Ten Year Anniversary of June 17, 2010, Tornado Outbreak - NWS Duluth, MN

Tornadoes:

Tornado - St. Croix River Tornado Chisago and Pine Counties, MN and Burnett County, WI Date June 17, 2010 Time (Local) 8:44-9:05 PM CDT EF Rating EF-2 Est. Peak Winds 111-135 mph Path Length 7.8 Max Width 400 yards (1200 feet) Injuries/Deaths 2/0 Summary: A National Weather Service damage survey team confirmed an EF-2 (what is the Enhanced Fujita Scale?) tornado path stretching from extreme northeast Chisago County, through southeast Pine County, and into far western Burnett County. This tornado began about 5 miles east-northeast of Rush City. The tornado moved northeast, roughly parallel to, and about 1/4 to 1/2 mile northwest of, the St. Croix River. The tornado crossed the St. Croix River into Wisconsin about 1.5 miles north of Highway 70, and dissipated about 3.5 miles northwest of Grantsburg. The most severe damage was found where the tornado crossed Highway 70 about 1/2 mile west of the St. Croix River in Pine County. At this locations, a strapped down mobile home was completely destroyed - resulting in two injuries. Minor structural damage was also noted to several surrounding homes and buildings, including two garages that were destroyed. A couple of structures had their roofs removed. Tree damage at this location was also substantial, with almost all trees either snapped off or uprooted. An EF-2 rating is being assigned for about a 1 mile length of the tornado damage path where it crossed Highway 70, but most of the tornado damage was EF-0 or EF-1 intensity. EF-2 damage corresponds to estimated 3-second wind gusts of 111-135 miles per hour. A map of the damage path is available above. Track Map

Tornado - 4 NW Grantsburg, WI Burnett County, WI Date June 17, 2010 Time (Local) 9:05 PM CDT EF Rating EF-0 Est. Peak Winds 75 mph Path Length 0.6 miles Max Width 120 yards Injuries/Deaths 0/0 Summary: There was also a brief EF-0 tornado in Burnett County, Wisconsin, immediately following the longer tracked, stronger tornado. This tornado was about 4 miles northwest of Grantsburg, and occurred around 9:05 PM CDT. Some tree damage was noted with this tornado. This tornado is the northeast of the two paths in the track map to the right. This storm continued to the northeast and rotation persisted as evidenced in the radar image, but no other tornado was reported with this storm. Track Map

Tornado - Haypoint, MN Aitkin County, MN Date June 17, 2010 Time (Local) 8:05 PM CDT EF Rating EF-0 Est. Peak Winds 65 mph Path Length Unk Max Width Unk Injuries/Deaths 0/0 Summary: A citizen near Haypoint, or about 7 miles south of Hill City, took this photo (bottom right) of a brief tornado touchdown with their cell phone. A storm survey team was not able to find any damage, though the tornado was located in the Moose Willow State Wildlife Management area, which has a limited road network. The tornado touched down at 805 pm. A radar image from around that time is at right in lieu of a track map. Radar Image                                                                                   Radar image from the time of the tornado.

Tornado - Cass County Cass County, MN Date  June 17, 2010 Time (Local)  5:37-5:48 PM CDT EF Rating  EF-0 Est. Peak Winds  65 mph Path Length  9.76 mi Max Width  200 yards Injuries/Deaths  0/0 Summary: This was actually the first tornado of the event in the NWS Duluth County Warning Area. The tornado crossed from Wadena County and tracked into Cass County from about 6.0 miles northwest of Poplar, to the west side of Deer Lake. The path in Cass County was 9.76 miles long and about 200 yards wide, and involved mainly tree damage. The tornado affected Cass County between 537pm and 548pm. This tornado was produced by the same parent thunderstorm that produced the EF-4 tornado in Wadena, Minnesota. Track Map

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

Storm Reports

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE DULUTH MN
1142 AM CDT SAT JUN 19 2010

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

1257 PM     HAIL             2 S BACKUS              46.79N 94.51W 
06/17/2010  E1.75 INCH       CASS               MN   TRAINED SPOTTER 

1257 PM     HAIL             BACKUS                  46.82N 94.51W 
06/17/2010  M1.75 INCH       CASS               MN   NWS EMPLOYEE    

            TIME IS APPROXIMATE. 1 INCH DIAMETER HAIL WAS OBSERVED 
            STILL LAYING ON THE GROUND AT 135 PM...AND WAS LIKELY 
            LARGER WHEN IT FELL. OTHER OBSERVERS SAID THERE WAS SOME 
            GOLFBALL SIZE HAIL WHEN IT ORIGINALLY FELL.

