930  
WTNT42 KNHC 120238  
TCDAT2  
 
HURRICANE OPHELIA DISCUSSION NUMBER 12  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL172017  
1100 PM AST WED OCT 11 2017  
 
SATELLITE IMAGES INDICATE THAT OPHELIA CONTINUES TO GET BETTER  
ORGANIZED. THE SMALL EYE HAS BECOME BETTER DEFINED WITH DEEPER  
CONVECTION NEAR THE CENTER THAN 6 HOURS AGO. INTENSITY ESTIMATES  
HAVE CONTINUED TO RISE, AND THE OBJECTIVE/SUBJECTIVE DVORAK VALUES  
RANGE FROM 77 KT TO 90 KT. THE INITIAL INTENSITY IS INCREASED TO  
75 KT, ON THE LOW END OF THE ESTIMATES SINCE OPHELIA IS OVER  
MARGINAL WATER TEMPERATURES AND MIGHT NOT BE AS STRONG AS THE  
SATELLITE SUGGESTS. FURTHER STRENGTHENING IS POSSIBLE GIVEN THE  
FAIRLY LOW SHEAR ENVIRONMENT AND MARGINALLY WARM SSTS, ASSUMING THE  
HURRICANE MOVES AROUND ENOUGH TO NOT UPWELL MUCH COOLER WATER.  
OPHELIA SHOULD KEEP HURRICANE-FORCE WINDS BEFORE IT TRANSITIONS INTO  
A STRONG EXTRATROPICAL LOW IN 3-4 DAYS. THE INTENSITY FORECAST IS  
HIGHER THAN THE PREVIOUS ONE, NEAR THE MODEL CONSENSUS. ALMOST ALL  
OF THE GUIDANCE NOW SHOW OPHELIA AS A POWERFUL EXTRATROPICAL LOW  
AFFECTING IRELAND, NORTHERN IRELAND AND GREAT BRITAIN EARLY NEXT  
WEEK.  
 
THE HURRICANE IS MOVING SLOWLY TOWARD THE NORTHEAST, CAUGHT IN AN  
AREA OF LIGHT STEERING SOUTH OF A FLAT TROUGH IN THE MID-LATITUDE  
ATLANTIC. THIS TROUGH IS FORECAST TO AMPLIFY OVER THE CENTRAL  
ATLANTIC LATE THURSDAY, WHICH SHOULD STEER OPHELIA NORTHEASTWARD OR  
EAST-NORTHEASTWARD AT AN INCREASING FORWARD SPEED FOR THE NEXT FEW  
DAYS. LITTLE CHANGE WAS MADE TO THE FORECAST TRACK, LEANING ON THE  
ECMWF SIDE OF THE CONSENSUS, WHICH RESULTS IN GENERALLY A FASTER  
TRACK THAN THE PREVIOUS PREDICTION.  
 
ALTHOUGH ALL OF THE GUIDANCE KEEP THE CENTER OFFSHORE OF THE  
AZORES, A TROPICAL STORM WATCH OR WARNING COULD BE NEEDED FOR THE  
EASTERN AZORES ON THURSDAY BECAUSE OF THE INCREASING WIND RADII IN  
THE NORTHWESTERN QUADRANT OF THE CYCLONE.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 12/0300Z 30.0N 35.7W 75 KT 85 MPH  
12H 12/1200Z 30.4N 35.3W 80 KT 90 MPH  
24H 13/0000Z 30.9N 34.6W 80 KT 90 MPH  
36H 13/1200Z 31.7N 32.9W 75 KT 85 MPH  
48H 14/0000Z 32.8N 30.2W 75 KT 85 MPH  
72H 15/0000Z 37.0N 22.0W 75 KT 85 MPH  
96H 16/0000Z 46.0N 14.0W 70 KT 80 MPH...POST-TROP/EXTRATROP  
120H 17/0000Z 56.5N 8.5W 55 KT 65 MPH...POST-TROP/EXTRATROP  
 

 
FORECASTER BLAKE  
 
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