Eric Berger

Good evening. I’d like to welcome our new readers to the site—whether you found us through a friend or family member, Google, Facebook, Twitter, Instagram, or of course our MySpace page. Just kidding about the last one, sorry Tom. Anyway, if you don’t want to miss our updates, you can subscribe to our email list in the box on this page. Doing so sends you our complete posts immediately after publication (and nothing else).

Alright, on to the forecast. We’re still really struggling with the evolution of Tropical Storm Laura, and a large part of the uncertainty involves the movement of its center over, or just south of Cuba the next day or so. Laura does not have a particularly well defined center and its interaction with the island may cause the center to re-form. Any of these perturbations could have implications for the storm’s track downstream. This is one reason why the models are struggling with how to handle Laura’s ultimate path.

Another factor is Marco, which we still don’t think will have a sensible effect on weather in the Houston metro area. It seems likely that a “stronger” Marco, maintaining hurricane strength on Monday as it nears the Louisiana coast, would amplify a ridge of high pressure over the southeastern United States. This would push Laura more westward, toward Texas. However, a weaker Marco would probably allow for Laura to follow a more northwest track across the Gulf of Mexico, toward Louisiana. These, and more details, are the reasons why overall confidence in Laura’s track remains low. Because of this uncertainty I thought it might be helpful to outline three scenarios that I think are possible, along with their likelihood of happening.

Scenario One (30 percent)

In this scenario the ridge of high pressure remains strong, and drives Laura toward Matagorda Bay or Galveston Bay very late on Wednesday, or early Thursday. This would allow for maximum time over the warm Gulf of Mexico, and we could see Laura coming ashore as a powerful Category 2, 3, or even 4 hurricane. This obviously would be a very bad deal for Galveston, Houston, and points east in terms of storm surge and winds. This would necessitate coastal evacuations and lead to widespread power outages, among other problems. Rainfall would be less of a concern because we expect Laura to scoot through fairly rapidly.

Scenario Two (50 percent)

In this scenario, which is basically the “skinny black line” on the National Hurricane Center’s forecast, a reasonably strong Category 2 Hurricane comes ashore near the Texas-Louisiana border, or just east of there. In this scenario Houston sees some briefly gnarly winds, possibly gusting to hurricane force on the east side of the city. But beyond some relatively short-lived power outages, conditions should not be too extreme in the metro area. This would, of course, be a bad storm for Beaumont and southwestern Louisiana.

Scenario Three (20 percent)

In this case Laura comes off Cuba and begins moving almost due northwest, toward New Orleans and southeastern Louisiana by late Tuesday night or Wednesday morning. With less time over the Gulf this is a weaker storm. Houston would see almost no significant impacts from such a scenario, but it could cause significant surges or flooding in New Orleans, Mississippi and Alabama.

For the last two runs the deterministic output from the European model has more or less depicted this third scenario, along with the Canadian model. For this reason we can’t entirely discount it.

We hope to have better answers for you tomorrow on all of this, when we’re going to reach the point when final decisions on evacuation and other preparation activities will need to be made for the metro area.

Our next update will be no later than 8:30 am CT.

Good afternoon. There’s a lot of ground to cover in this post, but we wanted to start with this: Tropical Storm Laura remains the region’s primary threat, and you really need to be paying attention. Today, you should be thinking about what you would do if a strong hurricane were to make landfall over the Houston-Galveston metro area on late on Wednesday or Thursday. Let us be clear: We are not saying that is going to happen. But it is well within the realm of possibility, and you should be thinking about what actions you would take, so that you are ready put them into play when the forecast tightens up.

For this post, we will discuss the forecast for Marco, briefly, and Laura. And we will also try to answer some of your basic questions about impacts, evacuations, and more.

