053  
WTNT42 KNHC 121432  
TCDAT2  
 
HURRICANE OPHELIA DISCUSSION NUMBER 14  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL172017  
1100 AM AST THU OCT 12 2017  
 
OPHELIA'S SATELLITE PRESENTATION CONSISTS OF A DISTINCT EYE IN  
INFRARED IMAGERY SURROUNDED BY A RING OF CLOUD TOPS OF -50C TO -70C.  
THE INITIAL INTENSITY OF 80 KT IS BASED ON A BLEND OF THE LATEST  
SUBJECTIVE AND OBJECTIVE DVORAK ESTIMATES, WHICH RANGE FROM 77 TO  
95 KT. LITTLE CHANGE IN INTENSITY IS EXPECTED DURING THE NEXT 48  
HOURS, AS OPHELIA WILL REMAIN OVER SSTS OF 25-26C AND IN A LOW  
TO MODERATE SHEAR ENVIRONMENT. AFTER THAT TIME, THE CYCLONE SHOULD  
BEGIN EXTRATROPICAL TRANSITION AS IT INTERACTS WITH A POTENT  
MID-LATITUDE TROUGH MOVING EASTWARD ACROSS THE NORTH ATLANTIC. THIS  
BAROCLINIC INTERACTION SHOULD MAINTAIN OPHELIA AT HURRICANE  
INTENSITY THROUGH 96 HOURS, WITH SLOW WEAKENING EXPECTED AFTER THAT  
TIME AS THE EXTRATROPICAL CYCLONE OCCLUDES.  
 
OPHELIA HAS MOVED LITTLE SINCE THE LAST ADVISORY, WITH THE CYCLONE  
CURRENTLY SITUATED SOUTH OF THE MID-LATITUDE WESTERLIES. THE  
INITIAL MOTION ESTIMATE IS A SLOW NORTH-NORTHEASTWARD DRIFT AT  
AROUND 2 KT. A STEADIER NORTHEASTWARD MOTION SHOULD BEGIN BY 12 H  
WHEN THE AFOREMENTIONED UPPER-LEVEL TROUGH BEGINS TO EXERT INFLUENCE  
ON OPHELIA'S MOTION. AN EAST-NORTHEASTWARD ACCELERATION IS EXPECTED  
AT 24 THROUGH 48 H, FOLLOWED BY A TURN BACK TO THE NORTHEAST AND  
NORTH-NORTHEAST AT DAYS 3 THROUGH 5 AS OPHELIA INTERACTS WITH THE  
SOUTHERN PORTION OF THE TROUGH. THROUGH THE FIRST 48 HOURS, THE NEW  
NHC TRACK FORECAST IS SIMILAR TO THE PREVIOUS ONE AND LIES NEAR THE  
MIDDLE OF THE GUIDANCE ENVELOPE. LATER IN THE FORECAST PERIOD,  
THERE REMAINS A FAIR BIT OF EAST/WEST SPREAD IN THE TRACK OF OPHELIA  
NEAR IRELAND AND THE UNITED KINGDOM, WHICH ISN'T USUAL AT THESE TIME  
RANGES. THE NHC FORECAST AT THESE TIMES IS SIMILAR TO THE PREVIOUS  
ONE AND LIES ON THE RIGHT SIDE OF THE DETERMINISTIC GUIDANCE  
ENVELOPE BUT IS NEAR THE MIDDLE OF THE ECMWF, UKMET AND GEFS  
ENSEMBLE MEMBERS. REGARDLESS OF THE EXACT TRACK, POST-TROPICAL  
OPHELIA IS LIKELY TO BRING SOME IMPACTS TO IRELAND AND THE UNITED  
KINGDOM AS A POWERFUL EXTRATROPICAL CYCLONE IN 4 TO 5 DAYS.  
 
WHILE THE TRACK GUIDANCE KEEPS THE CENTER OF OPHELIA EAST OF THE  
AZORES, A TROPICAL STORM WATCH OR WARNING COULD BE NEEDED FOR THE  
EASTERN AZORES LATER TODAY OR TONIGHT BECAUSE OF THE EXPECTED  
INCREASE IN THE SIZE OF THE TROPICAL-STORM-FORCE WINDS IN THE  
NORTHWESTERN QUADRANT OF THE CYCLONE.  
 
KEY MESSAGES:  
 
1. OPHELIA IS EXPECTED TO TRANSITION TO A HURRICANE-FORCE POST-  
TROPICAL CYCLONE BY MONDAY WHEN IT MOVES NEAR IRELAND AND THE  
UNITED KINGDOM. WHILE POST-TROPICAL OPHELIA WILL LIKELY BRING SOME  
DIRECT IMPACTS FROM WIND AND HEAVY RAIN TO PORTIONS OF THESE AREAS,  
AS WELL AS DANGEROUS MARINE CONDITIONS, GIVEN THE FORECAST  
UNCERTAINTY AT THESE TIME RANGES IT IS TOO SOON TO DETERMINE THE  
EXACT MAGNITUDE, TIMING AND LOCATION OF THE IMPACTS. RESIDENTS IN  
IRELAND AND THE UNITED KINGDOM SHOULD MONITOR THE PROGRESS OF  
OPHELIA FOR THE NEXT SEVERAL DAYS. FOR MORE INFORMATION ON LOCAL  
IMPACTS, RESIDENTS OF 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 12/1500Z 30.5N 35.6W 80 KT 90 MPH  
12H 13/0000Z 30.9N 34.9W 80 KT 90 MPH  
24H 13/1200Z 31.6N 33.4W 80 KT 90 MPH  
36H 14/0000Z 32.7N 30.8W 75 KT 85 MPH  
48H 14/1200Z 34.4N 27.3W 75 KT 85 MPH  
72H 15/1200Z 40.9N 18.8W 75 KT 85 MPH  
96H 16/1200Z 51.0N 12.5W 65 KT 75 MPH...POST-TROP/EXTRATROP  
120H 17/1200Z 60.5N 5.5W 55 KT 65 MPH...POST-TROP/EXTRATROP  
 

 
FORECASTER BRENNAN  
 
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