SCW Q&A: Loopy radar, conflicting forecasts, rising houmidity, weather stations, sudden storms

This installment of the Space City Q&A is particularly tasty: Y’all came up with some very good questions! Keep them coming: Hit the Contact link at the top of the blog, or leave a query in the Discourse comments below this post.

Q. I have a question as to how weather radars generate their one-hour plus future radar loop. Some recent rain showers have been from storms that kind of pop up on the radar, meander around for a bit and then dissipate. They usually don’t have an easily defined direction to them like they might have if they were spawned from a frontal boundary moving in. However, on most radar loops that I watched, as the radar passes from the older, real radar data to the projected data, the storms go from wandering with no direction to a well defined direction. In reality, as time moves forward the storms end up meandering and don’t go in the predicted direction. Any thoughts as to why this occurs?

A. I am not an expert in predictive radar apps, but I have done some research in this area in the past. So I’m going to dive in a little bit here because I think it’s a good question.

First of all, as you’ve suggested, these predictive apps work best when there are clearly defined storm motions, such as along a frontal boundary. This is because the “nowcast” for 0 to 60 minutes is based on current radar readings and inferred motion vectors based on storm intensity, speed, and direction. More sophisticated methods might also incorporate flow equations, such as the Lucas–Kanade method. (Dear reader, it has been 30 years since I took an advanced mathematics class, and I’m not going to try and explain how that works. Because I really don’t know.) These forecasts are quite accurate for storms with clearly defined motions, but less so for other storms. I would trust them for about 30 to 60 minutes out, at most.

Predictive radar features found in popular weather apps, such as this one from Apple, are most accurate at 30-60 minutes.

Then there are medium-term forecasts that run from 1 hour out to several hours. These generally rely on a single high-resolution model, such as the High-Resolution Rapid Refresh (HRRR), or a blend of models with some AI-enhancement thrown in. Again, for something like a line of storms ahead of a frontal passage, these can be pretty accurate. But if storms are just popping up around the city during the afternoon, they’re probably not going to reliably tell you if it is going to rain at your house three hours from now. I mean, sure, they’ll get lucky some time. But they’re also going to miss. I wouldn’t trust any predictive radar app more than a couple of hours out.

–Eric

Q. It’s not new, but it feels more noticeable lately with the new weather reporter at the Houston Chronicle. I usually read him, check your forecast, and glance at the iPhone app. A recent day offered a good example: he predicted highs in the upper 90s, possibly hitting 100. My iPhone said 89. You (correctly) called for mid-to-upper 90s. How can one source call for 100 while another is calling for 89? I guess it feels like the spread is getting wider, not narrower. I’d expect the opposite with improved technology. I assume it comes down to different models, how showers affect afternoon highs, and maybe even some editorial choices (the Chronicle does seem to lean into more dramatic weather headlines recently).

A. I can’t speak for the Chronicle’s forecasts, but I know Justin Ballard tries to do a good job. And if there are sensationalistic headlines, they’re generally coming from online editors pressured to drive up traffic numbers rather than the forecaster. I dealt with this when I worked for the newspaper, which is one reason why I very much prefer working for myself.

Anyway, I suspect it may be a combination of things. When I say the highs in Houston are likely to be the mid- to upper-90s, I’m referring to the central portion of the area, i.e. Harris County. Daytime temperatures in the summer will invariably be cooler in Galveston, near the water, and often warmer further inland, such as in Conroe or Sealy. Perhaps Justin was referring to the forecast at Bush Intercontinental Airport, and I was more considering Hobby. That would explain the variance in our forecast.

As to why the iPhone said 89 degrees, perhaps it was forecasting an afternoon shower to keep things cooler? I don’t really know. But in general, a lot of the variety in temperature forecasts for Houston are due to its large area (more than 90 miles from Galveston to Conroe), varied nature of the terrain, urban heat island effect for the city’s core, and surface temperatures of the Gulf of Mexico. It’s … a lot to balance.

