A rare weather phenomenon was occurring this weekend. One of the most populous regions in the United States was under threat from Hurricane (Henri). A severe weather event was also taking place in Tennessee and North Carolina. Numerous people were killed in the flooding, while many more are still missing. As a scientist, and former President of American Meteorological Society (AMS), I have long lamented the fact that flooding poses many challenges in the intersection of meteorology as well as risk communication. These are just three examples.
Vehicles are laid to rest in a stream in Waverly on Sunday, August 22, 2021. Heavy rains on Saturday caused flooding in Middle Tennessee, resulting in numerous deaths and damage to homes and roads. ASSOCIATED PRESS
First, a flood event's lead-up isn't as social media-worthy or telegenic as a hurricane or other tornadic weather events. A weather event that is described as an upper-level shortwave, high instability and top percentile precipitable waters will not generate much public attention beyond Weather Twitter and 24-hour meteor networks. These conditions caught the attention National Weather Service- Nashville who was advising about the impending flood in its Saturday evening messaging.
Hurricane Henri is approaching Long Island, and metropolitan New York City will be a little easier to reach. Ironically, the rains associated with Tropical Storm/Hurricane Henri might have taken many by surprise. The problem of a training band in New Jersey and New York is particularly troubling. It is concerning that people's perceptions of wind speed and track location can influence their mental models about a bad hurricane. In my Forbes article, I highlighted that messaging about storms such as Henri should be grounded in the impacts of all possible scenarios and not just one track or whether it is a strong Tropical Storm/weak hurricane.
Weather deaths in the United States during the past year, 10 and 30 years of National Weather Service
This brings me to the second challenge. This leads me to the second challenge. Jeanine Santucci reports in USA Today that at least eight people have been killed and 40 are missing in Humphreys County in Tennessee after Saturday's severe flooding.
Jordan McLeod (climatologist), was alarmed enough to send a message to me over the weekend. McLeod stated, "I have family in the area. They have received almost 17 inches of rainfall since midnight." Ten people were killed in their county, and 31 others are still missing. On August 21st, the National Weather Service – Nashville tweeted that McEwen, Tennessee's 17.02 inches of rain had broken the state's 24-hour rainfall record. Official confirmation is required. However, the new record will surpass the 13.60 inch record that fell on Milan, Tennessee, September 13th 1982.
The Nashville area has a range of rainfall totals, ranging from 8/20 to 8.21. NWS
Flooding can also be costly. Flooding can also be costly. Homes were literally washed away and important infrastructure was damaged or destroyed. According to Pew, flooding caused more than $260 Billion in American losses between 1980 and 2013. Federal flood insurance claims increased from 2006 to 2015. These trends are linked to climate change. New research suggests that precipitation changes are responsible for nearly 36% of flood damage costs (1988-2017).
Flood risk is not only a result of what falls from above. It also involves stormwater infrastructure, increased impervious surfaces (pavements, parking lots), climate change, individual decisions and the location and use of properties within floodplains. In the past, messaging has been dominated by cute slogans such as Turn around, Don't Drowse and layers of warnings or watches for floods. We need more layers for flood messaging. This is the third problem. The National Weather Service has a strategy that will not only address flood warnings, but there are other options.
An exchange with Amanda Schroeder (an ex-grad student of mine) led to her interest in developing a Flash Flood Scale/Index analogous to the Saffir Simpson and Fujita scales. Schroeder, Senior Service Hydrologist at the National Weather Service Fort Worth Office and a group of scholars published this index in 2016. A perfect scale or index number is difficult to calculate due to flood risks. However, the public is familiar with this approach so it has merit. Only time and research at the intersection between meteorology, social sciences, will determine if such scales are viable or effective.
Flood messaging should also consider the risk-reward mentality and optimism bias that people display when making decisions. Most people are aware that driving on flooded roads is dangerous. They may be more concerned about not being late to pick their child up from daycare. The Weather Channel's Immersive Mixed Reality tools offer great promise. IMR can show you the effects and experience of being swept away on roads by rushing water. For communities with low income and vulnerable to flooding, it is important to have a more consistent messaging strategy. Mobile homes are being swept away in images from the South this weekend.