July 20, 2006 Squall Line/Bow Echo Wind Storm

During the early morning hours on July 20th, an intense and severe squall line traversed across southern Wisconsin. The initial thunderstorms developed over southern Minnesota Wednesday evening, just north of a warm front that extended from northern Iowa into northern Illinois. The thunderstorms quickly intensified and merged into a bow echo, or squall line over western Wisconsin. The bow echo then raced across southern Wisconsin resulting in numerous reports of downed trees. Power lines were also reported down along with an impressive 82 mph measured wind gust 0.4 miles northeast of Monona in Dane County. There were also scattered reports of hail up to one inch in diameter. Squall lines or bow echoes often occur just north of a warm front as warm and moist air several thousand feet above the ground moves northward. It is this warm...moist air aloft that fuels and maintains the squall line.

Click on the thumbnails below to see radar images reflectivity images as the bow echo moved across
southern Wisconsin.



Radar Image
148 AM CDT
Radar Image
234 AM CDT
Radar Image
316 AM CDT
Radar Image
354 AM CDT

Here is a link to a radar animation that runs from 1:19 am through 3:50 am CDT during the morning of July 20th.


Wind Gust Plot
Wind Gusts
Tree Damage
Tree Damage
Tree Damage
Tree Damage



PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
926 AM CDT THU JUL 20 2006

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

0130 AM         HAIL                             4 W PARDEEVILLE                           43.53N 89.38W
07/20/2006    M0.88 INCH                COLUMBIA                        WI            TRAINED SPOTTER

0209 AM         TSTM WND GST        PORTAGE                                           43.55N 89.47W
07/20/2006    E60.00 MPH               COLUMBIA                         WI             TRAINED SPOTTER

0215 AM         TSTM WND DMG       DODGEVILLE                                     42.96N 90.13W
07/20/2006                                          IOWA                                   WI             LAW ENFORCEMENT

                         TREE LIMBS DOWN CAUSING POWER OUTAGES ACROSS THE ENTIRE COUNTY.

0218 AM          TSTM WND GST        5 N PORTAGE                                    43.62N 89.47W
07/20/2006     E60.00 MPH               COLUMBIA                        WI             AMATEUR RADIO

0227 AM          TSTM WND GST        PARDEEVILLE                                   43.53N 89.30W
07/20/2006     E60.00 MPH               COLUMBIA                        WI             AMATEUR RADIO

0234 AM          TSTM WND GST        4 WNW MIDDLETON                        43.12N 89.58W
07/20/2006     E60.00 MPH               DANE                                  WI             AMATEUR RADIO

                          THREE INCH LIMBS BROKEN OFF TREES.

0235 AM          TSTM WND GST        2 WSW MOUNT HOREB                  43.00N 89.77W
07/20/2006     E60.00 MPH               DANE                                  WI             AMATEUR RADIO

                          THREE INCH LIMBS BROKEN OFF TREES.

0238 AM          TSTM WND DMG       2 SW SHOREWOOD HILLS            43.06N 89.47W
07/20/2006                                           DANE                                  WI            TRAINED SPOTTER

                          SIX INCH DIAMETER TREE DOWN.

0240 AM          TSTM WND GST        0.4 NE MONONA                                43.10N 89.28W
07/20/2006     M82.00 MPH               DANE                                  WI             TRAINED SPOTTER

                          MEASURED GUST OF 82 MPH AND POWER OUT.

0240 AM          HAIL                              5 NW MADISON                                 43.13N 89.46W
07/20/2006     M0.75 INCH                DANE                                  WI              TRAINED SPOTTER

                          ALSO ESTIMATES WIND GUSTS TO 50 MPH. MINOR TREE DAMAGE.

0240 AM          TSTM WND GST        4 NNE SUN PRAIRIE                         43.24N 89.20W
07/20/2006     E60.00 MPH               DANE                                   WI             CO-OP OBSERVER

0243 AM          TSTM WND DMG       1 NW SUN PRAIRIE                           43.19N 89.25W
07/20/2006                                           DANE                                   WI             TRAINED SPOTTER

                          SEVEN INCH TREE LIMBS DOWN.

0243 AM          TSTM WND DMG       FITCHBURG                                         42.99N 89.43W
07/20/2006                                           DANE                                   WI              TRAINED SPOTTER

                          UP TO 2 INCH DIAMETER TREE LIMBS DOWN.

0245 AM          TSTM WND DMG       W MADISON                                          43.08N 89.39W
07/20/2006                                           DANE                                   WI              TRAINED SPOTTER

                          OAK TREE DOWN...POWER LINES DOWN.

0245 AM          TSTM WND GST         7 S MONONA                                        42.95N 89.33W
07/20/2006     E60.00 MPH                DANE                                  WI               AMATEUR RADIO

                          POWER LINES DOWN.
 
0255 AM          TSTM WND DMG       SSE MADISON                                      43.08N 89.39W
07/20/2006                                           DANE                                  WI               TRAINED SPOTTER

                          TOP HALF OF A 6 INCH DIAMETER MAPLE TREE BROKEN OFF.

