Category: Tropical weather

Matt here with a special Friday evening update for you, Houston. Yes, the late afternoon run of the GFS operational model showed a significant tropical system crashing into the Texas coast. Some of us in meteorology refer to this as the “happy hour” run of the GFS. I’m going to walk through a pretty basic forecasting approach to whether or not I would put much (any?) stock into the GFS operational model.

The model run

If you’re curious, here it is:

Today’s 18z “happy hour” GFS operational model spins a hurricane into Texas next weekend. No, we aren’t buying into it. (Tropical Tidbits)

No, you should not worry about it.

The trends

Why am I saying that? If you look at the last 10 runs of the forecast from this very same model valid for next Saturday night, today’s is the first to show a storm in Texas.

Of the last 10 GFS operational runs, only the latest one wants to bring a hurricane into Texas. (Tropical Tidbits)

Sure, the last couple runs have trended closer to Texas, but this model is volatile. It’s going to bounce around a lot. I’ve been watching this model for 15 years now. This isn’t an abnormal thing it does.

The ensemble

On top of all this, let’s look at what the GFS Ensemble shows for this same exact timeframe. The ensemble is still basically the GFS model, but it’s run multiple times with some tweaks to the model each time. The intent is to offer you more of a “spread” of possibilities in the forecast. Good forecasters use ensemble based forecasting techniques to help them craft forecasts. I’m focusing on one particular variable here: What each ensemble member shows for sea level pressure centers. Each circle I’ve added to this map is where an ensemble member places the center of something (tropical storm, hurricane, plain old tropical disturbance) next Saturday night.

The ensemble “spread” next weekend is still fairly large, most are much weaker than the operational, and the skew is to our east. (Tropical Tidbits)

So even the GFS model’s ensemble is saying that the operational model is probably a.) much too strong and b.) too far to the west.

Sidebar, the maps above are from Tropical Tidbits, which is a great site I use. If you’re into veering into the weather weeds, it’s worth perusing. By the way, the owner of that site is a hurricane researcher at Florida State University. He had this to say about that GFS model run:

The other models

Everyone loves the Euro, so I’ll just tell you, it doesn’t show this solution. What about the European ensemble. That ensemble contains 51 different members. All of one of them, shown below via another good weather model site, StormVista, has a closed off low pressure under 1007 mb (weak) next Saturday night.

The Euro ensemble is decidedly less aggressive with tropical development next week and weekend. (Storm Vista Weather Models)

There are other models we can look at, but truthfully, none is really reliable enough at this point to utilize with any confidence.

So what should I expect, then?

Here’s what we *do* know.

Based on forecaster experience, the GFS tends to grossly overdo tropical development, while the European model tends to underdo it. So I think the Euro probably isn’t giving enough credit to potential tropical development in the Gulf late next week, but the GFS is probably way too enthusiastic about it.

In my post this morning, I talked a little about what could happen:

Weather modeling indicates that rain chances should increase a little bit later next week as a tropical wave finds itself in the Gulf. Weather modeling indicates two real possibilities at this point. One is a disorganized, weak system heading toward the Florida Panhandle again. The other is just an increased slew of moisture heading toward deep south Texas (Corpus Christi and the Rio Grande). This could be what’s needed to kick start rain chances a bit more in Texas. With that said however, I am a little concerned it may get directed just a little too far south to really offer the Houston area much relief.

So, my thoughts have not changed at all today, truthfully. Why? I’ve been watching this pattern all week. At my day job, I’ve actually been discussing this setup since last week with my summer intern. If you look about 20,000 feet up in the atmosphere, you see high pressure extending across the Gulf into Texas next weekend.

As of right now, I think the upper level pattern over the northwest Gulf favors any tropical nonsense staying to our south and east, should it develop. (Tropical Tidbits)

My current thinking is that if this holds up, strengthens further, or a portion of it closes off over Texas and Louisiana, that would likely suppress any developing tropical system near the Yucatan to our south toward the Rio Grande or allow it to move north-northeast within a weakness in the ridge toward Florida. Should this high pressure weaken overall, yes, then maybe we might have to watch the Gulf a little closer. Or it could just be a stream of tropical moisture that finds its way up here and allows us to have daily afternoon showers and storms at a greater frequency next weekend.

I’m not just saying this to dampen hype. I truly believe this meteorologically: I don’t believe that whatever does develop in the Gulf will be anywhere near the scare-icane shown on today’s happy hour GFS model. But as always, we will continue monitoring.

