Labor Day 2011 Tornadoes and Heavy Rain from the
Remnants of Lee

The remnants of Tropical Storm Lee moved into the Tennessee valley from the Gulf coast region, and combined with a stalled frontal boundary in the mountains, created an environment for isolated tornadoes as well as copious amounts of rain.

The official track that Lee took out of the Gulf and into Louisiana while still a tropical storm is shown below, but this does not include the complex transition to a remnant low pressure center, which continued to move very slowly northeastward, but remaining south and west of the Appalachian chain.

Track of Lee

 

By Labor Day evening (Monday September 5th), the surface low pressure was still over Alabama, and had connected with a frontal boundary that had moved down from the northwest, but had then become stationary near the Blue Ridge (see map below)

Surface map Monday Evening, Sept 5th, 2011

This pattern allowed for tropical moisture to spread northward and then northwest over the frontal boundary, getting some additional lift from the mountains. Rainfall from early Monday morning September 5th to Wednesday morning September 7th (almost 60 hours) ranged from 3 to 9 inches along the Blue Ridge and the adjacent eastern foothills, with 1.5 to 3 inches over the rest off the area. This actually could have been worse, except that the deep tropical moisture moved fairly quickly off to the northeast of the area. While minor flash flooding was reported in a few locations, the very dry conditions leading up to this event helped prevent those problems from being worse.

The images below show a broader scale of the rainfall over a two week period in early September, most of which was associated with the remnants of Lee, and then a closer view of the Blacksburg County Warning area, for a 48 hour period Sept 5-6 when most of the rain associated with Lee fell over our area.

Eastern U.S. Rainfall Totals


Rainfall estimates over our area from this event

The heaviest rainfall shown in the image above occurred near the Blue Ridge, with totals of 5 to 9 inches.

As if often the case with remnants of tropical systems moving inland, heavy rainfall was not the only concern. Winds began to increase with height above the ground and turned sharply in direction with height as well with the system approaching. Combined with some daytime heating (mainly along and east of the frontal boundary), the ingredients were coming together for some stronger updrafts to develop within the rain bands, and to acquire rotation as they developed, thus presenting a threat for tornadoes. A Tornado Watch was issued for the area immediately to the south of the Blacksburg County Warning area at 3:45pm, and then another for much of the area near the Blue Ridge and points eastward in NC and VA by 6:30pm. Several tornado warnings were issued throughout the afternoon and evening on Labor Day, and two tornadoes were confirmed, one at about 5:20pm in the foothills of northern Wilkes County NC, and the other during the late evening (about 10pm) at the base of Blue Ridge in Cana (Carroll County) VA.

There were a number of rotational signatures seen in Doppler radar data across the region Monday afternoon and evening, and again early Tuesday morning. One of the strongest signatures was in fact associated with the Cana tornado, and the image below shows this couplet of higher outbound Doppler velocity (brighter red) close to higher inbound velocity (brighter green), just moments before an EF0 tornado very briefly touched down along Highway 52 (Fancy Gap Hwy) in Cana (not labeled on the map but indicated by the yellow arrow).

Rotational signature off radar south of Cana, VA

 

The maps below show the track (1.3 miles) for the Wilkes County tornado, and brief touchdown location for the Cana tornado, as well as some photos of the damage if you click on the blue pins. At the bottom of this page are a few frequently asked questions regarding tropical remnant tornadoes.


View Wilkes County Tornado September 5th, 2011 in a larger map


View Carroll County Tornado September 5th, 2011 in a larger map

...TORNADO CONFIRMED NEAR CANA IN CARROLL COUNTY VIRGINIA...

LOCATION...CANA IN CARROLL COUNTY VIRGINIA
DATE...SEPTEMBER 5, 2011
ESTIMATED TIME...10:03 PM EDT
MAXIMUM EF-SCALE RATING...EF0 (CORRECTED)
ESTIMATED MAXIMUM WIND SPEED...80 MPH
MAXIMUM PATH WIDTH...90 YDS
PATH LENGTH...20 YDS
BEGINNING LAT/LON...36.584N / 80.661W
ENDING LAT/LON...36.584N / 80.661W
* FATALITIES...0
* INJURIES...2

* THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO
CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS
STORM DATA.

...SUMMARY...
THE NATIONAL WEATHER SERVICE IN BLACKSBURG VA HAS CONFIRMED A
TORNADO NEAR CANA IN CARROLL COUNTY VIRGINIA ON SEPTEMBER 5, 2011.

THE TORNADO...RATED AS AN EF0 WITH MAXIMUMA WINDS OF 80 MPH... 
TOUCHED DOWN VERY BRIEFLY AT A GAS STATION ON U.S. 52...ALSO KNOWN 
AS FANCY GAP HIGHWAY...AND BLEW THE ROOF OFF AND INTO THE AWNING 
COVERING THE GAS PUMPS. WHILE THERE WAS NO OTHER DAMAGE TO TREES OR 
STRUCTURES ON EITHER SIDE OF THE HIGHWAY...A PIECE OF WOOD FROM THE 
ROOF WAS FOUND A FEW HUNDRED YARDS UP THE ROAD TOWARD THE NORTHWEST. 
THE STORM WAS TRAVELING TOWARD THE NORTH-NORTHEAST. TWO PEOPLE 
INSIDE THE GAS STATION SUFFERED MINOR INJURIES. THERE WAS ALSO MINOR 
STRAIGHT LINE WIND DAMAGE NEARBY TO LARGE LIMBS AND SMALL TREES.

**************************************************************************

...TORNADO CONFIRMED NEAR ABSHERS IN WILKES COUNTY NORTH CAROLINA...

LOCATION...ABSHERS IN WILKES COUNTY NORTH CAROLINA
DATE...SEPTEMBER 5, 2011 
ESTIMATED TIME...520 PM EDT 
MAXIMUM EF-SCALE RATING...EF1 
ESTIMATED MAXIMUM WIND SPEED...100-105 MPH
MAXIMUM PATH WIDTH...250 YARDS 
PATH LENGTH...1.3 MILES 
BEGINNING LAT/LON...36.371N / -81.086W
ENDING LAT/LON...36.390N / -81.083W
* FATALITIES...0
* INJURIES...0

* THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO
CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS
STORM DATA.

...SUMMARY...
THE NATIONAL WEATHER SERVICE IN BLACKSBURG VA HAS CONFIRMED A
TORNADO NEAR ABSHERS IN WILKES COUNTY NORTH CAROLINA ON SEPTEMBER
05, 2011.

IT WAS DETERMINED THE DAMAGE WAS CAUSED BY AN EF1 TORNADO...WITH
MAXIMUM WIND SPEEDS OF 100-105 MPH. THE TORNADO FIRST TOUCHED DOWN
AROUND 5:20 PM EDT JUST SOUTH OF THE INTERSECTION OF LONGBOTTOM ROAD
AND GREEN STREET MOUNTAIN RESORT ROAD. IT TRACKED NORTH INTO
STONE MOUNTAIN STAKE PARK...DESTROYING 14 OUTBUILDINGS AND DOING
AT LEAST MINOR DAMAGE TO THREE HOMES. 

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.

Frequently Asked Questions Regarding Tropical Cyclones (Remnants) and Tornadoes

1) Why do tropical cyclones spawn tornadoes?

2) What parts of a tropical cyclone are most favored for tornado formation?

3) Why are TC tornadoes especially difficult to deal with?