September 8, 2005.gmt (z) The dynamics of the vortex system in the Atantic is building. Hurricane Maria which is furthest to the right is up to 100 knots. The equivalent is 115 mph. ONE KNOT = 1.15 miles. Hurricane Nate, the middle hurricane is currently, 75 knots. Ophelia is 45 knots, approximately 52 mph. A Cat One begins at 74 mph.