Good morning. We’ll run down both storms this morning, though at a high level our concern and interest is primarily focused on Laura at this time.
Marco
Tropical Storm Marco continues to try and become a hurricane this morning in the Gulf.
Marco continues to lift NNW across the Gulf and is flirting with hurricane strength this morning. (Weathernerds.org)
Marco is expected to continue lifting just west of due north today, and it is aiming for a landfall somewhere in eastern Louisiana before making a fairly hard left turn and basically falling apart over southern Louisiana.
Marco is expected to come into eastern Louisiana, and it should then meander westward while significantly weakening. (NOAA)
We have seen a model or two bring the remnants more west along the coast, which would increase some storm chances for us and deliver some localized heavy rain on Tuesday, but right now those issues aren’t expected to be too serious.
Marco’s heaviest rainfall continues to look to stay well off to our east. Coastal areas may stand the chance for some locally heavy rain, but nothing serious expected right now. (Weather Bell)
Rainfall through Tuesday evening is expected to be mostly minor, with the best chance of something heavier along the immediate coast and lesser chances inland. The heaviest rain remains directed into eastern Louisiana.
The brief summary on Marco: Perhaps a small hurricane into southeast Louisiana before it dissipates while shuffling west across southern Louisiana, keeping most heavy rainfall well off to our east.
Laura
Tropical Storm Laura looks impressive this morning, mainly because it’s coming out of the typical nighttime peak in thunderstorms, and because it is doing this while interacting with Hispaniola, which often rips these things apart. Laura is the unfortunate one that actually gets by Hispaniola without a lot of trouble because it was disorganized to begin with.
Laura is not terribly strong this morning, but that has helped it begin to exit Hispaniola with an impressive area of thunderstorms. (Weathernerds.org)
If you want to provide some criticism of Laura, it’s that the storm is somewhat lopsided. But short of that it has a healthy core of storms, some developing outflow, and it is now exiting the highest hurdle it needed to survive, Hispaniola. Cuba comes next, but the bottom line here is that Laura has the skeleton it needs to become a healthy tropical system when it eventually finds a more hospitable environment for strengthening, likely Tuesday and Wednesday over the Gulf.
Laura’s track has shifted a little to the west since yesterday, but if you read between the lines in the National Hurricane Center’s discussion, there are likely to be more westward shifts to come.
Laura’s track is now shifting slowly to the west, and further shifts are possible if not likely today and tomorrow. (NOAA)
The battle lines right now are between some of the typical global models we use for day to day forecasting, which take Laura farther west, more into Texas and the tropical models we use for situations like this, which have skewed a little farther east, more into western Louisiana. Laura is going to basically work around the periphery of high pressure off to our north and east. Typically, we would expect the global models to have a better handle on the steering situation, so there is a reason to put some trust in them over the hurricane ones for track right now. Once Laura works across Cuba and emerges into the Gulf tomorrow, we will have a better idea of whether Corpus, Houston/Galveston, Port Arthur, or central/eastern Louisiana are most at risk. Right now, all we can tell you is that trends since yesterday have only served to give us more pause about how close Laura may come to southeast Texas. We continue to urge you to pay close attention to this storm and make your preparations today in case they need to be implemented quickly tomorrow and Tuesday.
How strong will Laura be when it gets where it’s going? That’s a great question, and right now, the reliable model intensity guidance ranges from a low-end category 1 storm to a high-end category 3 storm. Given the history of the Gulf, the fact that it’s going to be in a fairly favorable environment for strengthening, and frankly how it has performed so far, we would likely lean toward the higher end of things with respect to intensity right now. The NHC forecast is calling for a category 2 hurricane at max, which is right in the middle of reliable guidance at this time. Hurricane intensity remains a very, very difficult thing to predict and though we are bullish on this storm’s strength right now, there are still risks equally spread that we may be too aggressive or not aggressive enough. More clarity on this should come tomorrow.
