September 11th, 2017 Tornado

***Tropical Storm Irma Produces an EF0 Tornado in***

***Bamberg County*** on ***September 11th, 2017***

Statistics Summary of the EF-0 Tornado in Bamberg County on Sep 11th 2017
Location	Estimated Start Time	Maximum EF-Scale Rating	Estimated Maximum Wind Speed	Maximum Path Width	Path Length	Fatalities	Injuries
Olar, SC	7:01 PM	EF0	85 MPH	50 yards	2 miles	0	0

* This information is preliminary and subject to change pending final review of the event(s) and publication in NWS Storm Data.

Overview

On September 11th 2017 at 2 pm EDT, the center of Tropical Storm Irma was located near the Florida/Georgia border. The extent of tropical storm force winds was large and reached into the southern portions of North Carolina (below). The Midlands and Central Savannah River Area (CSRA) were in the front-right quadrant of Tropical Storm Irma, which is historically favorable for tropical tornadoes.

Sep 11, 2017, 2 PM EDT Advisories on Tropical Storm Irma (National Hurricane Center)

During much of the day, the Midlands and CSRA experienced cool, low-level flow from the northeast. This created a stable environment which is unfavorable for tornadoes. However during the evening, Irma had moved far enough to the north to produce southeasterly winds over portions of the southern Midlands. This would draw warm, moist air from over the Atlantic shoreline into the region. Very strong 0-1 km Storm Relative Helicity (Figure 1) would allow small vortices to form in the bands of convection. The warming surface temperatures provided just enough surface-based instability (Figure 2) to stretch these small vortices to the ground in the form of a tornado.

Figure 1. Sep 11, 2017, 7 PM EDT 0-1 km Storm Relatively Helicity (SRH)â€‹ and Storm Motion Vector (Mesoanalysis from Storm Prediction Center)

Figure 2. Sep 11, 2017, 7 PM EDT surface based Convective Available Potential Energy (J/kg) and surface winds (knots) (Mesoanalysis from Storm Prediction Center)

Bamberg County Tornado

Storm Relative Velocity images (Figure 3) from the KCAE radar show a rotational couplet tightening just before 7 pm. The tornado touched down at approximately 7:01 pm just north of Olar, SC based on the NWS Damage Survey. It crossed several small roads, snapping branches and uprooting trees before dissipating approximately 4 minutes after touchdown, just west of Govan, SC.

Note that the sudden change in color seen as the rotational couplet nears Govan, SC is an artifact of the radar due to the high wind speeds associated with Tropical Storm Irma.

Figure 3. Sep 11, 2017 KCAE 0.5° Storm Relative Velocity (SRV) Loop from 6:53 pm to 7:09 pm.

Summary and Storm Track of Tornado

EF0 Tornado Confirmed near Olar, SC in Bamberg County

Rating:                 EF0
Estimated Peak Wind:    85 mph
Path Length /statute/:  2 miles
Path Width /maximum/:   50 yards
Fatalities:             0
Injuries:               0

Start Date:             September 11 2017 
Start Time:             7:01 PM EDT
Start Location:         0.5 miles NNW of Olar, SC
Start Lat/Lon:          33.19/-81.19

End Date:               September 11 2017
End Time:               7:05 PM EDT
End Location:           1 mile W of Govan, SC
End Lat/Lon:            33.22/-81.20

Click image for larger view

...Summary...
The National Weather Service in Columbia has confirmed a tornado
near Near Olar in Bamberg County South Carolina on 09/11/2017.

The tornado was associated with the remnants of Hurricane Irma. The 
tornado touched down just northwest of the town of Olar along Thunder 
Road. The tornado continued north-northwest for approximately 2 miles. 
The tornado crossed Thunder Road...Red Fox Road...Memorial Church Road 
and dissipated before reaching Earhardt Road. The tornado downed a few
trees and several large limbs along it's path. The tornado was brief, 
only staying on the ground for approximately 4 minutes.

Trees uprooted from EF0 tornado on September 11, 2017.

For reference: the Enhanced Fujita Scale classifies tornadoes
into the following categories:

EF0...Wind speeds 65 to 85 mph
EF1...Wind speeds 86 to 110 mph
EF2...Wind speeds 111 to 135 mph
EF3...Wind speeds 136 to 165 mph
EF4...Wind speeds 166 to 200 mph
EF5...Wind speeds greater than 200 mph