Matt Lanza

In brief: Hot and humid weather with daily shower chances awaits Houston over the next several days, typical for August but perhaps encroaching on 100 degrees at times. Today, we also dive in deep on the tropical noise that’s been percolating on some weather models.

IAH hit 100 degrees again yesterday. Before you go stand outside Terminal B with pitchforks due to construction the perceived hot bias, there were a string of 99s and 100s yesterday recorded across the north and west side of town. Wednesday’s 100 felt a little less valid. But again, compare IAH to IAH, not to the rest of the city. We saw mid to upper 90s mostly, and we’ll probably do it again today. Nothing unusual for August.

Today

We’ll have one more slightly hotter than usual day today with highs approaching 100 degrees in spots, especially north of I-10. Isolated to scattered showers and thunderstorms are likely with daytime heating again, and any of those storms could produce some brief downpours and the potential for some gusty winds.

We may still have residual haze, especially this morning. That’s due to wildfire smoke from Canadian wildfires. This is a problem that much of the country has been dealing with at times in recent years.

Weekend

Both days should be fairly typical for August. We’ll see highs in the mid to upper-90s, possibly leaning more toward mid-90s on Sunday with slightly higher coverage of showers and storms. But, sunny, hot, and humid with daily isolated to scattered downpours and thunderstorms.

Next week

There’s nothing particularly notable about next week’s weather right now. It looks like we’ll have a few isolated to scattered showers or storms each day, especially on Monday or Tuesday. Temperatures may try to rebound back closer to the upper-90s again. But overall, it looks like very basic August.

Tropics

First and foremost, we’re good here for the next 7 to 10 days in Houston. We’ve got no concerns noted on modeling right now.

All that said, it’s getting to be the time of year where we do start watching more and more things, even some of the innocuous looking ones. We’ve had some deterministic (operational) model guidance (the GFS, the Euro, etc.) go crazy in the day 14 to 16 timeframe lately. This bears repeating. The day 14 to 16 timeframe. Deterministic modeling has virtually no skill at that timeframe. So, while we are certainly empathetic to people getting a little unnerved when they see bad things in that timeframe, Eric and I both are realists and recognize that those runs, even if 2 or 3 in a row show something similar, are somewhat meaningless. Put another way, if I had a buck for every time a deterministic model wrecked a major Gulf Coast city on days 14 to 16, I’d be getting wrecked on some tropical island somewhere far, far away living the dream. I’m just saying!

So what do we do instead? We look at ensemble guidance for clues. What can the ensembles tell us about the potential for a tropical system in a more distant timeframe? Ensemble modeling is where you take a single model and run it 30 to 50 times but tweak the initial conditions, or what the model starts from. We can’t get a perfect snapshot of the entire atmosphere over the entire globe, so we have to improvise a little. Ensemble guidance is that improv.

Okay, let me show you a perfect example of this. Here’s last night’s GFS operational model for hour 294, which is day 13.

That’ll get your attention! And it has been showing this for a few days, though it varies in location between the Caribbean, the Carolinas, and out to sea. But what do the ensembles show?

Not all lines on a spaghetti plot chart are created equal. Some of the lines above may be ensemble members that are slightly more skilled than others. That’s a tough lift to figure out specifically in every situation. But the point is this: Yes, the GFS operational model may be right! But according to the ensembles there are a bunch of other options too, including many that go out to sea and a handful that come into the Gulf.

I show you this for a couple reasons. First, I want you to recognize that the scary images you often see on social media are almost always from operational models. Second, when you look at the ensemble guidance, it offers a far more nuanced take on all this that suggests the operational models are just one possible solution of many. We go through this exercise every season. It’s the same culprits from the same places with the same intentions. They’re basically preying on people’s fears to drive engagement under the guise of “we’re not saying this is a forecast (it is), but we want to just let you know what’s out there!” In reality, the picture is nuanced, complex, and not at all straightforward. A deterministic model showing Armageddon on day 13 does not make that scenario any more likely than any of the possible outcomes on the ensemble chart I showed you above. Hurricane season is a months’ long marathon. We just want you to keep your sanity.

In this specific situation: Yes, we should keep an eye on this tropical wave as it comes west over the next 10 to 12 days. It is August, and we should keep an eye on all tropical waves this time of year. Rest assured, if there’s a threat that seems realistic to Texas, we’ll be talking about it here well before it happens. You can also use The Eyewall to follow along with more of the day-to-day details.

In brief: Unsettled weather will return to Houston today through Sunday or Monday. Isolated heavy downpours are possible in spots, along with some locally stronger thunderstorms, especially Saturday and Sunday. A return to strong heat is looking likely later next week.

Welcome to August, widely considered the worst month of the year in Houston. I, Matt, disagree because I think September is worse, psychologically at least. Whatever the case, this August will start hot but not ridiculously so as thunderstorm chances re-enter the picture. By next week, we may be back on August blast furnace watch again. Another scorcher.

Today

We’re starting off today with a couple showers and downpours up in Liberty County that are drifting southward. I’d suspect those continue toward Trinity and Galveston Bays, so if you live on the east side, don’t be shocked to see some raindrops this morning.

