Dangerously hot conditions are occurring today in southeast Oklahoma, the ArkLaTex, lower Mississippi Valley, and Puerto Rico. Hot temperatures surround this area throughout the southern U.S. Excessive Heat Warnings and Heat Advisories in effect. Excessive rainfall may lead to flash flooding today over parts of northern Alabama into eastern Tennessee and the Cascades. Read More >
| 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 |
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)​ 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)
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.
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
Radar
Current Weather
Rivers & Lakes
Satellite
Forecast Maps
Hour by Hour Forecast
Tropical Weather
Graphical Hazards
Climate Plots
Weather Briefing
Regional Observations
Fire Weather
Forecaster's Discussion
Skywarn
Drought
Text Bulletins
Follow us on Twitter
Follow us on Facebook
Follow us on YouTube
CAE RSS Feed