Bill Ryan report.
At 0800 EDT, Matthew was located near 24.6 N, 77.5 W or 30 miles SSW of Nassau, Bahamas. Winds are at 110 kts and movement was to the NW (320 deg) at 10 kts. Central pressure was 940 mb.
Matthew is currently a CAT 3 major hurricane with hurricane force winds extending ~ 40 miles from the center and tropical storm winds 160 miles. Bear this in mind as Matthew approaches the Florida coast.
One note on the minimum central pressure: An aircraft observation at 0819 EDT measured the central pressure at 937 mb. This represents a drop of 24 mb in 9 hours. In the usual case, this would lead to increasing winds over the next few hours and the NHC now expects an increase to 125 kts (CAT 4) by midnight tonight as Matthew approaches the FL coast. Nothing is ever completely clear, however, and the eyewall of Matthew does show some raggedness on the west side which would mitigate against strengthening. For now, it is probably best to expect the worst, particularly with water temperatures near 30 C along its path.
The NHC track forecast is roughly in the middle of the forecast model guidance although the latest runs of the best track models (Euro, GFS) and best hurricane-specific models (HWRF, GFDL) are slightly further to the west both in FL and further up the coast in GA and SC.
The closest approach to to FL will be around midnight tonight somewhere in the vicinity of Jupiter Island and, unfortunately, close to high tide. That said, we are approaching the 1st quarter (Oct 9) so the tide range will not be extreme. Matthew will then move more or less parallel to the coast line, either just offshore or just onshore.
Storm surge will be a major issue. At this time, a surge of 6-9′ is expected from Sebastian Inlet (near Melbourne) to the Savannah River. Lesser amounts north and south of this area. Rainfall is expected to be 4-8″ with spots up to 12″. A fresh water flooding threat is likely.
The largest variations in the track forecast at this time are along the GA/SC coast. The NHC forecast is slightly east of the latest model guidance but this is well expressed in the current uncertainty cone (see link)
Net Result: The Florida coast north of Miami is going to take a beating from winds and storm surge with some fresh water flooding thrown into the mix. The worst time will be from roughly midnight tonight in the south to midnight Friday in the north. The worst surge is expected from near Melbourne to Savannah.
The jury is still out on effects in GA and SC with the most recent guidance showing a greater threat.
Matthew will begin to weaken beginning Friday morning as it interacts with land and moves into a drier environment with increasing wind shear. However, the rate of weakening will be slow and Matthew will still be a hurricane when it heads out to sea on Sunday.