We have plenty of time to watch, should things change. But I’m going to sleep easy tonight, and you should too. Meanwhile, if the gloom and doom posts scare you, it’s a good time to brush up on hurricane season preparations.

Hurricane season is here—and we’re all ready

Posted by Matt Lanza at 10:00 AM

In our second story to mark the beginning of the 2018 Atlantic hurricane season, Matt discusses how meteorologists are preparing for life after Harvey. If you missed part one, you can find it here.

In early October of 2017, I had just completed an invigorating 4 mile, 2,100 foot climb to Observation Point in Zion National Park, Utah. It marked one of my prouder moments as a person, because as hiking goes this was considered strenuous for someone like me who isn’t exactly crushing it at the gym every week. And I conquered it. The view was spectacular, but unfortunately, the cell service was great too. At the top of this beautiful overlook, an email was pushed to my phone, asking if I was certain that then Tropical Storm Nate was not going to threaten Texas. And I was reminded that the 2017 hurricane season was almost never going to end, nor was the job of a meteorologist. Even in the middle of nowhere.

The author (and his hat) at Observation Point in Zion National Park last October.

Here we are eight months later, officially beginning a new hurricane season. Obviously, the season began in May with Alberto, which thankfully stayed away from Texas. All the same, I have mixed emotions going into this season. It feels too soon, memories are too raw, and I look at things differently after last year. I’m less meteorologically fascinated and more consumed by personal impacts to people. I think many meteorologists feel similarly. Yes, we stand at the ready to inform and help guide folks through the season ahead, but for most of us, it just feels too soon.

We know so many people in the Houston area, Texas in general, Florida, and Puerto Rico also think it’s much too soon for hurricane season to be upon us once again. But we have to accept that hurricane season is a part of life in these places. It’s a risk we have to live with. After the devastation and misery of last year, I reached out to a handful of folks to “take our temperature” as we head into a new season. We learned much from last year, and we need to apply those lessons in the 2018 season. Here are some thoughts on both the challenges ahead and the progress made.

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Hurricane season officially begins later this week, but as we’ve seen with Subtropical Storm Alberto, Mother Nature doesn’t care overly much about arbitrary dates. Nevertheless, it is the time of year to begin thinking about the tropics, and so we’re going to help you get ready with some questions and answers.

Why does hurricane season occur now?

The easy answer is “warmer water,” and it is true that sea surface temperatures above 80 degrees Fahrenheit are generally needed for tropical storms to form, and strengthen into hurricanes. However, seas in the tropics are generally warmest in October, when hurricane season often begins to wind down. There is another factor, wind shear, that is critical. When winds are rough, and blowing as cross directions at different altitudes, storms simply cannot form. Typically, tropical storms will thrive only when wind shear values near the center are below 20 knots. The following graphic, from FEMA’s Michael Lowry, shows why the hurricane season lasts from June through November, but typically peaks during early September.

(Michael Lowry/FEMA)

Help! I’ve seen a really scary forecast on Facebook

Already this season we’ve seen some hyperbolic forecasts on Facebook. In March, a post forecasting doom and gloom for the 2018 Atlantic season went viral, and more recently a post showing a major hurricane hitting Texas in June got passed around. Such “social mediarology” plays on the fears of people, and therefore tends to get shared widely. If you’ll promise to not fall for these kinds of fear-mongering posts, we’ll make a pledge to you: If we believe there is a credible threat to Houston, we will report that immediately. And if we haven’t written about it, the post you’ve seen on Facebook is probably garbage.

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Storms possible near Houston again on Sunday

Posted by Matt Lanza at 11:59 AM

Yesterday’s thunderstorm activity probably came as a bit of a surprise to many of us, not so much because they happened but because of how potent they were. We saw a few reports of hail and wind damage around the region. And some incredible sky pictures.

Our Friday forecast suggested the most activity would be east of US-59 on Saturday, and it was, but I’d be lying if I told you I was expecting the potency that it came with. So why did it happen?

A confluence of factors led to a busy Saturday evening. Storms early in the day in western Louisiana and eastern Texas likely produced some boundaries in the atmosphere, and with winds directing weather in the less common northeast to southwest direction, they ended up moving our way. We probably saw cold air aloft, necessary to help regenerate storms as they moved across southeast Texas. We had sea breeze interaction with some of those boundaries also. There was decent jet stream and upper level support in the northeast flow that helped add extra support. Then, it also hit 94° at IAH, so you had plenty of instability. All these factors came together just right, and we ended up exceeding most people’s expectations, including my own.

So that begs the question: Will we do it again today?

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