Severe Storms and Gustnadoes: June 14, 2008

Plenty of sunshine was the rule during the day on Saturday, June 14 over much of central Minnesota. The ground had ample time to heat up and encouraged development of strong thunderstorms over west central Minnesota by evening. The thunderstorms turned severe and moved swiftly across the state, making the journey from Alexandria to the Twin Cities in about two hours. A strong gust front developed out ahead of the storms and produced "gustnadoes" or tornado look-a-like formations. This lead to many false tornado reports that day. There were pockets of damage due to the winds. Trees and branches were blown down due to the strong winds, and sent many people who were enjoying the day scurrying for cover.

The National Weather Service in Chanhassen commented on the gustnadoes associated with this event. Below is a recap that was posted on their Web site.


What was with all those Tornado Reports Saturday evening?

Saturday evening saw a rash of severe weather across central Minnesota, 
as a powerful squall line raced down I-94 through western Minnesota and 
into the Twin Cities.  Trained spotters and law enforcement agencies provided many 
valuable reports of hail as large as nickels, measured wind speeds as high 
as 65 mph, and downed trees, tree limbs, and structural damage from 
the high winds.  

However, those are not the only reports received at the NWS in Chanhassen 
on Saturday evening.  There were also many independent reports of tornadoes, 
as the line of storms swept southeastward across central Minnesota.  
The first reports came from the Alexandria and Long Prairie vicinities, 
with the emergency dispatch centers from Douglas, Pope, and Todd counties
calling to notify us of reported tornadoes in their respective counties.  
Not long after these reports were received, calls began pouring in from 
Kandiyohi, Meeker, and Stearns counties, including a report near 
New London, where two law enforcement officers and two trained spotters 
independently reported a tornado.

As these calls flooded the NWS office, the meteorologists watching 
and warning for the storms were a bit surprised.  The radar data showed 
no rotation conducive to even a small tornado spin-up, and the very 
dry atmosphere made the environment unfavorable for tornado development.  
As the reports were coming into the office, personnel concluded that 
these were likely "gustnadoes" on the gust front boundary emanating 
from the squall line, and these thoughts were relayed to the various
law enforcement agencies and other spotters in the area.  
Photos and video of several of these tornado reports have been received 
and reviewed, confirming the initial thoughts that these were harmless "gustnadoes".

Some of you may be asking...  What is a gustnado?  Is it a tornado?  
Is it dangerous?

A gustnado is a rotating column of air that forms as a result of turbulence 
along a thunderstorm gust front boundary.  Gustnadoes are associated with 
shelf clouds, a cloud structure that is often confused with a wall cloud, which 
is sometimes a tornadic cloud feature.  A gustnado is not a tornado, and
it is not dangerous.

On Saturday evening, the gust front boundary was clearly evident in radar 
data from the Chanhassen Doppler radar, and often, many of the reports 
occurred several miles ahead of the main area of precipitation with the 
squall line, which is where the gust front was located.  As the shelf 
cloud associated with the squall line moved over the NWS office in 
Chanhassen, meteorologists observed the turbulence within it, seeing 
how it could be confused with a more dangerous wall cloud feature and 
consequently, result in the volume of tornado reports.

We very much appreciate all of the valuable reports from the volunteers 
that we receive during active weather in Minnesota and Wisconsin, and 
we would like to thank you all for the service that you provide for us 
and the safety of the communities you live in.

Listed below are Local Storm Reports from the National Weather Service.

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
830 PM CDT SUN JUN 15 2008

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

0713 PM     HAIL             ALEXANDRIA              45.87N 95.38W
06/14/2008  E0.75 INCH       DOUGLAS            MN   TRAINED SPOTTER

            WIND GUST OF 56 MPH MEASURED AT ALEXANDRIA AIRPORT.

