGH THE ISLANDS. INTERESTS IN THE AZORES SHOULD REFER TO  
PRODUCTS ISSUED BY THE AZORES WEATHER FORECAST AND WATCH CENTER.  
 
KEY MESSAGES:  
 
1. OPHELIA IS EXPECTED TO BE A POWERFUL EXTRATROPICAL CYCLONE WITH  
HURRICANE FORCE WINDS MONDAY WHILE IT MOVES NEAR IRELAND AND THE  
UNITED KINGDOM. DIRECT IMPACTS FROM WIND AND HEAVY RAIN IN PORTIONS  
OF THESE AREAS ARE LIKELY, ALONG WITH DANGEROUS MARINE CONDITIONS.  
FOR MORE DETAILS ON THE MAGNITUDE, TIMING, AND LOCATION OF IMPACTS  
FROM POST-TROPICAL OPHELIA, RESIDENTS IN IRELAND SHOULD REFER TO  
PRODUCTS ISSUED BY MET EIREANN, AND RESIDENTS IN THE UNITED KINGDOM  
SHOULD REFER TO PRODUCTS ISSUED BY THE MET OFFICE.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 14/2100Z 35.9N 23.7W 100 KT 115 MPH  
12H 15/0600Z 38.0N 20.0W 95 KT 110 MPH  
24H 15/1800Z 42.8N 15.3W 85 KT 100 MPH  
36H 16/0600Z 48.8N 12.3W 75 KT 85 MPH...POST-TROP/EXTRATROP  
48H 16/1800Z 54.0N 9.3W 60 KT 70 MPH...POST-TROP/EXTRATROP  
72H 17/1800Z 59.5N 3.5W 40 KT 45 MPH...POST-TROP/EXTRATROP  
96H 18/1800Z...DISSIPATED  
 

 
FORECASTER ZELINSKY  
 
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