Flood Risk on the Illinois and Mississippi Rivers

Mississippi River at Quincy, IL, on May 26, 2013.
Mississippi River at Quincy, IL, on May 26, 2013.

The heavy rainfall across the Midwest in recent weeks has increased the risk of flooding on the Illinois and Mississippi Rivers. Rainfall totals were highest in western Illinois, northern Missouri, much of Iowa, southeastern Minnesota, and western Wisconsin, and ranged from 6 to 12 inches in the last 30 days. See the MRCC map below.

The National Weather Service produces forecasts of river levels based on current conditions and precipitation over the next 24 hours. At Quincy Lock and Dam, the Mighty Mississippi River is expected to be in “major” flood by sometime Thursday (first graph). See the latest forecast for this site here.

It is a similar story on the lower Illinois River. The current and forecasted river stage at Hardin, IL (second graph) shows that the river will reach “major” flood stage by next Monday. See the latest forecast for this site here. Of course, more rainfall in coming days will change these forecasts.

Mississippi River at Quincy Lock & Dam 21

Illinois River at Hardin

Memorial Day Weekend Rains Push Illinois Records

More rain fell over Illinois over the Memorial Day weekend. The heaviest amounts were in the central part of the state and ranged from 2 to 6 inches (yellow to dark red in the map below).

Right now the statewide average rainfall for May stands at 5.03 inches, based on preliminary data. More rain is forecasted for today and much of this week. So this total is likely to increase as we go through the week. By contrast, Illinois received only 2.5 inches in May 2012.

Click to enlarge.
Click to enlarge.

County Level Tornado Tracks in Illinois

Tornado risk has been on a lot of minds after the events in Moore, OK. For the first time that I can recall, the local TV station (Champaign) ran an advertisement for pre-constructed storm shelters.

In 2011, we produced county-level tornado track maps for all counties in Illinois to measure the historical risk of tornadoes across the state. These maps were based on data from the NOAA Storm Prediction Center for the period of 1950 to 2010. For example, below is the map for Cook County that shows tornado tracks and touchdowns, color-coded by (E)F-scale.

To me, the strongest reminder that a strong tornado can pass through Chicago is the April 21, 1967, Oak Lawn F-4 event that killed 33 and injured 500.  Here are some pictures of from the Oak Lawn Public Library of that event that look a lot like the damage in Moore, OK. 

You can see the rest of the maps on the Tornado Maps page at the Illinois state climatologist website.

Tornado tracks and touchdowns in Cook County. Click to enlarge.
Tornado tracks and touchdowns in Cook County. Click to enlarge.

Nation Cut in Two by Drought

Click to enlarge.
Click to enlarge.

The latest US Drought Monitor map from May 14, 2013, shows a Dr. Jekyll/Mr. Hyde nation when it comes to drought. Much of the country to the west of the 96° longitude is in some stage of drought while the country to the east of that line is largely drought free for the moment. Hardest hit have been the Plains states which in some cases are in year 2 or 3 of this drought.

By the way, the US Drought Monitor began about 13 years ago to provide one, unified map of drought across the United States. It is produced in partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration with lots of input from scientists, state climatologists, state and local agencies, university extension, landowners, farmers, etc.  Maps are updated weekly and released on Thursday mornings.

Click to enlarge.
Click to enlarge.

The precipitation pattern so far this year reflects these differences between east and west. The map is the current year to date departure from average precipitation produced by the NWS. Areas in green and blue are 2 to 8 inches above average and include much of the Midwest and Southeast. Areas in yellow are 2 to 6 inches below average. Hardest hit so far has been the West Coast with departures more than a foot below average.  There are large areas shaded gray which show near-average conditions. However, much of the west needs many more months of average precipitation or even above-average precipitation to start a recovery from their current drought situation.

Click to enlarge.
Click to enlarge.

The National Climatic Data Center has a product that gives a rough idea of the amount of precipitation needed over the next 6 months to recover from drought. I say “a rough idea” because the timing and intensity of the precipitation is important as well. The effect of getting 3 inches in 30 minutes is different than getting 3 inches over 3 days. The first will cause lots of runoff while the second will have a better chance of recharging soil moisture. As you can see, it will take a considerable amount of precipitation in the Plains states to get out of their current situation.

