The SCW Q&A: Physics vs. AI; hype or reality; potential cyclones; tornado or not; our day jobs are safe

Houston may be settling into its summer weather doldrums, but let’s face it: In June, the skies over the region were a happenin’ place. As happens this time of the month, Eric and Matt have cracked open their inboxes and answered your queries.

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Q. So I’m curious which model actually panned out (regarding TS Alberto). Was it the regular models or the AI models? I remember it being mentioned that there were some differences between them a few days ago.

Thanks for the question. We took a look at this in the immediate aftermath of Alberto, and in terms of track the physics-based models significantly outperformed most of the AI-models. Essentially, some of the AI models wanted to bring the tropical system much further north into the Gulf of Mexico (toward Texas) whereas the traditional models kept it bottled up in the Southern Gulf, which is what ultimately happened.

I’ve also been looking at the AI guidance more frequently for non-storm events and so far I’m not convinced it’s any better (or even as good as) the physics-based models. Of course this is just my personal experience. The best way to determine the value of these new models will be using rigorous, comparative studies of what the models predicted across a range of variables against what ultimately happened. Now that the AI forecasts are coming out in real time, those kinds of studies can be done. I look forward to seeing the results in the coming months and we’ll be sure and share any interesting findings here.

–Eric

Q: Is the news media hurricane prediction for 2024 hype or more on the real side? I am debating getting a generator, but don’t want to buy into the hype if that’s what it is.

A: It’s certainly not hype. But you have to look at it logically. The data almost unanimously suggests that this should about as active a hurricane season as we could have. Thus, the seasonal forecasts are all quite bullish on hurricane development.

Colorado State has a generally good track record with seasonal forecast predictions, so their bullish outlook for 2024 has raised eyebrows and alarm in some circles. (Colorado State)

In fact, one thing we did at our companion site The Eyewall back in early June was to expand on ways that the active hurricane season forecasts could bust. The reality is that it could bust. Absolutely. Would that mean the preseason forecasts were all hype? As a scientist, I will tell you certainly not. As a member of the public, I get why you’d have that opinion though. So we encourage people to look at the decisions they make with regard to seasonal hurricane forecasts with nuance.

Were you probably going to get a generator anyway? We’ve had far more events non-tropics related that have caused extensive power outages in our area in recent years. Just consider the whole picture. And in this case consider a busted forecast a good thing if it happens.

–Matt

Q. Why is Potential Tropical Cyclone One not called “Tropical Depression One”? I thought a storm was called a tropical depression before it became a tropical storm?

It’s all a bit confusing, isn’t it? But the intent here by the National Hurricane Center is good. A “Potential Tropical Cyclone” is sometimes issued before a tropical system becomes a ‘depression’ or a ‘tropical storm.’ This happens when a system could bring tropical storm or hurricane conditions to land within 48 hours.

Essentially, forecasters from the hurricane center do this when they want to highlight the threat of a tropical system to land, but that system has not yet formed. Why do this? Because sometimes a tropical storm does not intensify until very shortly before landfall, at which point formal warnings are often too late to be actionable. The hurricane center started doing this in 2017, and you can find more information here.

–Eric

Q: Curious to know how the NWS determines if a tornado occurred and categorizes it after the event? Is it based on eyewitness accounts, damage, etc?

A: There are a few ways to confirm a tornado has occurred. Some larger tornadoes have “tornadic debris signatures” on radar, where you can see the radar showing you lofted debris from tornado damage. The most obvious and easiest way to suspect a tornado is eyewitness accounts.

But sometimes well-meaning people think something is a tornado when it is not. That’s why the NWS usually sends out a survey team to go investigate damage after a storm if a tornado is suspected. They can combine spotter or eyewitness accounts with radar data to determine exactly where to look for tornado damage. Generally speaking, if the damage is all pointed in one direction, that’s a tell-tale sign of straight line winds, or a microburst/downburst, not a tornado.

But if the damage is more chaotic or pointed down in different directions, that’s a probable sign of a tornado. This page from the NWS in Binghamton, NY shows sort of how they go about this process.

Rating the tornado’s intensity is another matter. There is some subjectivity involved, but in general, the damage indicators as provided in the Enhanced Fujita scale provide a decent categorization for a tornado.

–Matt

Q. You are all hype. I thought your website was dedicated to providing weather insight for Houston without the hype but your Stage 2 flooding article was all hype!! Don’t quit your day job!

