Matt Lanza

In brief: Summer’s here, and through Memorial Day you will find little to no relief in the area. From there, the weather pattern may get a little more unsettled next week, but nothing stands out that we can hang our hat on just yet.

I know that no one wants to talk about hurricane season after last week, but NOAA’s extremely active seasonal forecast released yesterday should remind us to plan for the season to come. We wrote about their forecast and the current state of the tropics yesterday at our companion site, The Eyewall. We’ll be updating that site every day or two going forward as the weather requires.

For those struggling with continued poor air quality thanks to the haze and smoke from agricultural fires in Central America and Mexico, I don’t think we will see much relief this weekend. I am hopeful we get a shift in wind next week though.

Yesterday’s low temperature at Hobby Airport was 80 degrees, the third time already we’ve failed to drop below that mark this year. We’ve already tied for the earliest first 80 degree morning on record at Hobby this year, on May 21st, matching the previous record set in 2022. We are running about a month and a half ahead of normal, for whatever “normal” is worth anymore. Today will be the seventh morning where the low temperature has failed to drop below 78 degrees, which sets a new record at Hobby for the most before June 1st. We should add at least three or four more days to that before we get a wee bit of relief next week just before the calendar changes.

Anyway, I write all this to say that this is not a normal start to summer. It’s hitting strong and fast. And don’t be shocked to see a heat advisory this weekend. Practice heat safety this weekend. Yeah, it’s Houston and it’s always hot in summer. But we are not yet acclimated to these temperatures for the season, so heat illness can come on quick and unexpectedly. Some of us are still cleaning up from last week or even still without power. Check on those folks, keep your pets cool, and look before you lock.

Today through Sunday

The front portion of the holiday weekend looks partly to mostly sunny and hot. Expect highs in the mid-90s and lows near 80, or essentially normal weather for late July, not late May.

I would not be entirely floored to see an isolated thunderstorm roll through areas north of Houston, perhaps as close as The Woodlands or Magnolia. Most people will not see one, but if you do, it could rain hard for a short time, with lightning, gusty winds, or even some hail. Again, this is most likely to be isolated and north of Highway 105, but perhaps as close as Montgomery or northern Harris County.

Memorial Day

This should be the hottest day of the stretch. Expect mid to upper 90s and a mix of sun and clouds with just a slight chance of a late shower or storm north and west.

Sunday and Monday’s heat will border on “extreme” levels, so maximum heat precautions should be taken here.

Rest of next week

Things start to change a bit next week. Temperatures will shift to become a little “less hot,” which means more like low-90s than mid-90s. Nighttime lows may drift back more into the mid-70s. A series of disturbances may try to erode away the northeast portion of the ridge of high pressure over Texas, so that could be just enough to fire back up some thunderstorms after Monday. I don’t even want to begin to speculate on timing or details or any of that. Just know that the stagnant pattern of this weekend may change a bit next week.

In brief: This post explains what a derecho is, where the term came from, and talks a bit about some past thunderstorms of note in Houston.

What is a derecho?

The National Weather Service has concluded that Thursday’s severe storms in Houston constituted a derecho. So what does that mean?

First off, it’s pronounced “deh-REY-cho.” Meteorologists have debated what the definition of one of these things actually is for years. And we still don’t have a concrete, universally accepted definition. However, progress was made after a 2011 storm that hit the Southeast and a 2012 derecho that ravaged the Mid-Atlantic and Midwest to work toward something more widely accepted. Ultimately, NOAA/NWS defines a derecho as a continuous or intermittent path of wind damage from a squall line of thunderstorms, bow echo, or quasi-linear convective system (QLCS) that extends at least 400 miles and is at least 60 miles wide. In other words: It’s a swath of wind damage from mostly non-tornadic thunderstorms that extends for 400+ miles and is at least 60 miles wide.

What makes it different than typical severe thunderstorms?

A derecho, as noted above can be a squall line, bow echo, or QLCS. We get several of those types of events every year in Houston. What sets a derecho apart is the wind damage. It’s not normal. It’s not a couple trees on power lines. It’s a lot of wind damage over a long path.

Are all derechos the same?