May Precipitation In Illinois – Wet in the West, Dry in the East

Here is the latest map of May precipitation in Illinois through the morning of May 16, showing the generally wetter conditions in western Illinois and parts of southern Illinois. Amounts were on the order of 3 to 6 inches with a few heavier amounts around White Hall. Areas in the southeast, east-central and much of northern Illinois were drier with amounts of 0.5 to 2 inches common.

There was a strong relationship between temperature and precipitation this month (second figure). Areas with heavier rainfall amounts (western and southwestern IL) had temperatures 2 to 4 degrees below average. Meanwhile areas in east-central and northern Illinois had temperatures near to slightly above average.

May 1-16, 2013 precipitation.
May 1-16, 2013, temperature departures from average.
May 1-16, 2013, temperature departures from average.


New NWS Outlooks for June and June-August

Today, the NWS Climate Prediction Center released their temperature and precipitation outlooks for June and June-August and beyond. You can see their full suite of outlooks here.

There isn’t much to report for Illinois (below). We are in the EC zone which means we have equal chances of above, below, and near-average temperatures and precipitation for the next three months. The only exception is that far southern Illinois has a slightly higher chance of above-average temperatures for June-August.

NWS Climate Prediction Center outlooks released May 16, 2013.
NWS Climate Prediction Center outlooks released May 16, 2013. Click to enlarge.

All Quiet on the Severe Weather Front

As of May 8, 2013, the severe weather statistics for Illinois this year are relatively low (see first map). There have been 2 tornado reports (red dots), 25 hail reports (green dots), and 62 wind damage reports (blue dots). By this point last year, we had 22 tornadoes including the deadly February 29 tornado at Harrisburg, IL, that killed 8 people.

Harold Brooks of the NWS has an interesting post on the current “tornado drought” in the US for the period from May 2012 to April 2013. He says,

The 12-month period from May 2012 to April 2013 was remarkable for the absence of tornado activity and tornado impacts in the United States.

The number of tornadoes in the US was the lowest on record (197) and the number of deaths (7) was the second lowest during this 12-month period. Brooks’ looked at tornadoes that were rated EF-1 or greater. Those tornadoes tend to be better documented over time than the relatively weak EF-0 events. Those records go back to 1954. The number of tornado deaths were based on records going back to 1875.

A possible explanation for the low numbers during this May 2012 to April 2013 period was that much of the central US was in drought in 2012 (see second map). This was followed by a late, cold spring in 2013 (see third map). Both of these conditions seem to produce fewer severe thunderstorms, at least in Illinois.

There has been lots of discussion about whether the low numbers this year or the high numbers in 2011 either prove or disprove climate change. It is hard to track historical climate changes in the tornado reports in Illinois and the US because of major changes in how the data were collected over time. Furthermore, climate models used for understanding future climate change are not designed to simulate severe weather at such a small scale. As a result, the Intergovernmental Panel on Climate Change last year stated there was “low confidence” in finding historical trends or making projections of possible future tornado activity (IPCC, 2012 pdf). You can find a short discussion on historical tornado trends in Illinois on my website.

While these are interesting statistics, it’s important to keep in mind that things can change in a hurry. All it takes is one day with the right conditions, especially now that we are finally getting warmer, and Illinois could be faced with another tornado outbreak. Stay alert!

Severe weather reports for 2013 through May 8, 2013. Figure courtesy of the NOAA Storm Prediction Center.
Severe weather reports for 2013 through May 8, 2013. Figure courtesy of the NOAA Storm Prediction Center. Red dots are tornadoes, green dots are hail, and blue dotes are wind damage.
Map of percent of average precipitation for May, June, and July of 2012. Areas in yellow or red are drier than average.
Map of temperature departures from average for February, March, and April. Areas in green are below average and areas in blue are much below average.
Map of temperature departures from average for February, March, and April. Areas in green are below average and areas in blue are much below average.