Using UAS Technology to Obtain Aerial Storm Damage Imagery

-Mike SporerNWS Blacksburg

Sometimes the best way to view damage

is from the air

The National Weather Service routinely conducts damage surveys following severe weather events.

Observed damage indicators are analyzed to

determine a likely cause and intensity

What appears to be minor tree damage from the ground…

Can be part of a more significant damage path when viewed from above

Track of EF1 tornado, Botetourt county VirginiaApril 27, 2011

Today, UAS technology makes it possible to respond quickly and rapidly share aerial imagery

Traditionally aerial support has come from local emergency services or agencies such as the

Civil Air Patrol

Why Drones?

• Extremely efficient

• Highly flexible in the field

• Can focus on very small areas of interest

• Provide high resolution imagery

• Value added digital datasets (3D mapping, NDVI)

• Access to debris fields unsafe for ground inspection

• Not restricted by road network

• Aerial imagery can be critical to NWS operations

when performing a post-storm damage assessment.

• However, current policy prohibits individual NWS

offices from procuring or using drones for any

purpose.

• Additionally, individual NWS offices currently have

no budgetary allowance to purchase aerial imagery.

• Given the tight constraints currently in place, the NWS

has two viable options to obtain drone imagery when

conducting a storm damage survey:

▪ Partner with other agencies with access to drones, or who can purchase UAS services

▪ Rely on properly obtained imagery from the public -“citizen science”

Hobbyist Resources:

Air Bears: www.airbears.org

Academy of Model Aeronautics: http://suas.modelaircraft.org

Piedmont Virginia Community College: www.pvcc.edu

FAA:

http://knowbeforeyoufly.org

http://www.faa.gov/uas/b4ufly

What does the NWS look for in aerial images of storm damage?

Distinctive patterns that will determine if damage was caused by

Straight line winds:

Downburst/MicroburstSquall Line

Rotating winds:

TornadoGustnado

Some folks may not know what an uprooted treelooks like from the air

Downburst

Sudden, short lived localized wind that

diverges from the center

Microburst is a smaller scale and more intense

downburst where winds can reach up to 150 MPH!

Winds are usually stronger in the direction of storm motion.

Typical straight line wind damage pattern from a downburst.

Damage usually appears to “fan out” from the center.

Squall Line

Squall lines are a complex of thunderstorms organized in a linear structure. They can be more than 100 miles long and

last for extended periods of time.

While squall lines primarily produce damage from straight line

winds, it is not uncommon for embedded tornadoes to spin-up.

Bow Echo

Some squall lines start to curve as strong winds develop behind the line and push forward. These squall lines are

called “bow echoes”.

Derecho

The strongest squall lines that produce significant damage over a large area are called derechos.

Typical straight line wind damage from a strong squall line

Damage is uni-directional and usually does not “fan out”

-Non Supercell Tornadoes-

Gustnadoes

A term meaning “gust front tornado”: short lived low level vortices that form on the gust front, or under the shelf cloud.

Small areas of rotational damage from a gustnado can be embedded in a larger pattern of straight line wind damage and therefore hard to detect, even from the air.

Supercell Thunderstorm

Supercell thunderstorms can produce tornadoes as well as straight line wind damage.

Real world example:

Appomattox county, Virginia EF-3 Tornado

February 24, 2016

Overview and Ground Survey

On February 24, 2016 a tornado caused seven injuries, one fatality, and significant damage in Appomattox county, Virginia. There was considerable damage to over 100 structures, including some well-built brick homes, as well as many snapped and downed trees.

A ground based survey team from the National Weather Service (NWS) Blacksburg office deployed within 24 hours to Appomattox county, VA.

No drones used for initial survey- Winds too high for safe flight- Restricted air space to accommodate survey by the governor illustrates the importance of coordination!

Preliminary findings:- EF-3 tornado (140-145 mph)- track length of 13 miles

Aerial Survey

On February 26 NWS Blacksburg returned to Appomattox county with Autonomous Flight Technologies (AFT) for a more thorough assessment of the tornado track.

The UAS imagery provided by AFT proved to be extremely useful by locating additional areas of damage not visible from the ground.

By using aerial drone imagery, an additional 4 miles of damage were discovered which increased the total tornado track length from 13 to 17 miles – an increase of 30% from the ground survey!

Damage from a tornado will be more chaotic than is found with straight line winds.

Debris from a tornado will converge toward the center of the path

Damage from a tornado may show obvious signs of rotation with debris

strewn in the direction of the rotating winds

Analysis of drone imagery added 4 miles (30%) to length of February 24, 2016 Appomattox, VA tornado track compared to ground survey alone

Don’t forget about georeferences!

3D digital rendering of damage in Evergreen, VA from EF-3 tornado Feb 24, 2016

Closer inspection of 3D digital rendering of damage in Evergreen, VA from EF-3 tornado Feb 24, 2016 (still from video)

Conclusions

• Access to aerial drone imagery has already demonstrated significant benefits

• increased the surveyed path length 30% by revealing damage not easily viewable/accessible from the ground

• UAS survey proved to be quicker and more efficient for inspecting remote portions of the tornado track

• The NWS currently has the capability to seamlessly integrate basic aerial imagery into storm damage assessments

• Aerial images entered into Damage Assessment Toolkit (DAT)

• Thorough coordination with emergency management is critical to the successful use of UAS during a damage survey

• The NWS is seeking to build productive partnerships to acquire aerial drone imagery

• Please remember to share any aerial imagery of storm damage with the NWS!

Thank You!