EF1 Tornado Occurs Near Manderson - June 1

A tornado damaged a ranch about nine miles east of Manderson along Wyoming Highway 31 around 4:00 p.m. on Monday, June 1 (see map below).  A National Weather Service storm damage assessment the following morning determined the tornado to be rated EF1 with peak winds of around 90 mph.  The tornado was about 100 feet wide and traveled about one-half mile from north-to-south, crossing the highway before dissipating.  Several trees, two fences, and a wooden corral sustained considerable damage.  An All-Terrain Vehicle (ATV) was lifted, spun 180 degrees, and moved about 15 feet.  A bicycle was tossed onto the roof of the ranch home and several water bins were tossed about.  Damage photos are included at the conclusion of this article.

The tornado occurred in a post-cold frontal environment.  A cold front moved through Manderson around 9:30 a.m. MDT on Monday leaving northwest wind of 30 to 40 mph in its wake.  Solar heating continued to warm the surface while colder air streamed into the region aloft.  This helped set the stage for an unstable atmosphere during the afternoon.  The final piece to the puzzle appeared to be a west-moving boundary from showers to the east of Manderson in the Bighorn Mountain foothills.  A series of visible satellite pictures is provided below.  This boundary interacted with other clouds to create a rapid increase in vertical motion near the ranch around 4:00 p.m.  This upward motion drew together the converging winds near the surface, thereby increasing the speed of rotation and resulting in the brief tornado.  Think of a figure skater who begins her spin with her arms outstretched only to increase the speed of her spin when her arms are drawn in.

 

Click any thumbnail to view
a larger image.
Map of General Area of Tornado East of Manderson   Captions shown below
all images.
  Map of General Area of Tornado
East of Manderson. (NWS Map)
 
 Damage to backyard of ranch.  Damage to corral and backyard fence showing circulation.  Plastic livestock drinking tub impaled on a corral gate.

Damage to backyard fence.  ATV
was lifted and spun 180 degrees.
Metal drinking tub was lifted,
emptied of its contents, and moved
about 25 feet.
(Photo courtesy of the Scott Family)

Corral fence (background) and yard
fence (foreground).  Note the
differing directions of damage
indicative of circulation rather than
straight-line wind. (NWS Photo)
Plastic livestock drinking tub
impaled on a corral gate.
(Photo courtesy of the Scott Family)
 Visible satellite image from 3:30 p.m. MDT.  Tornado location marked with red symbol.  Visible satellite image from 4:00 p.m. MDT.  Approximate tornado location marked with red symbol. Time of touchdown estimated at 3:58 p.m.  Visible satellite image from 4:15 p.m. MDT.  Approximate tornado location marked with red symbol.
Visible satellite image from 3:30
p.m. MDT.  Approximate tornado
location marked with red symbol.
(NWS Image)
Visible satellite image from 4:00 p.m. MDT.  Approximate tornado location marked with red symbol. Time of touchdown estimated at 3:58 p.m.  (NWS Image) Visible satellite image from 4:15
p.m. MDT.  Approximate tornado
location marked with red symbol.
(NWS Image)



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