80F is the minimal threshold to sustain a hurricane. The Gulf buoy near NOLA yesterday was at 77F. If a storm does manage to squeeze through and strike the central Gulf coast or Big Bend, it will not be a serious danger. This season is just about over for the CONUS.
And yet in 1985 Hurricane Kate hit us in Panama City and the Gulf water temp offshore was 74 degrees. A hurricane that has already formed and strengthened can still cross some cooler waters an maintain itself on inertia before substantially diminishing (still enough left to cause a mess).
We had a similar thing happen with Hurricane Opal that crossed sea water temps in the mid 70's and hit us with both barrels in 1995.
Once it gets its "mainspring" wound up, water temps in the 70's are still warm enough to let it finish the trip if it doesn't have to go too far.
The storm needs 26 degrees C/79 degrees F to form, but it can coast a surprising distance before it loses that head of steam...happened to me twice in exactly ten years. Kate landed a few days before Thanksgiving in '85.
The first hurricane I worked was Camille in '69 then Agnes '72, Eloise '75, Elena '85, Kate'85, Erin and Opal both in '95.
These were just the ones that hit at or near enough to Panama City to do considerable damage.