Hurricane Marco

Marco became a hurricane today, with 75 mph winds. The storm is moving north-northwest at 14 mph, and this should bring its center very near the Louisiana coast by Monday evening. We still aren’t sure whether this storm will move all the way onshore Louisiana, or remain near the shore, and then start to fall apart as it tracks westward along the Louisiana coast toward Texas. However, because most of the winds and heavy rainfall should remain to the east and north of the center, we do not anticipate severe conditions in the Houston region from Marco.

Probably the most significant thing about Marco now is that it seems plausible that the storm will slow down enough to potentially interact with Laura. This would not create some kind of “super storm” but may play some role in the track of Laura. Here’s one possibility:

A note on the 12Z ECMWF:

The rightward track of #Laura into SE Louisiana appears to be due to #Marco falling apart on the model, leaving its remnants in the gulf, which then pivot Laura to the right. Can’t guarantee this doesn’t happen, but so far, Marco is holding together. pic.twitter.com/3f9puGOiFQ

— Levi Cowan (@TropicalTidbits) August 23, 2020

Tropical Storm Laura

This system remains the key threat. Laura has moved across Hispaniola and maintained a reasonable structure. It will now spend Sunday night and most of Monday moving across Cuba before emerging into the Gulf of Mexico on Monday evening. Thereafter Laura will have 48 to 60 hours over warm waters, and an atmosphere favorable to intensification. It is reasonable to expect anything from a Category 1 to Category 4 hurricane to spin up on Tuesday or Wednesday over the open Gulf of Mexico. The situation is further complicated by Marco, which will not be all that far ahead of Laura, and the two systems may interact in ways that are difficult to predict even by the most sophisticated computer models in the world.

We simply have not received much clarity today in regard to a track forecast today. As a result, the National Hurricane Center’s 10am CT forecast track for Laura (shown below) is unlikely to shift much. Because of the broad uncertainty in the global model ensembles we are still reasonably looking at a track anywhere from Matagorda Bay, up through Houston, Beaumont, and across much of the Louisiana coast. For this reason, it’s probably not worth paying much attention to the “skinny black line” right now.

I think the hurricane center’s forecast is about as good as you could get considering all the uncertainties, but the bottom line is that this forecast can and probably will shift rapidly over the next day or so. Sorry, I know you want definitive answers. We don’t have them, and I wouldn’t trust anyone who says they do.

Alright, let’s get to some your most frequently asked questions below.

See full post

Good afternoon. We’re finally starting to get a better handle on what is likely to happen with Tropical Storm Marco today, which is a good thing because the storm may make landfall as soon as Monday along the northern Gulf Coast. We have less certainty about Tropical Storm Laura, which is a cyclone most of the Gulf Coast needs to continue to watch.

Tropical Storm Marco

Marco has done two things today that increase our confidence that it will follow a more northerly track across the Gulf of Mexico. For one, it has continued to intensify, up to 65 mph sustained winds as of 1pm CT, allowing it more control over its track. Second, an Air Force reconnaissance plane found a center east of where it was expected. All of this suggests the storm will track more toward Louisiana rather than Texas over the next two days—if you read our early morning post on Space City Weather, this was Scenario One that we outlined.

While we cannot rule out a more westward track toward Texas (and of course, we’ll continue to monitor the system), at this point it appears most likely that Marco will come ashore over Louisiana, or even Mississippi. Because we can expect the strongest winds, waves, and rains to the east of the land-falling center, this means the most likely outcome for Houston is moderate to minimal effects. The northern Gulf of Mexico coast will need to watch Marco closely over the next couple of days. Although Marco now seems likely to become at least a moderate hurricane, it should encounter enough wind shear to weaken to a tropical storm before landfall a couple of days from now.

Tropical Storm Laura

This system has strengthened some today as its center has become a little better defined. Shortly before 1pm CT, the center was located just offshore the southern coast of Puerto Rico, and it may briefly come ashore later today. In this morning’s post we outlined some of the factors surrounding Laura’s potential to intensify over the next day or two as it encounters Puerto Rico, Hispaniola, and Cuba (i.e. to shred, or not to shred). From this image you can see how predicting this is touch-and-go.

