[This is a reprint (21 Sep 2017) from Dr. Roy Spencer’s blog (drroyspencer.com) in which he makes the point that two category 4 hurricanes making landfall in the same year is far more likely than the recent eleven year period with no major hurricane landfalls that preceeded the two category 4 hurricanes. Assuming the 177 year return period for no major hurricanes in 9 years estimated by NASA was correct, we agree with Dr. Spencer that the return period for no major hurricanes in 11 years would be 560 years. Ed.]
Weather.com published an article noting that the two Cat 4 hurricane strikes this year (Harvey and Irma) is a new record. Here’s a nice graphic they used showing both storms at landfall.