–Eric

Q: As far as climate change goes, rising global temperatures get a lot of attention, I was wondering if global humidity levels are trending upward, too? This year may be more an extreme example, but I was wondering: As the temperature rises, and more water evaporates from the oceans and other bodies of water, giving precipitation events “more to work with.” i.e. Has there been a noticeable shift upward in global average humidity levels?

A. When you think about humidity here in Houston – or “houmidity,” as we sometimes call it – you (should) think about dewpoint. Dewpoint is a measure of moisture in the air; it’s the temperature that the air would need to cool to for it to be saturated. When dewpoints are high, it feels very humid, hence why Houston’s summers are so generally awful; we have dewpoints often in the mid-70s to even upper-70s at times. Periodically, the immediate Gulf Coast can see dewpoints of 80°, and there have been instances of some places in the Middle East (Iran in particular) seeing dewpoints over 90°!

Why does it feel so humid? Warmer air holds more moisture. You could have a relative humidity of 100% with a temperature of 50° and a dewpoint of 50°. That feels damp or clammy, but it isn’t oppressive. But if you have a dewpoint of 75° and an air temperature of 75°, that feels disgusting. The relative humidity is 100% in that case too. But because the air temperature is warmer, it’s holding more moisture.

Houmidity is front and center in the Space City Weather app. (And remember, that spelling is a not a bug, it’s a feature!)

Thus, as climate change continues, we will see global humidity levels increasing too. A warmer planet has more capacity to hold moisture, so generally the humidity and dewpoints will be higher. You can read more from the UK Met Office here. Thinking about this locally, 2025 sure seemed like a fairly mild summer by almost anyone’s standards in Houston. But it was the 6th warmest on record because our nighttime lows were second highest on record. Put simply, the daytimes weren’t so bad, but the nighttimes were persistently very warm, even by Houston standards. Some of that is certainly urban heat island affect (more concrete = warmer nights). But it doesn’t explain why Bush, College Station, Galveston, and Hobby have all had top 20 or 30 hot summers every summer since 2016 (with the exception of 2017 in Galveston). That is likely because the atmosphere is warming, the Gulf is warming, and it’s able to hold more moisture and keep nighttimes much warmer than usual.

–Matt

Q: Are the CenterPoint Energy weather stations available to the public? If so, how do I locate and see the one near me?

A. Yes they are!

All the data from the sensors is being pushed out publicly through a company called “Synoptic,” which acts as a data source for various sources of weather observation data. The data can be accessed through a NOAA website (that’s a fantastic resource beyond just CNP weather stations). Within the Weather & Hazards data viewer, you’ll be presented with a buffet of sites you can choose from. These are not just CenterPoint weather sensors, but they include everything from Harris County Flood Control to Union Pacific Railroad to major airport sensors like at Bush and Hobby. You’ll have to click around a bit to find a CenterPoint one, but it’ll be a number 1-100, a location name, and then a suffix of CE. You can toggle the variable you want to see, including wind gusts, dewpoint, or rainfall, among others. There’s even a historical data mode on this site if you want to see observations from a particular date and time. It’s just a great site to bookmark!

NOAA’s Weather & Hazards Data Viewer. Click on a station to see its name. You can change the data you want to see at right. Bookmark the historical observations (3 day/7 day in the pop up bubble) for quick access to a site’s latest observations in the future. (NOAA)

There are also links to 3 day and 7 day histories as well. Those can be bookmarked for real time access updated every 10 minutes (such as this one for Sugar Land), and I would encourage you to bookmark the ones from any source closest to your house!

–Matt

Q: I live in Tomball off Texas 249/99 and we have had some intense storms Monday evening and Tuesday morning. It got so bad Monday evening that I got my family in the bathroom as winds had to be 40-50mph and were getting quarter size hail. The same thing happened this morning to where the wind was so intense that we had trees down in our neighborhood. I looked on my radar app and at the time, there was not even a Special weather statement. Later on they did issue it after it had passed through. I have seen storms that were severe warned that were much less intense. How a storm can be that intense and the NWS didn’t have any warning on it?