A. Let me put your weary and worried mind at ease: we won’t be quitting our day jobs. My day job is writing about space exploration for Ars Technica. Matt is a meteorologist for an energy company in Houston. Would you believe that Space City Weather is hobby for both of us, a second job we do to try and help the community?

I do think it is useful to revisit our thinking about issuing a Stage 2 flood alert on Sunday, June 16. Here’s the post, which we published at 9:53 a.m. Note that this was Father’s Day, and Matt and I spent a couple of hours that morning strategizing, thinking, and writing about the forecast. I mention that just so you understand we’re pretty dedicated to this stuff.

That morning we actually gave some thought to issuing a Stage 3 warning for coastal areas, but I decided it was best to hold back for a time. At the time some of the modeling was rather dire (showing upwards of 20 inches of rain across parts of Houston in some instances). The ‘official’ precipitation forecast from NOAA showed a bullseye of 12 inches of rain just south of Houston, and the flood threat was very real for coastal areas. In any case, we felt it was time to raise the alarm about the potential for significant flooding in the Houston region for the coming week. So we pulled the trigger.

NOAA rainfall accumulation forecast issued on Father’s Day morning. (Weather Bell)

Some uncertainty definitely remained—we caveated our forecast with the following statement, “Our forecast modeling remains a bit split as to whether the heaviest rain will fall near Galveston, or further south closer to the Coastal Bend.” The latter is precisely what happened.

In forecasting, you win some, and you lose some. All we can really do is to try and do our best, and that’s just what we do here.

–Eric

Slight chance of thunderstorms today and tonight as hot weather continues

In brief: Although high pressure is largely dominant, Houston will have a couple of chances to see some spotty thunderstorms today and tonight. Mostly, however, we’re going to see continued hot and sunny weather, with temperatures in the mid- to upper-90s and plenty of humidity. That forecast holds for as far as the eye can see.

Monthly Q&A

Be sure and check back on the site later this morning, as we’ll be releasing our monthly Q&A at 10 am CT, in which Matt and I answer questions submitted by readers. There are some fun ones this month!

Wednesday

Skies will be mostly sunny today, with highs in the mid- to upper-90s. Generally, the further inland you live, the warmer the temperatures will be. Winds will remain light, from the south at just 5 mph. The real intrigue today and tonight is rain chances. They’re not high, but we could see some briefly lived thunderstorms.

With 2+ inches of precipitable water in the atmosphere there is plenty of moisture to support some showers today. The question is whether we can break the capping inversion. (Weather Bell)

The first opportunity comes during the mid-afternoon hours, as daytime heating combines with the seabreeze to potentially spark some showers and thunderstorms in central Houston, or perhaps closer to the coast. These should be fairly isolated and short-lived. There is also a chance of some storms along a dying front moving south into the region this evening or tonight. Frankly, our model guidance is all over the place, so we could see anything from nothing (probably most likely) to a fairly broad line of storms moving southward late tonight or early Thursday (far less likely). In any case, something to be aware of.

Thursday

Expect continued hot and muggy weather. We could see some additional, isolated showers and thunderstorms due to daytime heating. Overall rain chances are probably only about 10 or 20 percent, however.

Houston’s heat levels remain high, but not extreme heading into next week. (Weather Bell)

Friday, Saturday, and Sunday

Expect more hot weather, with highs in the mid- to upper-90s for the area and plenty of humidity. We’ll continue to see low, but not non-existent rain chances through the weekend as daytime heating sparks seabreeze showers. These probably will be a bit more likely for areas along and south of Interstate 10. But for the most part, it’s just going to be sunshine and heat. We may also see some haze, as a plume of Saharan dust pushes into the area over the weekend.

Next week

To be honest, next week doesn’t look much different from this week, weather-wise. We’ll continue to be very hot, but not extremely so for Houston in the summertime.

Hot and mostly sunny, with a smattering of rain chances for awhile

In brief: Houston is fairly well locked into a summertime pattern for the foreseeable future, with high temperatures in the mid- to upper-90s. The only real question each day is the extent to which we see some afternoon showers and thunderstorms develop. Overall chances are low each day, in the 10 to 30 percent range, but that’s better than nothing. Wednesday afternoon may be interesting.

Tuesday

We have reached the point of summer in Houston where not much changes. High pressure has developed over much of the southern United States, and for us that means mostly sunny skies and hot temperatures. However, for much of the forecast period Houston will lie along the periphery of this high, so it means our rain chances each are not zero. (For example, as I write this, some spotty showers have developed near Lake Jackson in southern Brazoria County).

