Of the 13 named storms so far in 2017, seven have been hurricanes, a number matched or exceeded at this point in the season only four times since 1995. Four of the seven — Harvey, Irma, Jose and Maria — have reached Category 3 or higher, the threshold for a major hurricane on the Saffir-Simpson scale. Only five other seasons since 1995 have had that many by Sept. 18.
More named storms have developed in the first three and a half months of the six-month hurricane season than developed in the entirety of the 1997, 1999, 2002, 2006, 2009, 2014 or 2015 seasons, according to National Hurricane Center and Weather Underground data. “We’re running at about twice the pace of a typical season,” Mr. Henson said.
A few caveats are in order. August, September and October are almost always the peak of the season, and it isn’t uncommon for several storms to develop on each other’s heels, as Harvey, Irma, Jose, Katia, Lee and Maria did from Aug. 17 to Sept. 16. And the phrase “above average” loses some of its significance when 10 of the 15 most active hurricane seasons since antebellum America have occurred in the past two decades.
What stands out is the combination of frequency and intensity. It may not be unheard-of for six storms to develop in a month, but it is very unusual for two Category 4 and two Category 5 hurricanes to do so.
It is also extremely unusual for three major hurricanes to pass through the same region in three weeks, as Irma, Jose and Maria have in the northeastern Caribbean.
The last time the northern Leeward Islands experienced two major hurricanes in the same season was 1899, and now it is looking at three in the same month. Residents of some islands barely had time to assess the wreckage of a Category 5 hurricane before another bore down on them. Others fled their homes to escape Irma, only to find themselves in the cross hairs of Maria.
A full reckoning of 2017’s place in hurricane history will not be possible until the season…