I think Karl last year should have been a wake-up call,as should have Lisa.
Lisa became a hurricane over 40 north last year,which is roughly around the same latitude as New york with winds of 65kts,here is a fax chart showing the system,not to mention the SSt's were below 25C in that area,yet it managed to keep itslef going thanks to a massie convective burst near its center and on the southern half the system:
http://www.wetterzentraleforum.de/archi ... 041002.gif
it retained its tropical features until it was about 500 miles south-west of the U.K!
and Karl,although becoming extra-tropical at the time,had windspeeds of 80kts at the same latitudes,and bare in mind both those storms are in the Mid-atlantic,imagine if the strong cat-4 Karl went up the gulf stream,it would probably remain as a weak cat-3.