EF1 tornado in Monroe County, Florida

Summary: A waterspout or funnel cloud was observed backlit by

lightning over Florida Bay shortly before making landfall as a

tornado at Indian Mound Trail of the Indian Waterways subdivision of

Plantation Key, Islamorada. Large gumbo limbo tree limbs were downed

as well as the top of a palm tree, landing 20 yards from streetside

the front steps of a residence. And adjacent residence had a rolling

driveway gate completely dislodged from its mounts, pushed into a

trailered boat and car. The tornado continue to produce mostly

damage to large limbs of hardwood trees, including gumbo limbo and

mahogany, in a path rarely exceeded two residential properties in

width toward the east-northeast. An entire gutter and downspout

system was removed from a residence. Numerous loose items, including

filled trash cans and lawn/patio furniture was moved from the

backyards and understory of homes onto front lawns and streets. Most

of the observed damage in the Indian Waterways community were

consistent with 60 to 70 mph, with possible spot values near 75 mph.

The tornado crossed a patch of mangroves and undeveloped forest, and

reached greatest intensity at San Pedro Catholic Church. There, a

large tree split at the trunk, and an old-growth mahogany was

uprooted, falling toward the east onto a portion of the structure

connecting the rectory with the main church. Fortunately, the upper

portion of the tree did not substantially damage the roof, with no

leaks observed in the downpour that followed. However, several

barrel tiles were removed from the peak ridges forming the hip roof

pattern over the rectory, as well as from the southeast edge of the

church, onto the top of the church's main entrance. Numerous large

limbs were downed toward the east, with lightweight free-standing

signs deposited northward cross the tornado path from right to left.

Estimated wind speeds were maximized in the range of 90 to 100 mph

with maximum width near 60 yards. Good impact reference made to the

observed wind impacts at this location from recent Hurricane Irma,

all having previously been removed or repaired.

The tornado continued toward the east-northeast, crossing U.S.

Highway 1 and the Old Highway, but weakened such that only large

tree limbs were downed. From this point, the tornado likely moved

out over the oceanside as a waterspout into Hawk Channel, southwest

of the oceanside entrance to Tavernier Creek.

A fast-moving pre-frontal squall line passing through the upper Florida Keys developed an embedded supercell thunderstorm with attendant mesocyclone along the Florida Bay side of Upper Matecumbe Key. The supercell thunderstorm moved east-northeast, producing a waterspout which made landfall on the bayside of Plantation Key, Islamorada. The tornado crossed the Overseas Highway, exiting oceanside just southwest of Tavernier Creek. The waterspout then made a second landfall oceanside in Tavernier southeast of Tavernier Creek before dissipating.