No! Derecho events are broken down into three categories: Serial, progressive, and hybrid. A serial derecho is basically where you have one giant squall line that is hundreds of miles long with multiple embedded bow echoes producing widespread wind damage. A progressive derecho is the one we experienced in Houston last week that is typically no more than about 250 miles wide. You also have hybrid outcomes, which basically share characteristics of the two others.

Why is it called a derecho?

According to NOAA, Dr. Gustavus Hinrichs, who was a professor at the University of Iowa coined the term in 1888. The literal Spanish translation of derecho is “straight ahead” or “direct” or even “right.” Here’s where the etymology gets kind of fun. “Tornado” derives from the Spanish “tronada,” which literally means thunderstorm. But there is also a Spanish word “tornado” which essentially means “twisted,” and it derives from the Spanish verb “tornar,” which means “to twist.” So essentially, Hinrichs took the “opposite” of twisted and decided that derecho (or “straight”) would be a good way to distinguish tornado-like wind damage that was not caused by a tornado.

Are derechos common?

The short answer is: Kind of. The most recent derecho prior to Thursday’s in Houston occurred back on April 1-2 from just west of Missouri through West Virginia. A storm that almost met derecho criteria occurred just this past weekend in Kansas and Missouri. There were derechos in 2023, 2022 in Canada, 2021, and so on. In fact, the quad-state area around Kansas, Missouri, Arkansas, and Oklahoma northeast of Tulsa averages more than one derecho per year.

Derechos are most common in May, June, and July. Keep in mind that a lot of the areas that see derechos every 1 to 2 years are more rural, so it’s likely you hear less about them than when they hit places like Chicago or DC or Houston directly, causing billions in damage.

You can read about a bunch of pre-2012 events across the country here. Some even occur out West. I was introduced to derechos when I worked in Upstate New York early in my career. The memories of the 1998 Syracuse derecho were still incredibly sharp, much like Houstonians will remember last week’s. That was followed up by a second derecho event that moved from Michigan to New York City. The 1995 Adirondack derecho (or Adirondack blowdown) was responsible for knocking over more than half the trees in 100,000 acres of Adirondack Park.

The Houston area’s history with derechos and thunderstorm wind events

There are a few thunderstorm wind events and derechos that have stood the test of time in this area. First and foremost was just last summer when a squall line delivered a 97 mph wind gust to Bush Airport.

That storm on June 21st was one in a series last June that caused damage across the area. It was not a derecho, but it certainly caused severe damage north of downtown Houston.

A storm system in 2002 did a good bit of damage, including to the I-10/Gessner area, according to the Houston Chronicle’s archives. Just shy of $1 million in damage was reported with fortunately no injuries.

In early May 1993, a powerful squall line knocked out power to 200,000 homes in Harris County and went on to rampage Galveston County, causing at least $50 million in damage and delivering a 98 mph wind gust to Scholes Field in Galveston.

There was also an event the year after this in March that brought 100 mph winds to the less populous western end of Galveston Island.

Texas Boaters’ Derecho (May 1986)

While not Houston, the “Texas Boaters’ Derecho” of May 1986 makes the list of memorable derecho events in the United States. You can read a full summary of the event on page 20 of the May 1986 NOAA StormData publication.

It’s tough to find a lot of good information on how this particular event impacted Houston specifically, but it is infamous due to the fact that it drowned six. There was a fishing tournament and boat race on Lake Livingston that day when the storm hit, bringing winds estimated to be 90 mph and waves of 10 feet on the lake. Much like we see with the damage from this year’s derecho, there were pockets of more significant damage within a broad damage field during the 1986 storm.

May 1983 storms

Thanks to Bill Read for pointing this one out to us last week. Three years prior to the ’86 derecho, a particularly bad thunderstorm event impacted much of the Houston area.

According to NOAA’s May 1983 StormData, approximately four downburst events, including one over the city of Houston, combined with eight tornadoes for a deadly severe outbreak in our area. Winds were estimated at 75 mph or stronger in spots, with several transmission towers crumpled over, much like in this month’s event.

Over 300,000 customers were left without power in that storm, which would have been a bit less proportionally to this year’s storm. Winds were measured as strong as 110 mph during a tornado in Nederland, near Beaumont with this one. According to a Houston Chronicle recap of this event at the time, the spokesman for the Houston-Harris County Civil Defense stated that the damage was worse than in Hurricane Carla in 1961.

