In brief: Ironically, Thursday was “National Love a Tree Day.” Instead of loving trees, however, a line of storms ripped through the heart of Houston and tore many thousands of them down, killing a handful of people, damaging homes and vehicles, and bringing down power lines. In this post we’ll provide some meteorological data about what happened Thursday, and a forecast looking ahead to calmer weather.

Tornadoes

The National Weather Service has completed a survey of damage from two confirmed tornadoes that struck Houston on Thursday evening, one at 5:44 pm near Pine Island in Waller County, and the second at 6:08 pm near Jersey Village in Harris County. Here is the summary of those investigations:

Waller County tornado

• Rated EF1
• Peak winds: 100 mph
• Path length: 0.71 miles
• Path width: 100 yards
• No fatalities or injuries
• Duration: 5:44 to 5:45 pm CT
• Significant tree damage, large metal barn destroyed, metal debris thrown up to 1,000 yards away.

Cypress tornado

• Rated EF1
• Peak winds: 110 mph
• Path length: 0.77 miles
• Path width: 100 yards
• No fatalities or injuries
• Duration: 6:08 to 6:09 pm CT
• Numerous single family homes had roof damage and broken windows. Damage path well defined.

This is a preliminary report that may be adjusted in the future.

Straight-line wind damage

As Matt noted yesterday, most of the damage in the region was caused by straight-line winds, and what appeared to be something of a mini-derecho. The National Weather Service has also collected maximum wind reports from around the area on Thursday afternoon and evening. Some of the highest values were recorded at Texas A&M University, 71 mph, and the Houston Ship Channel, 74 mph.

Very strong winds just above the surface were able to break through, and get down to the ground. These winds a few hundred feet above the ground were even stronger than what was observed at ground level. This is likely the reason why some skyscrapers in downtown Houston observed significant damage at their upper levels.

Power outages

About one-quarter of customers in Harris County are still without electricity this morning. In an update to the media on Friday evening, CenterPoint Energy said restoration could take “several days or longer” for the hardest hit areas.

“As crews continue to uncover damage and encounter new challenges while making repairs, restoration may take more time than customers typically experience following a routine storm event,” the company said. “CenterPoint Energy appreciates customers’ patience, and the company will work around-the-clock until the last customer is restored.”

We genuinely appreciate the hard work by all of the lineman working to restore power. It is a hard and hot business to rapidly repair storm damage, I know first-hand how hard the men and women are working out there.

Flooding

The heaviest rainfall on Thursday occurred north of the area, in locations such as College Station and Livingston, which have already been inundated over the last 30 days. Significant river flooding is likely along the East Fork of the San Jacinto River later this weekend, whereas the Trinity River is already cresting today before a slow fall next week.

Fortunately the entire southeast Texas region will now get a chance to dry out. Our weather is about to get boring.

Forecast

After the fog lifts this morning we’ll see sunny and hot conditions today, with highs likely in the low 90s. And that’s pretty much your forecast for the next week, at least. The only change will be gradually warming nights. Lows this morning got to below 70 degrees for most locations. It was, almost, nice? Well, except for the mosquitoes. By Wednesday or Thursday morning, our lows are likely to only dip into the upper 70s. Rain chances are nil for the foreseeable future.

We wish everyone the best this weekend as you recover from Thursday’s storms, and thank everyone who is out there helping to pick up the pieces. This community is at its best in moments like these, when we’re all working together.

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: A line of severe storms moved through Houston on Thursday evening bringing heavy rainfall, and instances of damaging winds and tornadoes. We’ll have a full rundown tomorrow, but it has been a wild few hours. The point of this post is to let you know that that’s it for the night. And after some residual showers tomorrow, that’s it for spring storm season in Houston.

Wow, that was strong

Yes it was. We expected some severe weather this afternoon and evening, and forecasted as much this morning. But it’s fair to see we did not quite anticipate the severity of what developed. There are widespread reports of trees downed, damaged fences, and other significant problems associated with straight-line winds and a couple of tornadoes that developed this evening. On the excitable dogs scale from 1 to 10, this was an 11.5.

