NW Wisconsin deadly tornadic supercell  6/18/01     (information accumulated by Jon Davies, Wichita, KS)

As an overview, following are selected maps, satellite, and radar images from the NW Wisconsin tornadic supercell event the evening of 6/18/01. 

A large tornado struck Siren, Wisconsin (Burnett Co.) around 8:25 pm CDT, killing 3 and injuring 8 seriously, according to preliminary reports.  From the model analysis profiles and SPC-generated mesoanalyses shown below, low-level and deep layer shear and low-level CAPE (suggested by low LFC heights) came together over EC Minnesota and NW Wisconsin to provide a very favorable environment for tornadic supercells.  The southernmost storm of the group that formed east of St. Cloud between 23 UTC and 00 UTC organized into a large supercell that prompted tornado warnings by 0030 UTC.  Burnett Co. in Wisconsin was under a tornado warning for nearly an hour before the large 1/2 mile wide tornado struck Siren. 

A satellite view of the damage path through this wooded area is at http://www.news.wisc.edu/newsphotos/siren.htm.   Al Pietrycha's review and material on this case are at http://stormeyes.org/pietrycha/vortex/010618/010618.html.

<23 UTC 6/18/01 sfc map    <2321 UTC 6/18/01 MPX lradar base ref.

<2345 UTC 6/18/01 visible satellite GOES-8

<00 UTC 6/19/01 sfc map    <0037 UTC 6/19/01 MPX radar base ref.

<01 UTC 6/19/01 visible satellite GOES-8   

<01 UTC 6/19/01 sfc map    <0102 UTC 6/19/01 MPX radar base ref.

SPC Mesoscale Analysis fields 01 UTC 6/19/01 (low-level and deep layer shear, CAPE, low-level thermodynamics):
<0-1km EHI  <CAPE & BRN shear  <LFC ht AGL

  <0130, 0153 UTC 6/19/01 DLH radar base ref.  (Siren WI was struck shortly before 0130 UTC.)

<00 UTC RUC-2 analysis profile for RZN (Webster/Siren area).  This is a profile that appears very supportive of supercell tornadoes with plenty of shear (> 65 kts 0-6 km shear!) and s-r flow at all levels, as well as good low-level CAPE (113 J/kg below 3 km AGL).

Compare the RZN profile with:
<00 UTC RUC-2 analysis profile for ONA (Winona/Eau Claire area).  This profile was associated with a supercell near Osseo (100+ miles S of Siren) which had a tornado warning based on radar, but failed to produce a tornado.  The CAPE is similar and the low-level shear is stronger even than the Siren profile, but the s-r mid and upper flow is not as good, and low-level CAPE is sparse (less than 20 J/kg below 3 km AGL).  Sfc-based CIN is also 3 times larger and distributed through a deeper layer than with the Siren profile.   The lack of favorable low-level thermodynamic factors further south may have contributed to more low-level stability and less potential for tornadoes in spite of the strong low-level shear, although this is certainly unclear.  See primer on low-level buoyancy for more information about low-level thermodynamic factors..

Below are selected warnings and statements for this storm from MPX and DLH NWS offices between 23 and 02 UTC:

SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
611 PM CDT MON JUN 18 2001

THE NATIONAL WEATHER SERVICE IN THE TWIN CITIES HAS ISSUED A
* SEVERE THUNDERSTORM WARNING FOR...
BENTON COUNTY IN CENTRAL MINNESOTA
MILLE LACS COUNTY IN EAST CENTRAL MINNESOTA
* UNTIL 700 PM CDT

* AT 611 PM CDT...RADAR INDICATED A SEVERE THUNDERSTORM WITH LARGE
HAIL OVER GILMAN...OR ABOUT 13 MILES WEST OF MILACA...MOVING EAST
AT 25 MPH.

* SOME LOCATIONS AFFECTED BY THIS STORM INCLUDE...
RONNEBY. PEASE. MILACA. GILMAN. FORESTON. FOLEY.

