Summary of July 19, 2019 Severe Weather Event

Tornadoes:

Tornado - Horseshoe Lake POLK COUNTY Date 7/19/2019 Time (Local) 5:22 PM CDT EF Rating EF-1 Est. Peak Winds 90 Path Length 3.0 miles Max Width 0.33 miles Injuries/Deaths 0/0 Summary: An EF-1 tornado uprooted and downed trees in a concentrated path beginning 3.3 miles northwest of the Village of Turtle Lake, WI on Friday evening. The tornado ended 1 mile east of the Village of Turtle Lake, WI. Track Map Downloadable KMZ File

Tornado - Little Blake Lake POLK COUNTY Date 7/19/2019 Time (Local) 5:28 PM CDT EF Rating EF-0 Est. Peak Winds 75 Path Length 0.8 miles Max Width 50 yards Injuries/Deaths 0/0 Summary: A brief EF-0 tornado caused uprooted and downed trees alongside damage to roof panels and outbuildings on a farmstead 2.9 miles northwest of the Village of Turtle Lake, WI on Friday evening. Track Map Downloadable KMZ File

The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:

EF0 Weak 65-85 mph	EF1 Moderate 86-110 mph	EF2 Significant 111-135 mph	EF3 Severe 136-165 mph	EF4 Extreme 166-200 mph	EF5 Catastrophic 200+ mph

Wind & Hail:

Wind

As thunderstorms congealed into a line, severe winds became the primary hazard. In addition to the two tornadoes, widespread straight line winds raked across northern and eastern Polk County and most of Barron County. Most of the damage was to trees, although some light structural damage was also noted. Trees fell toward the east southeast, which is consistent with the strong west northwest wind. Maximum wind was estimated at 90 mph given the tree damage and a measure gust of 84 mph in Cushing, WI (Polk County). The same weather station measured a sustained 73 mph wind for 5 minutes.

Swath of blown down trees near Beaver, WI	Damage to a farm near Beaver, WI	More damage near Beaver, WI	Tree damage near Beaver, WI

Hail

Discrete supercells were the dominant storm mode from 11am to 5pm on Friday, July 19th. While the low-levels of the atmosphere were very warm, significant hail was still able to fall to the surface before melting. This is a testament to the strength of the supercell updrafts.

2.25" hail just north of Little Falls, MN (Photo taken by Julie Mushel)	Broken windshield from baseball size hail near Rock Creek, MN (Photo taken by Justin Sorensen)	2.25" hail near Randall, MN (Photo taken by Kevin Dirks)	Golf ball size hail near Donnelly, MN (Photo taken by Alan Uphoff)

Photos & Video

During Event

Supercell near Alberta, MN at 11:50am (Photo taken by Eric Tomoson)	Supercell near Mora, MN at 4:02pm (Photo taken by Jordan Woods)	Incoming storms at Rock Fest in Cadott, WI (Photo by Kaylee Pickering)

Radar

Radar Snapshots

Base reflectivity of supercell over Donnelly, MN at 11:52am	Base reflectivity at 2:19pm	Base reflectivity at 3:39pm	Base reflectivity at 5:34pm

Environment

A broad shortwave trough was located over the High Plains the evening of July 19th, 2019. Unusually fast summertime upper-level flow allowed for strong low-level dynamical responses. Rich, deep moisture was advected into Minnesota and surface temperatures rose into the low-90s.

July 19, 2019 7pm 300mb map	July 19, 2019 7pm 850mb map	July 19, 2019 7pm Surface map

The very warm dewpoints and surface temperatures created extremely unstable air. This combined with the strong, directional vertical wind shear (from the unusually strong summertime upper-level winds) generated a very favorable environment for strong, rotating thunderstorms.

July 19, 2019 7pm Most-unstable CAPE and Wind Shear map	Color-filled contours show where most unstable air is located. Red (850mb) and blue (500mb) wind barbs show where there is strong directional vertical wind shear.	July 19, 2019 3pm Supercell composite map: Values over 10 usually mean a favorable environment for supercells. A value of 66 is analyzed in central MN.

The data recorded by our 4pm weather balloon confirmed that the an extremely unstable environment was in place over Minnesota. This was likely one of the most volatile severe weather environments we've captured observations for.

July 19, 2019 4pm sounding at MPX	4pm weather balloon being released at MPX	Visible/Infrared satellite loop