As far as rainfall goes? That is always a concern, but Laura is expected to keep moving and no models indicate a slowing or stalling. For all intents and purposes, we are viewing this a tropical threat (storm surge, wind) first and foremost and a rainfall flooding threat secondarily. Again, please stay aware and ready to act.
Eric will have our next update posted no later than 3 PM today.
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 has moved into the Gulf this evening as a 65 mph tropical storm, although most of its storms and winds are north and east of the center. (Weathernerds.org)
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.
Marco should roughly track toward eastern Louisiana, possibly becoming a hurricane and maintaining low-end hurricane intensity up to landfall. (NOAA)
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.
Rainfall from Marco is expected to be heaviest well to the east of Houston, deep into Louisiana. (Weather Bell)
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.
A satellite loop of Laura this evening shows a lot of storms but weak organization with a loose center on the south side of Hispaniola. (Weathernerds.org)
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.
Laura’s NHC forecast takes it into the Gulf as a hurricane, with a turn north somewhere in the western Gulf, with areas from Texas through the Florida Panhandle still in the cone. (NOAA)
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 morning. We’ve got a full rundown on Tropical Depression 14 here today, and we’ll touch on Tropical Depression 13 as well. First, let’s get you through Sunday’s forecast.
Today through Sunday
The next three days have some similarities, and they should be mainly sunny with slight shower chances. The maximum coverage of showers may be today and particularly focused south and west of Houston. Saturday should see a bit less coverage but maybe more of a chance in other parts of the area. As the broader circulation from TD 14 nears on Sunday, we could see offshore winds develop, or at least more of a northeasterly component to them, which would probably shut down rain risks, especially south and east of Houston. Basically, you shouldn’t be expecting rain this weekend, but you shouldn’t be surprised if you see some either, especially Friday and Saturday.
Look for highs in the middle or upper-90s and lows generally in the 70s through Monday morning.
Monday and beyond (or the TD 14 discussion)
Alright, on to the main event. There is good news and bad news today on the Tropical Depression 14 front. The good news is that the storm is not any better organized this morning. The bad news is that because the storm is not any better organized this morning, we remain with more questions than answers.
Let’s start with a satellite loop of the system this morning.
A morning satellite loop of TD 14 shows a broad circulation which masks disorganization a bit, along with limited thunderstorms at the center. (Weathernerds.org)
Most folks will look at that loop and basically see a “swirl,” which is what you expect, even if thunderstorm coverage is a bit sparse. Well, the “swirl” is actually in the mid-levels of the atmosphere, not at the surface. At the surface, which matters greatly for the future of this thing, the National Hurricane Center (NHC) says that satellite passes and earlier reconnaissance aircraft data can’t really hone in on one defined center. Broadly speaking, this means TD 14 is disorganized this morning. That’s a good thing, of course, but it’s also a tricky one because without a defined starting point, you degrade the forecast of your ending point, thus increasing uncertainty in the forecast after a day or two.
Let’s look at the official NHC outlook as of 4 AM CT.
The official forecast brought TD 14 to hurricane strength in the Gulf at 10 PM last night, and it holds there today. Although the rough center line points right at the east side of Galveston Bay, it cannot be emphasized enough that there is a *wide* spread in possible options for a potential landfall point early next week and impacts in the Houston area will vary depending on where that is located. (NOAA)
The NHC track remains pointed right at Houston, and the wrinkle overnight was that it explicitly shows a hurricane in the Gulf as it approaches. How do you interpret the map above? While the forecast shows the track pointed at Houston, by day 5, the reality is that the center could be anywhere from near Matagorda Bay to perhaps near New Orleans. We always say “look at the cone, not a point on a map.” You really need to take that advice with this system, because there is an inordinate amount of uncertainty still today.
We know that TD 14 will emerge in the Gulf on Sunday. It will probably be a tropical storm at that point, but given the current situation off Honduras, that’s not a guarantee. It may be weaker. Over the Gulf, it should find some opportunity to strengthen a bit given very warm water temperatures (as noted yesterday afternoon).
But there are three significant hurdles that will impact how TD 14 may or may not strengthen and track.
