A 2010 study found “global warming is the main cause of a significant intensification in the North Atlantic Subtropical High that in recent decades has more than doubled the frequency of abnormally wet or dry summer weather in the southeastern United States.” Below, meteorologist Dr. Jeff Masters relates how wild climate swings are becoming the norm in the Midwest, too. — JR
By Jeff Masters, via Weather Underground
It seems like just a few months ago barges were scraping bottom on the Mississippi River, and the Army Corps of Engineers was blowing up rocks on the bottom of the river to allow shipping to continue. Wait, it was just a few months ago — less than four months ago! Water levels on the Mississippi River at St. Louis bottomed out at -4.57′ on January 1 of 2013, the 9th lowest water level since record keeping began in 1861, and just 1.6′ above the all-time low-water record set in 1940 (after the great Dust Bowl drought of the 1930s.)
But according to National Weather Service, the exceptional April rains and snows over the Upper Mississippi River watershed will drive the river by Tuesday to a height 45 feet higher than on January 1. The latest forecast calls for the river to hit 39.4′ on Tuesday, which would be the 8th greatest flood in history at St. Louis, where flood records date back to 1861. Damaging major flooding is expected along a 250-mile stretch of the Mississippi from Quincy, Illinois to Thebes, Illinois next week.
At the Alton, Illinois gauge, upstream from St.Louis, a flood height of 34′ is expected on Tuesday. This would be the 6th highest flood in Alton since 1844, and damages to commercial property in the town of Alton occur at this water level. In addition, record flooding is expected on at least five rivers in Illinois and Michigan over the next few days. A crest 1.5′ above the all-time record has already occurred on the Des Plaines River in Chicago. This river has invasive Asian Carp that could make their way into Lake Michigan if a 13-mile barrier along the river fails during an extreme flood. Fortunately, NPR in Michigan is reporting today that U.S. Army Corps of Engineers crews stationed along the 13-mile Asian carp barrier have seen no evidence of the fish breaching the structure, and it would have taken a flood much larger than today’s record flood to breach the structure. A crest on the Grand River in Grand Rapids, Michigan nearly 4′ above the previous record (period of record: at least 113 years) is expected this weekend. At this flood level, major flooding of residential areas is expected, though the flood wall protecting downtown Grand Rapids will keep the commercial center of the city from flooding.
Figure 1. The rains that fell in a 24-hour period ending at 7 am EDT Thursday, April 18, 2013 over Northern Illinois were the type of rains one would expect see fall only once every 40 years (yellow colors), according to METSTAT, Inc. (http://www.metstat.com.) METSTAT computed the recurrence interval statistics based on gauge-adjusted radar precipitation and frequency estimates from NOAA Atlas 14 Volume 2, published in 2004 (http://dipper.nws.noaa.gov/hdsc/pfds/.) METSTAT does not supply their precipitation recurrence interval forecasts or premium analysis products for free, but anyone can monitor the real-time analysis (observed) at: http://metstat.com/solutions/extreme-precipitation-index-analysis/
Damages from the April 2013 Midwest U.S. flood in Illinois, Michigan, and Missouri are likely to run into the hundreds of millions of dollars. Some of the impacts at the flood levels predicted include:
St. Louis, MO:Major flooding begins. At this level the Choteau Island Levee, protecting 2400 acres, is overtopped. Also, Lemay Park just south of Lemay Ferry Road will begin flood
Cape Girardeau, MO:Many homes in the Cape Girardeau area are affected and evacuations may be required. Over 100,000 acres is flooded. Numerous roads are closed.
Hannibal, MO:The Sny Island and South Quincy levees are overtopped between River Mile 315.4 and 264.3, flooding 110,000 acres. The South River levee is overtopped between River Mile 320.5 and 312.1, flooding 10,000 acres.
Quincy, IL:Missouri Highway 168 east of Palmyra near the BASF plant closes; Quincy Waterworks inundated.
Note that sandbagging efforts may be able to prevent some of these flooding impacts from occurring. Wunderground’s weather historian Christopher C. Burt discusses the latest rainfall and flooding records from this week’s epic storm in his latest post. He plans on an update Friday afternoon.
Figure 2. Water levels on the Mississippi River at St. Louis are predicted to crest at 39.5′, near major flood stage, on Tuesday. This would be the 8th greatest flood in history at St. Louis. Records at the St. Louis gauge to back to 1861. (Image credit: National Weather Service)
Figure 3. Water levels on the Mississippi River at St. Louis bottomed out at -4.57′ on 01/01/2013, the 9th lowest water level since record keeping began in 1861, and just 1.6′ above the all-time low-water record set in 1940, after the great Dust Bowl drought of the 1930s. (Image credit: National Weather Service)
Flood-Drought-Flood Weather WhiplashResidents along the Mississippi River have experienced a severe case of flood-drought-flood weather whiplash over the past two years. The Mississippi reached its highest level on record at New Madrid, Missouri on May 6, 2011, when the river crested at 48.35′. Flooding on the Mississippi and Missouri rivers that year cost an estimated $5 billion. The next year, after the great drought of 2012, the river had fallen by over 53′ to an all time record low of -5.32′ on August 30, 2012. Damage from the great drought is conservatively estimated at $35 billion. Next Tuesday, the river is expected to be at flood stage again in New Madrid, 40′ higher than the August 2012 record low. Now, that is some serious weather whiplash.
I’m often asked about the seemingly contradictory predictions from climate models that the world will see both worse floods and worse droughts due to global warming. Well, we have seen a classic example in the Midwest U.S. over the past two years of just how this kind of weather whiplash is possible. A warmer atmosphere is capable of bringing heavier downpours, since warmer air can hold more water vapor. We saw an example of this on Thursday morning, when an upper air balloon sounding over Lincoln, Illinois revealed near-record amounts of moisture for this time of year. The precipitable water — how much rain could fall if one condensed all the water vapor in a column above the ground into rain — was 1.62″, just barely short of the Illinois April record for precipitable water of 1.64″ set on April 20, 2000 (upper air records go back to 1948.) Thursday’s powerful low pressure system was able to lift that copious moisture, cool it, and condense it into record rains. So how can you have worse droughts with more moisture in the air? Well, you still need a low pressure system to come along and wring that moisture out of the air to get rain. When natural fluctuations in jet stream patterns take storms away from a region, creating a drought, the extra water vapor in the air won’t do you any good. There will be no mechanism to lift the moisture, condense it, and generate drought-busting rains. The drought that ensues will be more intense, since temperatures will be hotter and the soil will dry out more.
The new normal in the coming decades is going to be more and more extreme flood-drought-flood cycles like we are seeing now in the Midwest, and this sort of weather whiplash is going to be an increasingly severe pain in the neck for society. We’d better prepare for it, by building a more flood-resistant infrastructure and developing more drought-resistant grains, for example. And if we continue to allow heat-trapping gases like carbon dioxide continue to build up in the atmosphere at the current near-record pace, no amount of adaptation can prevent increasingly more violent cases of weather whiplash from being a serious threat to the global economy and the well-being of billions of people.