460  
WTNT42 KNHC 132042  
TCDAT2  
 
HURRICANE OPHELIA DISCUSSION NUMBER 19  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL172017  
500 PM AST FRI OCT 13 2017  
 
OPHELIA'S EYE HAS BECOME BETTER DEFINED OVER THE PAST 6 HOURS.  
ALTHOUGH CLOUD TOPS NEAR THE INNER CORE OF THE HURRICANE ARE WARMER  
THAN 24 HOURS AGO, A RING OF -50 DEG C OR COLDER CLOUD TOPS STILL  
SURROUNDS THE EYE. DVORAK CURRENT INTENSITY ESTIMATES HAVE NOT  
CHANGED SUBSTANTIALLY, AND A BLEND OF OBJECTIVE AND SUBJECTIVE  
CLASSIFICATIONS STILL SUPPORTS AN INITIAL INTENSITY OF 85 KT.  
 
LITTLE CHANGE IN STRENGTH IS EXPECTED WHILE OPHELIA REMAINS A  
HURRICANE, SINCE THE RELATIVELY COOL SSTS ALONG THE HURRICANE'S PATH  
WILL LIKELY BE OFFSET BY LOW SHEAR AND COLD UPPER-LEVEL TEMPERATURES  
FOR THE NEXT 36 H. EXTRATROPICAL TRANSITION WILL LIKELY BEGIN  
SHORTLY AFTER THAT TIME, AS OPHELIA BEGINS TO INTERACT WITH A LARGE  
UPPER-LEVEL TROUGH APPROACHING FROM THE WEST. THE DYNAMICAL  
GUIDANCE SUGGESTS THAT OPHELIA WILL DEEPEN IN RESPONSE TO THE  
TROUGH, AND ALTHOUGH THE FORECAST DOES NOT EXPLICITLY SHOW IT, I CAN  
NOT RULE OUT THAT OPHELIA WILL BRIEFLY INTENSIFY AS IT UNDERGOES  
EXTRATROPICAL TRANSITION. BY 72 HOURS, THE CYCLONE IS EXPECTED TO  
OCCLUDE AND BEGIN WEAKENING, THOUGH THE EXPANSION OF THE WIND FIELD  
WILL RESULT IN IMPACTS OVER PORTIONS OF THE BRITISH ISLES,  
REGARDLESS OF ITS EXACT LOCATION OR STRENGTH. BY 96 HOURS,  
CONTINUED WEAKENING AND INTERACTION WITH LAND WILL LIKELY CAUSE THE  
SURFACE CIRCULATION TO BECOME ILL-DEFINED, AND DISSIPATION IS  
EXPECTED SHORTLY THEREAFTER.  
 
OPHELIA IS BEGINNING TO ACCELERATE TOWARD THE EAST-NORTHEAST AND THE  
INITIAL MOTION ESTIMATE IS 060/11 KT. VERY LITTLE CHANGE HAS BEEN  
MADE TO THE OFFICIAL TRACK FORECAST. OPHELIA IS STILL EXPECTED TO  
CONTINUE PICKING UP SPEED ON AN EAST-NORTHEAST HEADING WHILE PASSING  
SOUTH OF THE AZORES DURING THE NEXT 24 TO 36 HOURS. BY 48 HOURS,  
INTERACTION WITH THE AFOREMENTIONED UPPER-LEVEL TROUGH WILL CAUSE  
OPHELIA TO TURN TOWARD THE NORTHEAST AND APPROACH IRELAND AND THE  
WESTERN UK IN ABOUT 72 H. THE TRACK GUIDANCE IS TIGHTLY CLUSTERED,  
ESPECIALLY THROUGH 72 H, AND THE NEW NHC TRACK FORECAST IS CLOSE TO  
THE VARIOUS MULTI-MODEL CONSENSUS AIDS. ALTHOUGH THE CENTER OF  
OPHELIA IS NOT EXPECTED TO REACH IRELAND OR THE UK UNTIL ABOUT DAY  
3, WIND AND RAIN EFFECTS 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  
BEGINNING LATE SATURDAY OR SATURDAY NIGHT DUE TO AN APPROACHING COLD  
FRONT. ANY DEVIATION TO THE LEFT OF OPHELIA'S FORECAST TRACK COULD  
BRING STRONGER WINDS TO 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 BECOME A HURRICANE-FORCE POST-TROPICAL  
CYCLONE BY MONDAY BEFORE 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 13/2100Z 32.3N 31.8W 85 KT 100 MPH  
12H 14/0600Z 33.4N 29.5W 80 KT 90 MPH  
24H 14/1800Z 35.2N 25.4W 80 KT 90 MPH  
36H 15/0600Z 38.2N 20.3W 80 KT 90 MPH  
48H 15/1800Z 43.1N 16.0W 80 KT 90 MPH  
72H 16/1800Z 53.2N 10.4W 65 KT 75 MPH...POST-TROP/EXTRATROP  
96H 17/1800Z 60.5N 2.5W 45 KT 50 MPH...POST-TROP/EXTRATROP  
120H 18/1800Z...DISSIPATED  
 

 
FORECASTER ZELINSKY  
 
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