Flash Flooding/Heavy Rain Event & Tornado Outbreak
July 22, 2010
Flash Flooding and Storm Highlights
Parts of south-central and southeast Wisconsin experienced several rounds of record-setting torrential heavy rains during the afternoon and evening hours of July 22, 2010 that led to flash flooding and damage. The Milwaukee Metro Area endured the brunt of the flash flooding and resultant damage. Additionally, several tornadoes spun up, resulting in minor to moderate damage (see tornado information in bottom half of this Top News of the Day story).
There was one fatality - the body of a 19-year-old male was found in Lincoln Creek near N. 32nd St. and W. Hampton Ave. in Milwaukee. He was swept from his vehicle when Lincoln Creek flooded. He was spotted swimming against the current, but eyewitnesses were unable to assist.
Two people were injured by a lightning strike.
One person was injured in the city of Milwaukee when their vehicle plunged into a sink hole.
A lightning strike in Green County killed 8 milk cows.
County Executive Scott Walker issued a Declaration of a Major Disaster for Milwaukee County since more than 7 inches of rain fell around the county, and an estimated $23.9 million in damage in the private sector and over $10 million in the public sector which includes protective measures and clean-up costs.
The Milwaukee Fire Department logged 50 rescues from homes and streets.
The Milwaukee Metropolitan Sewerage District (MMSD) reported that the storm resulted in a combined sewer overflow of around 2 billion gallons. All Lake Michigan beaches in Milwaukee were closed through the following weekend of July 24th and 25th due to sewer contamination. The City of Milwaukee received at least 2000 calls for sewer backups into basements of homes. It appeared that the northern half of the city of Milwaukee was hardest hit.
In the city of Milwaukee suffered a massive sink hole 20 feet deep and some 20 to 40 feet wide at the intersection of Oakland and North around 830 pm. It swallowed a Sport Utility Vehicle and a street light. The driver of the SUV was injured and treated at a hospital. Electrical power cables and other cable lines were damaged by the sink hole.
Milwaukee Mitchell International Airport was closed late Thursday night (22nd) through 2 pm Friday (23rd) due to flooded runways. One runway was opened at 2 pm Friday, however there were additional delays.
In Milwaukee County, several thousand homes were minimally affected, and a few were destroyed. Over 4,400 homes reported water-filled basements in the city of Milwaukee alone.
About 32,000 We Energy utility customers lost electrical power throughout southeast Wisconsin due to the flooding and lightning.
As of 7 pm Thursday evening, Nicolet High School in Milwaukee had a flooded basement and 16” of water on the main floor.
Total rainfall amounts for the 24-hour period from about 7am Thursday July 22nd through about 7 am Friday July 23rd ranged from 5 to 9 inches in parts of Milwaukee County, and 2 to 6 inches in other surrounding counties.
On July 24th, 11 rivers throughout southeastern Wisconsin still remained under a flash flood warning.
During the heavy rains of July 22nd, we received a telephone call from the broadcast meteorologist's who work for WTMJ -4 in Milwaukee. They mentioned that they had measured some 7 inches of rain over a 2.5 hour period of time. That's a ton of rain! So after the dust settled, we asked them to provide us with specific information about rainfall amounts. WTMJ-4 is located on Capitol Drive north of downtown Milwaukee. Here is Chief Meterologist John Malan's e-mail reply:
We are certain that the one-hour rainfall was 6.73 inches between 5:15 and 6:15 in the late afternoon/evening. I am not sure how much fell before and after that one hour period. The twenty-four hour rainfall (midnight to midnight July 22nd) was 8.31 inches. We also received another inch after midnight on July 23rd, so the two day total was 9.31 inches.
Below is an image showing those areas that reported flash flooding (left picture), and locations of the flood-related death, the sink hole, and a couple extreme rainfall reports. Images produced by Laura Schutte, Student Volunteer.
Below are a couple pictures taken by Lori Getter of Wisconsin Emergency Management. The one on the left shows the sink hole in the city of Milwaukee, and the one on the right shows the high-water mark on the wall of Nicolet High School in Glendale.
