In brief: Tropical Storm Alberto is about to move inland into Mexico, ending the threat of tropical rainfall across the Houston metro area. However, we are still likely to see at least some scattered showers and thunderstorms for several days—mostly passing downpours. After a few days with highs around 90 degrees, we’ll start to warm up this weekend into the low- to mid-90s.
How did the new AI models do?
Recently, I mentioned that Matt and I were assessing the value of relatively new weather forecast models, which are based in machine learning. These AI-based models have been ‘trained’ on historical datasets and have shown some promise in limited testing. They’re now starting to become publicly available in real-time, and we’ll be using them for the Atlantic hurricane season. (You can find some of them here).
Anyway, the evolution of Alberto offered the season’s first test. Last Friday, the models offered a distinct difference in forecasts. The majority of traditional, physics based models that crunch through complex physical equations to reproduce the atmosphere, produced a system that remained largely in the Southern Gulf of Mexico. I saved the output from the U.S.-based Global Forecast System model that was initialized on Friday morning. Here is its five-day forecast for the morning of Wednesday, June 19:
At the same time, the AI-based version of the European model, or AIFS, had for several runs been bringing Alberto much further north, toward the central Texas coast. This is what the output from the model, initialized at the same time as the GFS model shown above, looked like for Wednesday, June 19:
That is a lot different, and certainly would have been more eye-popping for the Houston area. I frequently appear on the Houston Matters radio program with Craig Cohen, and we discussed this difference in output at the time. I told him it would be a good test. Five days later, on Wednesday morning, here’s where the tropical system, which had just formed as Tropical Storm Alberto, was:
As you can see, the physics-based GFS model was spot on, whereas the AI-based model misfired. This was not universally true, but the majority of physics-based models were much closer on track accuracy, whereas the AI-based models tended to have a more northerly track for Alberto (Huawei’s Pangu model was a notable exception, nailing the position). In our forecasts at Space City Weather, we relied on the physics-based models since they seemed more in-line with the overall atmospheric setup.
That’s track. None of the models did a great job with precipitation. There were several runs where the GFS model splashed 25 inches of rainfall over Houston, and the AI models that have rainfall outputs were also considerably more bullish than what Houston ultimately experienced. In any case, it’s going to be a long hurricane season. One test case proves nothing, but nevertheless I thought it was interesting to share.
Thursday
After coastal waters rose fairly high on Wednesday, due to the winds and surge of Alberto, they’re starting to recede some this morning. They’ll become less and less of a problem today and tonight now that the tropical system is inland. We’ll still see some gusty winds from the east today, perhaps up to 25 mph, but they’ll also be less than those of Wednesday.
In terms of precipitation, showers will be considerably more scattered today after much of Houston picked up 1 to 2 inches of rainfall on Wednesday. The most likely time for showers will be this afternoon, but they could come at any time, especially for coastal areas. Skies will turn partly sunny this afternoon, with highs of about 90 degrees. Lows tonight will drop into the mid-70s.
Friday
Another partly sunny day, with perhaps a 30 to 50 percent chance of showers and thunderstorms. Most of this activity will be fleeting. Highs will be around 90 degrees, with lows again in the mid-70s.
Saturday
Skies should be mostly sunny, with highs in the low- to mid-90s. Rain chances will be much lower, perhaps on the order of 10 percent.
Sunday and beyond
Our weather for next week is a bit uncertain due to the development of another tropical disturbance in the Southern Gulf of Mexico. However, this system is likely to be smaller, with lesser impacts. As a result I don’t think we’ll see nearly the winds and high seas we experienced from Alberto. Rather, for Sunday and most of next week, I expect we’ll see partly to mostly sunny skies, highs in the low- to mid-90s, and a decent daily chance of showers as tropical moisture pushes in from the Gulf. At this time there is no clear threat of heavy rainfall. So the weather looks pretty typical for late June.
