Matt Lanza

Heading into the holiday weekend with more questions than answers in the Atlantic basin

Headlines

  • Sluggish tropical development is a low possibility in the northwest Gulf of Mexico as low pressure forms off the Texas and Louisiana coasts.
  • Though a serious system is not expected to develop, locally heavy rain and flash flooding are a good bet along the coasts of Texas and Louisiana into next week.
  • The Atlantic tropical wave continues to have mixed chances to develop, but the ceiling is high enough to continue watching closely.
  • An additional wave behind that one will probably stay out at sea, but conditions may continue to get more and more conducive to development as September progresses.

Gulf of Mexico

Let’s start closer to home first. We’ve been discussing it all week, but low pressure has now officially formed in the Gulf, with a surface low analyzed offshore of Galveston and Sabine Pass. The National Hurricane Center now highlights this area with a 20 percent chance of development.

A broad area of low pressure at the surface has formed off the Texas coast. Development is unlikely but could slowly occur in the coming days. (NOAA WPC)

The surface low is rather broad, so it’s not as if we have a rapidly intensifying tropical system off the coast. But we have low pressure in the Gulf, which is always something of note. Any development risk from this is very low-end in terms of winds and waves. But in terms of rain, this will be a source for some serious coastal rainfall in the coming days, development or no development. Rain totals through next week may tally up an additional 5 to 10 inches between Galveston and Vermilion Bay in Louisiana.

Localized flooding is a possibility on the coast of Texas and Louisiana into next week, with another 5 to 10 inches of rain likely through Wednesday. (Pivotal Weather)

While there are no flood watches posted currently (except in the New Orleans and Baton Rouge areas), there is some potential for flooding to occur in coastal counties and parishes. Places like Galveston, Port Arthur, and Cameron through Morgan City and New Orleans could definitely see at least localized street flooding crop up. With a surface low now offshore, most of the rain will likely consolidate around that feature, meaning that inland places like Houston and perhaps Lake Charles see less rain, less often.

Surface low pressure is broadly spinning offshore of Texas and Louisiana. Organization, if any, will be sluggish. (Weathernerds.org)

This will be a very coastal-focused feature. The low should meander in the days ahead offshore. Thankfully, upper level conditions aren’t super conducive for development, so again any organization or strengthening would probably be very sluggish and the ceiling from this is rather low it seems. As the low meanders, it could end up onshore in Louisiana or back toward the middle Texas coast, so proximity to land will also act against its development.

Rainfall along coastal Louisiana and back toward New Orleans will also be heavy in spots with localized flash flooding a concern here as well. (Pivotal Weather)

Bottom line: This is not a major concern, but it bears some watching and it will, at the least, deliver locally heavy rain and flash flooding potential on the Texas and Louisiana coasts.

Caribbean development chances

We continue to monitor a tropical wave in the Atlantic that has about a 40 percent chance of development as it moves into the Caribbean next week.

Tropical development should be slow from this wave as it moves into the Caribbean next week, but it does have enough potential to monitor for the northwest Caribbean and Gulf. (NOAA NHC)

To be clear out of the gate: We have no real good feel about the future of this system. It may not develop, or it could become a serious system to watch. We see legitimate arguments for both outcomes right now. We do know that there are a couple features to watch that will influence the outcome of this system. First, high pressure off Bermuda will help dictate steering flow for this, which is why we’ve seen the NHC outlooks gradually shift more and more to the south and west with time. Second, a cold front dropping into the northern Gulf of Mexico next weekend affiliated with an unusually deep trough of low pressure in the Eastern U.S. may also play a big role in this. Third, the intensity of the system itself will be important, as a stronger storm is more apt to turn north faster, whereas a weaker one will get farther west before turning.

What does it mean? It means we just need to continue watching.

The European ensemble probability of a tropical storm in the Caribbean next week and weekend is only around 20 to 30 percent right now. (Weather Bell)

The European ensemble and ICON model are generally the most bullish on development from this system. But even the ensemble can only muster about a 20 to 30 percent chance of development. There are a couple ensemble members that are very bullish on intensity with this. While they remain in the minority, that’s enough reason to keep watching. As we work through the holiday weekend, I am sure we will glean more information on this. For now, while frustrating, it’s prudent to acknowledge there is a great deal of uncertainty with this.