Detailed Meteorological Information
Prior to the afternoon and evening torrential rains, a large area of moderate to heavy rain moved through southern Wisconsin Thursday morning, dumping 1.5 to 2 inches of rain across areas west of Madison, and .50 to 1.5 inches of rain east of Madison, including the Milwaukee metropolitan area. Milwaukee's Mitchell International Airport received 1.44 inches of rain during that morning round. Madison's Dane County Regional Airport received 1.47 inches. This helped set the stage for the major flooding that ensued later in the day.
During the afternoon, a persistent band of strong to severe thunderstorms developed and moved very slowly over south central and southeast Wisconsin through the evening hours. The individual storms were moving quite fast, about 40 to 50 mph, but the line containing these storms didn't, resulting in storms repeatedly training, or moving, over the same area. Widespread 3 to 4 inch amounts were reported along and either side of the I-94 corridor, with locally higher amounts of 5 to 8 inches. The greatest rain amounts fell in Milwaukee County.
Hourly rainfall amounts of 2 to 4 inches were reported, and WTMJ TV-4 on Milwaukee's northeast side measured 7 inches of rain in about 2.5 hours ending at 745 pm Thursday evening.
Mitchell Field recorded 5.61 inches for the day, breaking a record for the date. The previous record was 1.26 set in 1948. This also is the second highest daily rainfall total on record for Milwaukee. The greatest one-day precipitation record was the 6.81 inches which fell on August 6, 1986.
Madison also set a record for precipitation for the date at 3.62 inches. This beat the previous mark of 2.21 inches set in 1885. The 3.62 inches ranks 13th for the most precipitation in one day. The record is the 4.96 inches which fell on August 8, 1906.
With so much rain falling in such a short period of time, our river gauges rose rapidly above flood stage. Below are a couple examples - one on Oak Creek in South Milwaukee, and the other one on the Root River in Franklin.
Many rivers in south central and southeastern Wisconsin nearly reached or will near record flood levels. Click here to see a list of these rivers.
Total Rainfall - 7/22/2010
Roughly 7 AM Thursday Through 7 AM Friday
 Southern Wisconsin |
 Wisconsin |
 Radar Rainfall Estimate |
 Radar Animation: 330PM-Midnight 30 minute increments (1.8mb) |
The images above are a graphical depiction of the rainfall amounts that fell across south central and southeast Wisconsin on Thursday July 22nd. The exact span of the measurement runs from 7 AM on 7/22/2010 through 7 AM on 7/23/2010.
Here are text listings of the various rainfall reports received this morning (7 AM 7/22/2010 - 7 AM 7/23/2010)
Rainfall listing sorted from highest to lowest amounts
July 22, 2010 Tornadoes
A total of 10 tornadoes have been documented for July 22nd.
Many individual thunderstorm cells affected south-central and southeast Wisconsin during the late afternoon and evening hours of July 22, 2010. A good number of these thunderstorms developed rotations wtihin their updraft towers. These rotations, called meso-cyclones, may ultimately lead to tornado development, however research suggests no more than 10 to 15% of all thunderstorms with mesocyclones result in tornado situations. We suspect this was the case on July 22nd.
Here is a map showing the locations of the tornadoes and the powerful thunderstorm downburst wind event in Walworth County:
EF2 Tornado (Enhanced Fujita Scale) in the Big Bend area of Waukesha County, 18 miles southwest of downtown Milwaukee. The EF2 scale runs from 111-135 mph, this tornado is rated at 115-120 mph.
EF1 Tornado (Enhanced Fujita Scale) west of Albion area in southeast Dane County, about 17 miles southeast of downtown Madison. The EF1 scale runs from 86-110 mph, this tornado is rated at 90 mph.
EF1 Tornado (Enhanced Fujita Scale) near Mt. Horeb in west-central Dane County, about 15 miles west-southwest of downtown Madison. The EF1 scale runs from 86-110 mph, and thiis tornado is rated at 95 - 100 mph.
EF1 Tornado (Enhanced Fujita Scale) just north of Dane in north-central Dane County, about 15.5 miles north northwest of downtown Madison. The EF1 scale runs from 86-110 mph, this tornado is rated at 90 mph.
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EF0 Tornado (Enhanced Fujita Scale) northeast corner of Dane County, east of East Bristol, about 20 miles northeast of downtown Madison. The EF0 scale runs from 65-85 mph, this tornado is rated at 65 mph.
EF0 Tornado (Enhanced Fujita Scale) between Lake Mills and Waterloo, started just inside Dane County about 19 miles east-northeast of downtown Madison. The EF0 scale runs from 65-85 mph, this tornado is rated at 65 mph.