A: I’ll give you a good example of this. I am assuming that your experience was during the storms we had near the end of August. One of them produced a 66 mph wind gust at Brazos Bend State Park (from a CenterPoint sensor actually!) at 5:10 PM on August 21st.

A rather innocuous looking storm that produced near 70 mph winds on August 21st at Brazos Bend. (RadarScope)

Looking at radar, I’m not especially close to issuing a warning on that storm based on what we see above. One issue with Houston is that we are such a sprawling city that we actually have some pretty healthy data gaps when storms push through the area. Radar is critical, but it is also imperfect sometimes. Even the higher resolution and slightly closer Hobby Terminal Dopper Weather Radar showed winds of only about 35 mph in the above example. No indication whatsoever that this storm is producing 60 to 70 mph winds, but it is.

So there are instances where storms can (literally) fly under the radar. The radar beam up your way is shooting up to around 3,500-4,000 feet above the surface. So there is a chance that in those cases it was missing what was occurring closer to the ground.

It’s also not granular in time, either. Periodically, something will happen with a storm where it does its dirty work over the course of a minute or two, and it could happen in between the 2 to 4 minute radar scans we often get. Also, storms here tend are often what we call “pulse” storms: They ramp up quickly and ramp down just as quickly. You can literally go from a shower to a 50 mph hail-producing storm in the course of minutes. If I am correctly recalling the day you’re discussing, those storms were in fact remarkably quick to rev up. NWS did issue warnings, but there was a bit of playing from behind going on because of the nature of those types of storms.

But the reality is that until we get to more substantial radar coverage at more granularity than we’re currently capable of right now, there will occasionally be a miss like this from time to time. It’s the nature of uncertainty. It’s also a good reminder that if you see something, report it! Send it to us, the NWS, or your favorite local meteorologist. We’ll try to make sure it gets to the right people.

–Matt

Hotter and sunnier for a few days before rain chances return this weekend with tropical moisture

In brief: In today’s post we talk about the impact of early season fronts along the Gulf coast, which are somewhat paradoxical. We also look ahead to increasing rain chances due to a front and potentially moisture from a tropical system in the Pacific Ocean.

The paradox of early season fronts

From a practical standpoint, it’s really a misnomer to call the first fronts of late summer and early fall “cold fronts.” In a strictly meteorological sense, they are. But when these early fronts usher in drier air and clearing skies (but not much cooler air) they make it more efficient for the lower atmosphere to heat up. And that’s what we are going to see over the next couple of days: sunshine, hottish days with lower humidity, and mild nights. In fact, some locations north and west of Harris County may dip into the upper 60s tonight. That is not “cold,” but it is a nice departure from very humid nights we’ve experienced since June. It’s also a foretaste of what is to come in a few weeks, when we should see some stronger fronts trundling down into the area.

Low temperature forecast for Wednesday night into Thursday morning. (Weather Bell)

Wednesday

As a slightly drier air mass moves into place today we will see highs, generally, in the mid-90s across the region. We cannot rule out a slight chance of showers for areas south of Interstate 10 later this afternoon, with daytime heating, but most of us should remain dry. Skies, otherwise, will be sunny with a light northwest wind in place. Lows tonight will drop into the low- to mid-70s in Houston, with cooler conditions in place for areas further inland.

Thursday and Friday

With a drier air mass in place we can expect sunny days with hot temperatures in the mid-90s in Houston, and upper-90s for areas further inland. Nights will drop into the 70s for most of the region. The air will be a little drier, but not crazily so.