Beyond the Caribbean

Another system moving off Africa will have a chance to organize in the deep tropics but even that seems less than super exciting right now. It should hopefully end up out at sea as high pressure builds more to the west in the Atlantic, opening the exit door a bit in the east. We continue to see signs of an uptick in activity overall, and in fact, yesterday’s Euro weekly forecast for final full week of September is the first I’ve seen to show above normal storm intensity in some time.

The week 4 of the Euro weeklies yesterday shows above normal ACE for the final week of September, indicating that things will likely pick up as the month progresses. (ECMWF)

Based on this and some other data I’ve been looking at, I think September may play out interestingly. The first few systems we’ll probably see struggle to organize or struggle to get a handle on. The next batch will probably struggle to organize less, and then the final third of the month may be when the door barges open on an active period. A lot to watch in the weeks ahead, but fortunately still some time to keep tabs on things.

Gulf of Mexico trying to bring some noise as we ease our way into a busier period

Headlines

  • Slow tropical development is becoming a growing possibility in the western Gulf of Mexico heading into next week.
  • Though there are no signs of rapid development, any organized tropical system would be slow to move and may impact rainfall forecasts for next week in Texas, Louisiana, or Mexico.
  • The Atlantic tropical wave may hold off on development until it moves across the Caribbean, and it merits watching beyond later next week.

Watching the Gulf because we can’t not

For anyone who forecasts or lives on the Gulf Coast, during hurricane season you know that when stuff just kind of festers offshore you at least want to pay attention. That’s where we are right now. There’s no imminent sign of development, modeling is generally muted on development over the next week, and it’s pretty clear that the primary issue on the Gulf Coast over the next five to seven days will be rainfall.

The rain forecast over the next week continues to flag anywhere from 4 to 8 inches of rain on the Gulf Coast, along and south of I-10 in southeast Texas and Louisiana. (Pivotal Weather)

The good news for now is that the pace of the rain will come steady enough to hopefully avoid any meaningful flooding risks. Still, flash flooding and street flooding are always issues on the Gulf Coast in these patterns, so you should expect at least that.

Back to the chances of tropical development. If you look at a satellite loop over the western Gulf today, you definitely see a lot of thunderstorms.

Clouds indicate thunderstorms over the western Gulf (right side of the image), associated with a weak upper level low pressure system. (College of DuPage)

The good news is that these storms are associated with an upper-level low, not a surface low. Tropical storms and hurricanes develop at the surface, not upper levels. That being said, it’s not unprecedented for a setup like this to eventually yield a surface low. If that happens, you could perhaps see some slow tropical development. You could also see the heavier rainfall totals shift around into next week. Some modeling does bring a surface low to fruition over the next five or six days.

A minority of European ensemble members develop a surface low off the Texas coast through Labor Day weekend. (Weathernerds.org)

A handful of European ensemble members shown above do this. There’s a pretty consistent signal for this in the ICON model as well, not a one-off that leads to its somewhat divisive reputation as a tropical model. There are also hints of this in European model AI guidance too.

A loop of the surface and precip forecast from the ICON model from Sunday through Wednesday. Note the surface low developing in the western Gulf and not moving much. (Tropical Tidbits)

So what am I saying? We have enough model support to justify this as a potential area to watch over the next several days. Now, the good news is that none of these models develops the system into a hurricane. That said, a slow-moving system sitting off the Texas coast could produce some heavy rainfall, even beyond what’s currently forecast. Steering currents in the western Gulf are essentially dead calm next week, which means anything that does organize would move very slowly. If this just sits offshore and rains offshore, that’s no problem at all. But if things move farther north or west, then you have another story for parts of Texas, Louisiana, or Mexico.

So in summary…

  • Tropical development may not necessarily be likely, but it’s a very real possibility over the next 5 days or so off the Texas coast.
  • Any tropical system would likely be slow to organize and slow to move.
  • There could be volatility in rainfall forecasts for next week if this comes to fruition.
  • As always, uncertainty exists, so stay tuned and check back each day for the latest.