0808 PM     HAIL             MELROSE                 45.68N 94.81W
06/14/2008  M0.88 INCH       STEARNS            MN   AMATEUR RADIO

0818 PM     HAIL             4 W ATWATER             45.14N 94.86W
06/14/2008  M0.25 INCH       KANDIYOHI          MN   TRAINED SPOTTER

0834 PM     HAIL             ST CLOUD                45.55N 94.17W
06/14/2008  M0.88 INCH       STEARNS            MN   TRAINED SPOTTER

0838 PM     TSTM WND GST     7 S HILLMAN             45.91N 93.89W
06/14/2008  M60.00 MPH       MORRISON           MN   TRAINED SPOTTER

0844 PM     HAIL             4 N SPICER              45.29N 94.94W
06/14/2008  M0.75 INCH       KANDIYOHI          MN   TRAINED SPOTTER

0848 PM     HAIL             ATWATER                 45.14N 94.78W
06/14/2008  M0.88 INCH       KANDIYOHI          MN   TRAINED SPOTTER

            COUNTY RD 2 AND 28

0855 PM     TSTM WND GST     MONTICELLO              45.30N 93.80W
06/14/2008  M63.70 MPH       WRIGHT             MN   TRAINED SPOTTER

0858 PM     TSTM WND GST     CLEARWATER              45.41N 94.04W
06/14/2008  M53.00 MPH       WRIGHT             MN   MESONET

0900 PM     HAIL             GROVE CITY              45.15N 94.68W
06/14/2008  M0.75 INCH       MEEKER             MN   TRAINED SPOTTER

0900 PM     TSTM WND DMG     MONTICELLO              45.30N 93.80W
06/14/2008                   WRIGHT             MN   TRAINED SPOTTER

            11 INCH BRANCHES DOWN

0900 PM     TSTM WND GST     MILACA                  45.76N 93.65W
06/14/2008  M57.00 MPH       MILLE LACS         MN   MESONET

0908 PM     TSTM WND GST     LESTER PRAIRIE          44.88N 94.04W
06/14/2008  M66.00 MPH       MCLEOD             MN   MESONET

0910 PM     TSTM WND DMG     BIG LAKE                45.34N 93.75W
06/14/2008                   SHERBURNE          MN   TRAINED SPOTTER

            8 INCH TREE DOWN 4.6 MILES NORTH OF HWY 10 ON COUNTY ROAD
            5

0910 PM     TSTM WND DMG     MAPLE GROVE             45.11N 93.46W
06/14/2008                   HENNEPIN           MN   BROADCAST MEDIA

            SIX TO TEN INCH DIAMETER TREE DOWN

0912 PM     TSTM WND GST     WINSTED                 44.97N 94.05W
06/14/2008  E60.00 MPH       MCLEOD             MN   TRAINED SPOTTER

0912 PM     TSTM WND DMG     WAYZATA                 44.97N 93.51W
06/14/2008                   HENNEPIN           MN   TRAINED SPOTTER

            60 FOOT TREE DOWN ACROSS POWER LINES WITH POWER OUTAGE IN
            AREA

0915 PM     TSTM WND DMG     ST LOUIS PARK           44.95N 93.36W
06/14/2008                   HENNEPIN           MN   TRAINED SPOTTER

            ONE FOOT DIAMETER TREE DOWN WITH STRUCTURE DAMAGE TO ROD
            IRON RAILING

0915 PM     TSTM WND GST     MAPLE PLAIN             45.01N 93.66W
06/14/2008  E60.00 MPH       HENNEPIN           MN   TRAINED SPOTTER

0917 PM     TSTM WND DMG     WACONIA                 44.85N 93.79W
06/14/2008                   CARVER             MN   NWS EMPLOYEE

            3-FOOT DIAMETER TREE SNAPPED OFF TWO TO THREE FEET ABOVE
            GROUND

0917 PM     TSTM WND DMG     WACONIA                 44.85N 93.79W
06/14/2008                   CARVER             MN   LAW ENFORCEMENT

            LARGE TREES DOWN

0919 PM     HAIL             DASSEL                  45.08N 94.31W
06/14/2008  M0.75 INCH       MEEKER             MN   TRAINED SPOTTER

0920 PM     TSTM WND DMG     CHASKA                  44.82N 93.61W
06/14/2008                   CARVER             MN   PUBLIC

            SHINGLES TORN OFF ROOFS AT THE UNIVERSITY OF MINNESOTA
            ARBORETUM.