Remnants of Lorena may help to increase our rain chances this weekend. (National Hurricane Center)

Saturday and Sunday

By later on Friday we should see the resumption of an onshore flow that will increase atmospheric moisture levels. This will generate some clouds, and lower daytime temperatures, likely in the lower 90s on Saturday and pushing us into the upper 80s on Sunday. There are a couple of things we just don’t know enough about that will drive rain chances and amounts this weekend. First up is a slow-moving front that will be pushing toward (and possibly into) the region. This will destabilize the atmosphere. The region may also see a surge of moisture from Hurricane Lorena, which is presently in the Eastern Pacific Ocean and will be moving into Mexico and West Texas this weekend. All of that to say, we will perhaps see rain chances in the vicinity of 40 percent on Saturday, and 60 percent or higher on Sunday. Something to monitor if you have plans this weekend.

Next week

Our weather next week will depend on whether the region sees any impacts from the aforementioned front. Generally I would expect highs in the vicinity of 90 degrees, with some lingering rain chances to start the week followed by a drier pattern. We’ll see!

Seven-day tropical outlook. (National Hurricane Center)

Atlantic Tropics

There’s a rather ominous looking red blob at the moment in the National Hurricane Center’s seven-day tropical outlook. At this point there is no clear guidance on where this storm will go, or how strong it will get. My general sense is that the odds of something making it into the Gulf from this system are fairly low, however. Head over to The Eyewall for all of the gory details.

August is over. So how did this summer stack up? The answer may surprise you.

In brief: Today’s post reviews the summer of 2025 in Houston. Some residents may believe this one felt cooler than is typical. We see what the data says about that. Additionally, we look ahead to this week’s weather in the wake of a front that finally pushed through over the weekend.

A review of summer 2025

August has come to an end. For most of us, in terms of weather at least, that is cause for celebration. Not because the kids are back in school, and teachers back at work. Not because summer vacation is over. But rather, because August is the hottest and most severe month for weather in Houston, and cooler conditions are on the horizon. September 1 also marks the start of meteorological fall, so it allows us to step back and ask, how hot was this summer?

My immediate reaction is that this summer felt fairly mild. There were no prolonged periods of high pressure and blazingly hot days. However, when we dig a little deeper, we find a different answer. Matt already wrote about this in one of our monthly Q&A’s, but this summer has been sneakily hot. When we look at the “average” temperature for June, July, and August of this year, we get a value of 86.0 degrees. This is simply the daily high, and daily low, divided by two for the last three months. It turns out this summer was the sixth hottest June, July, and August in nearly 150 years of Houston temperature records.

Top ten warmest summers on record in Houston. (NOAA)

You might say, well, it did not feel that hot. And you’re right, the days were not blistering hot. In terms of daily highs, our average of 94.9 degrees only ranked 12th on record in Houston. My sense is that summer days felt cooler because a) we had more clouds and periodic rainfall to help cool days off, and b) recent summers such as 2022 and 2023 were so incredibly hot that they have reset our expectations of normal. Where this summer was exceptionally hot, however, was at night, when the daily minimum temperature averaged 77.0 degrees. This is tied for second, all time, behind only 2023 (77.4 degrees).

So what’s going on here? Well, it’s complicated. Certainly the urban heat island effect (widespread sprawl and concrete, which absorbs more heat) is playing a role. But Galveston and College Station also recorded summers that ranked in the top 10, in terms of overall heat. So there is more happening in the background here. The main driver of our warmer nights is the Gulf, which greatly influences our nighttime temperatures. This is due in no small part to warmer oceanic temperatures around the planet. Our world is heating up, and in Houston we are experiencing that even during a “mild” summer.

Tuesday

Following widespread rainfall over the holiday weekend, showers this morning are mostly offshore after a weak front has moved into the area. I think we’ll still see a slight chance of rain later this morning (30 percent, maybe) for areas along and south of Interstate 10, but the trend is clear. We are going to see an influx of moderately drier air over the next couple of days. Skies today should be mostly sunny, with high temperatures in the vicinity of 90 degrees. Low temperatures tonight will drop into the mid-70s in the city, with slightly cooler temperatures possible for inland areas.