Approximately 10 people died with over 100 injured from this storm. Arguably, this was the previous worst non-hurricane wind storm in Houston until last week’s. It’s tough to find an official estimate on the damage caused by the May 1983 event, but it was likely in the tens of millions of dollars at the time.

Other events that seemed to garner some attention were a combination of severe storms and tornadoes on May 2, 1979, which primarily impacted western and northwestern parts of the area. On May 7 of 1976, significant wind damage occurred east and southeast of Houston, along with a few tornadoes nearby. The Exxon facility in Baytown apparently observed winds of 90 to 95 mph with considerable damage in that community. Back on June 4, 1962, a torrential squall line of storms seems to have had something of a similar impact on parts of the city as the recent derecho. Many people lost power, wind gusts hit at least 75 mph, and some windows were blown out downtown.

While last week’s derecho was extreme by any real definition of Houston thunderstorms, I think we can assume that perhaps the return period on such a storm may be less than we might have thought. And Houston can now add destructive thunderstorm winds to a litany of periodic weather disasters including freezes, floods, hurricanes, extreme heat, and drought.

In brief: There will be some showers this morning south and east of US-59 to the coast. Some thunder is possible. No severe weather is expected. The rest of the forecast through Monday and Tuesday is quiet and turning hotter.

We have a few showers southwest of Houston that will push in this morning. The steadiest rain will be south and southeast of the city, areas that saw a bit less action yesterday. We then clear out and dry out for later and tomorrow, Sunday, and Monday. Highs will nudge into the 90s with lows slowly increasing through the 70s into next week.

Trying to make sense of Thursday

This will be a different post than typical. I want to walk through what happened yesterday from a forecaster’s perspective. About 750,000 customers remain without power this morning, and because of the extensive, widespread damage, this number will very slowly decrease today and tomorrow. Some may be without power until next week.

So how did we get here? As a refresh, here is Eric’s post from yesterday morning. We were all really focused on the threat for heavy rain, and with the high risk in place yesterday to our north, that shouldn’t be a surprise. In fact, 4 to 5 inches of rain did fall as expected, basically north of highway 105 through Conroe.

Eric did note the severe weather and correctly underscored the chances of wind and an isolated tornado. The Storm Prediction Center had the right idea on severe weather yesterday too. But again, I think most of us the significant messaging was heavily focused on the rain.

Through most of yesterday morning, not a whole lot seemed to change. Eric, Dwight, and I met up for lunch at a Pappas BBQ but not the one we originally planned on, which, thanks Apple Maps. Or Google Maps. Who’s to say? Anyway, we touched briefly on the day’s weather but were not particularly concerned about anything else happening. We checked radar while leaving and all looked good.

I got back to my desk and noticed a few people pinging me about a Reed Timmer tweet discussing rain-wrapped tornado potential in southeast Texas. Reed’s a good guy and a very smart meteorologist, but he also has tons of enthusiasm. His brand is to dominate and never stop chasing. My first reaction admittedly was to roll my eyes, but then I checked out the HRRR model, one of our hourly updating high-resolution weather models. Indeed, it lit up with supercells by 2 PM. But it was 2 PM. And there were no supercells.

So clearly it was overdoing it, and it would be necessary to watch subsequent runs to see what changes, as well as radar to observe the evolution of the storms. I decided to look at some other data, and I was surprised to see that despite clouds, haze, and mist (or even a heavy drizzle at times), the atmosphere was extremely unstable over the area.

And when you would dig deeper into the models, everything pointed to severe potential. But we also just went through this a few days ago with a major hail threat that basically failed to materialize with any consequence in Houston. In that case, we had the same situation in theory: Impressive instability and an atmosphere primed to rock. As a meteorologist, you look at this two ways: We just came off a semi-bust and you need to make sure you are more confident in something than normal before pushing it, and secondly you also can’t deny that the ingredients were there. A tornado watch was issued, which was a little surprising, though given the parameters there was no good reason to argue much against it.

