EFU Tornado — Lassen, California

2020-08-15 · near Plumas, Lassen, California

Event narrative

Bystanders along CA 70 and US 395 near Hallelujah Junction captured multiple videos and photographs of an anticyclonically rotating tornado pendant to the base of a pyrocumulonimbus cloud. The tornado caused no damage from which the NWS could assign an EF-scale rating as it traversed across an area of burned sagebrush. From photographs and video evidence, the approximate path of the tornado was calculated. The tornado traveled along a 3.16-mile path from the head of Roberts Canyon to 1.33 miles southwest of Hallelujah Junction. The maximum path width was approximately 156 yards. No injuries or deaths occurred with this tornado.

Wider weather episode

Dry conditions and anomalously low fuel moisture, in combination with an unstable low-to-mid-level atmosphere, allowed the Loyalton wildfire to develop extreme fire behavior on the afternoon of 15 August 2020. Robust heat and moisture fluxes from the wildfire caused rapid smoke plume deepening and lofting of pyrometeors above the lifting condensation level, which led to the formation of two vertically extensive pyrocumulonimbi and three tornadoes.

View location on OpenStreetMap → (39.7310, -120.1009)

Source: NOAA Storm Events Database, event_id 916735. Narrative written by the NWS forecast office that issued the report.