Dorian may hit Florida at worst possible time.
Byline: The Washington Post
Timing is everything.
Hurricane Dorian is forecast to approach the Florida coast as a major Category 4 storm while hitting the brakes and possibly stalling near the coast for a time.
This will maximize the storm's potential storm surge flood threat in a state that is already Ground Zero for sea level rise-related risks. Storm surge, which is the storm-driven rise in water above normally dry land at the coast, rides atop background tide levels.
Storm surge flooding can engulf communities, as ocean water pours into homes and businesses and over roads, sometimes rising 10 or more feet high.
Adding to the storm surge, background tides will be running at some of their highest levels of the year this weekend into early next week due to the alignment between the Earth, sun and moon, and the resulting gravitational "pull" on the ocean.
"King Tide" lacks a scientific definition, but rather is a term used to describe exceptionally high tides. As sea levels rise as a result of human-caused global warming and land subsidence, coastal areas have become more vulnerable to flooding during King Tides. In Florida, low-lying areas of Miami, for example, regularly flood during exceptionally high tides.
This summer, Miami set daily high tide records for more than a week straight for the period bridging late July and early August. Neighborhoods were flooded and some roads turned into rivers.
A hurricane moving from east to west into Florida would cause a life-threatening storm surge at any time of year, but given the King Tides, this storm presents an extreme risk from a historically deadly threat in its arsenal.
For example, in Miami, Melbourne (Port Canaveral), Jacksonville, Savannah, and Charleston, each of which could see storm surge flooding from Dorian, tides will be elevated above normally dry ground through Tuesday or Wednesday. In Miami, for example, the afternoon high tide on Monday looks to bring 0.55 feet of water above normally dry ground even without any influence from the hurricane at all. Having water elevated above normally dry ground doesn't equal flooding, however.
Miami starts flooding at 16 inches above normally dry ground, for instance. Given sea level rise during the period, there has been a 3.2-fold increase in how often Miami sees nuisance flooding. That flooding occurs without any storm around, including on sunny days with light winds.