HOLT, Fla., Sept. 8, 2017, 9 a.m.–The National Hurricane Center adjusted Irma’s track through the Florida peninsula back to the east based on overnight data.
The 5 a.m. EDT forecast cone’s westerly five-day boundary shifted east a bit, but can change slightly with each data run.
It’s important to note that the one-to-three-day cone is the NHC’s best forecast of the hurricane’s track. The four-to-five-day cone has less confidence.
To form the cone, a set of imaginary circles are placed along the forecast track at the 12-, 24-, 36-, 48-, 72-, 96- and 120-hour positions, where the size of each circle is set to enclose 67 percent of the previous five-years’ official forecast errors.
Because the western panhandle is not included in the four-to-five-day cone does not mean the area will not feel any effects of the storm.
Hurricane-force winds extend outward up to 70 miles from the center and tropical-storm-force winds extend outward up to 185 miles. That gives Irma’s size as more than 500 miles in diameter.
Irma is moving toward the west-northwest near 16 mph and the NHC predicts this motion to continue for the next day or so with a decrease in forward speed.
A turn toward the northwest is expected by late Saturday, according to the NHC.
The eye of the storm should move near the north coast of Cuba and the central Bahamas today and Saturday and be near the Florida Keys and the southern Florida peninsula Sunday morning.
Some fluctuations in intensity are likely during the next day or two, but Irma is forecast to remain a powerful category 4 hurricane as it approaches Florida, according to the NHC.
After landfall, the NHC expects a fairly quick decay in maximum winds due to land interaction and increased shear, although Irma’s large wind field is likely to continue to produce hurricane-force winds over a large area.