Twin Cities, MN

Weather Forecast Office

August 27 2018 Severe Weather Summary

Overview

On August 27, 2018 a line of storms moved across eastern Minnesota into Wisconsin. These storms caused widespread wind damage and produced two EF-0 tornadoes in Rice and Goodhue Counties. These tornadoes were short-lived and formed out of a mesovortex-like feature. Downburst wind damage was also found along the path of the mesovortex. Portions of the city of Red Wing had extensive wind damage with the Red Wing Regional Airport automated station measuring a wind gust of 82 mph.

Storm Reports from the Storm Prediction Center

Radar 517pm

Zoomed map of the Nerstrand and Vasa tornado tracks.

Tornado
Wind
Radar and Satellite
Storm Reports
Environment

Tornadoes:

Tornado - Nerstrand
Rice County

Date	August 27, 2018
Time (Local)	5:17 - 5:21 PM CDT
EF Rating	EF-0
Est. Peak Winds	70 mph
Path Length	2.3 miles
Max Width	100 yards
Injuries/Deaths	0/0
Summary: A mesovortex developed on the leading edge of the line and produced a quick spin-up resulting in an EF-0 tornado.

Track Map

Downloadable KMZ File Available soon


Radar reflectivity (left) and velocity (right) from 5:17 PM CDT. The tornado warning is shown by the pink polygon.	Zoomed in radar reflectivity (left) and velocity (right) from 5:17 PM CDT. The tornado warning is shown by the pink polygon.	Radar reflectivity (left) and velocity (right) from 5:18 PM CDT. The tornado warning is shown by the pink polygon.	Zoomed in radar (left) and velocity (right) from 5:18 PM CDT. The tornado warning is shown by the pink polygon.


A barn was completely destroyed after catching fire when power lines landed on top of the roof from a falling power pole.	A few pine trees were broken at their midsections.	Large branches were broken and fell onto the homeowner's yard

Tornado - Vasa
Goodhue County

Date	August 27, 2018
Time (Local)	5:37 - 5:42 PM CDT
EF Rating	EF-0
Est. Peak Winds	85 mph
Path Length	2.2 miles
Max Width	150 yards
Injuries/Deaths	0
Summary: A second tornado developed within a mesovortex on the leading edge of the line of storms.

Track Map

Downloadable KMZ File Available soon


Radar reflectivity (left) and velocity (right) from 5:39 PM CDT. The tornado warning is shown by the pink polygon.	Zoomed in radar reflectivity (left) and velocity (right) from 5:39 PM CDT. The tornado warning is shown by the pink polygon.	Radar reflectivity (left) and velocity (right) from 5:41 PM CDT. The tornado warning is shown by the pink polygon.	Zoomed in radar reflectivity (left) and velocity (right) from 5:41 PM CDT. The tornado warning is shown by the pink polygon.


A distinct tornado path is visible in this photo. Nearly all of the corn in the path is flattened and mangled. On top of the hill on the right, the edge of the standing corn marks the edge of the tornado.	Half of the roof has been torn off of this shed.	The tornado tore most of the tin roof off of the low-lying barn.	A large portion of another shed was also destroyed as the tornado passed through.

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:

Wind - Red Wing
Goodhue and Pierce Counties

Date	August 27, 2018
Time (Local)	5:50 PM CDT
Meas. Peak Winds	82 mph
Injuries/Deaths	0
Summary: Severe wind gusts were produced by the line of storms as it passed through Red Wing. A significant severe wind gust of 82 mph was measured by the Red Wing Regional Airport automated station.

Map of Reports (Green Dots are Wind)

Downloadable KMZ File Available soon


Radar reflectivity (left) and velocity (right) from 5:49 PM CDT.	Severe winds broke a large tree near the base in Red Wing.	Severe winds split a large tree, which landed on a house.	At the Red Wing Regional Airport, a hangar that was under construction was destroyed by severe winds.

Satellite/Radar Images


3:00 PM CDT - GOES 16 Geocolor and MRMS radar reflectivity	4:00 PM CDT - GOES 16 Geocolor and MRMS radar reflectivity	5:00 PM CDT - GOES 16 Geocolor and MRMS radar reflectivity


6:00 PM CDT - GOES 16 Geocolor and MRMS radar reflectivity	7:00 PM CDT - GOES 16 Geocolor and MRMS radar reflectivity	8:00 PM CDT - GOES 16 Geocolor and MRMS radar reflectivity

Storm Reports

...Summary of 53 Severe Weather Reports from Monday, August 27, 2018...

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0329 PM     TSTM WND DMG     WELCOME                 43.67N 94.62W
08/27/2018                   MARTIN             MN   PUBLIC

            TREE DOWN ON TRAILER. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0340 PM     TSTM WND DMG     NORTHROP                43.73N 94.43W
08/27/2018                   MARTIN             MN   PUBLIC

            SOCIAL MEDIA PHOTO OF TREE AND POWER LINES
            DOWN IN NORTHROP. TIME ESTIMATED FROM RADAR.