1259 PM     HAIL             BACKUS                  46.82N 94.51W 
06/17/2010  E1.50 INCH       CASS               MN   PUBLIC          

            ALSO GUSTY WINDS REPORTED.

1259 PM     HAIL             BACKUS                  46.82N 94.51W 
06/17/2010  E1.00 INCH       CASS               MN   LAW ENFORCEMENT 

0110 PM     HAIL             HACKENSACK              46.93N 94.52W 
06/17/2010  E1.00 INCH       CASS               MN   TRAINED SPOTTER 

0147 PM     HAIL             6 SW BENA               47.28N 94.30W 
06/17/2010  E2.75 INCH       CASS               MN   PUBLIC          

            STARTED SMALL...GRADUALLY INCREASED TO GOLFBALL SIZE. A 
            FEW LARGE STONES UP TO BASEBALL SIZE WERE FOUND. REPORTED
            AT AND NEAR THE NEW LEECH LAKE CAMPGROUND. ALSO MENTIONED
            A SECOND HAND REPORT OF HAIL DAMAGE TO 
            VEHICLES...AWNINGS...AND BUILDINGS AROUND THE CITY OF 
            BENA TO THE NORTHEAST.

0147 PM     TSTM WND DMG     6 SW BENA               47.28N 94.30W 
06/17/2010                   CASS               MN   PUBLIC          

            SUBSTANTIAL WIND DAMAGE. THE WIND BLEW HARD ENOUGH TO 
            BLOW WATER THROUGH SEALS AROUND WINDOWS ON THE CAMPGROUND
            LODGE DURING HEIGHT OF STORM. A 100 LB ACCESS COVER ON 
            THE ROOF WAS THROWN THE ENTIRE LENGTH OF THE ROOF. DAMAGE
            TO SIDING AND SHINGLES. COVERS WERE TAKEN OFF THE BOAT 
            LIFT. TREES WERE DOWNED...AND A FEW WERE UPROOTED OR 
            SHEARED OFF. WINDS COULD HAVE BEEN IN EXCESS OF 70 MPH 
            BASED ON THE UPROOTED/SNAPPED TREES.

0200 PM     HAIL             BENA                    47.34N 94.21W 
06/17/2010  E1.75 INCH       CASS               MN   TRAINED SPOTTER 

            DELAYED REPORT FROM NEAR BENA.

0201 PM     HAIL             2 NW BENA               47.36N 94.24W 
06/17/2010  E1.00 INCH       CASS               MN   PUBLIC          

            UP TO QUARTER SIZE HAIL AT THE NODAK LODGE AND RESORT.

0210 PM     HAIL             8 NE BENA               47.42N 94.09W 
06/17/2010  E1.00 INCH       CASS               MN   PUBLIC          

            ALSO TREE LIMBS WERE DOWNED BY STRONG WINDS.

0215 PM     HAIL             11 NE BENA              47.45N 94.04W 
06/17/2010  E1.00 INCH       ITASCA             MN   PUBLIC          

            ALSO 60 MPH WINDS /ESTIMATED/ THAT BLEW DOWN TREES. 
            REPORTED AT THE LAKE WINNIE RESORT AND CAMPGROUND AT 
            INTERSECTION OF HWY 9 AND HWY 46.

0215 PM     TSTM WND DMG     6 SW INGER              47.49N 94.08W 
06/17/2010                   ITASCA             MN   LAW ENFORCEMENT 

            SOME SMALL TREES WERE BLOWN DOWN ACROSS A ROAD NEAR EAST 
            END OF LAKE WINNIBIGOSHISH.

0230 PM     TSTM WND DMG     2 NW BOWSTRING          47.56N 93.83W 
06/17/2010                   ITASCA             MN   TRAINED SPOTTER 

            LARGE BRANCHES ABOUT 8 TO 10 INCHES IN DIAMETER AND A FEW
            TREES DOWNED. DELAYED REPORT.

