The Ohio River at Cairo, Illinois continues to fall today, with a level of 59.3′, 2.5′ below the all-time peak of 61.8′ set on Monday night. On Monday night, the Army Corps of Engineers was forced to intentionally destroy a levee at Birds Point on the west bank of the Mississippi, just downstream from Cairo, Illinois, in order to relieve pressure on the levees in Cairo and save that city from a billion-dollar levee breach. The destruction of the Birds Point levee also helped slow the rise of the Mississippi River just south of its confluence with the Ohio River, but the river is still rising slowly, and has now set all-time records at New Madrid, Missouri, Tiptonville, Tennessee, and Caruthersville, Missouri–a 70-mile stretch of river downstream from Cairo. Currently, the Mississippi is expected to reach its 2nd highest level on record at Memphis on May 10, cresting at 48.0′. The all-time record at Memphis occurred during the great flood of 1937, when the river hit 48.7′. Downstream from Memphis, flood waters pouring in from the Arkansas River, Yazoo River, and other tributaries are expected to swell the Mississippi high enough to beat the all-time record at Vicksburg, Mississippi by 1.3′ on May 20, and smash the all-time record at Natchez, Mississippi by six feet on May 22, and by 3.2 feet at Red River Landing on May 23. Red River Landing is the site of the Old River Control Structure, the Army Corps’ massive engineering structure that keeps the Mississippi River from carving a new path to the Gulf of Mexico. I’ll have a detailed post talking about the Old River Control Structure next week. Its failure would be a serious blow to the U.S. economy, and the great Mississippi flood of 2011 will give the Old River Control Structure its most severe test ever. Also of concern is the forecast for the Mississippi to crest at 19.5 feet in New Orleans on May 24. The levees in New Orleans protect the city for a flood of 20.0 feet–that is not much breathing room. Fortunately, only 0.5 – 1.5 inches of rain are expected over the Missouri/Illinois region over the next five days, which should not raise flood heights significantly.Good links to follow the flood:
Summary forecast of all crests on Lower Mississippi and Ohio Rivers.
Wundermap for Cairo, IL with USGS River overlay turned on.
National Weather Service “May 2011 Mississippi River Flood” web page

Figure 1. Flooding of the farmland along the Birds Point-New Madrid Floodway due to the intentional destruction of a levee along the west bank of the Mississippi River in Southeast Missouri is obvious in this pair of before and after photos. Image credit: NASA Earth Observatory.

Lake Champlain hits highest level since 1869; record flooding in Canada
The Governor of Vermont declared a state of emergency yesterday in Vermont due to flooding along Lake Champlain. Heavy rains over the past ten days, combined with snow melt have combined to push the lake ot three feet above flood stage, and the lake has now broken its previous record high, set in 1869. The flooding has caused numerous road closures but no evacuations in the U.S. The story is different in Quebec, Canada, where flood waters from Lake Champlain coursing down the Richelieu River have created a 150-year flood, forcing the evacuation of 1,000 people and the flooding of 3,000 homes and businesses in the Richelieu Valley, just south of Montreal. The lake level is expected to crest Saturday morning, then slowly fall. Lake Champlain is 120 miles long with nearly 600 miles of shoreline, making it the sixth largest natural lake in the U.S., trailing only the Great Lakes in size.

Figure 2. Five to eight inches of precipitation has fallen over much of the Lake Champlain watershed over the past two weeks. Image credit: NOAA/AHPS.

A third tornado from the April 27 Super Outbreak rated an EF-5
Yesterday, the Jackson, Mississippi office of the NWS upgraded the violent tornado that hit Neshoba, Kemper, Winston, and Noxubee Counties in the northeast part of the state to EF-5 status, with top winds of 205 mph. This tornado continued into Alabama and had a total path length of 92.3 miles. Three people died in the tornado, which was so powerful that it dug out the ground to a depth of two feet over an area 25 – 50 yards wide and several hundred yards long. This is the third tornado rated EF-5 from the April 27 outbreak; tornadoes that hit Smithville, MS and Hackleburg, AL also received EF-5 ratings.

Figure 3. EF-5 damage from the April 27, 2011 Neshoba tornado in Mississippi. The tornado was so powerful that it dug out the ground to a depth of two feet over an area 25 – 50 yards wide and several hundred yards long. Image credit: NWS.

Rare EF-2 tornado hits New Zealand
A tornado ripped through New Zealand’s largest city, Auckland, on Tuesday, killing one person at a shopping mall and injuring at least fourteen others. The damage was rated EF-2, making the tornado one of the strongest in New Zealand’s history. Below is some footage of the twister, showing why it is dangerous to be in a car during a tornado. (Note also the clockwise rotation of the tornado–this is the Southern Hemisphere, where storms rotate clockwise.)