For today, we’ll see mostly sunny skies with highs in the mid-90s for much of Houston. Some inland areas will see upper 90s. Winds will be light, generally from the south at 5 to 10 mph. We’ll see some additional showers this afternoon, but overall chances are probably only 10 to 20 percent. Low temperatures tonight will drop to around 80 degrees.

Our nighttime heat will creep into ‘elevated’ temperatures by this weekend. (Weather Bell)

Wednesday

This will be another hot and mostly sunny day. However, some of our model guidance indicates at a bit of a disturbance may work its way southward across the region, bringing a slightly better chance of showers and thunderstorms on Wednesday afternoon or evening. So let’s peg rain chances a little bit higher, perhaps 30 percent. We’ll see. Nights remain warm and sultry.

Thursday, Friday, and Saturday

Expect hot and mostly sunny weather, with highs in the mid- to upper-90s. Rain chances each day will be about 20 percent. Anything that develops is likely to do so during the afternoon hours, along the seabreeze. Skies may also appear hazy as we see an influx of Saharan dust—this would have the benefit of making for some nice sunsets.

Saharan dust may reach the Texas coast on Friday and Saturday. (NASA)

Sunday and beyond

Rain chances improve a bit by Sunday and Monday, with perhaps a bit wider coverage of afternoon showers and thunderstorms. This is no guarantee, however, as high pressure is lurking. Mostly I just anticipate hot conditions, with highs in the upper-90s for much of the area away from the coast. July is going to do July things in Houston. My way too early forecast for the July Fourth holiday is hot and sunny, with partly clear skies for fireworks.

Summer really sets in this week for Houston, so let’s talk about the best way to measure heat

In brief: Houston will experience full-on summer conditions this week with hot days, mostly sunny skies, and sultry nights. To better characterize this heat, we will start using wet bulb globe temperatures more, and we explain them in today’s post.

Wet bulb globe temperatures

As we get into the heart of summer—and yes, that’s just what we’re in for during the next 80 days or so—it’s useful to talk “wet bulb globe temperatures.” Now this is a confusing name, and it’s not a simple calculation. To derive a wet bulb globe temperature, one need take three different measurements: air temperature (with a thermometer), mean radiant temperature (with a black globe thermometer), and natural wet-bulb temperature (a water-soaked thermometer). Like I said, it’s complicated.

However, interpreting a wet bulb globe temperature is easy, and we’re going to use it a lot this summer on Space City Weather. Quite simply, it is a measure of how heat affects you: it factors in temperature, humidity, wind speed, sun angle and cloud cover. It differs from the heat index, which is less precise. Using this metric is especially useful if you’re going to be outdoors, and not beneath shade. Basically, “high” temperatures are very warm, and “extreme” levels are borderline intolerable unless you’re in a swimming pool. Note that last year, during this week, we were already at “extreme” heat levels. This year we’re not quite that hot, but it’s still going to be very warm.

Wet bulb globe temperatures in Houston for the week ahead. (Weather Bell)

Monday

Our weather this week will largely be dominated by high pressure, which will lead to mostly sunny days and highs generally in the mid-90s, with some inland locations reaching the upper-90s. There is plenty of moisture in the atmosphere, but a capping inversion is going to be difficult to break most days. However, I do think areas south of Interstate 10 and closer to the coast have a better chance of seeing some spotty afternoon showers along the seabreeze this week. I’d peg daily chances at 10 to 20 percent, with lesser odds for inland areas. Overnight lows will be sultry, with temperatures only briefly dropping below 80 degrees in Houston, if they do at all.

Tuesday, Wednesday, Thursday

More of the same: Mostly sunny days, highs in the mid- to upper-90s, some isolated seabreeze showers, and warm nights. Winds will generally be from the southeast at 10 mph, with gusts up to 15 mph.

Rain chances this week? Not good. (Weather Bell)

Friday, Saturday, and Sunday

The forecast remains more or less the same for the weekend: mostly sunny and hot. I do think rain chances may bump up slightly into the 20 to 30 percent range, but I want to see how the forecast evolves for high pressure. Will it give a bit, or will it be relentless? We shall see.

Tropics

After the formation of Tropical Storm Alberto last week in the southern Gulf of Mexico, and a couple other disturbances, it looks like the tropics will go into quiescent mode for awhile now. This is perfectly normal for June, which is but an appetizer for the tropical main course, which comes in August and September for Texas.