EF0 Tornado (Enhanced Fujita Scale) southwest and south of Ft. Atkinson in Jefferson County, about 27 miles southeast of downtown Madison. The EF0 scale runs from 65-85 mph, this tornado is rated at 75 - 80 mph.
Photo of the tornado south of Fort Atkinson (picture taken NW of Milton, looking NE):
EF0 Tornado (Enhanced Fujita Scale) midway between Whitewater and Cold Springs in Jefferson County, 25 miles southeast of downtown Madison. The EF0 scale runs from 65-85 mph, this tornado is rated at 65-70 mph.
EF0 Tornado (Enhanced Fujita Scale) southeast of Farmington (east-northeast of Jefferson), about 33 miles west of downtown Milwaukee. The EF0 scale runs from 65-85 mph, this tornado is rated at 65 mph.
EF0 Tornado (Enhanced Fujita Scale) southeast side of Verona in Dane County, about 11 miles southwest of downtown Madison. The EF0 scale runs from 65-85 mph, this tornado is rated at 65 to 70 mph.
Note: All information above is preliminary and subject to change as additonal information is gathered.
The atmosphere on July 22nd had a lot of low-level moisture and consequently the cloud bases were low and there was plenty of low-hanging scud cloud fragments attached to the underside of storms as well as to the underside of rotating wall clouds. In most cases, because of the distance to the bottom of the storm and the viewing angle - hills, trees, and buildings blocked a person's view of the ground directly beneath the storm and/or rotating wall cloud. This gave some people the false perception that they were observing a so-called "tornado touchdown" since it appeared that the cloud fragments or rotating wall cloud or funnel cloud was touching the top of trees.
Below are a couple pictures taking just north of Palmyra, looking southeast. Two thunderstorms with rotating wall clouds at their base moved west to east through the Palmyra-Eagle area. You are looking at the first of the two storms. Notice that the hills and trees give you a viewing angle that gives you the false impression that you have a tornado - however, there was no ground contact. We could not find any tree or structural damage along the paths of the two storms.
Therefore, we ended up with many more tornado reports than actual tornadoes - and it takes time to weed things out.The deciding factor whether we classify something as a tornado is based on a combination of 3 factors:
1. Structural or vegetative damage at the ground level. The debris pattern and characteristics of the damage determine whether it was a tornado or a downburst, straight-line wind event. The lack of any damage means there was no event.
2. An observable dirt/dust debris spray or swirl at the ground level.
3. There was a radar-detected rotation (mesocyclone) inside a convective cloud or thunderstorm. In most cases, this happens.
Note: In the future, if you are e-mailing us a weather related picture, it would be greatly appreciated if you used the following format in explaining your pictures:
Picture 1234 - taken at 530 pm on July 22, 2010. I'm standing at the intersection of Highways X and Y, about ZZ miles west of SomeCity. I'm looking south-southeast. I saw strong rotation in the funnel cloud. The funnel cloud never touched the ground. ....and so on with any other detail that explains what you are looking at......
If you follow the format shown above, you make it easier for us to figure out exactly what you are looking at and which storm it is associated with. In short, you save us time and make our documentation process more efficient. Thank you very much!
Various weather map animations,
looping from 3 PM through 11 PM, July 22, 2010
In addition to the very heavy rain, the atmosphere was supportive of the development of weak tornadoes. Many of the thunderstorms that developed began to rotate almost immediately and a few of these strengthened enough to cause a brief, weak touchdown of a tornado. The atmosphere was loaded with ample low level shear, as seen in the 0-1km shear animation below. The deeper shear, 0-6km, was supportive as well. But, the bigger story was the amount of moisture available for these storms to work with. The warm and extremely moist atmosphere lead to incredibly high rainfall amounts. The precipitable water animation below helps to highlight this with values well in excess of 2 inches. The surface pressure map animation shows the existence of a low pressure system near the borders of Wisconsin/Iowa/Minnesota with a warm front stretching across southeast Wisconsin early in the loop. The cold front stretches east to west back across northern Iowa. The mixed layer CAPE shows how unstable the atmosphere was.
 0-1KM Shear |
 0-6KM Shear |
 850mb Map |
 Mixed Layer Cape |
 Surface Pressure Map |
 Precipitable Water Map |
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