Good evening. Eric’s update from this afternoon has most of the situation covered. I’m here to just refresh what’s going on, and I also want to talk a little bit about Laura.

Marco

As of this evening, Marco has moved past the Yucatan channel and into the southern Gulf of Mexico.

Marco still has maximum sustained winds of 65 mph and is still moving just slightly west of due north around 10 to 15 mph. I put a tropical storm icon on the satellite image above to indicate where Marco was located. It’s worth noting how lopsided Marco’s thunderstorms are, with basically everything north and east of the center. This has implications on the rainfall forecast for Marco after landfall.

There has been little to no change in terms of expected track with Marco relative to what we thought most of the day.

The National Hurricane Center’s forecast track takes Marco broadly toward eastern Louisiana. The storm is expected to become a hurricane, and it could maintain hurricane intensity up to landfall. Marco is compact, so any hurricane-force winds will only extend out a few miles from the center, mainly to the east of where it tracks.

As far as rainfall goes, we feel the bulk of it will end up well into Louisiana, Mississippi, and Alabama. The map of rainfall below (through Tuesday evening) will look a little odd because it’s a composite of various National Weather Service offices putting together their own forecasts, so some may be older or newer and not smoothed out. But it shows that the heaviest rain is expected to be closer to New Orleans than Houston.

If for some reason Marco starts to weaken tonight and ends up falling into disarray tomorrow, there is some chance it could drift back west of the forecast cone. We feel that possibility is highly unlikely however, and we are not going to worry about significant rainfall from Marco in our area. Marco should fall apart after coming onshore, drifting into northwest Louisiana, Arkansas, or northeast Texas as a remnant low with isolated pockets of heavy rainfall. We should be able to close the books on Marco by Tuesday night or Wednesday morning.

Laura

Let’s talk about Tropical Storm Laura. I’m going to be really honest about this one: We do not know who is most likely to see landfall from Laura when it gets to the Gulf. There is a plausible risk that it could go toward the Florida Panhandle, the central Gulf, Louisiana, southeast Texas, or even Matagorda, Corpus Christi, or Brownsville. So quite literally no one (save maybe the Florida Peninsula) can let their guard down with respect to Laura. We really want folks in Southeast Texas to be prepared in case this does come this way. There will likely be some element of “Well, y’all were fired up about Marco and look what it’s gonna do” from some people out there. With Marco, we laid out scenarios because we knew there was no answer key (til today). With Laura, we’re in that same scenario phase right now, and there is no clear model or forecast that is able to see Laura’s future clearly at this point.

We have laid out some of the factors involved with Laura’s interaction with Hispaniola through the day today. As of this evening, it appears Laura may be choosing to set itself up on the south side of Hispaniola.

This and other such interactions with Hispaniola and Cuba are critical to Laura’s future. They are also unpredictable. The current NHC forecast takes Laura generally off to the west or west-northwest.

But each shift like this, with a center possibly forming farther south keeps the storm disorganized and following the bottom or left side of the cone.

The rule of thumb: As with Marco, the weaker the storm is, the more likely it will come farther west before turning northward. So if Laura continues to struggle in the islands and remains weak, there’s a pretty good chance it will follow the bottom of the cone more than the top of it, which puts it farther south to start in the Gulf and gives it a much easier route to get as far west as Texas. A stronger storm will be more apt to lurch poleward and help limit the impact of high pressure over the Southeast, meaning it would likely turn well before it gets to Texas, either near Louisiana or east of there. As of Saturday evening the weaker option is winning out, which is why it’s important to continue to stay tuned in tomorrow and Monday. We are going to still have questions tomorrow, but I predict that by Monday, we’re going to have a good idea if this is an ominous threat to Texas or another miss to our east. Stay tuned.

Our next update will be posted no later than 9 AM on Sunday.

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.

Good evening. Much as two tropical systems are swirling around in the Caribbean Sea this evening, forecasters are wallowing around in ignorance as we try to parse what will happen in the days to come as Tropical Depression 14, which is likely to soon be named Marco by the National Hurricane Center, and Tropical Storm Laura will do. (Update: The system was named Marco at 10pm CT). What does seem increasingly clear is that Laura may ultimately pose the bigger threat to interests along the Gulf of Mexico. Let’s start with the nearer storm.

TD 14

This system seems to becoming better organized, and it would not surprise me to see Marco forming tonight or Saturday morning as it nears the Yucatan Peninsula. This system is now likely to only graze the Yucatan as it moves northwest—which would therefore not substantially disrupt its organization—and this may allow for it to intensify through about Sunday, possibly reaching hurricane status over the Central Gulf of Mexico.

A stronger storm would likely to continue to push north or northwest, but it now seems that wind shear and other factors will work to weaken the storm. This probably will allow the system to be driven westward, into the central Texas coast. (We are still not particularly confident in a track, so stay tuned). So far the models are not overly excited about the rainfall potential of this depression as it moves westward, but obviously that is something we’ll have to keep tabs on.

Tropical Storm Laura

We have lots of questions about Laura, but we can be pretty confident that this system will enter the Gulf of Mexico late Sunday or Monday morning, having come near, or across Cuba. As it crosses the central Gulf of Mexico, Laura may find more favorable conditions to intensify. Several models now show it fairly quickly becoming a hurricane by Monday night or Tuesday over the Gulf’s warm waters.

Then, there is the question of track. Laura’s path will depend upon the extent of a ridge of high pressure building over the Southeastern United States. Some guidance depicts this ridge weak enough by Tuesday or Wednesday to allow Laura to bend northward toward Louisiana. However, the latest (18z) run of the European model finds nearly all of its ensemble members driving Laura westward, toward Texas, with some kind of land-falling system on Thursday. We will have to see whether this trend holds in subsequent runs, and whether other models follow the European on a more western track. We may know more tomorrow.

So where does this leave us on a Friday night? Besides at home and in need of a glass of wine, that is? We’re still left with the need to watch two tropical systems. For now, it appears that TD 14/Marco may be somewhat benign as it moves toward Texas early next week, but that is far from guaranteed. Interests in Texas and Louisiana should also keep more than a wary eye on Laura, which appears to have better potential to develop into a hurricane, and possibly a powerful one, next week.

Our next update will come on Saturday morning before 9 am CT.