Low temperature forecast for Thursday morning. (Weather Bell)

Wednesday, Thursday, and Friday

These will be the driest days, which in early September means there still will be some humidity. Still, it should feel a little bit drier outside, with highs likely reaching the lower 90s in Houston, and mid-90s for some inland areas. Skies will be sunny, with virtually no chance of rain. I think Wednesday night into Thursday morning will see the “coolest” weather, with some inland locations potentially hitting the upper 60s. Obviously this is not cold, but the nights and mornings should feel a little bit more mild.

Saturday, Sunday, and beyond

Some time on Friday, probably, the pattern will change as the onshore flow returns. This will raise humidity levels and should give us a warmer night on Friday, and start to increase rain chances this weekend. At the same time another front will approach our area from the north. It is not entirely clear whether this front will push down into Houston and off the coast, or stall. But the bottom line is that we probably will go from highs in the low 90s on Saturday to the upper 80s on Sunday and Monday, with a decent chance (maybe 30 percent) of showers on Saturday and better chances on Sunday into early next week. I don’t think we’ll see a repeat of the heavy rains we experienced over Labor Day weekend, but I cannot be sure of that. Most of next week should see highs in the vicinity of 90 degrees.

After a soaking Sunday in spots, Houston should see one more day of rain chances before calmer, less humid weather

In brief: Another smattering of downpours is likely today, however, it will probably favor the southern fringe of Houston (Galveston/Brazoria Counties). Much calmer weather begins tomorrow, along with less humid weather thanks to our cold front as well. It still looks hot, but it will be much more tolerable at times, especially in the mornings.

Yesterday saw some impressive rains resulting in some street flooding and a flash flood warning near and just southeast of downtown Houston. Rain totals over 3 inches are plotted below.

Rain totals north of 3 inches that occurred yesterday dotted the east side of Downtown to just north of Hobby. (NOAA)

We had just shy of 6 inches near 45 and the South Loop, just shy of 5 inches at Hirsch and Tidwell, and over 3 inches on the University of Houston campus. Overall, it was quite an active afternoon.

As for today, we’ll probably take down the Stage 1 flood alert we put in yesterday by this evening. There will still be downpours around today, and I think areas south of I-10, particularly down near Galveston or in Brazoria County will have the highest odds of some localized street flooding. Just a heads up for anyone returning from the coast from the holiday weekend.

Otherwise, look for intervals of sun and clouds with highs generally in the upper-80s to low-90s.

Rest of this week

A rather tranquil early September week awaits Houston. In terms of thunderstorms, other than an isolated one tomorrow, it looks like our next real chance at showers will wait til the weekend. Our first “front” of autumn is here now, and this about as good as we can hope for in the first week of September. We will actually see daytime highs increase this week, owing to a combination of fewer storms and drier air. In fact, by Thursday or Friday, we could be pushing the upper-90s again. But that drier air means it will be less humid than usual for the first week of September.

Extremely dry air for September will overtake Texas this week making it feel a good bit less oppressive than usual. (Pivotal Weather)

Less humid air should also translate into mornings that feel half-decent; not cool by any means but quite tolerable. A few locations on the outskirts of the metro area should see lows in the 60s I would imagine by Wednesday or Thursday morning. Overall, I’m not sure you could realistically script a much nicer week to open September with!

Another cool front is going to try and approach again later this week. This one will have limited luck in pushing through, but this could again reinforce the somewhat drier air mass over Texas early next week as well.

Tropics

The tropics continue to look calm in the Gulf. There is one area with (at least) a 40 percent development chance in the Atlantic, but this one will take a few days to get moving and is over a week out from the islands, not a concern for the Gulf at this point.

One area to watch in the Atlantic seems unlikely to be a Gulf concern at this time. (NOAA/NHC)

We have about 4 to 5 weeks of peak Texas hurricane season remaining. The first one looks good. Fingers crossed.