There were two extreme weather events within a couple of days of each other this last week of July. First off, a huge supercell thunderstorm formed in central south dakota on the afternoon of july 23, 2010. This storm moved into the town of vivian, south dakota where it dropped the record hailstone. vivian is 30 miles south of pierre on I-90 and i've driven by vivian numerous times in my years of living in south dakota. the record stone ended up being 8" in diameter, and 18.625" in circumference! it also weighed almost 2 pounds. as a comparison, a volleyball is only about a 1/2" bigger in diameter, but is much bigger in circumference due to it being perfectly spherical. The previous record was for a 7" diameter stone that fell several years ago in Aurora, Nebraska, and that stone still has the record for circumference at 18.75"!! one home had 18 holes punched through it's roof, with a few of the holes coming through the ceiling, so the stones were laying on the floor inside the house! the record setting stone was actually larger, but it wasn't found until an hour and a half after the storm ended. also the person that found the stone, lost power during the storm so his freezer wasn't working for several more hours!! it is believed that it was possible for some of the stones to be as large as 10 or 11 inches!! many 6" or larger stones were also found. for those who don't know how hail forms, intense updrafts in a thunderstorm are needed to push the hail higher and higher so it can continue to freeze and add more ice. meteorologists estimate that the updrafts in this storm had to be 160-180 mph in order to hold hailstones this size!!!
here's some links and pics from this storm:
http://www.crh.noaa.gov/abr/?n=stormdamagetemplatehttp://www.mitchellrepublic.com/event/article/id/45038/
divot left in ground from stone
Then on july 26th, an EF-3 tornado touched down in northeast montana, killing 2 people and injuring 1 other. Tornadoes in Montana are fairly rare, but are more common in july. However, especially strong tornadoes are very uncommon. This was only the 3rd EF-3 tornado ever recorded in the state. The tornado was in a very sparsely populated area of the state, but it did hit a large ranch, where the fatalities occurred. i've included the damage survey and the cnn story with a video below:
http://www.cnn.com/2010/US/07/27/montana.tornado.deaths/?hpt=T2http://www.wrh.noaa.gov/ggw/PRSheridan_Tornado.pdf
1 comment:
Hi,
Thanks for writing about the Montana tornado. It's actually the 4th on record, NCDC doesn't have the 1946 storm in it's database, but Tom Grazulis does have it in the Significant Tornadoes book. Three days of severe weather this week, and another slight risk tomorrow. Busy, busy!
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