Eric Berger

Good Saturday morning! We’ll be with you here all weekend on Space City Weather to track the progress of Tropical Storm Beta, and its effects on Houston, Texas, and Louisiana. Broadly speaking our forecast has not changed a whole lot. For now, on our Flood Scale, we are still calling for a Stage 2 flood for areas south of Interstate 10, and a Stage 1 flood for areas north of Interstate 10.

With this system we are most concerned about the potential for heavy rainfall next week, and then rising seas along the coast due to a prolonged period of winds from the east-northeast. Probably the most important thing we can tell you this morning is that there is still a lot of uncertainty in the track forecast for Beta, and where the storm’s heaviest rains will fall. We suspect this storm will have some surprises in store.

Track

As anticipated, Tropical Storm Beta has moved north overnight, and now lies nearly 300 miles due east of the mouth of the Rio Grande River. Pretty soon we expect the storm will run into a ridge of high pressure and take a westward turn, gradually moving toward Texas. We are reasonably confident that the storm will then approach the Texas coast somewhere between Corpus Christi and Matagorda Bay on Monday, potentially as a strong tropical storm or a Category 1 hurricane. Through Monday this track should keep most of the heaviest rainfall just along, or off the coast. So far, so good.

The problem is that, after this point, we’re not really sure what will happen. The National Hurricane Center’s official track brings the storm to the northeast on Tuesday, along the Texas coast, as weakening high pressure allows for an exit. However, it also seems possible the storm could move 50, or even 100 miles inland before making this turn, or remain 100 miles offshore. I know what you’re thinking, slow-moving storm, landfall near Corpus, moving inland—Eric, that sure sounds a lot like Hurricane Harvey. Well, I’ll agree, but there are some key differences here. Most significantly, Beta lacks Harvey’s organization, and will be fighting dry air as it moves toward Texas. This may help to limit inland rainfall. Moreover, the storm really should move away by Tuesday or Wednesday, so we are probably not looking at a four- or five-day heavy rainfall event.

Rainfall

So how much is it going to rain next week? The global models have trended slightly downward in terms of rainfall accumulation during recent runs, and I think a good general expectation is 2 to 8 inches across much of the Houston metro area, with coastal areas potentially seeing 6 to 12 inches between later Sunday and Thursday. That much rain over four days is manageable, so our concerns are very high rainfall rates—which tropical storms produce—and higher than anticipated totals. We can’t rule out some 20-inch bullseyes, but so far there’s not much support for this in our best models. I think the bottom line is that we need to prepare for heavy rainfall through Wednesday or so of next week, and the possibility of flash flooding. But it may not come to that.

Storm surge

The other issue we’re going to face is storm surge as Beta produces strong easterly winds over the area. For now, Hurricane Laura’s water levels, plus one or two feet, is probably a good guide for what to expect from Beta along Galveston Island, Bolivar Peninsula, and Galveston Bay. However, this part of the forecast remains very much subject to change, given Beta’s track and intensity.

Winds

Winds will begin to increase across the area on Sunday and Monday, and there is a 30 to 40 percent chance that the Houston metro area will see tropical-storm force winds next week, with higher chances along the coast. This forecast, too, is very dependent on track and intensity so winds are a work in progress. But right now the expectation is that wind should not be too disruptive in terms of power outages across Houston.

Our next update will be posted no later than 2pm CT today.

Welcome to another crazy day in the tropics. While we we’ve been waiting for Tropical Depression 22 to strengthen into a tropical storm, a system in the deep tropics became Wilfred this morning. And then, at noon, Subtropical Storm Alpha improbably formed off the coast of Portugal. Neither of these storms remotely concern the Gulf of Mexico, so our focus will remain on the depression that will become—checks notes—Tropical Storm Beta later today.

We are issuing our first Flood Scale forecast for this depression, with the caveat that this is subject to change. Simply put, there remains a healthy amount of uncertainty about where the heaviest rains will come over the next five or six days. However, for now, we are calling for a Stage 2 flood for areas south of Interstate 10, and a Stage 1 flood for areas north of Interstate 10. The biggest rainfall risks for Texas are right along the coast, from Brownsville to Galveston.

Now let’s talk track, because that ultimately will determine what happens with the depression’s rainfall.

Where will Beta bend?

This will be the story of two turns. The following graphic shows the National Hurricane Center’s official forecast track (as of 10am CT Friday) in black. I’ve made several annotations that I want to talk through to help you understand the track forecast and the uncertainties that we’re dealing with.