THIS IS A DANGEROUS STORM...STAY INDOORS AWAY FROM WINDOWS. SEVERE
THUNDERSTORMS CAN PRODUCE TORNADOES WITH LITTLE OR NO ADVANCE
WARNING.
----------------------------

TORNADO WARNING
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
714 PM CDT MON JUN 18 2001

THE NATIONAL WEATHER SERVICE IN THE TWIN CITIES HAS ISSUED A
* TORNADO WARNING FOR...
KANABEC COUNTY IN EAST CENTRAL MINNESOTA
ISANTI COUNTY IN EAST CENTRAL MINNESOTA
* UNTIL 745 PM CDT

* AT 714 PM CDT...RADAR INDICATED A DEVELOPING TORNADO 7 MILES
SOUTHEAST OF OGILVIE...OR ABOUT 9 MILES SOUTH OF MORA...MOVING EAST
AT 30 MPH.

* SOME LOCATIONS IN THE PATH OF THIS TORNADO INCLUDE...
OGILVIE.  GRASSTON.  BRAHAM.

GO TO THE BASEMENT OR A SMALL INTERIOR ROOM ON THE LOWEST FLOOR!
----------------------------

TORNADO WARNING
NATIONAL WEATHER SERVICE DULUTH MN
731 PM CDT MON JUN 18 2001

THE NATIONAL WEATHER SERVICE HAS ISSUED A
* TORNADO WARNING FOR...
BURNETT COUNTY IN WISCONSIN
SOUTHERN PINE COUNTY IN MINNESOTA

* UNTIL 830 PM CDT

* AT 731 PM CDT DOPPLER RADAR INDICATED A DEVELOPING TORNADO 3 MILES
SOUTH OF HENRIETTE...OR ABOUT 15 MILES SOUTHWEST OF HINCKLEY...
MOVING EAST AT 35 MPH.

* THIS TORNADO WILL BE NEAR...
PINE CITY THROUGH 750 PM  GRANTSBURG AROUND 755 PM CDT  YELLOWLAKE AROUND 820 PM CDT

THERE HAVE BEEN REPORTS OF FUNNEL CLOUDS IN SOUTHWEST PINE COUNTY.
GO TO THE BASEMENT OR A SMALL INTERIOR ROOM ON THE LOWEST FLOOR!
-----------------------------

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE DULUTH MN
821 PM CDT MON JUN 18 2001

...A TORNADO WARNING CONTINUES UNTIL 830 PM CDT FOR BURNETT COUNTY...

AT 820 PM CDT LAW ENFORCEMENT OFFICIALS REPORTED A TORNADO ON THE
GROUND 5 MILES WEST OF SIREN. TORNADO IS MOVING EAST AT 45 MPH.
SEEK SHELTER NOW!

AN EXTREMELY POWERFUL AND DANGEROUS TORNADO IS ON THE GROUND. IF YOU
ARE IN OR NEAR THE PATH OF THIS TORNADO...TAKE COVER NOW!
-------------------------------

TORNADO WARNING
NATIONAL WEATHER SERVICE DULUTH MN
830 PM CDT MON JUN 18 2001

THE NATIONAL WEATHER SERVICE HAS ISSUED A
* TORNADO WARNING FOR...
BURNETT COUNTY IN WISCONSIN
WASHBURN COUNTY IN WISCONSIN
* UNTIL 930 PM CDT

* AT 830 PM CDT LOCAL LAW ENFORCEMENT OFFICIALS REPORTED A TORNADO
OVER SIREN...OR ABOUT 31 MILES SOUTHEAST OF HINCKLEY...MOVING EAST
AT 25 MPH.

* THIS TORNADO WILL BE NEAR...
SIREN THROUGH 845 PM CDT  HERTEL AROUND 845 PM CDT  SPOONER AROUND 910 PM CDT
SHELL LAKE AROUND 915 PM CDT  SARONA AROUND 920 PM CDT

AN EXTREMELY POWERFUL AND DANGEROUS TORNADO IS ON THE GROUND. IF YOU
ARE IN OR NEAR THE PATH OF THIS TORNADO...TAKE COVER NOW!
----------------------------