0345 PM     HAIL             4 WNW SEDAN             45.60N 95.31W
08/27/2018  M1.00 INCH       POPE               MN   LAW ENFORCEMENT

            REPORTS OF QUARTER SIZED HAIL AND WIND GUSTS
            ESTIMATED GREATER THAN 60 MPH.

0357 PM     TSTM WND DMG     1 WNW TRUMAN            43.83N 94.45W
08/27/2018                   MARTIN             MN   TRAINED SPOTTER

            LARGE BRANCHES AND A TREE DOWN. ESTIMATED
            WIND GUSTS OF 70 MPH.

0405 PM     HAIL             2 E WESTPORT            45.72N 95.14W
08/27/2018  M1.25 INCH       STEARNS            MN   TRAINED SPOTTER

            TRAINED SPOTTER REPORTED QUARTER TO HALF
            DOLLAR SIZED HAIL.

0430 PM     TSTM WND DMG     KASOTA                  44.29N 93.96W
08/27/2018                   LE SUEUR           MN   LAW ENFORCEMENT

            MULTIPLE TREES DOWN IN THE KASOTA AREA.

0432 PM     TSTM WND DMG     2 ESE ST. PETER         44.32N 93.94W
08/27/2018                   LE SUEUR           MN   PUBLIC

            TELEPHONE POLE DOWN. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0433 PM     TSTM WND DMG     2 N ST. PETER           44.36N 93.96W
08/27/2018                   NICOLLET           MN   PUBLIC

            MULTIPLE TREES DOWN.

0442 PM     TSTM WND DMG     2 W LE CENTER           44.38N 93.77W
08/27/2018                   LE SUEUR           MN   LAW ENFORCEMENT

            TREES DOWN. REPORT RELAYED VIA DISPATCH.
            TIME ESTIMATED FROM RADAR.

0448 PM     TSTM WND DMG     LE SUEUR                44.46N 93.91W
08/27/2018                   LE SUEUR           MN   LAW ENFORCEMENT

            TREES DOWN IN LE SUEUR. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0450 PM     TSTM WND DMG     5 SSW MORRISTOWN        44.15N 93.47W
08/27/2018                   WASECA             MN   PUBLIC

            TREES DOWN. REPORT RELAYED VIA DISPATCH.
            TIME ESTIMATED FROM RADAR.

0505 PM     TSTM WND DMG     FARIBAULT               44.30N 93.27W
08/27/2018                   RICE               MN   LAW ENFORCEMENT

            1 TREE DOWN IN FARIBAULT. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0510 PM     TSTM WND DMG     JORDAN                  44.67N 93.63W
08/27/2018                   SCOTT              MN   LAW ENFORCEMENT

            POWERLINE DOWN. REPORT RELAYED VIA DISPATCH.
            TIME ESTIMATED FROM RADAR.

0517 PM     TORNADO          2 WSW NERSTRAND         44.32N 93.11W
08/27/2018                   RICE               MN   NWS STORM
SURVEY

            STORM SURVEY RATED TORNADO EF-0.

0518 PM     TSTM WND DMG     3 SW NERSTRAND          44.31N 93.10W
08/27/2018                   RICE               MN   PUBLIC

            BRANCHES SNAPPED AND METAL POLE BENT. REPORT
            RELAYED VIA DISPATCH. TIME ESTIMATED FROM
            RADAR.

0519 PM     TSTM WND DMG     1 S NERSTRAND           44.33N 93.06W
08/27/2018                   RICE               MN   LAW ENFORCEMENT

            TREES BRANCHES DOWN AND CORN DOWN. REPORT
            RELAYED VIA DISPATCH. TIME ESTIMATED FROM
            RADAR.

0523 PM     TSTM WND DMG     1 E NERSTRAND           44.34N 93.04W
08/27/2018                   RICE               MN   LAW ENFORCEMENT

            WINDMILL FELL ON SHED. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0527 PM     TSTM WND DMG     8 S CANNON FALLS        44.40N 92.88W
08/27/2018                   GOODHUE            MN   PUBLIC

            PINE TREE SNAPPED NEAR BASE. DAMAGE TO A
            GAZEBO. TIME ESTIMATED FROM RADAR.

0527 PM     TSTM WND DMG     4 E NERSTRAND           44.34N 92.98W
08/27/2018                   GOODHUE            MN   TRAINED SPOTTER

            LARGE TREE LIMB DOWN. ESTIMATED WINDS GUSTS
            GREATER THAN 50 MPH.

0535 PM     TSTM WND GST     CANNON FALLS 7SSE       44.41N 92.86W
08/27/2018  M57 MPH          GOODHUE            MN   MESONET

            MESONET STATION MN042, CANNON FALLS 7SSE.

