Extreme Temperature Diary- Thursday May 21st, 2020/ Main Topic: Anatomy of Recent U.S. Flooding With Climate Change Connections

Thursday May 21st… Dear Diary. The main purpose of this ongoing blog will be to track United States extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉

Main Topic: Anatomy of Recent U.S. Flooding With Climate Change Connections

Dear Diary. As discussed on this blog, global warming is changing the polar vortex, which is shrinking with a tendency to release many small upper lows, forming due to a buckling jet stream. Relatively small cold pockets, or upper lows, are becoming more numerous across the planet, squeezing out available moisture, producing life threatening and altering flooding with devastating effects, compounded by the fact that a warming atmosphere can hold more moisture.

In the last couple of days we have witnessed another couple of eye opening flooding cases, one in Michigan and another ongoing threat in the Carolinas and Virginia. Today let’s use a little basic meteorology using 500 millibar charts to see why these two flood situations developed.

First, here was the pattern we had during the tragic Michigan flooding where a couple of very flawed dams broke a couple of days ago:

Wow! Notice how many upper lows there are around and in North America. What a convoluted jet stream mess brought about by an overall anomalously warm pattern at 500 millibars. Flooding is occurring in Michigan due to the upper low, which formed and stalled over Illinois by this Monday. Usually flooding occurs in the eastern quadrant of these upper level devils, which was the case early this week.

Dynamics in association with upper levels lows produce convergence or forcing and vertical lift, which can really wring out any available moisture from the atmosphere. There are other ways for flooding to occur in meteorology besides that from upper air cold, closed low features, though.

The upper low moved southward on Tuesday then stalled once more over Tennessee by Wednesday. This action led to train echo patterns across the Carolinas leading to more flooding:

One reason the upper low is moving so slowly is called what us meteorologists have termed a “Rex Block,” or when an upper level warm ridge forms north of a cold upper low, a pattern that historically is slow to break down, locking in flooding dynamics for hours and sometimes days. This pattern will break down on Friday but not before much damage is done and more homes and businesses are underwater in the Carolinas and Virginia.

Hazard Map

For more on what happened in Michigan here is a repost of Bob Henson’s fine article from Weather Underground:

https://www.wunderground.com/cat6/aging-dams-changing-climate-a-dangerous-mix

Aging Dams, Changing Climate: A Dangerous Mix

Bob Henson  ·  May 20, 2020, 3:08 PM EDT

Above: An aerial view of floodwaters flowing from the Tittabawassee River into the lower part of downtown Midland on May 20, 2020 in Midland, Michigan. Thousands of residents have been ordered to evacuate after two dams in Sanford and Edenville collapsed causing water from the Tittabawassee River to flood nearby communities. (Gregory Shamus/Getty Images)

The failure of two dams near Midland, Michigan, led to a flooding catastrophe Wednesday—one that highlighted the U.S. peril from the neglect of hundreds of aging dams coupled with the rise in intensified precipitation extremes from human-produced climate change. The collapse of the Edenville Dam on the Tittabawasse River, and the downstream overtopping of the Sanford Dam, led to massive flooding that swamped much of Midland (pop. 42,000) on Wednesday.

About 10,000 people were hastily evacuated after the dam failures on Tuesday afternoon. As of 2 pm CDT, water levels appeared to have stabilized just over a foot above the previous record of 33.89’ (Sept. 30, 1986) on the Tittabawassee River gauge at Midland. A worker with the U.S. Geologic Survey quickly installed a temporary gauge on Wednesday morning in anticipation that the existing gauge might be knocked out of service by the unprecedented flooding.

Water levels on the Tittabawassee River at Midland, Michigan, as of 1:15 pm CDT Wednesday, May 20, 2020. Water levels may fall just short of the predicted peak by Wednesday evening of 38 feet. (NOAA/NWS/AHPS)

A major Dow Chemical plant in Midland said in a statement that “there were floodwaters commingling with on-site containment ponds” as of 10 am CDT Wednesday. The facility includes a 53-year-old nuclear research reactor that was already closed because of the coronavirus pandemic. See the weather.com article for more on Midland-area flood impacts.

The FEMA catalog of flood policies by county shows that as of Feb. 29, 2020, there were only 337 federal flood insurance policies in effect for all of Midland County. Since only about 5% of U.S. flood policies are from the private sector, this implies that the vast majority of homeowners in Midland County are not flood-insured.

“We need to do a much better job at communicating to U.S. homeowners—before, not during, events—that their standard home insurance policy does not cover flood damage,” tweeted Steve Bowen (Aon).

The perilous state of aging, privately held U.S. dams

A U.S. Corps of Engineers database, the National Inventory of Dams, shows that the Edenville and Sanford dams were both built in 1925 and owned by Boyce Hydro Power (which also owns two other dams on the Tittabawasse River). Both the Edenville and Sanford dams were rated as “high hazard”, meaning that loss of human life is likely were the dam to fail.