0925 PM     TSTM WND DMG     ANOKA                   45.21N 93.39W
06/14/2008                   ANOKA              MN   AMATEUR RADIO

            4 INCH DIAMETER BRANCHES DOWN

0926 PM     TSTM WND GST     FRIDLEY                 45.08N 93.26W
06/14/2008  M60.00 MPH       ANOKA              MN   AMATEUR RADIO

            AT INTERSTATE 694 AND HWY 65

0928 PM     TSTM WND DMG     EDINA                   44.89N 93.36W
06/14/2008                   HENNEPIN           MN   TRAINED SPOTTER

            SEVERAL TREE BRANCHES 3-4 INCHES IN DIAMETER FELLED.

0928 PM     TSTM WND DMG     EDINA                   44.89N 93.36W
06/14/2008                   HENNEPIN           MN   TRAINED SPOTTER

            THREE INCH BRANCH DOWN AT HWY 62 AND TRACY AVENUE

0930 PM     TSTM WND DMG     3 NNW BLOOMINGTON       44.87N 93.34W
06/14/2008                   HENNEPIN           MN   TRAINED SPOTTER

            RETIRED NWS EMPLOYEE REPORTS AT LEAST 8 UPROOTED LARGE
            TREES IN A CONCENTRATED AREA ON HIBISCUS AVENUE BETWEEN A
            SMALL LAKE AND LAKE EDINA PARK. ESTIMATED SPEEDS OF 75
            MPH OCCURRED. TIME ALSO ESTIMATED.

0930 PM     TSTM WND DMG     EDEN PRAIRIE            44.85N 93.46W
06/14/2008                   HENNEPIN           MN   FIRE DEPT/RESCUE

            TWO 24-INCH TREES DOWN AT EDEN PRAIRIE ROAD AND JUST
            NORTH OF HWY 5

0930 PM     TSTM WND DMG     5 NNE MINNEAPOLIS       45.03N 93.23W
06/14/2008                   HENNEPIN           MN   TRAINED SPOTTER

            THIRTY TO 36 INCH DIAMETER TREE DOWN AT 3417 BELDEN DRIVE
            IN ST. ANTHONY.

0935 PM     TSTM WND DMG     5 NNE MINNEAPOLIS       45.03N 93.23W
06/14/2008                   HENNEPIN           MN   TRAINED SPOTTER

            A 20 AND 30 INCH DIAMETER TREES TOPPLED. DAMAGE OCCURRED
            IN ST. ANTHONY AT 2415 30TH AVE.

0935 PM     TSTM WND DMG     5 NNE MINNEAPOLIS       45.03N 93.23W
06/14/2008                   HENNEPIN           MN   TRAINED SPOTTER

            A 28 INCH DIAMETER TREE FELLED AT 30TH AND STINSON AVE IN
            THE CITY OF ST. ANTHONY.

0935 PM     TSTM WND DMG     5 NNE MINNEAPOLIS       45.03N 93.23W
06/14/2008                   HENNEPIN           MN   TRAINED SPOTTER

            AN 18 INCH DIAMETER TREE TOPPLED AT 3205 BELLE LANE IN
            ST. ANTHONY.

0936 PM     TSTM WND GST     MINNEAPOLIS             44.88N 93.22W
06/14/2008  M62.00 MPH       HENNEPIN           MN   ASOS

0940 PM     TSTM WND DMG     MINNEAPOLIS             44.96N 93.27W
06/14/2008                   HENNEPIN           MN   AMATEUR RADIO

            TWO FOOT DIAMETER TREES DOWN AT 43RD AND XERXES AVENUE
            SOUTH

0941 PM     TSTM WND GST     ST PAUL                 44.93N 93.06W
06/14/2008  M60.00 MPH       DAKOTA             MN   ASOS

0941 PM     TSTM WND DMG     MINNEAPOLIS             44.96N 93.27W
06/14/2008                   HENNEPIN           MN   AMATEUR RADIO

            6 TO 8 INCH BRANCHES DOWN AT CEDAR AVENUE AND NAKOMIS

0943 PM     TSTM WND DMG     COTTAGE GROVE           44.82N 92.93W
06/14/2008                   WASHINGTON         MN   TRAINED SPOTTER

            TENTS AND STAGE ITEMS BLOWN OVER AT CITY FESTIVAL. TWO
            PEOPLE RECEIVED MINOR INJURIES WHEN TENT STRUCK THEM.

