May 14, 2013 Thunderstorms & Heat Burst

Isolated thunderstorms caused extensive wind damage across portions of south central and southeast Wisconsin during the evening hours of Tuesday, May 14th.  The thunderstorms were weakening as they moved across southern Wisconsin. However, rain falling into dry air near the ground evaporated completely in some areas and only partially evaporated in others. This explains the light returns on the radar reflectivity as the decaying storms moved through the region. But, it was this evaporative process that generated the strong winds.  Below is a loop of radar reflectivity from 730 to 930 pm.  The circled areas highlight where the worst wind damage was occuring.  Note how weak the radar returns look for storms that caused so much damage.

MKX Radar Reflectivity

The evaporating rain caused the air to cool, become more dense than the air around it, and sink rapidly to the ground.  The event last night showed signs of being a heat burst event.  In a heat burst, all of the water in the sinking air is evaporated before it reaches the ground, and the air begins to warm before it hits the ground.  The air rushes to the ground as a sudden burst of hot, gusty wind.  For more information about heat bursts, visit the NWS Norman, OK website at http://www.crh.noaa.gov/oun/?n=heatburst_info .

The weather instruments at our office near Sullivan reported nearly a 10-degree temperature rise coincident with sustained winds of 20 mph and gusts up to 39 mph between 8 and 9 pm.  See the image below.

 MKX Observations

The seemingly "weak" thunderstorms produced damaging straight-line winds from northern Dane county all the way east to Lake Michigan and also in portions of Rock and Walworth counties.  Strong winds can be detected by Doppler radar.  Below is a loop of radar velocity from 730 pm to 930 pm.  The green colors indicate that air is moving toward the radar (the black dot near the middle of the radar image), and the red colors show the air moving away from the radar.  The brighter green/blue and red/pink/orange colors correlate with the strongest winds.  The general path of the wind damage is annotated at the beginning of the animation.

 MKX Radar Velocity loop

There were numerous reports of downed trees and power lines across Dane, Jefferson, Waukesha, Milwaukee, Rock and Walworth counties Tuesday evening.  The Local Storm Report (LSR) graphic and text summary are posted below: 

 

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1105 PM CDT TUE MAY 14 2013

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

0800 PM     TSTM WND GST     SAUK CITY               43.27N 89.73W
05/14/2013  E50.00 MPH       SAUK               WI   TRAINED SPOTTER

            3 INCH DIAMETER TREE BRANCHES BLOWN DOWN. CONSTRUCTION
            BARRELS BLOWN OVER. REPORT RELAYED FROM NWS-LA CROSSE.

0800 PM     TSTM WND GST     SUN PRAIRIE             43.18N 89.23W
05/14/2013  E60.00 MPH       DANE               WI   TRAINED SPOTTER

            MULTIPLE POWER LINES DOWN AND/OR SNAPPED OFF, LIGHT POLE
            DOWN, WINDSPREAD 2 FT DIAMETER TREES DOWN

0815 PM     TSTM WND GST     ASHIPPUN                43.21N 88.52W
05/14/2013  E50.00 MPH       DODGE              WI   PUBLIC

            HWY 67 AND 0.

0815 PM     TSTM WND DMG     MARSHALL                43.17N 89.06W
05/14/2013                   DANE               WI   TRAINED SPOTTER

            6 INCH TREE LIMBS DOWN, SIDING, GUTTERS, DOWNSPOUTS TORN
            OFF HOUSE

0820 PM     TSTM WND DMG     WATERLOO                43.18N 88.99W
05/14/2013                   JEFFERSON          WI   PUBLIC

            LARGE BARN BLOWN DOWN AND 4 X 4 POSTS RIPPED OUT OF THE
            GROUND AT W7769 HIGHLAND ROAD. REPORT RELAYED BY
            JEFFERSON COUNTY SHERIFF AT 1040 PM.

0835 PM     TSTM WND GST     2 SE OCONOMOWOC         43.09N 88.47W
05/14/2013  E50.00 MPH       WAUKESHA           WI   TRAINED SPOTTER

            SUSTAINED 50 MPH WINDS WITH GUSTS UP TO 65 MPH

0840 PM     TSTM WND GST     OCONOMOWOC              43.11N 88.50W
05/14/2013  M68.00 MPH       WAUKESHA           WI   TRAINED SPOTTER

            TIME ESTIMATED. SOCIAL MEDIA REPORT.

0855 PM     TSTM WND DMG     HARTLAND                43.10N 88.34W
05/14/2013                   WAUKESHA           WI   BROADCAST MEDIA

            WAUKESHA COUNTY SHERIFF REPORTED TREES AND POWER LINES
            DOWN IN HARTLAND...MERTON AND DELAFIELD AREAS. RELAYED BY
            TV MEDIA VIA SOCIAL MEDIA.

0857 PM     TSTM WND DMG     3 E PEWAUKEE            43.09N 88.19W
05/14/2013                   WAUKESHA           WI   PUBLIC

            60 FOOT PINE TREE DOWN. TIME ESTIMATED. RELAYED VIA
            SOCIAL MEDIA.

0900 PM     TSTM WND DMG     DELAFIELD               43.07N 88.39W
05/14/2013                   WAUKESHA           WI   LAW ENFORCEMENT

            WIRES AND TREES DOWN IN THE DELAFIELD...MERTON...AND
            HARTLAND AREAS.

0905 PM     TSTM WND GST     WAUWATOSA               43.06N 88.03W
05/14/2013  E50.00 MPH       MILWAUKEE          WI   TRAINED SPOTTER

            ESTIMATED SUSTAINED WINDS OF 30 MPH WITH GUSTS TO 50 MPH
            ON I-94/MILWAUKEE COUNTY ZOO. CONSTRUCTION BARRELS BLOWN
            AROUND AND LOOSE CARDBOARD DEBRIS FLYING IN THE AIR.

0920 PM     TSTM WND DMG     3 SW MILWAUKEE          43.00N 87.96W
05/14/2013                   MILWAUKEE          WI   BROADCAST MEDIA

            MILWAUKEE FIRE DEPARTMENT REPORTED SEVERAL TREE
            FIRES...LIVE WIRES DOWN AND TREES DOWN. TIME ESTIMATED.
            HOUSE FIRE DUE TO LIVE WIRES ON HOUSE. RELAYED BY TV
            MEDIA VIA SOCIAL MEDIA.

0930 PM     TSTM WND DMG     WEST ALLIS              43.01N 88.03W
05/14/2013                   MILWAUKEE          WI   PUBLIC

            LARGE BRANCHES DOWN NEAR 71ST AND BECHER STREET. SOCIAL
            MEDIA REPORT.

0941 PM     TSTM WND DMG     3 N MILWAUKEE INTERNATI 42.99N 87.90W
05/14/2013                   MILWAUKEE          WI   AMATEUR RADIO

            AT INTERSECTION OF HOWELL AND MORGAN AVENUES...6 INCH TO
            8 INCH DIAMETER TREE ACROSS THE ROAD.

0945 PM     TSTM WND GST     MILWAUKEE C-MAN         43.05N 87.88W
05/14/2013  M39.00 MPH       MILWAUKEE          WI   C-MAN STATION

            34 KNOT WIND GUST AT MILWAUKEE LAKESHORE SITE...MLWW3.

0957 PM     TSTM WND DMG     2 NW CLINTON            42.58N 88.89W
05/14/2013                   ROCK               WI   LAW ENFORCEMENT

            TREE DOWN.

 


National Weather Service - Milwaukee/Sullivan

Cronce, Davis



Return to News Archive

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.