1.) Wind shear: We know wind shear is expected to be low as it emerges in the Gulf. But per the NHC, it’s expected to increase in the northern Gulf. According to the SHIPS model, by late Monday or Tuesday, shear is around 15 to 25 knots. That’s not massive, but it’s enough to give a tropical system some problems. Alternatively, there is some risk that the wind shear will lessen or focus more inland. In that case, it may actually help TD 14 to strengthen a bit as it approaches land. This remains a difficult item to pin down, but the going theory is that TD 14 will have to fight some wind shear as it approaches Texas or Louisiana.
2.) Dry air: If you look at the GFS model on Monday evening at 7 PM, you’ll see TD 14 probably as a moderate tropical storm in the Gulf. If you look at relative humidity on the GFS model, you’ll see the storm is lopsided with the best moisture north and east of the center and a pretty significant amount of dry air south and west.
The GFS model forecast of relative humidity Monday evening shows a substantial amount of dry air close to the center, which could be a significant hurdle to strengthening. (Tropical Tidbits)
We have had some lower humidity than usual lately here, right? You’ve felt that. It’s still plenty hot, but dewpoints (at IAH) have been as low as 59 degrees in recent days! That’s really, really comfortable for Houston in summer. And rare too. That’s the first time that has occurred in August since 2015, and of the 7,180 August hours in the last 10 years, only 20 (0.25%) have had air that dry. Well, dry air is going to linger a bit longer, and it would seem that it will impact TD 14 in some capacity. Could TD 14 fight off dry air? Sure, but it better get its act together quickly if it can become robust enough a storm to accomplish that feat.
3.) Tropical Depression 13: One of the most common questions I’ve seen from people is some variation of “Could TD 14 merge with TD 13 as it comes into the Gulf and create a Category 6 megacane, which would be soooo 2020!?”
Here is the forecast track of TD 13, by the way:
Tropical Depression 13 is also expected to become a hurricane in the Gulf early next week, though uncertainty is equally high with this system. How TD 13 and TD 14 will impact each other’s track, if at all, is still unclear. (NOAA)
The answer to that one is complicated. For the sake of time and simplicity, I’ll be brief here. There is a meteorological process known as the Fujiwhara effect. You can read about it here. In a nutshell, if two tropical systems get within about 800 miles of each other, one can impact the circulation of the other. The diagram below shows this in the case of a much stronger storm. In this case replace Bopha with “TD 14” and Saomai with “TD 13:”
The Fujiwhara effect occurs when two cyclones (tropical systems) get close enough to each other to begin orbiting around one another. (NOAA via Wikipedia)
In an idealized Fujiwhara situation (unlikely), what would likely happen is that TD 13 would move into the Gulf from south of Florida, and as it comes north, TD 14 would probably slow down offshore of Texas or Louisiana, allowing 13 to go inland (likely to our east) and 14 to meander for a day or so offshore before going inland too. Now, to be clear, this is not the base case; it’s not what we expect. However, there could very well be some element of interaction that occurs between TD 14 and TD 13 because of their expected proximity to one another. That would depend on strength, orientation, etc. And since we don’t really know those things right now, it’s difficult to say how that interaction will (or will not) occur. We have also never seen that before in the Gulf. Like, ever. We have had simultaneous systems in the Gulf, but they’ve never been close enough to each other to risk that sort of interaction. In that respect, this is basically unprecedented and there will be unknowns.
So to summarize: It is likely that TD 14 will enter the Gulf Sunday and strengthen, possibly to a hurricane, tracking broadly toward Texas or Louisiana. The Houston area is very much in the cone, and we’d advise folks to continue to prepare as if a hurricane were coming. There are some hurdles for TD 14 and numerous things we do not yet know, however, and impacts could realistically range from hardly anything to a full-blown hurricane in our area. Eric and I will keep you posted through the weekend.