Elsewhere, it’s quiet, but we should see showers and storms perk up in spots this afternoon with daytime heating. Many, if not most of us will stay dry today but those that see showers and storms could see some pretty hefty rainfall on the order of 1 to 2 inches in a short period of time. Otherwise, look for highs in the mid to locally upper-90s, not far off normal for this time of year.

Saturday

Coverage of showers and thunderstorms should pick up tomorrow. The combination of a dying cold front to our north and lots of moisture in place should allow downpours to blossom with daytime heating. Locally heavy rain is possible. The pattern of storms won’t be typical for this time of year, as we’ll see most of them form north of Houston and drop southward, unlike typical summertime sea breeze storms which come from the Gulf and work inland.

While we aren’t currently expecting severe weather, I’ve learned over the years to be cautious of north to south moving storms in spring and summer. I wouldn’t be shocked to see an isolated case of a storm misbehaving for a short time. Just something to be aware of. Clouds and showers should hold temperatures back some tomorrow, so look for generally mid-90s and possibly a bit less hot than that in spots.

Sunday & Monday

With high pressure anchored over the Southwest and a disturbance tracking across the Plains and Texas Sunday into Monday, we should continue to see scattered storms in the area, some of which may form in interior Texas and drop southward, more like late spring than late summer. Continued unsettled conditions will prevail to close the weekend and start next week.

High temperatures will likely be in the low to mid-90s.

Once all is said and done with the storms through Monday or Tuesday, expect 1 inch or less in most spots, however some more isolated, localized places could easily see up to 2 or 3 inches in locally heavier downpours.

Rest of next week

High pressure over the Southwest is going to flex its muscles beginning Tuesday or Wednesday, and it’s likely that we see some solid heat return to the area for a time later next week.

Our next swing at 100 degrees will probably occur next Thursday or Friday. We shall see.

In brief: Periods of rain and scattered thunderstorms will be with Houston today and tomorrow as a disturbance moves in from the Gulf. Then, we will get another round of heat heading into next week, peaking on Wednesday or Thursday.

Today

The tropical disturbance with 10 percent development odds that we’ve been discussing all week is on final approach to the Texas coast. The NHC pegs it just south of Vermilion Bay in Louisiana. On radar, we’ve clearly got a few showers across the area. There is a more robust area of rain closer to the disturbance itself that’s moving westward over the Gulf.

As the day goes on, look for that area of rain to move toward Galveston and/or Freeport. Inland areas will see quick moving downpours at times. Once the disturbance comes ashore tonight, there could be periodic downpours and even some thunder. Some areas will see little to no rainfall. Other places could pick up a quick inch or so in heavier downpours. I do think coastal areas may see a steadier rain later today, and thus they could see up to 2 inches or so of rain before all is said and done.

High temperatures this afternoon will struggle and may not even reach 90 degrees in many spots. Look for upper-80s to low-90s (if the sun gets out) and a bit more humidity than we’ve had this week.

Saturday and Sunday

This tropical disturbance is not slowing down for anyone. By tomorrow afternoon, the fingerprint of the disturbance should be past I-35 and into West Texas. We will still see scattered thunderstorms across the area, with an increase in coverage as temperatures warm up tomorrow.

On Sunday, the chance of rain drops even a bit more, but again not to zero. While Saturday will probably top off in the low-90s, Sunday could be in the low to mid-90s.

Next week

So what’s next? First, we’re going to get a surge in heat once more. Houston should peak in the mid-90s on Monday with a chance of a storm, mid to upper-90s on Tuesday, and upper-90s to near 100 degrees on Wednesday and perhaps Thursday.

After Thursday, it almost looks like yet another Gulf disturbance may enter the picture, though this one could be even a bit farther north (possibly over land) than the current one. No real development risk by any means, but we’ll see if this can’t help enhance shower and thunderstorm chances and lower our temperatures to close out next week.

In brief: The Gulf tropical disturbance is unlikely to develop, but it will bring some rain to the area tomorrow and Saturday. We have one more shot at 100 today before a brief break. More 100 chances return next week. Today we also dive into Bush Airport and talk about why it seemed to be such an outlier on Tuesday.

First, the tropics

Let’s start quickly this morning with the tropics and on this disturbance we have moving across the Gulf today and into our region tomorrow. There continues to be little to no chance of development with this. For Greater Houston, that means an increase in rain chances tomorrow and Saturday. And even that should be manageable.

Now, how much rain? Well, Friday will be interesting. It could go one of two ways I think. The first way? The disturbance approaches Texas and we get a solid rain shield offshore, so coastal areas see a fair bit of rain in the morning, with inland areas seeing just a few scattered afternoon thunderstorms. Alternatively, we see a small bit of rain in the morning at the coast and then more numerous showers and afternoon thunderstorms moving southeast to northwest across the region. I am leaning heavily toward the coastal rain outcome, where inland areas see some scattered storms but nothing too widespread. This means folks in Galveston could easily see a couple inches of rain, and more numerous showers and storms may push across Brazoria, Galveston, and Chambers Counties.

