Historic Tornado and Severe Weather Outbreak
Historic Tornado and Severe Weather Outbreak
of April 27th-28th, 2011
Note: Originally written on May 3, but updated for new confirmed tornado near Konnarock, Smyth County, as well as slightly longer path length for Halifax County tornado (May 6, 2011).
April 27-28, 2011 (Wednesday through early Thursday morning) will go down as one of the most historic tornado and severe weather outbreaks in United States history, comparable to and in many ways surpassing the "super outbreak" of April 3-4, 1974. As of this writing (May 3), assessments were still being conducted and statistics collected across most of the entire area impacted, but preliminary data indicates that it will far surpass the number of tornadoes that occured during the April 1974 event, and will mostly likely be a record number of tornadoes for any 24 hour period in U.S. history. Both of these two historic events had a significant impact on localities within the Blacksburg County Warning Area. For more information on preliminary comparisons between these two events, as well as a summary of the record-breaking month of April 2011, please Visit this link. You may also be interested in a summary of the April 3-4, 1974 outbreak.
This is a very prelimary plot of severe weather reports for the period 8am on April 27th to 8am on the 28th, but the final tornado count (in red) is expected to be higher.
Here in the Blacksburg County Warning Area, this event has resulted in two confirmed tornado paths that we know of so far (see maps below), both with EF2 damage, and many reports of severe weather damage and very large hail, mostly from long-lived supercell thunderstorms which were the dominant mode of thunderstorm structure on this day.
In fact, a mosaic of the life-cycle and evolution of the longest-lived supercell (which brought the devasting tornado to Tuscaloosa, AL) can be seen in this image, courtesy of Brian Tang at the National Center for Atmospheric Resarch (NCAR). Supercells also formed east of the Blue Ridge in the afternoon and evening well out ahead of the main frontal system, but also closer to the front coming from Tennessee and Kentucky very late in the evening and overnight hours. Most of these storms were rotating supercells, and almost all produced some kind of wind damage or large hail (up to at least baseball size). The map below shows that there were numerous tracks of strong rotational signatures as observed by Doppler radar in many of the storms that moved through our region. Those roational tracks within the area shown by this image that are known (as of May 2) to have resulted in tornadoes, are circled in purple. It is apparent that some of the stronger circulation areas (red and white colors) did not happen to result in tornadic damage.
Throughout the evening and overnight hours of April 27-28, the NWS in Blacksburg issued almost three dozen tornado warnings, and we remain a little surprised but grateful that only two known tornadoes occurred (although many storms tracked through heavily forested areas, so we may later become aware of additional damage). Unfortunately, one of these two tornadoes (Halifax County VA) resulted in one fatality and eight injuries, while on the ground for 13 miles. The other EF2 tornado (Smyth County VA) initially touched down in Washington County (covered by the NWS Morristown TN office), and reached EF3 intensity in the Glade Spring area, resulting in 3 fatalities and 50 injuries. It was on the ground for 25 miles in Washington County before crossing into Smyth County, where it continued for another 3 miles producing EF2 damage. For details of the damage surveys in the Blacksburg CWA, see the reports at the bottom of this page.
For more information about this and other tornadoes in far southwest VA and Tennessee, see this site from the Morristown NWS.
The total number of known tornadoes in the Blacksburg CWA for the month of April 2011 stands at 8, which is about as many as we tend to see in an especially active entire YEAR! The previous maximum number of tornadoes in a year within the Blacksburg CWA since the office opened in 1994 was 11 in 2004 (mostly from the remnants of Hurricane Ivan in September). The number of EF2 tornadoes within the Blacksburg CWA in April 2011 was 4. The total number of EF2 (or stronger) tornadoes in the 60 year period 1950 to 2010 was 10, so has now quickly jumped to 14. We have yet to experience an EF4 or EF5 in any of our 40 counties.
The rest of this event summary will focus on the April 27-28 event, and more specifically on the two tornadoes that occured in the Blacksburg CWA:
Another potent April 2011 cold front approached from the west during the daytime Wednesday April 27 and through early morning on the 28th, with surface winds shifting from south to southeast well ahead of this front (see map below). This combined with strong south winds a few thousand feet off the ground to even stronger southwest winds about 20,000 feet aloft, provided extremely high wind shear that developing thunderstorms can feed off to gain strength and rotation. The surface map below is from just after midnight early on the 28th. Green numbers indicate dew point temperature, and note the especially dry air immediately behind the front under the high pressure nosing in from the Southern Plains.