Quick note on rainfall: While we’re trying to figure out the tropical side of this thing, we are obviously sensitive to people’s concerns about rain, flooding, and a Harvey stall type scenario. Right now we do not expect a “stall” situation. No reliable model is hinting at that, and there’s nothing in the data right now that would argue that it’s a serious concern. The storm may slow down a little as it moves through, but slowing down is not equivalent to stalling and the differences are significant. We expect heavy rain, particularly if the storm comes in more to the southwest of Houston, and flooding is always possible in tropical systems. But we are not especially worried about any one possible outcome at this time. We will update you on the rainfall aspect more this weekend as things become clearer.
Good afternoon. Tropical Depression 14 formed late this morning from the disturbance previously dubbed Invest 97L. This is the primary system we will watch over the next few days as it moves toward the Gulf. Here’s a brief rundown of what we know and, more importantly what we don’t know.
Now
Tropical Depression 14 is located east of Honduras and south of Cuba over the western Caribbean Sea.
Tropical Depression 14 is moving west across the western Caribbean. (Weathernerds.org)
It’s basically what you would expect from a tropical depression: sort of messy, but with numerous storms both east and west of the center, so it’s not terribly asymmetrical.
The latest forecast from the National Hurricane Center has the system moving into the Gulf and remaining a tropical storm through early next week.
The official National Hurricane Center forecast cone for TD 14 brings it broadly toward the Texas or Louisiana coasts by Tuesday. (NOAA)
It’s important to note that while a “center line” points this right at Houston, the cone is the cone for a reason. The storm may track well to our east or well to our southwest. Our impacts here in Houston would vary considerably based on that, so this map should not be considered a license to panic or to write it off entirely.
Over the next two days, TD 14 will enter an environment that’s pretty conducive for strengthening. Shear will continue to relax. As it moves toward the Yucatan Peninsula of Mexico, look for this to intensify into a tropical storm and possibly a hurricane. Water temperatures in the western Caribbean are more than supportive of strengthening.
Sea surface temperatures are above normal everywhere in the Gulf and Caribbean, more than supportive of strengthening as TD 14 moves through. (Weather Bell)
Once it gets to the Yucatan and beyond, the questions begin to mount quickly.
Here is what we know:
We know that TD 14 should move across the northeastern part of the Yucatan Sunday morning. We know it will likely be at least a tropical storm. We know it will be pulled north by a trough over the South and nudged west by the Bermuda high as it expands westward across Florida. We know that ifimpacts occur in Houston, they would likely begin Monday night or Tuesday.
Here is what we don’t know:
We do not know where TD 14 will ultimately end up and how strong it will be when it gets there. I know this makes you throw your hands up in the air in frustration, but those are the realities.
We do not know how much wind shear TD 14 will encounter over the Gulf. As the trough over the South weakens and pulls out, there will be some wind shear left behind. If that ends up over the Gulf, that will help mitigate TD 14’s ultimate strength. If that wind shear goes north as the storm comes north, then we need to watch for TD 14 to intensify more significantly.
We also don’t even fully know how much land interaction TD 14 will have near Honduras and Mexico. The latest advisory suggests TD 14 is farther south than originally thought, so that is something that could ultimately impact the system.
We don’t know how much rainfall we will see, as it will depend on how organized TD 14 becomes and exactly where it goes.
We don’t know how TD 13 may impact what happens with TD 14, so there’s a good deal of uncertainty there.
More ambiguous things we can say:
A stronger storm would likely go to our east, whereas a weaker one would come closer to us. But weaker does not necessarily mean “weak,” so keep that in mind.
We do not expect a stall/Harvey scenario at this time or even an Imelda one but we are not entirely sure how things will play out. Flooding is possible in any tropical system, so we cannot rule any sort of flooding out right now.
The current rainfall forecast from NOAA stops on Thursday evening and shows the heaviest rain offshore, but some risk of heavier rain perhaps toward Houston with TD 14. Total rainfall will ultimately depend on the exact track and speed, things yet to be determined. (Pivotal Weather)
We should be able to narrow the cone a bit in the morning, and we should know a lot more later tomorrow and Saturday morning. So stay tuned.