0300 PM     HAIL             WIRT                    47.73N 93.96W 
06/17/2010  M0.88 INCH       ITASCA             MN   AMATEUR RADIO   

0300 PM     HAIL             NORTH STAR LAKE         47.56N 93.66W 
06/17/2010  M0.88 INCH       ITASCA             MN   TRAINED SPOTTER 

0330 PM     HAIL             BOWSTRING               47.54N 93.80W 
06/17/2010  E0.75 INCH       ITASCA             MN   TRAINED SPOTTER 

            DIME TO PENNY SIZE HAIL FOR THE LARGEST STONES. MOSTLY 
            PEA TO 1/2 INCH IN DIAMETER.

0436 PM     HAIL             10 E TOGO               47.82N 92.94W 
06/17/2010  E0.88 INCH       ST. LOUIS          MN   TRAINED SPOTTER 

0439 PM     TSTM WND DMG     SNAKE TRAIL             47.71N 93.05W 
06/17/2010                   ST. LOUIS          MN   LAW ENFORCEMENT 

            SEVERE WIND GUSTS BENDING PINE TREES TO THE 
            GROUND...REPORT ALSO INDICATED THAT A FEW TREES WERE 
            BLOWN DOWN.

0450 PM     TSTM WND DMG     LINDEN GROVE            47.86N 92.87W 
06/17/2010                   ST. LOUIS          MN   LAW ENFORCEMENT 

            A FEW REPORTS OF TREES DOWN...ALONG HIGHWAY 1 NEAR LINDEN
            GROVE...AND ALSO ALONG HIGHWAY 5 SOUTH NEAR SIDE LAKE.

0620 PM     TSTM WND DMG     4 SE FIFTY LAKES        46.71N 94.04W 
06/17/2010                   CROW WING          MN   TRAINED SPOTTER 

            SOME TREE BRANCHES BLOWN DOWN.

0645 PM     TORNADO          4 ENE BREEZY POINT      46.62N 94.14W 
06/17/2010                   CROW WING          MN   LAW ENFORCEMENT 

            SPOTTERS TRACKING A TORNADO ON THE GROUND NEAR PELICAN 
            LAKE.

0753 PM     HAIL             SWATARA                 46.90N 93.67W 
06/17/2010  E1.75 INCH       AITKIN             MN   TRAINED SPOTTER 

0820 PM     HAIL             JACOBSON                47.00N 93.26W 
06/17/2010  E0.88 INCH       AITKIN             MN   TRAINED SPOTTER 

0820 PM     HAIL             1 W HILL CITY           46.99N 93.61W 
06/17/2010  E0.88 INCH       AITKIN             MN   TRAINED SPOTTER 

0821 PM     NON-TSTM WND DMG 1 S AITKIN              46.52N 93.71W 
06/17/2010                   AITKIN             MN   TRAINED SPOTTER 

            12 INCH DIAMETER PINE TREE BLOWN DOWN SOUTH SIDE OF 
            AITKIN.

0827 PM     HAIL             JACOBSON                47.00N 93.26W 
06/17/2010  E1.50 INCH       AITKIN             MN   PARK/FOREST SRVC

            REPORTED BY A STATE FOREST EMPLOYEE. ALSO A FEW TREES 
            DOWN IN THE SAVANNA STATE FOREST...BUT ANY DAMAGE WAS 
            VERY SPORADIC.

0830 PM     HAIL             2 NW MOOSE LAKE         47.41N 93.72W 
06/17/2010  E0.75 INCH       ITASCA             MN   TRAINED SPOTTER 

0855 PM     TORNADO          5 W GRANTSBURG          45.78N 92.79W 
06/17/2010  F1               PINE               MN   NWS STORM SURVEY

            A STRONG EF1 TORNADO CROSSED HWY 70, A 1/2 MILE WEST OF 
            THE MN/WI STATE LINE. THREE INJURIES HAVE BEEN REPORTED. 
            HWY 70 IS CLOSED DUE TO DEBRIS AND POWERLINES OVER THE 
            ROAD. TIME ESTIMATED FROM RADAR. 

0900 PM     FUNNEL CLOUD     5 S GRANTSBURG          45.71N 92.68W 
06/17/2010                   BURNETT            WI   TRAINED SPOTTER 

            FUNNEL IS ROTATING AND GOING UP AND DOWN BUT NO DEBRIS 
            VISIBLE. 