Most U.S. dams (about 56%) are privately owned, according to FEMA. That’s not the case for roads, bridges, sewers, and other vital infrastructure. “In general, very large dams are owned and regulated by the federal government,” notes FEMA, adding: “Given the diffuse nature of dam ownership versus regulation in the United States, it is apparent that dam safety and security are often not solely a federal, state or local issue.”

A major analysis released by the Associated Press in November revealed the compromised state of many hundreds of U.S. dams. The AP found that 1688 high-hazard dams across 44 states and Puerto Rico were rated in poor or unsatisfactory condition.

“Deaths from dam failures have declined since a series of catastrophic collapses in the 1970s prompted the federal and state governments to step up their safety efforts,” noted the analysis. “Yet about 1,000 dams have failed over the past four decades, killing 34 people, according to Stanford University’s National Performance of Dams Program.”

The predominance of private ownership of U.S. dams complicates efforts to spur needed improvements. Boyce Power had been notified as far back as 1998 that the Edenville Dam’s spillway capacity needed to be increased to avoid failure, according to the Detroit News. In September 2018, the Federal Energy Regulatory Commission revoked the dam’s license to generate power but did not require it to make the specified improvements. A two-county authority agreed in January to buy the four dams and lakes owned by Boyce Power for $9.4 million, effective in 2022, with about $100 million for rehabilitation to be raised through a special tax district.

The most infamous example of catastrophe involving a privately held U.S. dam occurred in 1889, when a dam below a private lake owned by a group of wealthy industrialists failed catastrophically just upstream from Johnstown, Pennsylvania. The resulting flood took at least 2208 lives, making it one of the deadliest weather disasters in U.S. history. (See Christopher Burt’s 2019 post in Category 6 for more on this calamity.)

Sanford resident Clint Clark, 44, walks out into what was once the bottom of Wixom Lake after water washed out due to the failure of the Edenville Dam on Wednesday, May 20, 2020 in Edenville Township north of Midland, Michigan. (Jake May/The Flint Journal, MLive.com via AP)

Extreme rains fueled the Michigan flood, and Midwest precipitation is increasing and intensifying with climate change

This week’s dam failures in central Michigan came after two days of intense rainfall on the north side of a slow-moving cut-off low making its way from the Midwest to the Appalachians. Midland reported a 48-hour rainfall total on Monday and Tuesday of 4.79”, its third highest two-day total in 50 years of recordkeeping behind only 11.78” on Sept. 10-11, 1986, and 8.05” on Sept. 11-12, 1986 (both coming from the same multiday event that drove the previous record flood in Midland).

With 12 days left in the month, Midland is just 1.35” away from its wettest May on record (7.32” in 2004).

Although there have been some dry periods in 2020 across the Great Lakes states, it has been a wetter-than-average year thus far. This follows 2019, the wettest year on record from Michigan to the Dakotas, and 2018, which wasn’t far behind. The Central Lower Michigan climate division (Division 6) has seen a dramatic increase in overall precipitation over the last century, as shown below: the average yearly total has gone from about 28” at the turn of the 20th century to about 35” today.

Annual precipitation since 1895 in the Central Lower Michigan climate division. (NOAA/NCEI)

One of the recurring messages in decades of projections of human-produced climate change is that precipitation will tend to decrease in the subtropics and increase at northern midlatitudes. That’s exactly what is happening in central Michigan. What’s more, the intensity of multi-day downpours is rising in many parts of the world, including the United States, and the most-affected U.S. regions are the Midwest and Northeast, as noted by Climate Central.

“Storm water management systems and other critical infrastructure in the Midwest are already experiencing impacts from changing precipitation patterns and elevated flood risks,” said the 2018 U.S. National Climate Assessment. In a message that rings out, the assessment added: “Infrastructure currently designed for historical climate conditions is more vulnerable to future weather extremes and climate change.”

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

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Bob Henson

Bob Henson is a meteorologist and writer at weather.com, where he co-produces the Category 6 news site at Weather Underground. He spent many years at the National Center for Atmospheric Research and is the author of “The Thinking Person’s Guide to Climate Change” and “Weather on the Air: A History of Broadcast Meteorology.”
 

emailbob.henson@weather.com

Here are more notes on recent U.S. flooding:

Here is more climate and weather news from Thursday:

(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)

Now here are some of today’s articles and notes on the horrid COVID-19 pandemic:

(As usual, the most noteworthy items will be listed first.)

(If you like these posts and my work please contribute via the PayPal widget, which has recently been added to this site. Thanks in advance for any support.) 

Guy Walton “The Climate Guy”

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