On Saturday, we’ll probably see a repeat, except I think storms could be more numerous across the entire region. As we’ve been saying, it should not be a total washout, but you’ll want to have some rain plans in place on both Friday and Saturday if you’re planning outdoor activities.

Rain totals will be on the order of probably 1 to 2 inches at the coast and a gradual trailing off of rain inland down to about a half-inch to inch inside the 610 Loop and less than that farther inland on average. Some areas may see little to no rain. Other isolated pockets, especially south and east of Houston could see 3 to 4 inches of rain.

Next, the heat

We hit 99 degrees yesterday, and we will make another run for 99 or 100 today probably. With clouds and showers around, Friday and Saturday should be substantially less hot. But look for the heat to return Sunday or Monday, and we will be making another run at 100 degrees by Tuesday or Wednesday.

Is the IAH thermometer rigged?

The fun thing about weather is that no matter where you live, if something looks the slightest bit suspicious, people start weighing in with lukewarm and hot takes about why there’s something wrong with a temperature sensor, someone has an agenda and is purposefully fudging data, and on and on. One of my favorites is when Washington, DC gets snow, virtually the entire city gets mad at whoever measures the snow at Reagan Airport because it is obviously too low. In Philadelphia, you get the opposite, the snow totals almost always get yelled at by people for being inflated.

Well, we’ve got ourselves a fun game of this happening in Houston now. On Tuesday, when IAH hit 100 degrees, many people were convinced it made no sense.

And, honestly, looking at that map above, I get it. IAH does stand out. Out of an abundance of caution, the NWS sent their electronics technician out to look at the thermometer at IAH. It was fine. It was reading where it should have been, and there have not been any recent changes near the thermometer. Turns out, it’s just hot at IAH. If you look at the high temperatures on Tuesday from a number of additional weather stations, filtered for most of the clearly bogus values (50s, 110s), you’ll see multiple spots hit 100 degrees.

I’m not going to say that each of these weather sensors is sited perfectly or calibrated perfectly, but based on what I saw from sensors that I trust on Tuesday, I would have expected IAH to top off around 98-99 degrees. So, 100 doesn’t exactly shock me. But it’s definitely at the top end of temps for our area.

So, what is the deal with IAH, and can we trust it as a long-term indicator of our climate? It’s a complex and complicated question to answer. In most cities, historical data did move from essentially the center of town “back in the day” to airports. Official readings are now almost always taken at airports, where no one actually lives, of course.

A few places are unique or have complexities: Think Central Park in New York City; not an airport and a good, long historical data record. In Austin, you get to choose from Bergstrom Airport or Camp Mabry, two locations that can be very, very different during certain events. Downtown Los Angeles has also had a checkered history, with a weather station that has now moved 8 times. The linked article is from 2014, when USC housed the official Downtown L.A. sensor. It now sits on the south side of Dodger Stadium. The next time I visit SoCal, I intend to wear an Altuve jersey, go stand by it, and boo it. When stations like this move, there’s a process called “threading” that occurs. This process is by no means perfect, but it does a fairly good job of ensuring that station discontinuities are accounted for and the extremes we’re measuring against historically are as unified and realistic as possible.

Is IAH a reliable indicator of Houston’s weather history? Ten people will have ten opinions on this, but the reality is that it’s not really any worse than any other spot in the area. Houston is constantly evolving, growing, and changing. IAH isn’t perfect, but I think the important takeaway would be that there’s a difference between being representative of where people live versus being representative of reality at a given point. IAH isn’t a reliable indicator of every neighborhood’s weather history in Houston. But it is reliable as a location for our climatology today. In other words, compare IAH to IAH, not IAH to elsewhere. IAH hit 100 on Tuesday. Compared to previous records at IAH, it was one degree shy of a record high. That doesn’t mean that Sunnyside was 1 degree shy of a record. Or Sheldon was 1 degree shy of a record. IAH was. And since our official records are kept there, “Houston” was. You could make a similar argument about DFW Airport, which keeps Dallas’s official records or O’Hare in Chicago or Logan Airport in Boston.

Going back to the 100 on Tuesday, one of the key reasons for it may have been the lower humidity we saw that bubbled up in a pocket of the city. We can assess that with dewpoint values, as seen below. Also, IAH had 42% relative humidity at 3 PM, right around when it hit 100 degrees, which was one of the lowest relative humidity values in the city at that time.

Drier air heats up more efficiently than more humid air, and when you have an air mass this hot, it doesn’t take a massive change in humidity to lead to a somewhat outsized change in temperature. Bottom line? It seems that a localized pocket of low humidity impacted the area near the airport. When combined with the already generally hot location of IAH, it led to a bump to 100 degrees on Tuesday, when most other locations were more like 96 to 98 degrees.

Does this settle the debate? Never. Everyone will still have opinions on this. Weather is a bit like sports in that regard, I guess. But when thinking of IAH, it’s a microcosm of all the things influencing our history here: Urban heat island, sprawl, a warming Gulf, and climate change all playing roles. But we wanted to share some of the plausible reasons why it happened, as well as add some color on IAH. Not perfect, but it’s what we’ve got.