0958 PM     TSTM WND DMG     BLOOMINGTON             44.83N 93.32W
06/14/2008                   HENNEPIN           MN   TRAINED SPOTTER

            6 TO 8 INCH BRANCHES DOWN AT HWY 169 AND OLD SHAKOPEE RD.


1002 PM     TSTM WND DMG     COTTAGE GROVE           44.82N 92.93W
06/14/2008                   WASHINGTON         MN   TRAINED SPOTTER

            SMALL TREE FELL OVER ROAD

1003 PM     TSTM WND DMG     MAPLEWOOD               44.99N 93.02W
06/14/2008                   RAMSEY             MN   TRAINED SPOTTER

            FOUR INCH TREE DOWN

1028 PM     TSTM WND DMG     CLAYTON                 45.32N 92.17W
06/14/2008                   POLK               WI   TRAINED SPOTTER

            THREE TO FOUR INCH DIAMETER BRANCHES DOWN.

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS
947 PM CDT SAT JUN 14 2008

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
           ..REMARKS..
0530 PM     HAIL             4 W BORUP               47.18N 96.59W 
06/14/2008  E0.88 INCH       NORMAN             MN   PUBLIC          
            DIME TO NICKEL SIZED HAIL COVERING THE GROUND IN SPOTS.

0535 PM     TSTM WND DMG     FARGO                   46.88N 96.82W 
06/14/2008                   CASS               ND   AMATEUR RADIO   
            BRANCHES 2 INCHES IN DIAMETER DOWN ALONG WITH SOME STREET
            SIGNS. 4 INCH BRANCHES DOWN AT INTERSECTION OF 26TH ST   
            AND 13TH AVE. MORE AND MORE LARGER BRANCHES DOWN AS YOU           
            MOVE EAST CLOSER TO THE RED RIVER.

0545 PM     TSTM WND DMG     WEST FARGO              46.87N 96.90W 
06/14/2008                   CASS               ND   AMATEUR RADIO   
            TREE DOWN IN THE NORTH END OF WEST FARGO.

0612 PM     FUNNEL CLOUD     4 W FERGUS FALLS        46.28N 96.15W 
06/14/2008                   OTTER TAIL         MN   TRAINED SPOTTER 

0643 PM     HAIL             ELBOW LAKE              45.99N 95.98W 
06/14/2008  E0.75 INCH       GRANT              MN   TRAINED SPOTTER            
            HAIL LASTED FOR FIVE MINUTES.

0816 PM     TSTM WND GST     2 NNW FARGO             46.90N 96.83W 
06/14/2008  M63.00 MPH       CASS               ND   ASOS            
            MEASURED AT KFAR FARGO HECTOR AIRPORT. 

0830 PM     TSTM WND GST     BELTRAMI                47.54N 96.53W 
06/14/2008  E60.00 MPH       POLK               MN   FIRE DEPT/RESCUE

0840 PM     TSTM WND DMG     HENDRUM                 47.26N 96.81W 
06/14/2008                   NORMAN             MN   LAW ENFORCEMENT 
            POWER OUT DUE TO TRANSFORMER DAMAGE.

0840 PM     TSTM WND DMG     ADA                     47.30N 96.51W 
06/14/2008                   NORMAN             MN   LAW ENFORCEMENT 
            POWER OUT IN ADA AREA...TRANSFORMERS DAMAGED AND TREES 
            DOWN.

0840 PM     TSTM WND GST     5 ESE MOORHEAD          46.84N 96.66W 
06/14/2008  E60.00 MPH       CLAY               MN   TRAINED SPOTTER 
            JUST NORTH OF I-94 AT MP 5.

0921 PM     TSTM WND GST     2 S MAHNOMEN            47.29N 95.97W 
06/14/2008  M58.00 MPH       MAHNOMEN           MN   MESONET         
            MEASURED AT THE MNDOT RWIS SITE NEAR HWY 59.