June 5 - Goshen County Tornado Given Official Rating of EF2

The Goshen County, Wyoming tornado of June 5th, 2009 has been given an official rating of EF2 on the Enhanced Fujita (EF) Scale, according to Meteorologist-in-Charge, John Eise of the National Weather Service Office in Cheyenne, Wyoming.

Preliminary wind measurements provided by the Verification of the Origins of Rotation in Tornadoes Experiment 2 (VORTEX2) were added to the damage reports from the storm assessments on June 6th, 2009.  These two factors were considered in the new rating.

First, the storm assessment team considered the damage to the power poles along the path of the tornado.  They were snapped off near the ground.  This would indicate an expected wind speed of 118 miles per hour (mph), though the range of potential wind speeds could be from 98 to 142 mph.

Second, VORTEX2 wind measurements were evaluated.  The data show that the winds at 10 feet were about 130 mph.  Also, the fastest winds recorded below 328 feet were 143 to 148 mph.

Therefore, the National Weather Service has assigned an EF2 rating with a wind speed of 130 mph to the Goshen County, Wyoming tornado of June 5th, 2009.

Additional information inquires can be directed to John Eise at (307) 772-2468 ext. 642 or John Griffith, Warning Coordination Meteorologist at (307) 772-2468 ext. 726.


 

Image 0.5 reflectivity (upper left), 0.5 base velocity (lower left), 0.9 reflectivity (upper right), 0.9 base velocity (lower right).

Image taken by the Vortex2 Doppler on Wheels east of the tornado at 4:19 PM MDT. (Center for Severe Weather Research / National Science Foundation)

 

 

A picture of the wall cloud from the storms located east of La Grange Wyoming taken by the VORTEX2 team. (Center for Severe Weather Research / National Science Foundation)

 

 

 
 

The tornado that touched down in Goshen County at  407 pm MDT  about  11 miles west of La Grange, Wyoming and continued to move to the east. The tornado lifted at 431 pm MDT. (Center for Severe Weather Research / National Science Foundation)

 

 
 
   
 At 410 pm MDT, the VORTEX2 team received softball size hail (4.5 inches in diameter) that broke their wind shield. (Center for Severe Weather Research / National Science Foundation)

 

 

 The warnings issued between 327 pm and 430 pm and the preliminary local storm reports

 

The damage assessment that was completed by NWS staff early on Saturday, June 6th and VORTEX2 during the late afternoon/early evening on the same day.  The notes from each respective damage assessment have combined on this map. 

 

 Snapped tree trunk along Bear Creek.  This damage was the western-most of the NWS Survey.

 

 Deciduous tree uprooted along Bear Creek west of Phillips, Wyoming.

Additional tree damage at the same location along Bear Creek as the uprooted tree.

 

 
 Telephone pole snapped along along Road 55 / Four Corners Road southeast of Phillips, WY.

 

 



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