DAMAGE SURVEY FOR July 11 2017 TORNADO EVENTS

From the Grand Forks National Weather Service Office

.OVERVIEW…Several supercell thunderstorms spawned tornadoes on
this day across northeast ND and portions of northwest MN. One
especially large supercell produced 4 of these tornadoes, including
the three strongest and longest tracking tornadoes. Both a ground
survey and an aerial survey were conducted over this long track.
An additional tornado or two may yet be uncovered associated with
other warned storms.

.Rocklake ND Tornado…

Rating: EF-0
Estimated peak wind: 70 mph
Path length /Statute/: 0.5 miles
Path width /Maximum/: 100 yards
Fatalities: 0
Injuries: 0

Start date: July 11 2017
Start time: 516 PM CDT
Start location: 4 E Rocklake / Towner Co.
Start Lat/Lon: 48.7923 / -99.1760

End date: July 11 2017
End time: 518 PM CDT
End location: 4.5 E Rocklake / Towner Co.
End_lat/lon: 48.7909 / -99.1669

THE FUNNEL WHICH PRECEDED THIS TORNADO WAS VIEWED BY
MULTIPLE STORM SPOTTERS As IT TRACKED THROUGH MAINLY
OPENED COUNTRY.

.Clyde ND Tornado…

Rating: EF-0
Estimated peak wind: 70 mph
Path length /Statute/: 0.5 miles
Path width /Maximum/: 100 yards
Fatalities: 0
Injuries: 0

Start date: July 11 2017
Start time: 548 PM CDT
Start location: 5 E Clyde / Cavalier Co.
Start Lat/Lon: 48.7727 / -98.7997

End date: July 11 2017
End time: 550 PM CDT
End location: 5.5 E Clyde / Cavalier Co.
End_lat/lon: 48.7707 / -98.7848

BRIEF TOUCHDOWN NOTED BY OBSERVER LOCATED NEAR THE CORNER
OF CR5 AND CR20. THE TORNADO TRACKED OVER MAINLY OPENED
COUNTRY WITH ONLY A DUST SWIRL OR TWO NOTED.

.Northwood ND Tornado…

Rating: EF-1
Estimated peak wind: 90 mph
Path length /Statute/: 4.5 miles
Path width /Maximum/: 150 yards
Fatalities: 0
Injuries: 0

Start date: July 11 2017
Start time: 625 PM CDT
Start location: 4 NNW Northwood / Grand Forks Co.
Start Lat/Lon: 47.8059 / -97.5988

End date: July 11 2017
End time: 637 PM CDT
End location: 2 ENE Northwood / Grand Forks Co.
End_lat/lon: 47.7556 / -97.5235

THIS PARTIALLY RAIN WRAPPED TORNADO TRACKED TO THE SOUTHEAST
WITH INTERMITTENT TOUCHDOWNS. IT BROKE DOWN LARGE BRANCHES
AND SNAPPED A FEW TREE TRUNKS IN SHELTER BELTS ALONG IT PATH.

.Adams ND Tornado…

Rating: EF-1
Estimated peak wind: 105 mph
Path length /Statute/: 7 Miles
Path width /Maximum/: 150 yards
Fatalities: 0
Injuries: 0

Start date: July 11 2017
Start time: 630 PM CDT
Start location: 5 NW Adams / Walsh Co.
Start Lat/Lon: 48.4692 / -98.1467

End date: July 11 2017
End time: 646 PM CDT
End location: 2 ENE Adams / Walsh Co.
End_lat/lon: 48.4304 / -98.0177

THIS ROPE TORNADO TRACKED FOR ROUGHLY 7 MILES TO THE EAST
SOUTHEAST AND EVENTUALLY PRODUCED A SUBSTANTIAL DUST SWIRL
BEFORE IT ENDED ABOUT 2 ENE OF ADAMS BY 646 PM CDT. IT WAS
VIEWED AND PHOTOGRAPHED FROM MULTIPLE LOCATIONS AND THOUGH
IT REMAINED OVER LARGELY OPENED COUNTRY IT DID SNAP A FEW
HARDWOOD TREE TRUNKS AT A COUPLE OF LOCATIONS.

.Manvel ND Tornado…

Rating: EF-0
Estimated peak wind: 75 mph
Path length /Statute/: 1.7 miles
Path width /Maximum/: 150 yards
Fatalities: 0
Injuries: 0

Start date: July 11 2017
Start time: 650 PM CDT
Start location: 4 NNW Manvel / Grand Forks Co.
Start Lat/Lon: 48.1253 / -97.2038

End date: July 11 2017
End time: 656 PM CDT
End location: 3.5 NNE Manvel / Grand Forks Co.
End_lat/lon: 48.1165 / -97.1729

THIS TORNADO WAS OBSERVED AND REPORTED BY SPOTTERS LOCATED
NEAR MANVEL AND AlSO ALONG HWY 81 AT CR1 ABOUT 6 MILES
NORTHWEST OF MANVEL. THE TORNADO CROSSED INTERSTATE 29 JUST
SOUTH OF EXIT 157. IT BROKE DOWN LARGE TREE BRANCHES AT
MULTIPLE SHELTER BELTS AND GROVES ALONG ITS PATH.

