Erin Strengthens to a Hurricane; Heavy Rainfall Possible in Puerto Rico and the Virgin Islands, the Upper Midwest, South Texas

Hurricane Erin may bring isolated flash and urban flooding, landslides or mudslides, and possible tropical storm conditions to Puerto Rico and the U.S. Virgin Islands this weekend. Scattered thunderstorms and heavy rainfall may bring areas of flooding this weekend over the Upper Midwest. A tropical disturbance will bring locally heavy rain and mainly urban flash flooding to far southern Texas. Read More >

Overview

Widespread showers associated with an area of low pressure grew into low-topped supercells across eastern Minnesota during the afternoon as the activity encountered greater instability. Strong low level shear helped produce six tornadoes from central and east central into northwest Wisconsin. There were three EF1 tornadoes and three EF0s. To many, the Silver Lake tornado appeared stronger than an EF1, but this was likely due to the high amounts of moisture in the air which allowed the condensation funnel to grow large. Damage along its path suggested a peak wind speed of 105 mph, a high end EF1.

Tornadoes
Photos & Video
Radar
Environment

Tornadoes:

Tornado - Biscay, MN
MCLEOD COUNTY

Date	7/28/2019
Time (Local)	3:17 PM CDT
EF Rating	EF0
Est. Peak Winds	85 mph
Path Length	4.0 miles
Max Width	200 yards
Injuries/Deaths	0/0
Summary: Corn was flattened and tree damage occurred along the path.

Track Map

Downloadable KMZ File

Tornado - 3 SSE Silver Lake, MN
MCLEOD COUNTY

Date	7/28/2019
Time (Local)	3:38 PM CDT
EF Rating	EF0
Est. Peak Winds	65
Path Length	0.3 miles
Max Width	25 yards
Injuries/Deaths	0/0
Summary: A brief satellite tornado spun up and produced little damage. Tornado captured on video.

Track Map

Downloadable KMZ File

Tornado - Silver Lake, MN
MCLEOD COUNTY

Date	7/28/2019
Time (Local)	3:36 PM CDT
EF Rating	EF1
Est. Peak Winds	105 mph
Path Length	2.6 miles
Max Width	1/4 mile
Injuries/Deaths	0/0
Summary: Tornado spun up southeast of Silver Lake and quickly became 1/4 mile wide as it tracked northeast across Highway 7 and then dissipated. Corn was flattened, a few outbuildings were destroyed, and many trees and power lines were damaged.

Track Map

Downloadable KMZ File

Tornado - Forest Lake, Scandia, & Lindstrom, MN
WASHINGTON, CHISAGO COUNTIES

Date	7/28/2019
Time (Local)	4:28 PM CDT
EF Rating	EF1
Est. Peak Winds	90 mph
Path Length	7.6 miles
Max Width	1/4 mile
Injuries/Deaths	0/0
Summary: A tornado spun up on the south side of Sylvan lake (east of Forest Lake), and continued northeast on a broken path through Bone Lake, then entered Chisago County, east of Morgan St, on 240th Street North. The tornado continued along a broken path with damage south of Spider Lake where it destroyed a barn, then it damaged a private wedding venue along Olinda & 259th Street. The worst damage occurred to a farm near on 268th Street, east of Olympic Trail. The damage was rated an EF1 with severe damage to a shed and pole barn. Other damage was mainly confined to trees snapped or uprooted along the tornadoes path.

Track Map

Downloadable KMZ File

Tornado - Luck, WI
POLK COUNTY

Date	7/28/2019
Time (Local)	5:31 PM CDT
EF Rating	EF1
Est. Peak Winds	90 mph
Path Length	5.0 miles
Max Width	100 yards
Injuries/Deaths	0/0
Summary: Tornado spun up 5 miles northeast of Balsam Lake, crossed Bone Lake, then dissipated 6 miles east of Luck, WI. Tree damage occurred along the path.

Track Map

Downloadable KMZ File

Tornado - Barron, WI
BARRON COUNTY

Date	7/28/2019
Time (Local)	6:41 PM CDT
EF Rating	EF0
Est. Peak Winds	74 mph
Path Length	0.4 miles
Max Width	25 yards
Injuries/Deaths	0/0
Summary: Brief tornado produced some damage to a farm outbuilding, corn crops, and trees.

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

Photos & Video

Header


Tornado west of Biscay, MN. Photo courtesy of Amanda Hill.	Tornado east of Silver Lake, MN. Photo courtesy of Amanda Hill.	Tornado east of Silver Lake, MN. Photo courtesy of Amanda Hill.	Clear evidence of convergent damage at the beginning point of the Biscay tornado. Photo by NWS personnel.


Biscay tornado beginning point and track northeast through corn fields. Aerial photography courtesy of the Civil Air Patrol.	Tornado track through corn field. Photo by NWS personnel.	Shed destroyed by Silver Lake tornado. Photo by NWS personnel.	Silver Lake tornado damage at its widest (1/4 mile). Photo courtesy of the Civil Air Patrol.


Structural damage east of Silver Lake, MN. Photo courtesy of Amanda Hill.	Tree damage near Forest Lake, MN. Photo by NWS Personnel.	Tree damage near Forest Lake, MN. Photo by NWS Personnel.	Damage to a farm near Bone Lake, WI. Photo by NWS personnel.

Radar

Velocity and Correlation Coefficient (CC)


Velocity (left) shows strong rotation just west of Biscay. CC (right) shows debris in the air, likely leaves and crop debris. This is a radar confirmed tornado.	Velocity (left) shows very strong rotation over Highway 7 east of Silver Lake. CC (right) shows debris in the air. This is a radar confirmed tornado.	Velocity (left) shows very strong rotation near the Washington/Chisago County border. CC (right) shows debris in the air. This is a radar confirmed tornado.
Radar Loop Of Sunday Afternoon/Evening Reflectivity (Left) SRM (Right)

Environment

An unusually strong shortwave trough moved across the Upper Midwest during the afternoon of Sunday, July 28th. Both the 300 MB, and 500 MB analysis indicated a strong shortwave and good upper level diffluence moving across Minnesota during the afternoon. Surface conditions indicated a weak area of low pressure across central Minnesota, with winds backing to the southeast ahead of the surface low.


300 MB Heights & Winds	500 MB Heights & Winds	Surface Pressure, Winds, Moisture & Temperature

Instability was not overly high, but the combination of increasing wind shear, both speed and direction, and modest instability, led to rotating storms in the afternoon. Once the storms became surface based, and winds backed to the southeast, surface helicity (similar to a spinning top which lifted in the boundary layer) increased and led to the tornadoes. One of the weather parameters that uses instability and wind shear, the Conditional Probability of Significant Tornado, showed a maximum over southeast Minnesota and west-central Wisconsin.


MUCAPE (Contour) MLCIN (Shaded) & Effective Bulk Shear	Supercell Composite Parameter (Eff Layer & Storm Motion)	Conditional Probability of Significant Tornado (Percentage)

Atmospheric Sounding from 7pm July 28th


Chanhassen, MN Sounding

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Erin Strengthens to a Hurricane; Heavy Rainfall Possible in Puerto Rico and the Virgin Islands, the Upper Midwest, South Texas

Summary of the July 28, 2019 Tornadoes - Updated 8/3 9:15 AM