64 A Noteworthy Year for Supercells and Tornadoes in the Western United States in 2018

Monday, 22 October 2018
Stowe & Atrium rooms (Stoweflake Mountain Resort )
Jared L. Guyer, NOAA/NWS, Norman, OK
Manuscript (1.2 MB)

While the overall tornado counts have been very low this year across the United States, above normal tornado activity has occurred with intense supercells in areas near the Rockies Front Range (particularly including eastern Wyoming) into the Intermountain West. During the afternoon of 27 May, a cyclic tornadic supercell produced at least EF2-rated damage northwest of Cheyenne, Wyoming. An EF3 tornado occurred near Gillette, Wyoming, on 1 June. On 6 June, multiple strong tornadoes, which included a 45-minute-duration tornado with EF3 damage as well as a satellite EF2 tornado, occurred north of Laramie, Wyoming. The state of Wyoming averages around one (E)F2+ tornado in a given year, but the state has had at least four EF2+ tornadoes in 2018. In fact, Wyoming’s multiple EF3+ tornadoes in 2018 are a first in a calendar year since 1955 (two F3’s). Additionally, an intense long-lived supercell that produced a tornado in eastern Idaho on 31 May will also be highlighted. The meteorological ingredients and commonalities of these noteworthy tornadic supercells in the western United States will be discussed, one of which includes relatively high (well-above-normal) moisture content for the region.
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