0537 PM     TSTM WND DMG     7 SE CANNON FALLS       44.43N 92.82W
08/27/2018                   GOODHUE            MN   PUBLIC

            TREE UPROOTED. TIME ESTIMATED FROM RADAR.

0540 PM     TSTM WND DMG     EAGAN                   44.82N 93.16W
08/27/2018                   DAKOTA             MN   PUBLIC

            NUMEROUS TREE BRANCHES DOWN. TIME ESTIMATED
            FROM RADAR.

0540 PM     TSTM WND DMG     VASA                    44.50N 92.72W
08/27/2018                   GOODHUE            MN   LAW ENFORCEMENT

            ROOF DAMAGE AND TREES DOWN IN VASA MN.
            REPORT RELAYED VIA DISPATCH. TIME ESTIMATED
            FROM RADAR.

0540 PM     TORNADO          VASA                    44.50N 92.73W
08/27/2018                   GOODHUE            MN   NWS STORM
SURVEY

            STORM SURVEY RATED TORNADO EF-0.

0540 PM     TSTM WND DMG     VASA                    44.50N 92.72W
08/27/2018                   GOODHUE            MN   PUBLIC

            FARM SHEDS DESTROYED.

0540 PM     TSTM WND DMG     INNER GROVE HEIGHTS     44.84N 93.07W
08/27/2018                   DAKOTA             MN   PUBLIC

            SOCIAL MEDIA PICTURE OF TREE BRANCHES DOWN.
            TIME ESTIMATED FROM RADAR.

0545 PM     TSTM WND DMG     PINE ISLAND             44.20N 92.65W
08/27/2018                   GOODHUE            MN   PUBLIC

            LARGE TREE SNAPPED ABOUT 10 FEET OFF THE
            GROUND. TIME ESTIMATED FROM RADAR.

0547 PM     TSTM WND DMG     2 WSW RED WING          44.56N 92.57W
08/27/2018                   GOODHUE            MN   PUBLIC

            BUILDING DAMAGE. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0547 PM     TSTM WND DMG     2 WSW RED WING          44.56N 92.57W
08/27/2018                   GOODHUE            MN   LAW ENFORCEMENT

            TRACTOR TRAILERS TIPPED OVER. REPORT RELAYED
            VIA DISPATCH. TIME ESTIMATED FROM RADAR.

0550 PM     TSTM WND DMG     WOODBURY                44.92N 92.94W
08/27/2018                   WASHINGTON         MN   PUBLIC

            LARGE TREE LIMB SNAPPED. TIME ESTIMATED FROM
            RADAR.

0550 PM     TSTM WND DMG     2 WNW BAY CITY          44.59N 92.49W
08/27/2018                   PIERCE             WI   LAW ENFORCEMENT

            SIGNIFICANT BUILDING DAMAGE AT RED WING
            AIRPORT. REPORT RELAYED VIA DISPATCH. TIME
            ESTIMATED FROM RADAR.

0550 PM     TSTM WND DMG     4 W BAY CITY            44.57N 92.54W
08/27/2018                   PIERCE             WI   LAW ENFORCEMENT

            MANY LARGE TREES DOWN. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0550 PM     TSTM WND DMG     OAK GROVE               45.33N 93.33W
08/27/2018                   ANOKA              MN   PUBLIC

            TREE TRUNK SNAPPED NEAR BASE. OTHER LARGE
            LIMBS DOWN. TIME ESTIMATED FROM RADAR.

0553 PM     TSTM WND DMG     NORTH RED WING          44.59N 92.52W
08/27/2018                   PIERCE             WI   PUBLIC

            LARGE TREES SNAPPED NEAR BASE. TIME
            ESTIMATED FROM RADAR.

0555 PM     TSTM WND DMG     2 WNW BAY CITY          44.59N 92.49W
08/27/2018                   PIERCE             WI   BROADCAST MEDIA

            HANGER COLLAPSED AT RED WING REGIONAL
            AIRPORT.

0555 PM     TSTM WND GST     RED WING AP             44.59N 92.50W
08/27/2018  M82 MPH          PIERCE             WI   AWOS

            AWOS STATION RGK, RED WING AP.

0556 PM     TSTM WND DMG     2 NW LAKE ELMO          45.02N 92.93W
08/27/2018                   WASHINGTON         MN   PUBLIC

            A COUPLE OF LARGE TREES WERE DOWNED ON THE
            SOUTH END OF LAKE DE MONTREVILLE.

0600 PM     TSTM WND DMG     2 SE HUDSON             44.95N 92.72W
08/27/2018                   ST. CROIX          WI   PUBLIC

            LARGE TREE LIMBS BLOCKING ROAD. TIME
            ESTIMATED FROM RADAR.

