EF0 tornado, Sugar Hill, Tennessee, August 31, 2017

1. EF065 to 85 mphthis tornado

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mph

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. EF2111 to 135 mph

   Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

4. EF3136 to 165 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. EF4166 to 200 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. EF5over 200 mph

   Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

7. Unrated

   The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

Rating

EF0

Date

August 31, 2017

Touchdown

4:19 PM CDT (21:19 UTC)

Lifted

4:20 PM CDT (21:20 UTC)

On the ground

1 minutes

Path length

0.3 miles (0.4 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

Property damage

$10,000

County

Perry County

Touchdown point

35.540, -87.733

Lift-off point

35.543, -87.736

Record number

1708311519-01

1 damage points were recorded along this path by NWS OHX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF0. The highest wind the damage implies is 81 mph.

• Photo from WDOC facebook page. Several trees also reportedly blown down around home. No other roads in area so will have to wait for high resolution satellite imagery to determine final path.

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

One week after Hurricane Harvey made landfall along the middle Texas coast, a weakened but still intense Tropical Depression Harvey moved across Middle Tennessee from Thursday August 31, 2017 into Friday September 1, 2017. Supercells rotating around Harvey spawned four weak tornadoes in Davidson, Maury, and Perry Counties. In addition, strong northeast winds up to 50 mph associated with the circulation of Harvey brought down numerous trees and power lines in areas along and west of I-65, knocking out power to thousands of residents. Finally, the heavy rainbands of Harvey produced 8-10 of rain in some areas, leading to major flash flooding of homes and roads. The flash flooding along with the strong winds continued into the morning hours on September 1.

A brief, weak EF0 tornado associated with Tropical Depression Harvey touched down on Cotton Branch Road in rural southeast Perry County and moved northwest. The porch and much of the metal roof was blown off a home and several trees were blown down.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down. One was issued for the county at another hour that day.

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The Storm Prediction Center had this point in a Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:57 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

NWS Nashville, TN wrote its last area forecast discussion before the tornado touched down at Aug 31, 12:42 PM CDT, 3 hours 37 minutes earlier.

Area Forecast Discussion
National Weather Service Nashville TN
1242 PM CDT Thu Aug 31 2017

.UPDATE...
FOR 18Z AVIATION DISCUSSION.

&&

.DISCUSSION...

At mid morning, the center of Tropical Depression Harvey was over
the northeast corner of LA. The heaviest rainfall was occurring
up across eastern AR. A relative dry slot was noted on the east
side, from eastern AL and western MS up into West and Mid TN. Mid
TN radar showed just scattered showers at this time.

For the near term update, we look for just scattered showers to
continue through midday. For this afternoon, as the low center
moves into northwest AL, a large shield of rain and embedded
thunder will spread across our southwest counties, and as far
northeast as Nashville by 6 PM CDT.

The increased shear, particularly at low levels, will bring the
potential for very isolated tornadoes on the east side of the
low, with the greatest risk over our southern counties late this
afternoon and evening.

We still look for the heaviest rainfall tonight into Friday
morning, especially for our northwest counties, where more than 6
inches of rain is likely. However, a quick look at latest model
data suggests we may need to expand the FFA slightly to cover
other areas where several inches of rain could fall. Look for
the FFA update within the next hour.

&&

.AVIATION...
18Z TAF DISCUSSION.

BNA/MQY/CKV/CSV...Surface low from west central MS will move to
near BNA over the next 24 hours. Widespread showers and isolated
thunder will accompany the low. The area of heaviest rainfall will
impact CKV and BNA overnight.

Through 21Z, look for just scattered showers or isolated thunder.
E wind will be increasing to 10-15KT. 21Z-09Z, showers will
become widespread with scattered thunderstorms. Expect mainly MVFR
with episodes of IFR in the heavier showers. ESE winds will
become gusty to 25KT. By 09Z, the heaviest rainfall will be
focused over CKV, with scattered to broken rainfall elsewhere.
Varying IFR/VFR will be common.

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Friday evening FOR Cannon-Cheatham-
Clay-Davidson-De Kalb-Dickson-Hickman-Houston-Humphreys-Jackson-
Lawrence-Lewis-Macon-Maury-Montgomery-Overton-Perry-Pickett-
Putnam-Robertson-Rutherford-Smith-Stewart-Sumner-Trousdale-Wayne-
Williamson-Wilson.

&&

DISCUSSION......13
AVIATION........13

Hazardous Weather Outlook...UPDATED
National Weather Service Nashville TN
1147 AM CDT Thu Aug 31 2017

TNZ005>011-023>034-056>066-075-077>080-093>095-011000-
Stewart-Montgomery-Robertson-Sumner-Macon-Clay-Pickett-Houston-
Humphreys-Dickson-Cheatham-Davidson-Wilson-Trousdale-Smith-
Jackson-Putnam-Overton-Fentress-Perry-Hickman-Lewis-Williamson-
Maury-Marshall-Rutherford-Cannon-De Kalb-White-Cumberland-Bedford-
Coffee-Warren-Grundy-Van Buren-Wayne-Lawrence-Giles-
1147 AM CDT Thu Aug 31 2017

This Hazardous Weather Outlook is for portions of Middle
Tennessee.

.DAY ONE...This Afternoon and Tonight

A Flash Flood Watch is now in effect for most of Middle Tennessee.
Locations across the higher elevations of the Upper Cumberland
Region, southern portions of the Cumberland Plateau Region, and
far southern counties across central and eastern portions of the
mid state are not within this watch area currently.

There is a slight risk of severe storms for counties near the
Tennessee/Alabama border this afternoon through early this
evening. There is a marginal risk of severe storms for locations
around the I-40 corridor and southward up to the above mentioned
slight risk area for this afternoon through early this evening.
With any severe storms that do occur, the formation of isolated
tornadoes will be the primary threat.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Heavy rain will persist through Friday as Tropical Depression
Harvey moves across Middle Tennessee. Forecast rainfall amounts
from today through Friday afternoon range from up to 1 inch along
the Cumberland Plateau, to 3 to 5 inches across the Nashville
Metro Area, to 6 to 8 inches around Clarksville and Land-between-
the-Lakes.

Also, areas generally east of I-65 remain under a marginal risk of
severe storms on Friday, with isolated tornadoes once again being
the primary threat.

Winds will increase across most of Middle Tennessee tonight and
Friday as the center of Harvey tracks across the mid state.
Sustained speeds of 10 to 20 mph will be common, with gusts of
30 mph or greater in many areas, is expected.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon through Friday
afternoon for severe storms and possible flooding.

Spotter Thunderstorm Reporting Criteria
Tornado
Funnel Cloud
Flooding
Hail >= 1/2 INCH
Winds > 50 MPH (Measured)
Structural Damage
Trees or Power Lines Down

31

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

Levington - Parson Beech River (PVE), 44 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The Nashville radar (KOHX), 132 km away, was scanning. The volume nearest the touchdown began at 21:17 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2017 tornado in TennesseeEvery tornado in Tennessee since 1950Warnings in force in Tennessee nowThe forecast where you are

15 more were confirmed in the United States that day.

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.