Thunderstorm Wind — Ralls, Missouri

2021-07-09 · near Rensselaer, Ralls, Missouri

Event narrative

An NWS storm survey discovered a macroburst that first initiated to the north of Rensselaer, MO. This macroburst caused extensive tree damage in town, especially on the western side of Rensselaer where several large branches and trees were snapped or uprooted and a few roofs sustained damage. Winds in this area were determined to be around 80 mph. The large swath of damaging winds then pushed south towards Mark Twain State Park. Extensive tree damage was noted in the state park. In addition, the Blackjack Marina sustained quite a bit damage from straight line winds around 80 mph. These winds were strong enough to cause damage to several boats, damage to the metal roofing of the marina, and the winds were even able to pull part of the marina off its mooring. The dollar amount damage to the marina is estimated to be around a million dollars. The worst of the damage occurred to the south of the marina in the town of Perry, MO. Extensive tree damage was noted in this area along with some damage to roofs and siding to a number of residences. The degree of tree and structural damage was consistent with fairly widespread 80 mph winds across town, with localized areas of 90 mph present in some of the observed damage. Straight line wind damage continued to the south of Perry, but it became less intense and more scattered in nature south of town. No deaths or injuries were reported.

Wider weather episode

On the evening of July 9th, intense thunderstorms developed rapidly along a warm front draped from northwest to southeast across the area. There were two rounds of thunderstorms, the first being discrete, rotating storms called supercells. These supercell thunderstorms dropped large hail across portions of western Illinois (Mt. Sterling area) and also across the western St. Louis metro area. Hail in excess of 2 inches was noted in both of these supercells. Over time, the storms congealed into a large complex of thunderstorms known as a mesoscale convective complex (MCC). This line of storms contained damaging, sometimes destructive winds as they quickly pushed southeast across east-central Missouri into southwest Illinois. The worst damage was noted from Rensselaer, MO southward to Perry, MO, where straight-line winds of 90 mph were found. This same line of storms also affected the St. Louis metro area, bringing widespread 60-70 mph winds across the metro causing many large tree limbs to fall and many to be without power.

View location on OpenStreetMap → (39.6850, -91.5380)

Source: NOAA Storm Events Database, event_id 971826. Narrative written by the NWS forecast office that issued the report.