0612 PM     TSTM WND DMG     SPRING VALLEY           44.85N 92.24W
08/27/2018                   PIERCE             WI   LAW ENFORCEMENT

            MULTIPLE TREES DOWN. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0622 PM     TSTM WND DMG     KNAPP                   44.95N 92.08W
08/27/2018                   DUNN               WI   LAW ENFORCEMENT

            POWER LINES DOWN. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0624 PM     TSTM WND DMG     DOWNING                 45.05N 92.13W
08/27/2018                   DUNN               WI   LAW ENFORCEMENT

            TREE DOWN BLOCKING ROAD. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0626 PM     TSTM WND DMG     BOYCEVILLE              45.05N 92.04W
08/27/2018                   DUNN               WI   LAW ENFORCEMENT

            MULTIPLE TREES AND POWER LINES DOWN. REPORT
            RELAYED VIA DISPATCH. TIME ESTIMATED FROM
            RADAR.

0631 PM     TSTM WND DMG     MENOMONIE               44.88N 91.93W
08/27/2018                   DUNN               WI   PUBLIC

            TREE DOWN BLOCKING ROAD. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0633 PM     TSTM WND DMG     5 ENE WHEELER           45.06N 91.81W
08/27/2018                   DUNN               WI   PUBLIC

            5 LARGE OAK TREES UPROOTED AND BLOCKING
            690TH ST. NEAR 1070TH AVE.

0641 PM     TSTM WND DMG     ELK MOUND               44.87N 91.69W
08/27/2018                   DUNN               WI   LAW ENFORCEMENT

            TREE DOWN BLOCKING ROAD. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0644 PM     TSTM WND DMG     COLFAX                  45.00N 91.73W
08/27/2018                   DUNN               WI   LAW ENFORCEMENT

            TREE DOWN BLOCKING ROAD. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0649 PM     TSTM WND DMG     CHETEK                  45.31N 91.65W
08/27/2018                   BARRON             WI   LAW ENFORCEMENT

            TREES DOWN ACROSS TOWN. RELAYED FROM
            DISPATCH CENTER. TIME ESTIMATED FROM RADAR.

0649 PM     TSTM WND DMG     NEW AUBURN              45.20N 91.57W
08/27/2018                   CHIPPEWA           WI   LAW ENFORCEMENT

            TREE DOWN BLOCKING ROAD. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0649 PM     TSTM WND DMG     RIDGELAND               45.20N 91.90W
08/27/2018                   DUNN               WI   LAW ENFORCEMENT

            TREES DOWN. REPORT RELAYED VIA DISPATCH.
            TIME ESTIMATED FROM RADAR.

0650 PM     TSTM WND DMG     2 S EAU CLAIRE          44.78N 91.50W
08/27/2018                   EAU CLAIRE         WI   PUBLIC

            REPORTS VIA TWITTER OF TREE BRANCHES DOWN
            ACROSS SOUTH SIDE OF EAU CLAIRE. TIME
            ESTIMATED FROM RADAR.

0650 PM     TSTM WND DMG     ALMENA                  45.41N 92.04W
08/27/2018                   BARRON             WI   TRAINED SPOTTER

            NUMEROUS TREE LIMBS DOWN.

0655 PM     TSTM WND DMG     WEYERHAEUSER            45.42N 91.41W
08/27/2018                   RUSK               WI   LAW ENFORCEMENT

            TREE DOWN ACROSS ROAD. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0713 PM     TSTM WND DMG     CONRATH                 45.39N 91.04W
08/27/2018                   RUSK               WI   LAW ENFORCEMENT

            TREE DOWN ACROSS ROAD. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

0715 PM     TSTM WND DMG     GLEN FLORA              45.50N 90.89W
08/27/2018                   RUSK               WI   LAW ENFORCEMENT

            TREE DOWN BLOCKING ROAD. REPORT RELAYED VIA
            DISPATCH. TIME ESTIMATED FROM RADAR.

Environment

A shortwave trough in the upper level jet advected an elevated mixed layer over the Upper Midwest which led to MLCAPE values of nearly 3000 J/kg. Deep layer shear of around 40 kts was sufficient for organized convection. This event was primarily driven by the steep lapse rates and instability. The upper level jet contributed to the deep layer shear, and the storms moved from the southwest to the northeast. All images are valid at 3:00 PM CDT.


Figure 1: 500mb winds and heights showing the upper level jet over the Midwest.	Figure 2: Steep lapse rates were advected over the region ahead of this jet.	Figure 3: The combination of warm moist air at the surface together with the dry air aloft led to an unstable air mass.


Figure 4: A weak pressure trough was draped across the region.	Figure 5: Deep layer shear was sufficient for organized convection.	Figure 6: The low level storm relative helicity was fairly low, limiting the threat for tornadoes.

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