.Hatton-Hillsboro ND Tornado…

Rating: EF-2
Estimated peak wind: 135 mph
Path length /Statute/: 23 miles
Path width /Maximum/: 1200 yards
Fatalities: 0
Injuries: 0

Start date: July 11 2017
Start time: 655 PM CDT
Start location: 8 E Hatton / Traill Co.
Start Lat/Lon: 47.6331 / -97.3040

End date: July 11 2017
End time: 746 PM CDT
End location: 4 ENE Hillsboro / Traill Co.
End_lat/lon: 47.4269 / -96.9672

THIS MULTI-VORTEX TORNADO WAS WRAPPED IN RAIN AND HAIL FOR
MUCH OF ITS PATH AS IT TRACKED PRIMARILY TO THE SOUTHEAST.
AN AERIAL SURVEY SHOWED THAT AT TIMES THE GROUND TRACK
SHIFTED MORE EASTWARD OR MORE SOUTHWARD AS THE TORNADO CYCLED.
IT CROSSED I-29 JUST NORTH OF THE TAFT ELEVATORS THEN DOVE
SOUTH SOUTHEASTWARD TO A POINT ROUGHLY 2.5 ENE OF HILLSBORO
WHERE IT CURLED UP TO THE NORTHEAST…ENDING ABOUT 4.5 ENE.
COINCIDENT WITH THIS END…THE PARENT MESOCYCLONE APPEARED TO
HAVE FORMED A NEW TORNADO A FEW MILES TO THE SOUTH OF THIS
TRACK. THE TORNADO SNAPPED TREES AND DESTROYED SEVERAL FARM
BUILDINGS ALONG ITS PATH. AS THIS TORNADO PASSED THE NORTHEAST
OF HILLSBORO…AN EXTREME REAR FLANK DOWNDRAFT WIND OF FROM 80
TO 100 MPH PUSHED SOUTHWARD THROUGH THE COMMUNITY OF HILLSBORO
AND PRODUCED CONSIDERABLE TREE AND STRUCTURAL DAMAGES.

.Alvarado-Tabor MN Tornado…

Rating: EF-1
Estimated peak wind: 95 mph
Path length /Statute/: 10 miles
Path width /Maximum/: 250 yards
Fatalities: 0
Injuries: 0

Start date: July 11 2017
Start time: 707 PM CDT
Start location: 6 SSW Alvarado / Polk Co.
Start Lat/Lon: 48.1100 / -97.0500

End date: July 11 2017
End time: 730 PM CDT
End location: 3 E Tabor / Polk Co.
End_lat/lon: 48.0835 / -96.8045

THIS TORNADO TRACKED ACROSS NORTHERN NORTHLAND AND TABOR
TOWNSHIPS WITH ONLY INTERMITTENT DAMAGES. IT SNAPPED OR
UPROOTED A FEW SPRUCE TREES AND ALSO BROKE DOWN NUMEROUS
LARGE BRANCHES IN SHELTER BELTS ALONG ITS PATH. AT ONE
FARMSTEAD EAST OF TABOR IT TORE STEEL PANELS OFF OF A
SHED ROOF AND SNAPPED LARGE TREE LIMBS.

.Hillsboro ND to Halstad MN Tornado…

Rating: EF-2
Estimated peak wind: 130 mph
Path length /Statute/: 11 miles
Path width /Maximum/: 600 yards
Fatalities: 0
Injuries: 0

Start date: July 11 2017
Start time: 745 PM CDT
Start location: 4 ESE Hillsboro / Traill Co.
Start Lat/Lon: 47.3845 / -96.9755

End date: July 11 2017
End time: 810 PM CDT
End location: 4 ESE Halstad / Norman Co.
End_lat/lon: 47.3315 / -96.7468

THIS TORNADO DEVELOPED FROM THE PARENT MESOCYCLONE AS ITS
PREDECESSOR ROPED OUT ABOUT TWO MILS TO THE NORTH. IT THEN
TRACKED ESE FOR ROUGHLY 6 MILES BEFORE IT CROSSED THE RED
RIVER ABOUT 1W OF HALSTAD MN AROUND 8 PM CDT. IT CONTINUED
TO TRACK ESE FOR ANOTHER 5 MILES BEFORE ENDING. THIS TORNADO
SNAPPED ONE DOUBLE /H-POLE/ POWER POLE, CRUSHED STEEL GRAIN
BINS, SNAPPED NUMEROUS OAK AND ASH TREES, AND TOPPLED A
BARN ALONG ITS PATH.

.Borup-Ulen Tornado…

Rating: EF-2
Estimated peak wind: 125 mph
Path length /Statute/: 13 miles
Path width /Maximum/: 500 yards
Fatalities: 0
Injuries: 0

Start date: July 11 2017
Start time: 840 PM CDT
Start location: 3.5 N Borup / Norman Co.
Start Lat/Lon: 47.2389 / -96.5096

End date: July 11 2017
End time: 906 PM CDT
End location: 2 N Ulen / Clay Co.
End_lat/lon: 47.1174 / -96.2586

THIS TORNADO TRACKED TO THE SOUTHEAST BEFORE IT CURLED OUT
AROUND 2 MILES NORTH OF ULEN. THIS TORNADO COLLAPSED AT
LEAST ONE SHED, SNAPPED NUMEROUS TREES, AND TOSSED DOZENS
OF LARGE 2000 LB ROUND HAY BALES MORE THAN A HALF MILE ACROSS
A SUGAR BEET FIELD. IT ALSO SNAPPED AT LEAST A HALF DOZEN
WOODEN POWER POLES ALONG ITS PATH.

EF Scale: The Enhanced Fujita Scale Classifies
Tornadoes into the following categories.

EF0…Weak……65 to 85 mph
EF1…Weak……86 to 110 mph
EF2…Strong….111 to 135 mph
EF3…Strong….136 to 165 mph
EF4…Violent…166 To 200 mph
EF5…Violent…>200 mph

NOTE:
The information in this statement is PRELIMINARY and subject to
change pending final review of the events and publication in
NWS Storm Data.