Twin Cities, MN

Weather Forecast Office

A Look Back at the May 06, 1965 Tornadoes

Overview

May 6, 1965 was one of the worst tornado outbreaks in Minnesota history. Six tornadoes affected six counties around the Twin Cities with 13 fatalities and over 500 injured. The tornado outbreak lasted three hours and caused $51 million in damage. There were four F-4s, one F-3, and one F-2. Two of the F-4s crossed paths, causing even more damage. These tornadoes developed due to low pressure in North Dakota/Canada and unstable air behind a warm front over the Twin Cities region.

Weather Bureau, local officials, and the outstanding communications by local radio and television stations. Many credit the announcers of WCCO-AM with saving countless lives. It was also the first time in Twin Cities history that civil defense sirens were used for severe weather.

Top row: Minnetonka tornado (left) and Glencoe tornado (right)

Bottom row: Fridley tornado (left) and Hamburg tornado (right)

Tornado
Photos
Radar
Storm Reports
Environment

Tornadoes:

Tornado - Cologne
Carver and Hennepin Counties

Date	6 May 1965
Time (Local)	6:08 PM-6:40 PM CST
F Rating	F-4
Path Length	12.3 miles
Injuries/Deaths	3 fatalities, 175 injured
Summary: This tornado touched down east of Cologne, moved northeast, and dissipated northeast of Minnetrista and Orono.

Track Map

Tornado - Chanhassen, Minnetonka, Deephaven
Carver and Hennepin Counties

Date	6 May 1965
Time (Local)	6:27 PM-6:43 PM CST
F Rating	F-4
Path Length	6.9 miles
Injuries/Deaths	None
Summary: This tornado touched down near Lake Susan in Chanhassen and traveled north through Minnetonka and Deephaven.

Track Map

Tornado - New Auburn, Lester Prairie
Sibley and McLeod Counties

Date	6 May 1965
Time (Local)	6:34 PM-7:01 PM CST
F Rating	F-3
Path Length	15.5 miles
Injuries/Deaths	None
Summary: This tornado touched down three miles east of New Auburn, traveled northeast near Glencoe, and dissipated west of Lester Prairie.

Track Map

Tornado - Green Isle, Hamburg, Waconia
Sibley and Carver Counties

Date	6 May 1965
Time (Local)	6:43 PM-7:04 PM CST
F Rating	F-2
Path Length	11.2 miles
Injuries/Deaths	1 fatality, 175 injured
Summary: This tornado touched down two miles east of Green Isle, moved northeast near Hamburg and Norwood Young America, and dissipated two miles southwest of Waconia.

Track Map

Tornado - Fridley, Blaine
Anoka County

Date	6 May 1965
Time (Local)	7:06 PM-7:21 PM CST
F Rating	F-4
Path Length	6.8 miles
Injuries/Deaths	3 fatalities, 175 injured
Summary: This tornado touched down in the southwestern corner of Fridley, traveled northeast through Fridley, and dissipated northeast of Laddie Lake in Blaine.

Track Map

Tornado - Golden Valley, Fridley, Mounds View
Hennepin, Anoka, Ramsey Counties

Date	6 May 1965
Time (Local)	8:14 PM-9:02 PM CST
F Rating	F-4
Path Length	17.3 miles
Injuries/Deaths	6 fatalities, 158 injured
Summary: This tornado touched down in Golden Valley, traveled across north Minneapolis and into Fridley, through Mounds View, and finally dissipated west of Centerville.

Track Map

In 1965, the Fujita (F) Scale was used to classify tornadoes into the following categories:

F0 Weak <73 mph	F1 Moderate 73-112 mph	F2 Significant 113-157 mph	F3 Severe 158-206 mph	F4 Extreme 207-260 mph	F5 Catastrophic 261-318 mph

Photos:


Damage to a new home just completed in Chanhassen, but nobody was living in it yet.	Damage to a farmstead east of Hamburg and southeast of Norwood.	Damage to a farmstead just north of Highway #5, two miles southwest of Waconia.	Aerial view of Highway #5, roughly halfway between Waconia and Young America.


