Q&A: How hurricanes in the Gulf trigger storms in Virginia and North Carolina

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Across the Southeastern United States, hundreds of roads are closed, power outages continue to be reported and catastrophic flooding devastated mountain towns as the fallout from Hurricane Helene swept through parts of Georgia, the Carolinas and Virginia this weekend.

Majid Shafiee-Jood, a research assistant professor of civil and environmental engineering at the University of Virginia, discusses how and why this is happening. Shafiee-Jood researches decision-making based on hazardous weather information, including hurricane bulletins, flash-flood warnings and evacuation orders.

Why are we seeing spinoff storms as a result of hurricanes further south?

Hurricanes are rapidly rotating storm systems with strong winds and a spiral arrangement of thunderstorms. Hurricanes typically contain massive amounts of moisture, which could lead to heavy rainfall. Depending on the size or speed of the storm, they can generate massive flooding.

These are typically referred to as flash floods—flood events that occur in a short period after a storm, typically within six hours and often within three hours of the storm. This is different than flooding seen in coastal areas induced by storm surge, known as coastal flooding.

Flash floods happen because you have significant rainfall in one region in a short period of time. It can happen anywhere. In urban areas with significant development, it can happen because the rain doesn't have much space to penetrate into the ground.

In the mountainous areas with steep slopes, especially when soils are saturated, intense rainfall can rapidly turn into flash floods, which are sometimes accompanied by mudslides and landslides. That's what we're witnessing right now in western North Carolina and parts of Virginia.

Is this normal?

It's not unusual. Back in 2018, when Hurricane Michael happened, we had similar landfall in the Florida panhandle area that moved northward toward Georgia and the Carolinas. There's a small dam called Banister Dam in Halifax County, which nearly overtopped because of the significant amount of rainfall produced by then-Tropical Storm Michael.

You created the first-ever hurricane evacuation order database. How does it work?

One of my main areas of research is understanding how individuals and decision-makers make decisions when they receive hazardous weather information. For instance, in the case of Hurricane Helene, a couple of days before the hurricane made landfall, several Florida counties issued evacuation orders.

Over the past few days, many of us in the Charlottesville area received flash flood watch and warning messages on our cell phones. The question is how we respond to this information when the stakes are so high.

Fellow assistant professor Negin Alemazkoor; Harsh Anand, former UVA Engineering doctoral candidate; and I wanted to understand how effective hurricane evacuation orders are. Let's say the Emergency Management Office in Virginia issues a hurricane evacuation order; to what extent do people evacuate based on that information?

We were interested in quantifying that, then realized we needed a database of hurricane evacuation orders, looking at which counties and states issued evacuation orders, when, and what areas they covered.

When we quickly realized such a database did not exist, we spent more than a year putting it together. ... We analyzed social media accounts, news coverage and local government websites to document the evacuation orders issued in response to 25 hurricanes between 2014 and 2022. We're currently working on updating the database for the couple of major hurricanes we have had since 2022.

What further research are you doing that may help Virginians better understand how to be prepared for these emergencies in the future?

Well, we all receive flash flood warnings, but to what extent do we pay attention to these messages? To what extent do we make decisions and act upon receiving this information? One thing we have been trying to figure out using the database is to improve that messaging.

We are also trying to figure out how the responses vary among communities. How do communities across socioeconomic status, urban vs. rural settings, etc., respond differently to this information?

By getting these insights, we hope that we can help the National Weather Service and local weather forecast offices in terms of how they can better communicate the messages. This could also help FEMA and other emergency management offices better understand potential responses from different communities to better allocate their resources.

Provided by University of Virginia