363  
WTNT42 KNHC 150900  
TCDAT2  
 
HURRICANE OPHELIA DISCUSSION NUMBER 25  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL172017  
500 AM AST SUN OCT 15 2017  
 
ALTHOUGH THE SATELLITE APPEARANCE OF OPHELIA HAS BEEN SLOWLY  
DEGRADING THIS MORNING, THE CYCLONE REMAINS AN IMPRESSIVE HURRICANE  
DUE TO IT BEING OVER THE RELATIVELY COOL WATERS OF THE NORTHEASTERN  
ATLANTIC. A TESTAMENT TO OPHELIA'S STRENGTH IS A LATE ARRIVING BUOY  
REPORT 25 NMI SOUTHEAST OF THE CENTER OF THE EYE FROM AROUND 0200Z,  
WHICH INDICATED THAT THE PRESSURE IN THE SOUTHEASTERN PORTION OF THE  
LARGE EYE OR EYEWALL WAS 970.9 MB. HOWEVER, DVORAK INTENSITY  
ESTIMATES HAVE BEEN STEADILY DECREASING SINCE THAT BUOY REPORT, SO  
THE INTENSITY HAS BEEN LOWERED TO 90 KT FOR THIS ADVISORY.  
 
OPHELIA CONTINUES TO ACCELERATE AND THE HURRICANE IS NOW MOVING  
050/30 KT. WATER VAPOR IMAGERY INDICATES THAT A DEEPENING TROUGH  
JUST TO WEST OF OPHELIA IS MOVING QUICKLY EASTWARD, AND THAT THE  
CYCLONE IS NOW WELL EMBEDDED WITHIN THE DEEP-LAYER SOUTHWESTERLY  
FLOW ON THE EAST SIDE OF THE TROUGH. AS A RESULT, OPHELIA IS  
EXPECTED TO TURN TOWARD THE NORTH-NORTHEAST BY TONIGHT AND BE  
ACCOMPANIED BY A SLIGHT INCREASE IN FORWARD SPEED. THE NHC MODEL  
GUIDANCE REMAINS IN EXCELLENT AGREEMENT ON OPHELIA REACHING THE  
SOUTHERN COAST OF IRELAND IN 24-30 HOURS, AND THEN MOVE ACROSS  
THE REMAINDER OF THE COUNTRY MONDAY NIGHT, AND THEN MOVE ACROSS  
NORTHERN IRELAND AND NORTHERN GREAT BRITAIN ON TUESDAY.  
 
OPHELIA IS FORECAST TO BECOME A POST-TROPICAL CYCLONE BY 24 HOURS  
WHEN EXTRATROPICAL TRANSITION SHOULD BE COMPLETED, ALTHOUGH THE  
TRANSITION TO AN EXTRATROPICAL CYCLONE COULD OCCUR AS EARLY AS 12  
HOURS. REGARDLESS OF THE EXACT TIMING, POST-TROPICAL CYCLONE OPHELIA  
IS FORECAST TO REMAIN A POWERFUL STORM WITH HURRICANE-FORCE WINDS  
WHEN IT REACHES IRELAND ON MONDAY. THE SYSTEM IS FORECAST TO  
OCCLUDE AND INTERACT WITH LAND, WHICH SHOULD CAUSE A FASTER RATE OF  
WEAKENING IN 48 TO 72 HOURS, WITH DISSIPATION EXPECTED SHORTLY  
THEREAFTER.  
 
ALTHOUGH THE CENTER OF OPHELIA IS NOT FORECAST TO REACH IRELAND OR  
THE UK UNTIL MONDAY, STRONG WINDS AND RAINS WILL ARRIVE WELL IN  
ADVANCE OF THE CYCLONE CENTER. RESIDENTS IN THOSE LOCATIONS SHOULD  
CONSULT PRODUCTS FROM THEIR LOCAL METEOROLOGICAL SERVICE FOR MORE  
INFORMATION ON LOCAL IMPACTS.  
 
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 15/0900Z 39.0N 18.3W 90 KT 105 MPH  
12H 15/1800Z 43.0N 15.1W 85 KT 100 MPH  
24H 16/0600Z 49.0N 11.5W 80 KT 90 MPH...POST-TROP/EXTRATROP  
36H 16/1800Z 54.0N 8.6W 60 KT 70 MPH...POST-TROP/EXTRATROP  
48H 17/0600Z 57.7N 4.0W 50 KT 60 MPH...POST-TROP/EXTRATROP  
72H 18/0600Z 60.8N .1W 35 KT 40 MPH...POST-TROP/EXTRATROP  
96H 19/0600Z...DISSIPATED  
 

 
FORECASTER STEWART  
 
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