Because we don’t know precisely how much time the storm will spend over this at-times mountainous terrain, there’s not a whole lot intelligible we can say about Laura’s intensity upon entering the Gulf of Mexico on Monday. However, assuming some semblance of a circulation remains by then, conditions in the central Gulf of Mexico would allow Laura to strengthen, quite possibly into a hurricane.

We still have lots of questions about Laura’s track after reaching the Gulf. The storm seems eventually destined for Louisiana or Texas, but it could come as far east as the Florida Panhandle. If anything, the models this afternoon are leaning ever-so-slightly toward Louisiana over Texas, but we’ve seen plenty of flip-flops so our confidence is quite low. If Laura were to come to Texas, we probably would begin to see its effects by Wednesday night or Thursday.

ON THE BRIGHTER SIDE: I think we’ll have a better handle on Laura’s track over the next 24 to 36 hours, which should still allow several days for final storm preparations—if needed. So as usual, we’re asking you to hang in there with us for a little while longer. And if we can get through Laura, it looks like the tropics may quiet down for a bit, allowing all of us to take a breath.

Matt will have our next update, no later than 9pm CT Saturday.

Good morning. We still are trying to parse details about tropical storms Marco and Laura, and we still don’t have solid information about what will happen. The bottom line is that, from Monday through Friday, the greater Houston region needs to be prepared for the potential of tropical weather—from heavy rainfall, to storm surge and strong winds. None of these are guaranteed, and there is no cause to evacuate now. But you do need to be prepared for rapidly changing forecasts.

Tropical Storm Marco

It appears that Marco has begun to intensify further overnight, and the storm has 50 mph sustained winds. If Marco continues to strengthen further this weekend, up to hurricane strength, it likely will take a more northerly track, toward southeastern Louisiana. However a weaker storm is more likely to move more westward, toward the central or upper Texas coast. Why? Because a stronger storm might have more impetus to barrel into building high pressure over the southeastern United States, whereas a weaker one would be more steerable to the west. Here’s a map showing the National Hurricane Center forecast track (in black) along with a couple of scenarios:

Scenario One, in which Marco never really makes a leftward turn while over the Gulf, would lead to limited impacts for the Houston metro area and the potential for heavy rainfall in southern Louisiana. Scenario Two will bring a decent amount of rainfall to the Houston region—2 to 6 inches, maybe?—along with elevated tides. At this point I would weight these two scenarios equally, in terms of probability.

Because there is so much uncertainty in the track and intensity, projecting other effects such as a storm surge is sort of fruitless. However, probably a worst case scenario is seas about six feet higher than normal along Galveston by late Monday. Peak winds, of tropical storm strength, would likely arrive here by late Monday. All of this is subject to change. All of this.

Tropical Storm Laura

Oh, we have many questions about Laura as well. At present the system is fairly disorganized, and contending with its “center” moving over Puerto Rico. What happens over the next 24 to 48 hours will probably have important implications how how menacing Laura ultimately becomes when it moves into the Gulf of Mexico. Here’s what I mean by that:

Along the current National Hurricane Center track (shown in black) Laura will traverse the mountainous terrain of Hispaniola, followed by the spine of Cuba. If the system is already a struggling tropical storm, it is difficult to see how a particularly organized system emerges into the Gulf of Mexico. Therefore the threat of Laura becoming a hurricane next week diminishes. However, if the storm can find a track just south of the islands, then it has a chance to escape the shredder and move into the Gulf later on Monday poised to intensify.

In terms of track, anything is still possible. Under the “no-shred” track above, Texas would probably be threatened by a hurricane next Wednesday or Thursday. Under the shred track, a weaker system probably comes toward Louisiana. But our confidence in a track remains very low.

We will next update the site by 3pm CT.