Alright, so we’re fairly confident in the storm’s track today and tomorrow, when it should run into high pressure associated with the front that has moved through Houston already. This should push the system westward, toward Texas. The big question after this is how far west the storm will get—probably very close to the coast, and perhaps even a little bit inland (I’ve tried to highlight this area with the white rectangle). The storm does its coast-hugging, slow moving routine on Monday. At this time it will produce a lot of rain, but hopefully most of this will fall east of the center, offshore.

The second turn

By around Tuesday, the storm should begin to lift to the north and then northeast, perhaps moving close to the coast (as indicated by the official forecast), or further inland (wetter for Texas) or further offshore (drier). Because we have so little confidence in the track for Tuesday and beyond it’s hard to say how much rainfall we will see in the Houston region. For example, I could envision 5 inches of rain in Galveston, or 20 inches. I could envision 2 inches of rain in Houston, or 8 inches. We’re pretty confident that rain chances will perk up on Sunday, with the really heavy stuff possible from Monday through perhaps Thursday morning. For more precise totals you’re going to have to hang in there with us until we get a better handle on the storm’s track.

Coastal flooding

The other issue is coastal flooding. Generally, we anticipate the potential for water levels to rise 1 to 2 feet higher than the region experienced with Hurricane Laura three weeks ago. Waters will start to rise on Saturday, and increase on Sunday. After that any additional rises will depend upon the intensity of the depression—we still think it’s going to become a tropical storm or a Category 1 hurricane at most—and its track. So these hazards are to be determined as well.

That’s all we have for now. Matt will have our next update at 8:30pm CT this evening. By that time Beta probably will have formed. Alas, Beta won’t be a fish storm.

Good evening. The National Hurricane Center says a tropical depression has formed in the Gulf of Mexico, and this system may become Tropical Storm Wilfred in the next day or so. Before we get too deep into the forecast I just wanted to highlight a couple of changes from this morning’s post:

• The depression is expected to begin moving northward a little sooner than expected, so impacts for Texas could occur sooner
• The forecast models are now in a little better agreement that the tropical system will come near, or possibly even ashore the Texas coast, increasing the rainfall threat

Alright, now let’s jump into the forecast. The 6pm CT “track” prediction from the hurricane center highlights some of our uncertainty when it comes to the depression. After the storm moves slowly north on Friday and Saturday it should run into high pressure building over Texas after the passage of a front. This is what will likely push the system westward, toward Texas.

After Sunday we’re deep into the realm of speculation, as we’re not sure what will happen by Monday or so. The system could plow west or southwest into Southern Texas or Mexico (track “A”) in the map below. It could follow a track up the Texas coast (“B”). It may also essentially stop, and get pulled to the northeast, toward Louisiana, as the high retreats (“C”). We really do not know and anyone who says they do know right now is not being honest with you. Each of these tracks would have drastically different outcomes for Houston, which is why our overall confidence in next week’s weather is very low.

The National Hurricane Center anticipates the storm will gradually strengthen and come near hurricane strength by Sunday. While the Southern Gulf of Mexico is fairly warm—plenty so for strengthening—the storm will likely take on dry air from the north which will not help its organization. Moreover, a slow-moving system will churn up cooler water from deeper in the Gulf. Bottom line: While we’re always concerned about September storms intensifying in the Gulf, in this case we’re more concerned about the moisture from this system than winds.

As we’ve been saying, the depression has the potential to become a prodigious rainmaker over the next week for Texas and northern Mexico. We think the cold front and storm’s position will probably keep its heavy rainfall offshore through this weekend, but by Monday or so that may change. It is going to depend how close the storm’s center comes to Texas as most of the heavy rainfall should be near the center, and on the eastern half of its circulation.

Because of the track uncertainty, the entire Texas and Louisiana coasts need to be paying close attention to the potential for heavy rainfall next week. We don’t have to tell you about the potential for mischief from slow-moving tropical systems. But with that said, we are still very much in the wait-and-see mode with this system—the greatest likelihood is that the Houston area sees a few inches of rain next week, not a dozen or more.

Given that this system is likely to exist for at least the next several days we also have concerns about high tides. Coastal tides are already running about 2 feet above normal, and by this weekend may reach 4 to 5 feet above normal, which will pose problems in low-lying areas along the Gulf of Mexico and Galveston Bay. This is our largest concern after the potential for heavy rainfall.

Matt will have our next update on Friday morning by 7:30am CT.