Due to the strength of this frontal system, the amount of Gulf moisture streaming in ahead of the front, the dry air at the surface and aloft pushing in from the west (with origins in the southern Rockies and drought-stricken west Texas area), as well as the extreme wind shear mentioned above, the Storm Prediction Center in Norman OK identified this as a high risk pattern for severe weather and specifically a tornado outbreak across much of the southeast states. The two maps below show the predicted overall severe risk areas (top) and the specific threat levels expected for tornadoes (bottom), issued at 3pm on the 27th. Far southwest VA and northwest NC were
A long radar loop showing much of the evolution of the many storms developing and moving through the Appalachian and Mid-Atlantic region is available on YouTube (click here). You will notice isolated storms (many of them supercells) forming over central Virginia and North Carolina intially (during the late afternoon and evening). One of these storms tracking through Halifax County around 9pm was responsible for the first EF2 tornado (on the ground for over 13 miles). Later, a broad line of many more storms moved in from the west between about 11pm and 3am. Several of these were associated with tornadoes in eastern Tennessee, with one of the these moving into far southwest Virginia producing the Washington/Smyth County tornado (EF3 and EF2 damage).
Below are just a few radar images of the storms that we know produced tornadoes. These data are displayed using GR2Analyst, from Gibson Ridge Software.
Radar reflectivity (left) and Doppler velocity (right)at 8:39pm, about 5 minutes before the Halifax County tornado touchdown near Chatham Rd west of Halifax. The black line on the right-hand image shows the approximate path of the tornado, lifting near the Roanoke River. This is from the KFCX WSR-88D radar in Floyd County, viewing toward the east-southeast.
The next series of images are from the Washington/Smyth County storm:
The above two images are similar to the previous one described, but are from 1:04am and 1:13am respectively, showing the storm as it moved northeast from south of Abingdon to the Glade Spring area with a strong circulation. The approximate tornado path is shown by the black line on the right-hand side. These are from the KFCX WSR-88D radar in Floyd County, viewing back toward the southwest.
From 1:18am, after the tornado had crossed into Smyth County just northwest of Chilhowie. The tornado lifted at the base of Brushy Mountain on Carlock Creek Rd. Also from the KFCX radar in Floyd County.
Here are two maps showing the damage paths of these two EF2 tornadoes as surveyed by the NWS in Blacksburg, with tags to a few photos of the damage.
View Halifax Tornado, April 27th, 2011 in a larger map
View Smyth Co Tornado April 27, 2011 in a larger map
Other related links include:
Review of the April 8, 2011 Pulaski area tornadoes
Review of the April 16, 2011 tornado outbreak
NWS Blacksburg area Severe Weather Climatology
Tornado Safety Information
...TORNADO CONFIRMED NEAR HALIFAX IN HALIFAX COUNTY VIRGINIA...
LOCATION...HALIFAX IN HALIFAX COUNTY VIRGINIA
DATE...APRIL 27 2011
ESTIMATED TIME...838 PM UNTIL 908 PM
MAXIMUM EF-SCALE RATING...EF2
ESTIMATED MAXIMUM WIND SPEED...125 MPH
MAXIMUM PATH WIDTH...350 YARDS
PATH LENGTH...18.1 MILES
BEGINNING LAT/LON...36.782520N/79.094473W
ENDING LAT/LON...36.97958N/78.878608W
* FATALITIES...1
* INJURIES...8
* 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 HALIFAX IN HALIFAX COUNTY VIRGINIA ON 4 27 2011.
THE NATIONAL SERVICE STORM HAS CONFIRMED A TORNADO TOUCHDOWN IN
HALIFAX COUNTY. THE INITIAL TOUCHDOWN WAS NEAR HIGH ROCK TRAIL OFF
THOMPSONS STORE ROAD. THIS TORNADO MOVED NORTHEAST CAUSING THE MOST
DAMAGE INCLUDING ONE FATALITY AND 8 INJURIES IN THE LIBERTY ROAD
AREA. THE TORNADO PATH WAS INTERMITTENT AS IT MOVED NORTHEAST OF
ROUTE 603 OR LENNIG ROAD. THE TORNADO LIFTED JUST BEFORE REACHING
THE ROANOKE/STAUNTON RIVER IN NORTHERN HALIFAX COUNTY.
THE NATIONAL WEATHER SERVICE WOULD LIKE TO THANK HALIFAX EMERGENCY
MANAGEMENT AND LIBERTY VOLUNTEER FIRE DEPARTMENT.
________________________________________________________________________________
...TORNADO CONFIRMED 1.5 NW CHILHOWIE IN SMYTH COUNTY
VIRGINIA...
LOCATION...1.5 NW CHILHOWIE IN SMYTH COUNTY VIRGINIA
DATE...APRIL 28 2011
ESTIMATED TIME...115 AM EDT TO 120 AM EDT
MAXIMUM EF-SCALE RATING...EF2
ESTIMATED MAXIMUM WIND SPEED...115 MPH
MAXIMUM PATH WIDTH...0.5 MILES
PATH LENGTH...2.8 MILES
BEGINNING LAT/LON...36.816 N/81.725 W
ENDING LAT/LON...36.838 N/81.684 W
* FATALITIES...0
* INJURIES...1
* 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 THE COMMUNITY OF CHILHOWIE IN SMYTH COUNTY VIRGINIA
DURING THE EARLY MORNING HOURS OF APRIL 28 2011.
