What the Heck Is a Derecho? And Why Didn’t Houston See It Coming?

A powerful windstorm known as a derecho ripped through southeast Texas on Thursday evening, killing eight Houstonians and knocking out power for close to a million customers in Harris County. (As of Monday afternoon, around 200,000 were still without electricity.) With winds gusting up to 75 miles per hour in places, the storm shattered skyscraper windows, toppled trees and fences, and left a trail of destruction in its wake. Not since the 2021 winter storm has Houston seen such devastation. And unlike 2017’s Hurricane Harvey, which made landfall near Rockport, nearly two hundred miles south, the derecho struck almost without warning. Few meteorologists recognized the warning signs until right before the storm hit, giving residents little time to seek shelter. 

To understand why the derecho took Houston by surprise, and what it portends for the Atlantic hurricane season that begins on June 1, Texas Monthly spoke to meteorologist Matt Lanza, managing editor of the popular website Space City Weather. Lanza has lived in Houston for twelve years and endured his share of disasters, but told us he’s never seen anything like last week’s event.

Why did last week’s storm take so many meteorologists by surprise?

Initially, it didn’t look like anything out of the ordinary was going to happen. It just looked like a big thunderstorm was going to come through. We would probably get some gusty winds—a few trees down, a few power lines down. Around 4:30 or 5 [p.m.] we started to see the potential for some storms to rotate. Then it kind of balled into this fist of wind that just punched its way across central Harris County. I was looking at radar and thinking, This is not normal. The wind was 100, 150 miles per hour less than two thousand feet above the ground. Unfortunately the warning time was as little as twenty minutes in western Harris County, and maybe an hour for downtown. 

How did the storm develop so fast?

Usually you can see these kinds of thunderstorm winds coming from around 75 to 100 miles away. To see it develop this quickly over the western fringe of the city, and then continue to intensify as it moved over the city . . . I’ve never seen that before, at least not here. You see it every once in a while on the Great Plains, but that usually impacts rural areas. This time it was over the heart of the fourth-largest city in the country. 

This storm has officially been declared a derecho. Can you briefly explain what that is?

The accepted definition is that it has to travel at least four hundred miles and be about sixty miles in width, with significant wind damage reports. Derechos are really high-end wind-damage events that travel over long distances. 

Why are derechos in particular so hard to predict?

One reason is how they form. A lot of times they develop out of small-scale weather systems, as was the case last week. There’s just no way for weather modeling to resolve the small-scale features that would lead to something forming into that. 

In the wake of the storm, you tweeted that it will change the way you communicate about extreme weather. Can you expand on that?

I did not expect hundred-mile-per-hour wind to barrel straight across Harris County. That’s not something you can predict. You can predict that the atmosphere is capable of that, but you can’t say where it’s going to happen. So I think we meteorologists need to do a better job communicating when the atmosphere is favorable for extreme weather. That could mean hail, wind, rain, whatever. I also think that we need to educate people a little on the limits of what we can predict. We cannot predict this kind of storm more than thirty to sixty minutes in advance. It’s just not possible. 

Has Houston ever experienced a derecho before?

We have one every four or five years, but we’re usually at the starting point of an event that does damage in Louisiana and Mississippi and Alabama. We don’t really see a lot of damage here. There was one back in 1986 that went through Lake Livingston and killed several people as it moved over the lake.

What does last week tell us about Houston’s preparedness for a hurricane? 

We have not had significant wind damage from a hurricane since Ike, in 2008. This is a reminder to people, especially a lot of the new residents, that wind can do a lot of damage here. If we get hit by a hurricane, you can probably expect to be without power for at least two weeks. You’re going to be on your own for a while, and you just need to be prepared for that. This really needs to serve as a wake-up call. If you have not gotten prepared in years past, maybe it’s time. 

The Atlantic hurricane season starts in less than two weeks. How is the forecast looking?

With the oceans so warm, we expect it to be a really active hurricane season. The only potential good news for Houston is that we’re looking at early summer patterns not too dissimilar from what we saw the last few summers, where we had high pressure over us. It was really hot and dry, which kept hurricanes away. Whether that continues through September is anybody’s guess. The rest of the Atlantic is primed and ready. 

Can you talk about the role climate change plays in the increasing number of extreme weather events Houston is seeing? 

In recent years we’ve seen extreme rains, extreme heat, extreme drought, and now extreme thunderstorms. None of that falls outside the bounds of what’s to be expected in a warming climate. Whether climate change contributed to [last week’s] derecho, I don’t think you can really say. But it’s the kind of thing you can expect because of climate change. There’s certainly something to be said about the role of a warming Gulf in events like this. That could have added a bit of extra juice to the atmosphere here. When you have higher moisture, you get more instability in the atmosphere. That can strengthen thunderstorms even more. 

I’ve seen a lot of bizarre conspiracy theories on social media about the derecho. Do you have a favorite?

Oh, I’ve seen it blamed on everything from microwave beams to the High-frequency Active Auroral Research Program to the recent solar storms. It’s frustrating to me that people will ignore very obvious answers for why things happen in favor of these other things. I think we’re living in a strange time. A lot of people with strange theories are having their voices amplified by social media. 

Do all the recent weather disasters ever make you think about leaving Houston? 

They do, absolutely. Obviously you don’t like seeing destruction, suffering, and all that. But it’s a great place to be a meteorologist. There’s a lot to be learned here that can hopefully help people. At the same time, it’s exhausting. We just have to roll with it. Houston’s an amazing city, and the people are great. It’s a city I don’t ever want to give up on.