Localized Flooding of July 24, 2017

Localized Flooding (Jefferson County)
July 24, 2017

Overview

Satellite & Radar

Rainfall Totals

Creek Crests

Upper Air

Pictures

Videos

Overview

Mesoanalysis on the morning of July 24th, revealed multiple boundaries across Central Alabama and in the vicinity. Radar and satellite indicated several old outflow boundaries and differential heating boundaries were in place across the northeast half of the forecast area (see loop below). These boundaries were the primary mechanism by which convection initiated late that morning. Once convection was ongoing, outflow boundary collisions provided additional focus for thunderstorm development.

The localized flooding in and around the Tarrant and Birmingham Airport areas was the result of boundary/storm collisions, heavy rainfall, poor drainage and excessive runoff in the urban areas, and flashy creeks. Thunderstorms along a boundary moved south toward the airport and merged/collided with another storm near Irondale. This collision led to additional development and intensifying rainfall amounts. The nearly stationary storms dropped 2-3 inches of rain in just one hour. Storm total rainfall amounts of 3-4 inches were noted, with the Birmingham Airport reporting a total of 3.64 inches for the day. Significant flash flooding occurred along Hwy 79 in downtown Tarrant and along several streets near the airport, including Tallapoosa Street. and 14th Ave N. Several vehicles were stranded in the floodwaters. Much of the flooding was due to Fivemile Creek and Village Creek overflowing their banks. Thankfully, no injuries or deaths occurred.

Satellite & Radar

This satellite/radar combo loop from that morning clearly shows a distinctive boundary between the morning low clouds and the clear skies across the NE counties. You can see the first showers of the day develop on the north side of this differential heating boundary. Although not as noticeable, there are a couple of old outflow boundaries located across the northern portions of Central Alabama.

This loop of reflectivity (left) and velocity (right) shows the evolution of the heavy rain over the Tarrant and Birmingham Airport areas. At the beginning of the loop, you can see the storms to the N of the airport merge with the storm near Irondale. Afterward, an increase in reflectivity occurs, with the storms remaining nearly stationary for a while before finally building to the NW toward Fultondale.

Rainfall Totals

Creek Crests


Fivemile Creek at Ketona	Village Creek at 24th St	Village Creek at Ave W

KBMX Upper Air Soundings


KBMX Sounding 24 July 7 AM	KBMX Sounding 24 July 7 PM

Flooding Pictures


Hwy 79 Tarrant Courtesy of Jon Patterson (@tastypickles1)	Mountain Brook Country Club Courtesy of Rachel Callahan (@ObjectivityRach)	Mountain Brook Country Club Courtesy of Rachel Callahan (@ObjectivityRach)

Tallapoosa St Courtesy of @philipgreen__	14th Ave N Courtesy of @hunter_harris1	Tallapoosa St Courtesy of Susan Creel (@creelsx5)

Flooding Videos

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