A NATIONAL WEATHER SERVICE SURVEY TEAM DETERMINED THAT THE TORNADO
ENTERED SMYTH COUNTY FROM WASHINGTON COUNTY...AND CONTINUED ON THE
GROUND UNTIL LIFTING AT CARLOCK CREEK ROAD NEAR BRUSHY MOUNTAIN.
THE TORNADO CAUSED SIGNIFICANT DAMAGE TO THE ROOFS AND WALLS TO 5
HOMES ALONG THE STORM PATH. THREE MOBILE HOMES WERE OVERTURNED AS
WELL. THE TORNADO ALSO CAUSED MINOR TO MODERATE DAMAGE TO THE
ROOFS OF SEVERAL OTHER BUILDINGS IN THE PATH. NUMEROUS LARGE TREES
WERE EITHER SNAPPED MID TRUNK OR COMPLETELY UPROOTED.
ONE MINOR INJURY WAS CAUSED BY THIS TORNADO. SMYTH COUNTY OFFICIALS
HAVE DETERMINED THAT THIS TORNADO CAUSED BETWEEN 2 AND 2.25
MILLION DOLLARS WORTH OF DAMAGE ALONG THE PATH.
THE NATIONAL WEATHER SERVICE WOULD LIKE TO EXPRESS SINCERE
APPRECIATION TO THE SMYTH COUNTY EMERGENCY SERVICES FOR THEIR
ASSISTANCE IN PERFORMING THIS STORM SURVEY.
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.
_______________________________________________________________________
...TORNADO CONFIRMED EAST OF KONNAROCK IN SMYTH COUNTY VIRGINIA ON APRIL 28...
LOCATION...NEAR KONNAROCK IN SMYTH COUNTY VIRGINIA
DATE...04/28/11
ESTIMATED TIME...12:13 AM EDT
MAXIMUM EF-SCALE RATING...EF1
ESTIMATED MAXIMUM WIND SPEED...100 MPH
MAXIMUM PATH WIDTH...300 YARDS
PATH LENGTH...0.45 MILES
BEGINNING LAT/LON...36.684N / 81.541W
ENDING LAT/LON...36.689N / 81.537W
* FATALITIES...0
* INJURIES...0
* THE INFORMATION IN THIS REVIEW IS PRELIMINARY AND SUBJECT TO CHANGE PENDING
FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN STORM DATA.
...SUMMARY...
THE NATIONAL WEATHER SERVICE IN BLACKSBURG VA HAS CONFIRMED A TORNADO NEAR
KONNAROCK IN SMYTH COUNTY VIRGINIA ON 04/28/11.
AREAL PHOTOS FROM THE MEDIA LAST AS WELL AS A GROUND SURVEY BY THE NWS HAS
CONFIRMED A BRIEF TORNADO TOUCHED DOWN IN THE MOUNT ROGERS NATIONAL RECREATION
AREA...MAINLY CUTTING THROUGH THE GRINDSTONE CAMPGROUND. AT LEAST 200 TREES WERE
UPROOTED OR SNAPPED AT THE TRUNK...AND A BATH HOUSE WAS DAMAGED AS WELL. A FEW
PEOPLE WERE CAMPING AT THE TIME...SHORTLY AFTER MIDNIGHT EARLY THURSDAY MORNING
APRIL 28...BUT NO ONE WAS INJURED OR KILLED. THERE WAS NO DAMAGE TO ANY VEHICLES
EITHER. MANY OF THE TREES IN THE FAIRLY WIDE SWATH HAD FALLEN TOWARD THE NORTH AND
DOWNSLOPE...WITH THE STORM TRAVELING TO THE NORTHEAST...WHILE SOME TREES ON THE LEFT
EDGE OF THE PATH HAD FALLEN TOWARD THE EAST AND ON TOP OF THE OTHER TREES...WHILE SOME
TREES ON THE RIGHT EDGE NEAR THE END OF THE PATH ALONG EITHER SIDE OF ROUTE 603 HAD
FALLEN TOWARD THE WEST. THE DAMAGE ENDED A FEW HUNDRED FEET ON THE NORTH SIDE OF ROUTE
603 (LAUREL VALLEY RD).
AS FAR AS WE CAN TELL...THERE WAS NO OTHER TORNADIC DAMAGE UPSTREAM ON THE NORTH SLOPE
OF MOUNT ROGERS...EXCEPT FOR A VERY SMALL AREA OF DOWNED TREES JUST OFF ROUTE 600
BETWEEN KONNAROCK AND ELK GARDEN AT ABOUT 4,000 FT ELEVATION. THIS APPEARED TO BE
STRAIGHT LINE WINDS IN THIS LOCATION AND WAS LIKELY FROM THE SAME STORM THAT PRODUCED
THE TORNADIC DAMAGE AT GRINDSTONE.
THIS IS THE LATEST INFORMATION AVAILABLE FROM THE NWS IN BLACKSBURG VA.
THIS WILL BE UPDATED AS MORE INFORMATION BECOMES AVAILABLE
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