0300 AM          TSTM WND GST        S BELLEVILLE                                      42.86N 89.54W
07/20/2006     E60.00 MPH               DANE                                  WI                TRAINED SPOTTER

                          LARGE BRANCH DOWN ON SCHOOL ROAD WITH A POWER LINE DOWN.

0300 AM          TSTM WND DMG       NEW GLARUS                                       42.81N 89.63W
07/20/2006                                           GREEN                               WI                LAW ENFORCEMENT

                          CARS CRUSHED BY FALLING TREES.

0300 AM          TSTM WND DMG       WATERLOO                                           43.18N 88.99W
07/20/2006                                           JEFFERSON                      WI               LAW ENFORCEMENT

                          TREES AND POWER LINES DOWN.

0310 AM          TSTM WND DMG       BROOKLYN                                          42.85N 89.37W
07/20/2006                                           GREEN                               WI              LAW ENFORCEMENT

                          TREES DOWN. CARS ALSO CRASHING INTO FALLEN TREES ON THE ROADWAYS.

0315 AM          TSTM WND GST        W BRODHEAD                                    42.62N 89.38W
07/20/2006     E70.00 MPH               GREEN                               WI              TRAINED SPOTTER

                          LARGE ELM TREE DOWN...SEVERAL ANTENNAS MISSING.

0320 AM          TSTM WND DMG       ALBANY                                                42.71N 89.44W
07/20/2006                                           GREEN                               WI             LAW ENFORCEMENT

                          TREES AND POWER LINES DOWN.

0325 AM          TSTM WND DMG       JANESVILLE                                       42.68N 89.02W
07/20/2006                                           ROCK                                  WI            LAW ENFORCEMENT

                          NUMEROUS REPORTS OF TREES DOWN ACROSS THE COUNTY.

0325 AM          LIGHTNING                MILTON                                                42.78N 88.95W
07/20/2006                                           ROCK                                  WI            LAW ENFORCEMENT

                          LIGHTNING STRUCK A BARN AND STARTED IT ON FIRE.

0325 AM          TSTM WND DMG       ROME                                                   42.98N 88.63W
07/20/2006                                           JEFFERSON                      WI            LAW ENFORCEMENT

                          TREES DOWN ON COUNTY ROAD Y...JUST WEST OF THE VILLAGE OF ROME.

0330 AM          TSTM WND DMG       4 SSW DOUSMAN                             42.96N 88.50W
07/20/2006                                           WAUKESHA                       WI            NWS EMPLOYEE

                          TREE LIMBS DOWN ON HWY 67 ABOUT 1/2 MILE NORTH OF COUNTY ROAD ZZ. TWO TO 3’ DIAMETER TREE DOWN 1 MILE WEST OF 67 ON COUNTY ROAD C.

0340 AM          TSTM WND DMG        ELKHORN                                          42.67N 88.54W
07/20/2006                                            WALWORTH                     WI             LAW ENFORCEMENT

                          DOZEN TREES DOWN SCATTERED ACROSS THE COUNTY...TWO POWER LINES DOWN...CALLS RECEIVED BY DISPATCH STARTING AROUND 345 AM.

0345 AM          TSTM WND GST         BROOKFIELD                                   43.06N 88.12W
07/20/2006     E60.00 MPH                WAUKESHA                      WI            TRAINED SPOTTER

0351 AM          TSTM WND DMG        BROOKFIELD                                   43.06N 88.12W
07/20/2006                                            WAUKESHA                      WI            LAW ENFORCEMENT

                          POWER LINES DOWN.

0355 AM          TSTM WND DMG         BURLINGTON                                 42.68N 88.28W
07/20/2006                                             RACINE                            WI            LAW ENFORCEMENT

                          TREE LIMB DOWN ON POWER LINE IN BURLINGTON. MORE TREE LIMBS DOWN ACROSS WESTERN RACINE COUNTY.

0410 AM          TSTM WND DMG        PADDOCK LAKE                              42.57N 88.10W
07/20/2006                                            KENOSHA                        WI            LAW ENFORCEMENT

                          TREE LIMB BLOCKING ROAD WITH POWER OUTAGES.

0614 AM          TSTM WND DMG        5 S BLUE MOUNDS                        42.95N 89.83W
07/20/2006                                            DANE                                 WI            TRAINED SPOTTER

                          3 INCH TREE BRANCHES BLOWN DOWN.

0623 AM          TSTM WND DMG        NEW GLARUS                                  42.81N 89.63W
07/20/2006                                            GREEN                              WI            LAW ENFORCEMENT
 
                          TREES DOWN.

0630 AM          HAIL                              NEW GLARUS                                  42.81N 89.63W
07/20/2006     E0.25 INCH                 GREEN                              WI            LAW ENFORCEMENT

0642 AM          HAIL                              ALBANY                                              42.71N 89.44W
07/20/2006     E0.75 INCH                 GREEN                              WI            TRAINED SPOTTER


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