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EF1 tornado in St. Johns County, Florida

Tornado September 10, 2017 · St. Johns County, Florida

EF1
Rating
5.0 mi
Path length
200 yd
Path width
EF0EF1EF2EF3EF4EF5Unrated

The path drawn at its surveyed width of 200 yards (0.11 mi) — zoom in and the swath grows to true scale. Other tornadoes recorded nearby that day are shown faint.

What EF1 means. On the Enhanced Fujita scale, EF1 is moderate damage: roofs badly stripped, mobile homes pushed off foundations or overturned, windows broken, consistent with estimated gusts of 86–110 mph. The rating comes from a survey of the worst damage after the storm, not from a wind measurement, so it says as much about what the tornado hit as about how strong it was.

What the National Weather Service wrote

This tornado may have initiated as a water spout that moved onshore at Vilano Beach. Minimal damage was reported in Vilano Beach with greater tree damage discovered west of Vilano Beach where a few trees were snapped and uprooted. Roof damage was reported on 5th Avenue near Vilano Beach. Multiple trees were damage and there was minor roof damage observed along Jackson and North Blvds. The tornado then crossed Highway 1 and caused additional tree and roof damage from 4th Street toward Porter Road before dissipating in the 12 Mile Swamp Conservation Area. Radar indicated a tornado debris signature. This tornado had peak winds of 85-100 mph.

The wider storm

Hurricane Irma's eye passed west of the local forecast area, with the region on the storm's turbulent east side. Widespread tropical storm force winds with gusts to hurricane force were felt across much of the area, with the strongest winds surging up the Florida east coast during the pre-dawn hours of Sept. 11th. Extensive tree and power line damage occurred across the local area from the winds. One of the greatest local impacts exacerbated by Irma's rainfall and storm surge was river flooding. Prior to Irma's arrival, a local nor'eastern developed 3 days prior, with strong onshore flow pumping water into the St. Johns River basin. Elevated water levels of 1-2 ft above normal tidal departure were already ongoing for several tidal cycles before Irma's surge and rainfall. The nor'easter also brought localized heavy rainfall bands, with some areas near the coast realizing 4-6 inches in 24 hrs the days prior to Irma. In addition, precursor conditions to the nor'easter included an above average rainfall across the region during the summer months. Major, historic river flooding was forecast along Black Creek and the Sante Fe a week prior to Irma. Realized river values along the St. Johns surpassed prior record levels set by Hurricane Dora in 1964, during low tide the morning of Sept. 11th. The St. Johns River basin continued to rise with the combination of trapped tides due to the nor'easter, astronomically high tides heading into the spring tide season, storm surge of up to 5 ft in some areas, fresh water rainfall of 7-11 inches, and strong southerly winds pushing the water across the basin on the east side of Irma. Historic river flooding occurred across much of NE Florida Sept 11th through the following week as water levels were slow to funnel out of the St. Johns basin. Coastal infrastructure that was already weakened about 1 year ago due to Hurricane Matthew suffered the most damage from Irma's storm surge.

Began near Vilano Beach (29.9300, -81.3000).

Other tornadoes from the same storm system

5 more tornadoes the National Weather Service filed under this storm episode.

Source: NOAA Storm Events Database, event 720479. Narratives are written by the National Weather Service forecast office that issued the report.

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