Thursday, August 8, 2013

Bulls Eye on the Ozarks

For the last week the U.S. has been locked in a weather pattern more reminiscent of mid winter rather than mid summer. A strong upper low has been spinning over Hudson's Bay, keeping much of the northern and north-central U.S. cooler than normal and forcing the path of weather systems further south than usual.

500 millibar maps for August 2 (left) and August 7 (right), 2013

This has had the effect of establishing a quasi-stationary boundary from the east side of the Rockies to the east coast. Over the last week this front has oscillated from the central Midwest to the central Gulf Coast states and back as a series of minor waves have rotated around the upper low in Canada.

Surface map for 7:00 a.m. CDT 8/7/2013

These waves of energy interacting with the frontal boundary have generated prodigious rainfall amounts from south-central Kansas through southern Missouri and Tennessee. Unfortunately, the bulls eye of the heaviest rain is over the Missouri Ozarks. The Ozarks extend generally from northwestern Arkansas northeastward through Missouri to just south of St. Louis. The topography ranges from rolling to rugged making it a prime area for flash flooding. Rainfall this past week has exceeded 16 inches in parts of Missouri and 11 inches in northern Arkansas.  Here are some of the highest Missouri amounts:

The observer at Fort Leonard Wood 9.3 S (MO-TX-9) picked up 10.37 inches of the total 16.42 inches of rain so far this month in the 24-hour period ending Tuesday morning, August 6. Here's what the observer had to say in her observation notes that morning:

OH MY WORD!!! We emptied the gauge at midnight last night--there was 1.85 in the gauge. Between midnight and this morning I got the other 8.52!! I knew there might be a lot of rain in the gauge this morning, when I had to wade water on my front porch and slightly thru my living room to get outside!! AND, we live on a hill!! It had just rained so much that it had not drained off as yet! I am still stunned by the amount of rain--and it will still be going on for a few more days!! This could be quite the disaster--our communities all around are flooding and people being rescued! 

The radar loop from 1:00 a.m. CDT to 7:00 a.m. CDT shows how slowly the thunderstorms moved over the same area. Click here to see a 6-hour radar loop

The regional radar image at 2:03 a.m. CDT on August 6 shows the cluster
of thunderstorms already firing over south central Missouri.
It's no surprise that there was widespread flooding from the heavy rain.  A 14 mile stretch of Interstate 44 in Missouri was closed due to flooding. Many home were evacuated, and there are two confirmed fatalities from the flooding.

Five to more than 7 inches of rain in Middle Tennessee in the 24-hour period ending this morning caused widespread flash flooding there.

Unfortunately it doesn't look like there is going to be much of a break in the rain and a chance to dry out. The 7-day outlook for precipitation paints another several inches of rain over this same area.

Quantitative precipitation forecast for the 7-day period ending 7:00 p.m. CDT August 15.

No comments:

Post a Comment