Electricity remains a significant casualty. In Harris County, as of 7:30 pm CT, 40 percent of customers are without power. These storms actually weakened as they tracked across the region, so the outages are even worse just to the west of Houston, where power is out to 75 percent of customers in Waller County. It is beyond the scope of what we can forecast to predict when the power will come back on, but the storms are clearing the area relatively quickly. Crews should be able to respond to outages beginning this evening, and work overnight.

So what happened? Some of the parameters we look at to gauge severe weather, including instability, convective available potential energy, shear, and helicity all came in at or above expected levels as the storms approached the Houston metro area late this afternoon. This allowed them to bloom and produce destructive storms.

What comes next

The major line of storms has already moved through central Houston, and it is steadily weakening as it as moves toward the coast. If it has stopped raining at your location, that is basically it. We may see a few trailing showers in the next couple of hours, but nothing serious. Tonight looks quiet.

Tomorrow a final low pressure system will pass Houston, and may bring some additional showers to locations along and south of Interstate 10. I don’t expect these to be particularly severe, and they should develop mostly south of where the strong storms were today.

And then? That’s it. Spring is over. High pressure begins building over the area this weekend and we’re unlikely to see significant rain for days, if not weeks. Spring storm season ended with a fiery finale today.

In brief: Houston faces the threat of heavy rainfall, and possibly severe storms, on Thursday afternoon and evening. Beginning shortly after noon we’ll see stronger storms building north of Interstate 10. Eventually a (probably weaker) system will migrate toward the coast late this evening. Some additional rain is possible Friday before a prolonged period of hotter and sunnier weather.

The big picture

It may feel like déjà vu to be staring down yet another threat for storms and heavy rainfall, as it has been a truly wet spring for the Houston region. During the last 30 days, the majority of our area north of Interstate 10 has received at least 10 inches of rain, and locations further north, particularly in the Huntsville and Lake Livingston areas, have received in excess of 20 inches. This has led to significant river flooding, and we’re likely to see more of that in the coming days after storms this evening and overnight.

If you’re tired of it all, I don’t blame you. But I would also note, with some caution, that we’re about to experience a significant pattern change. High pressure will settle in, and after Friday the remainder of May looks very dry. Maybe not completely dry, but quite possibly so. This could set us up for another scorching June, not dissimilar to last year. So while significant flood relief is coming, we may begin to miss some rain in a few weeks. We’ll see.

Thursday

I’m not concerned about conditions on Thursday morning, which should bring cloudy skies and temperatures in the low-80s. However, beginning later this afternoon, perhaps around 1 to 3 pm, we’re likely to see the development of showers and thunderstorms to the north of Houston, in areas such as College Station and Huntsville. Conditions are ripe for heavy rainfall, as an upper-level system brings lift into an atmosphere filled with moisture.

Some of these storms may well be severe. There is enough instability to support the threat of damaging winds and possibly a few tornadoes. (Hail, at this point, looks like a lesser threat). However, my biggest concern lies with the potential for heavy rainfall. Most areas north of Interstate 10 are likely to see 1 to 4 inches, but with these kinds of storms bullseyes of 6 or more inches are possible this afternoon and evening. By or before midnight, the worst should be over for inland areas. Long-term, we’ll need to monitor ongoing flooding of the Trinity, San Jacinto, and Brazos river basins.

After battering inland areas, the system is likely to migrate southward later this evening, and push closer to the coast near midnight. Heavy rain remains possible south of Interstate 10, but the overall threat is less.

Friday

An additional, final round of showers and thunderstorms is possible on Friday morning. This activity should be clustered closer to the coast, where the boundary will get hung up. Expect highs in the mid-80s, with possibly some partially clearing skies by Friday afternoon or evening. Lows on Friday night will drop to around 70 degrees.

Saturday and Sunday

The weekend looks sunny. I’d expect highs to slot somewhere into the low-90s on both days, with nights in the low 70s. Southerly winds look light, so plan your outdoor activities with confidence (and sunscreen).

Next week

More sunshine is on the way. Generally we should see mostly sunny afternoons next week, with highs likely pushing into the low 90s for areas of Houston closer to the coast. Inland areas may get a few degrees warmer. It won’t be full-on summer, but it will be rather warm. Rain chances are not zero, but they’re close for most if not all of next week.