Looking in the Atlantic

So we’ve flip flopped today, focusing more on the Gulf than the Atlantic. That’s because support for any development of the tropical wave moving into the islands next week seems to have ebbed a good bit today. Not to say it’s impossible; there’s still a 20 percent chance shown by the National Hurricane Center. But model support seems to have peaked. That said, with slower development chances, this means the system may wait til it gets into the Caribbean to organize. You can see that on the ICON loop above which ends with the disturbance sitting south of Hispaniola by the middle of next week. Something like that seems reasonable right now. Any development looks slow.

So where would it go from there? Obviously, this is a bit of a shift west from earlier this week when it looked as if this might follow in Ernesto’s footsteps off the East Coast of the U.S. I would anticipate now that this follows the base of high pressure east of the Bahamas toward the northwest Caribbean. From there, all bets are off.

Tropical development from the Atlantic wave may be slow as it moves into the Caribbean, quite slow perhaps. But it bears watching as it comes west. (Weather Bell)

I would assume it comes into the eastern Gulf or toward the Yucatan, but it’s far too early to speculate much. Either way, while nothing is imminent with this one, it’s a sign to pay attention to things as we head into hurricane season’s peak month.

Behind this one, there continues to be model support for another wave emerging off Africa that could harmlessly turn north in the eastern or central Atlantic. We’ll keep tabs on that in case anything changes.

The NHC does have another area outlined in the open Atlantic southeast of Bermuda that has a very low chance of development, but it should not impact anyone.

Atlantic aiming to awaken after August nap, as we watch east of the islands

Headlines

  • Tropical development remains possible next week just east of the Caribbean islands.
  • No signs of anything imminently bad or significant yet, but it’ll be the primary area to watch.
  • The Gulf Coast will get soaked through next week with at least some low-end risk that something could try to form in the Gulf later next week.
  • An additional system or two will be possible heading into the week of the 12th, but details are minimal right now.

Atlantic to awaken

Even before Ernesto exited on August 20th, it was apparent that we were headed into a somewhat lengthy lull in tropical action in the Atlantic basin. The signs of the nap ending are continuing to stack up as we head toward next week. Let’s be clear right away: This doesn’t mean that things are going to go crazy all of a sudden (though one can’t rule that out this year), nor does it necessarily mean there’s an imminent threat to anyone. But there will be more noise than we’ve seen since Ernesto.

There’s a 20 percent chance of development over the next week in the central Atlantic per the NHC. (NOAA NHC)

An area of interest got identified yesterday by the National Hurricane Center with odds of 20 percent for development over the next week. Those aren’t especially high, but as we’ve seen from storms this year, they all started from generally low probability points. I personally think the chance over the next five days is close to zero, with chances rapidly increasing on days six to seven, so I would expect this potential to increase tomorrow and Thursday.

The area of note is from the mass of clouds in the Atlantic between the Caribbean and Africa, just southwest of the Cabo Verde Islands off Africa right now.

A satellite snapshot of the Atlantic basin today, with the area of interest just southwest of the Cabo Verde Islands. (College of DuPage)

This doesn’t look like much at this time, which is sort of the point. Any development from this area is going to be sluggish over the next five days or so, which is why I’m not particularly keen on anything here until next week.

But, support within modeling for this area to eventually develop continues to sustain today. Overnight runs of the European ensemble model and GFS ensemble model show at least marginal support for something to develop just east of the islands early next week. This may get off the ground slowly, but it should get off the ground. Looking at the GFS ensemble from this morning, you can see a decent signal for below average sea level pressure just east of the islands next Tuesday.

Support for below normal sea-level pressure east of the islands which could indicate some tropical development. (Tropical Tidbits)

This doesn’t mean a big storm or even a well-organized storm. But it’s a signal that adds to other signals that supports development.

From here, where would this go? Great question. There seem to be mixed signals today in modeling in terms of exact details on where high pressure will establish and move in the Atlantic next week. So, much like yesterday, I don’t want to overspeculate on where this could end up going. Just know that we continue to see potential next week just east of the islands, and those in the islands should monitor the progress of this forecast.

