Monthly precipitation as of 31 May 2021Fort Lauderdale: 2.07” (-3.49”)
Miami: 2.68” (-3.64”)
Avg. May rainfall for both stations: 5.6”
< 1.8” →
odds > 50% of MH impact in South FL**Miami-Dade, Broward, and Palm Beach counties
From the article:
Since 1925, eight of the nine major hurricanes -- storms with more than 110 mph winds -- hit Broward or Dade after a dry May, Lushine said.
And if it is an unusually dry May, the odds get worse for South Florida, Lushine said. May's average rainfall in Miami-Fort Lauderdale is 5.6 inches. If there is less than 1.8 inches of rain -- one-third the average amount -- the chances are better than even that South Florida will get hit with a major hurricane, he said.
There have been eight years since 1925 with less than 1.8 inches of rain. In five of those years -- including last year (1992 – ed.) -- a major hurricane struck, Lushine said.
So apparently the correlation between a dry May and MH impacts in South FL is not especially strong except in extremely dry Mays, given that chances of a MH impact were equal to or less than even in years that featured > 1.8” of rainfall in May but still finished with below-average precipitation for that month. This is why the forecaster who noticed the correlation focussed initially and primarily on the driest Mays. For instance, he
noted that the driest, second driest, and third driest Mays on record at Miami and Fort Lauderdale occurred in 1965, 1992, and 1935. While each of these years featured a MH strike on Florida, only Andrew (1992) actually made landfall in either Dade or Broward County. The 1935 Labor Day hurricane and Betsy (1965), by contrast, struck the Monroe County Keys, not the mainland of South FL. The 1935 hurricane might have produced MH gusts in far southwestern Dade County, near the Dade–Monroe county line in Everglades National Park, while Betsy, given
its RMW of ~30 n mi relative to its landfall and westward movement over Tavernier, probably produced sustained MH winds near Homestead in southern Dade County. The forecaster thus seems to lack a clear definition of what constitutes a MH impact on South FL, given that he apparently includes Palm Beach County as part of South FL, yet relies on rainfall data from MIA/FLL to assess MH impacts in Dade or Broward County. Perhaps he is referring to MH gusts over these two counties as constituting a direct impact.