Damage in Fridley in the trailer park.	Aerial view, looking east over Fridley. Mississippi Street is the east-west cross street, extending from the tip of the plane's wing and extending to the top center of the photo. In the lower center of the photo is City Hall (the brown roof building between Mississippi Street and the small pond), which took a direct hit.	Aerial view of Spring Park. The tornado then went through Navarre, just west of Wayzata, and ended near Hamel..	Airplane damage in Blaine/Anoka Co. Airport

Radar:

The loop to the right, and images below are from the Weather Surveillance Radar 57, or WSR-57. In 1959 this first "modern" radar was commissioned at the Miami hurricane forecast center. Over the next few years, this technology was installed across the country. The WSR-57 offered some improvement over the previous version (WSR-3), but with coarse reflectivity and no velocity data available, the ability to forecast tornadoes was limited.

In the late 1980s and early 1990s, the WSR-88D was deployed across the country. The "D" in WSR-88D stands for Doppler. And it is the Doppler technology that has revolutionized weather forecasting over the last decade by allowing meteorologists to observe storm motion. However, this technology was not available in 1965.

WSR-57 radar loop from May 06 1965 showing several storms with supercell structures (reflectivity hook) moving across the region.


(Day Prior) Radar image of supercells on May 5 at 7:10 PM CST.	(Morning of the Event) Radar image of late morning thunderstorms on May 6 at 12:05 PM CST. Notice the subtle outflow boundary just northwest of the radar.	(During the Event) Radar image of supercells on May 6 at 6:55 PM CST. Notice the "hook-like" appendage on the storm west of the radar.	(During the Event) Radar image of multiple supercells on May 6 at 7:09 PM CST.

Storm Reports


The map above shows storm reports from that day, with the red lines indicating tornado tracks, and the green dots indicating hail. Storm reports back then were not as readily available as they are today, so it is likely that more severe weather occurred than what this map shows.	The image above shows a zoomed-in map of the tracks from that day along with approximate timing.

Environment

On the morning of May 6, two upper-level low pressure systems were situated over the western U.S. and the North Dakota/Canada border. The flow/circulation associated with these lows created favorable conditions for instability. Later in the evening, warm moist air was located behind the warm front over the Twin Cities area. This environment led to convection and tornadic supercells.


500 mb analysis from 7pm on May 5.	500 mb analysis from 7am on May 6.	500 mb analysis from 7pm on May 6.


925 mb analysis from 7pm on May 5.	925 mb analysis from 7am on May 6.	925 mb analysis from 7pm on May 6.

In 1965 the Storm Prediction Center did not produce the outlooks that they do today. However, the images below are a mock up of what a potential outlook may have looked like from that event. Images courtesy of the Storm Prediction Center **Please keep in mind these were created in hindsight with only limited meteorological data**


Mock-up of what the Day1 tornado outlook may have looked like from May 06, 1965.	Mock-up of what the Day1 severe hail outlook may have looked like from May 06, 1965.	Mock-up of what the Day1 severe wind outlook may have looked like from May 06, 1965.

Lastly, numerical simulations based off the limited data from 60 year ago does show a signal for supercell thunderstorms with rotating updrafts. The simulated radar reflectivity loop to the right shows late morning convection across northern Minnesota, followed by late afternoon and evening storms across central Minnesota and the Twin Cities metro. Images and loops courtesy of Tom Hultquist.

**Please keep in mind these were created in hindsight with only limited meteorological data**

WSR-57 radar loop from May 06 1965 showing several storms with supercell structures (reflectivity hook) moving across the region.


Surface map from 4:00 PM CST showing a warm front lifting through central Minnesota.	Simulated Mean Layer Convective Available Potential Energy (MLCAPE) showing an unstable airmass across the Upper Midwest.	Simulated Max Run Updraft Helicity. This parameter is used as a proxy to identify the potential for supercell storms that have rotating updrafts. Notice the long tracks in the simulation across central Minnesota that match up with the tornadoes that occurred there.

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