Gulf soaker

Meanwhile, looking farther west, the Gulf continues to look unsettled well into next week. While there is very little signal for anything specific, just the fact that we have a lot of moisture, thunderstorm chances, and little movement means we’ll be seeing a lot of festering in the Gulf next week. We’ve got disturbances, stalled fronts, and more just sort of sitting there. It remains more of a curiosity than a concern at this point, but it will be an area I’d watch later next week out of an abundance of caution.

The western Gulf Coast will continue to get soaked by rain and storms into next week, with perhaps as much as 8 inches or more of total rain on the Texas or Louisiana coasts. (Pivotal Weather)

Regardless, the Gulf Coast will get soaked into next week. We could see as much as 4 to 8 inches or even more in spots between about Matagorda Bay and New Orleans. Coastal locations are most likely to see the heaviest rainfall. While flooding may not be a serious concern initially, after repeated rounds of rain, we could hear more about flooding risks in this area. We’ll continue to babysit things to be safe.

Beyond next week

After the Gulf disturbance and the system east of the islands, we’ve got one or two other waves emerging off Africa with some signals in the modeling showing up today. Nothing imminent or particularly likely, but this would make some sense. Regardless, expect things to get busier after next week.

Change may be in sight in the Atlantic as we march into September but not this week

Headlines

  • No tropical development is expected this week in the Atlantic.
  • A tropical wave has a growing chance to develop next week just east of the Caribbean islands and is worth watching.
  • The overall background in the Atlantic may become more conducive to tropical development by mid-September.
  • Hawaii will see modest impacts from the remnants of Hurricane Gilma this weekend.

Another quiet week

The Atlantic will remain quiet for another week here, as we have no real development chances anywhere in the basin of note. The Gulf Coast will be busy with showers and thunderstorms, but no development is expected from anything.

Rainfall over the next week or so is expected to be meaningful in the western Gulf, but this should come with no organized tropical systems. (Pivotal Weather)

The eastern Atlantic looks quiet for now as well, however there is a tropical wave sitting out there. While it is unlikely to organize this week, it is becoming increasingly plausible that we see this begin to organize a bit as it approaches the islands next week.

Disorganized thunderstorms southwest of the Cabo Verde Islands may try to organize as they come west toward the Caribbean islands next week. (NOAA)

Will we get Francine?

The next name on the list is Francine, and there seems to be growing support that we may see this emerge from the morass in the eastern Atlantic in time. The European model is on this with a moderate signal for possible development near the islands next Tuesday.

A decent number of European ensemble members show development of this wave next week just east of the Caribbean. (Weathernerds.org)

I think things are still a bit tenuous in the Atlantic in terms of dry air, sinking air, and other issues that are disrupting development right now. But the overall background state of the western Atlantic is likely to improve a bit beginning next week for possible development chances. There is also a minor signal in the Gulf for next week, but it remains a minority of model solutions. Still, this would signal that the wet pattern in the Gulf should continue next week as well.

As for the potential of Francine, whatever happens with this system in the Atlantic, it seems most likely to turn northwest at some point. But until we get some additional clarity on how this will shake out, I don’t want to over-speculate. At the least, it would be good for the islands to keep tabs on this possible development next week.

Beyond this one, as I noted above, it does seem as if the overall state of the basin will improve going into the middle of September. This should allow things to pick up. In addition, all this quiet has allowed the Atlantic basin’s sea surface temperatures to persist very warm. We sit at or above records everywhere right now.

Sea surface temperatures are at their 2023 records in the Atlantic main development region. (University of Arizona/Dr. Kim Wood)

So it would make sense to think that as long as the background state of the basin becomes more hospitable for tropical development, it will begin again in earnest. Stay tuned.

Hawaii threats continue

After taking swipe from Hurricane Hone with some considerable flooding on the Big Island and some decent wind gusts. You can see some of the reports here. Next up, the remnants of Hurricane Gilma, which should arrive in the Hawaiian Islands this weekend. On this track, the worst of the rain impacts would likely pass north of the islands. Still, some modest impacts would be possible across the islands this weekend as it approaches and passes.

Hurricane Gilma will weaken significantly on approach to Hawaii, but it could still bring enhanced rain chances and breezes to the islands this weekend. (NOAA NHC)

Behind Gilma, we have Tropical Storm Hector, which is not expected to become a serious threat to Hawaii.