July 15 2013 Oconomowoc Heavy Rain & Flood

Three separate, slow-moving thunderstorms moved through the Oconomowoc area late Monday afternoon and early evening and dumped very heavy rain.  The result was flooding of roads, backyards, basements, and a construction zone.

Below are three rainfall maps: 1) The one on the left is a map with approximate contours of rainfall totals based on actual rainfall reports, with the largest reported amount of 4.17 inches in downtown Oconomowoc, 2) The middle one is based on rainfall observations and was generated locally at WFO Milwaukee using an automation program that incorporates smoothing, 3) Radar-estimated precipitation totals with green colors showing rainfall amounts in the 1.5 to 2.5 inch range, pink colors 2.5 to 3.5, and dark blue around 4 inches.  Click on images for larger versions.

Rainfall contours  Precip total map  MKX radar-estimated precip total

Below are two pictures of the storm cloud over Oconomowoc.  Note there is very little "lean" to the storm which indicates very little vertical wind shear and weak winds aloft which push the storm forward.  Consequently, the storm moved slowly to the northeast and allowed for excessive rain amounts over a small area.  Additionally, the storm was similar to tropical thunderstorms since a very humid and warm air-mass was over southeastern Wisconsin.  Air temperatures were in the mid to upper 80s with dew-points in the lower 70s.  This is similar to conditions found in Hawaii.  So there was plenty of moisture for the storms to ingest.  Click on image for larger version.

Storm Cloud  SteveHentWauwatosa

Flooding pictures were taken by local residents and forwarded to WDJT CBS 58 in Milkwaukee.  Mark Mcginnis, Chief Meteorologist at TV-58, forwarded them to our office.  Click on images for larger versions.

Karen Hinkforth  Julie Van Leirsburg  Unknown Photographer

How much rain did you get?  Pass your report on to rusty.kapela@noaa.gov.  Do you have a picture of the flooding or the storm - want to share it?  E-mail it to Rusty.

Kapela, WFO Milwaukee

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