EF1 tornado, (Mlt)Millinocket Arp to Grindstone, Maine, August 5, 2017

1. EF065 to 85 mph

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

2. EF186 to 110 mphthis tornado

   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

EF1

Date

August 5, 2017

Touchdown

10:47 PM EDT (02:47 UTC)

Lifted

10:59 PM EDT (02:59 UTC)

On the ground

12 minutes

Path length

2.5 miles (4.1 km)

Path width

33 yards (30 m)

Deaths

0

Injuries

0

County

Penobscot County

Touchdown point

45.690, -68.690

Lift-off point

45.720, -68.660

Record number

1708052047-01

12 damage points were recorded along this path by NWS CAR, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 94 mph.

• across street, mixed forest
• looking NW, other side of road.
• Trees on edge of major damage path.
• Remaining trees in old loggin area, snapped off and uprooted. End of road damage.

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

Thunderstorms developed during the evening of the 5th in advance of a cold front crossing the region. A tornado developed along a line of non-supercell thunderstorms. The tornado tracked along a path through a wooded area between Millinocket and Grindstone. In excess of 1000 trees were toppled or snapped along the path before lifting. The same storm then produced a second brief tornado near Sherman in Aroostook county. The second tornado touch down tore a large section of a roof from a barn...destroyed a chicken coop and partially damaged another barn with two wagons inside. Another nearby resident had significant shingle damage to their roof. Several trees in the area were also uprooted.

A tornado developed along a line of non-supercell thunderstorms and tracked through a wooded area between Millinocket and Grindstone. Damage along the path consisted of over 1000 trees snapped or toppled. The average path width was around 30 yards. The estimated maximum wind speeds were between 90 and 100 mph. The forest was a mix of hardwood and softwood trees (DI 27, DI 28 , DOD 4).

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.

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 General Thunderstorms Risk. The outlook in force was issued at 01:00 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.

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.

The Caribou radar (KCBW), 77 km away, was scanning. The volume nearest the touchdown began at 02:47 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 MaineEvery tornado in Maine since 1950Warnings in force in Maine nowThe forecast where you are

1 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.