0900 PM     TORNADO          3 W GRANTSBURG          45.78N 92.75W 
06/17/2010                   BURNETT            WI   STORM CHASER    

            POWERLINES DOWN AND DAMAGE TO A HOME OBSERVED NEAR 
            GRANTBURG ON HIGHWAY 70. LIKELY TORNADO DAMAGE. 

0907 PM     TORNADO          2 ENE GRANTSBURG        45.79N 92.65W 
06/17/2010                   BURNETT            WI   TRAINED SPOTTER 

            OBSERVED TORNADO. THE TORNADO BLEW DOWN SOME LARGE 
            BRANCHES AND THREW SOME SMALL DEBRIS A COUPLE HUNDRED 
            YARDS. TIME IS APPROXIMATED BOTH FROM SPOTTER 
            RECOLLECTION AND RADAR DATA.

1008 PM     TORNADO          6 WNW WEBB LAKE         46.04N 92.25W 
06/17/2010                   BURNETT            WI   TRAINED SPOTTER 

            TORNADO REPORTED ON THE GROUND NEAR STAPLES LAKE ROAD.


&&

$$

Environment

A low pressure system rapidly deepened and intensified over the Dakotas on June 17th, drawing a warm, moist, and unstable air mass north into the Upper Midwest. The image to the left is a computer analyzed map from 3PM CDT that day. Black contours are sea level pressure, and thus you can pick out the area of low pressure in North Dakota. The shaded regions are surface dewpoints, with the brighter colors indicating higher dewpoints. Surface winds are indicated by the small barbs. Surface temperature is shown in colored contours.

Thunderstorms from overnight gradually weakened around dawn as they moved from eastern North Dakota into western Minnesota. A few thunderstorms developed along a warm front in central Minnesota late in the morning and then tracked into northern Minnesota in the early afternoon. Some of these storms were severe, particularly from Cass County into Itasca County - in the Backus to Squaw Lake corridor.

As a cold front surged east during the day into the humid air mass, thunderstorms began firing along the advancing front in the afternoon. This was the main round of severe weather, and the combination of strong instability and wind shear helped provide the necessary ingredients for supercell thunderstorms. These severe storms spread east across much of the state of Minnesota during the afternoon and early evening hours, spawning tornadoes, large hail, and damaging straight-line winds.

3PM CDT Surface Analysis	9PM CDT analyzed Significant Tornado Parameter (colored contours) - this parameter was developed to highlight areas where conditions are favorable for strong tornadoes. Values over 1 correspond to such environments and you can see these values extend up into the Pine and Burnett county areas.	9PM CDT analyzed instability (red contours). The axis of greatest instability extends north towards the western tip of Lake Superior.

Hail Producing Storms

Midday Storms in Cass and Itasca Counties

Thunderstorms developed around midday along a warm front near Cass County. Initially, the storms exhibited an intensity to rapidly fluctuate in intensity, and were not posing much of a threat for severe weather.

However, between Noon and 1 PM, a persistent severe thunderstorm developed and tracked through Cass County, eventually tracking to near Lake Winnibigoshish.

This storm produced golfball size hail in Backus in central Cass County. It was probably at its most intense over northeastern parts of Leech Lake where up to baseball size hail and destructive straight-line winds were reported. The large hail caused damage to some buildings and vehicles in and around Bena.

Radar derived hail size courtesy of the National Severe Storms Laboratory. You can see that a substantial hail swath extended through much of Cass County.	During the storm at the Leech Lake Campground courtesy Holly Ash.	An access cover ripped off the roof of the lodge at the Leech Lake Campground courtesy Holly Ash.

Evening Storms in Aitkin County

A swath of large hail also developed across northern Aitkin County during the evening hours. Up to golfball size hail was reported with this storm.

Radar derived hail size courtesy of the National Severe Storms Laboratory.

Photos

Photos from the damage survey in Pine County:

Photos from the St. Croix Landing camping area:

Aerial photos courtesy of the Pine County Sherif and Minnesota State Patrol, unless otherwise noted:

Northern Crow Wing County wall cloud photos courtesy Jason Rieber, Breezy Point Police Department:

Additional Information

Summaries from other NWS Offices

• Grand Forks, ND
• La Crosse, WI
• Twin Cities, MN