When I looked at model data, it appeared that any supercell risk would track from the southwest to northeast. I even highlighted a cell around Spring at about 4:25 that I thought was showing signs of trending toward something more meaningful. I went to pick up my oldest from school and came back intending to help him do some homework. Even by about 5:10 or so, it seemed pretty straightforward: A line of severe storms with gusty, maybe localized damaging winds was moving through Brenham and toward Waller County, and we’d probably get it through by 7 or 8 PM and that would be that.

Things began to change quickly about 15 minutes later. It was evident that rotation had begun to develop on the leading edge of the bowing line near Bellville. And it seems likely that a tornado may have been put down just east of there shortly thereafter. That is not necessarily uncommon. It’s often how we get our tornadoes locally, but it’s usually brief and disappears after 5 to 10 minutes. And indeed, the rotation weakened some, but at 5:35, it flared back up again, just west of FM 359 to the east of Bellville. Thereafter, it absolutely exploded near Pine Island and just south of 290 in Prairie View. By 5:40 to 5:45, we clearly had a problem.

I have been in Houston for about 12 years as of this week, and I cannot recall seeing this type of velocity signature (the right-hand panel) show up in this area. When you see this as a meteorologist, it either means a violent tornado is underway, or destructive winds are probable. At times, it looked like you could pick out a debris signature on radar that would essentially confirm a tornado, but it never took off, which led me to believe that this was becoming a major straight line wind event.

I had been texting a bit with Justin Ballard, the Houston Chronicle’s fine meteorologist earlier about the tornado watch. We both expressed some skepticism it would produce. He texted me at 6:07 in the middle of this saying, “Yeah, that doesn’t look like a bad decision after all.” Yes, many of us talk to one another. Yes, we occasionally have opinions on things.

Anyway, this continued to march east-southeast and slowly expand. At this point, it becomes straightforward: Monitor it and warn and clear. I had posted to Twitter in a tone I very, very rarely ever use. I don’t throw around language like “Treat this like a tornado” very often. We had gotten very few damage reports up to that point, but the radar was indicating 110 mph winds down to about 2,500 feet. By 6:23 PM, radar showed 120 mph winds down below 2,000 feet approaching Oak Forest. Does all that reach the ground? No. But a lot of it can. It also made me gravely concerned for the downtown high rises.

We’ll find out more today and tomorrow about specifics on damage and what was a tornado or straight line winds. Whatever the case, this was one of the most ferocious storms I’ve ever seen. This was a smaller scale version of what occurred in Iowa a few years back, when they had 140 mph winds down to about 1,000 feet but over a wider area. Whether or not this gets classified as a derecho will remain to be seen. I think it probably falls just short of that metric because of some discontinuity in the damage report path, but honestly, does it matter? It will take time to pick up from this one, and we hope our readers are safe. A major kudos goes out to the many media meteorologists and NWS meteorologists that assisted in keeping as many people safe and informed as possible. Saving lives is rarely a literal thing for a meteorologist. I am thinking that it was for many last night.

I’ll close with a bit of a sobering note: Hurricane season begins in about 2 weeks. What many of you witnessed last night would be experienced not over a few minutes but over several hours over a large area if a truly potent hurricane found its way into the Houston area. By living in this region, you have to accept the risks associated with that. We know a lot about flooding. Most of us know about surge. Very few knew about wind and what it’s really like. Many do now. Use this experience to inform your preparation for hurricane season just in case. Houston has been through an absolute meat grinder of weather disasters in the last 10 years. Candidly, it sucks, but we should know enough now to prepare for the next one.

In brief: If you have clear skies and minimal light pollution, look to the north for a chance that you may see the aurora borealis (or northern lights) here in Southeast Texas (Friday night, the 10th).

We’ll keep this brief. A massive, if not historic solar storm has unleashed a barrage of solar flares toward Earth. Those arrived today, the strongest solar storm in at least 20 years to impact us. We have seen reports all over Europe of the aurora being visible. Not just visible…VISIBLE. Those reports have spread into the U.S. now, with much of Georgia, parts of Mississippi, Mobile, AL, and now Pinehurst and The Woodlands and Lake Conroe reporting the aurora.

The aurora can be fickle, so there is no guarantee you will see it everywhere tonight, certainly not in the city of Houston where light pollution is likely too much to overcome. However, if you have the means and time to get out and look north, this may be a once in a lifetime opportunity here in Southeast Texas. Please send us pictures as you’re able.