Matt Lanza

Odds of Caribbean development inch up next week with few details available at this point

Headlines

  • Tropical development, while not likely in the Gulf cannot be entirely ruled out as heavy rain will continue to pile up for portions of coastal Texas and Louisiana.
  • The next wave in the Atlantic remains unlikely to develop til it gets to the Caribbean.
  • From there, we have a lot of questions and very few answers, but it bears watching, particularly for the Gulf and Caribbean.
  • Farther out in the Atlantic, we have some waves to watch, but none looks to be a concern at this time.

Gulf of Mexico: Low development odds, coastal soaking underway

We continue to see low pressure meandering around the northwest Gulf today. As of this morning, it was centered right along the coast near High Island, TX. Heavy rain was funneling in through Sabine Pass and Port Arthur. So far this week, portions of coastal Jefferson County, TX have seen about 7 inches of rain or more. And there are even hints on radar of 8 to 10 inches just east of Sabine Pass and across coastal Cameron Parish in Louisiana.

Heavy rain continues to pound coastal areas east of Houston, with as much as 8 to 10 inches of rain between Sabine Pass and Cameron. (NOAA MRMS)

Over the next few days, we’ll continue to see this low mosey about in the Gulf or along the coast. The proximity to land is one reason significant development is unlikely from this over the weekend. This will probably continue to trek back and forth between Matagorda Bay and Cameron Parish through Wednesday or Thursday before eventually kicking off to the east or northeast with an approaching cool front.

With tropical development possible but not especially likely, the main issue with this will continue to be locally heavy rainfall. Through Tuesday morning, we could easily see another 2 to 5 inches of rain, with higher amounts possible in coastal areas.

Heavy rain will continue to pelt coastal parts of Texas and Louisiana at times through Monday and Tuesday. (Pivotal Weather)

Inland areas, such as in Houston are likely to see some showers, drizzle, or rain but nothing serious. Flash flooding and street flooding are growing possibilities between Galveston and Cameron, with the Sabine Pass through Port Arthur areas probably the most susceptible at the moment. Flood watches remain hoisted east of this area for New Orleans and Baton Rouge as well. But the heaviest rains will fall closer to the Texas/Louisiana state line.

Caribbean system: Far too early to do much other than watch

The wave that we’re going to watch in the Caribbean remains east of the islands this morning, a bit strung out and very poorly organized.

A tropical wave east of the Lesser Antilles is poorly organized at the moment, with any development expected to occur very slowly. (Weathernerds.org)

This one is in no hurry to develop. In fact, I would not be shocked to see this struggle over the next four to five days. The latest NHC outlook has bumped odds to 50 percent over the next week. A look at last night’s European model shows the system south of Hispaniola by Wednesday morning. It would be unlikely to be developed much at this point. Conditions in the eastern Caribbean are far from ideal for tropical development, so it seems as if this is going to struggle for a bit.

The tropical wave will move across the Caribbean and should be sluggish to develop through at least midweek. (Tropical Tidbits)

Once it gets past about this point, conditions for development will steadily improve, likely leading to strengthening and organization. To what extent and how far it gets in that process remains to be seen. By about next Saturday this system would probably be somewhere between Belize or western Cuba. A weaker system would be more apt to stay south and track into Mexico or Central America, whereas a more rapidly developing system would start to turn more northwest. But for the sake of simplicity this far out, let’s assume it’s somewhere in that bubble. If we look at a weather map next weekend, we can see a cold front rather far off the Gulf Coast. This is associated with a pretty deep trough over the East Coast.

A cold front and associated trough over the East Coast of the U.S. would likely “capture” any type of stronger storm and draw it more northward. (NOAA WPC)

Meteorologically, I would think that any sort of meaningfully strong tropical system would be captured by this trough and forced northward at some point. A system that doesn’t develop would probably keep tracking west. When I looked at the European ensemble this morning, I noticed this sort of bifurcated outcome, with one cluster going west and one turning north at varying points. It’s way too early to speculate on anything specific here, so I’ll leave it at that. Anything in the western Caribbean is of concern.

The ocean heat content anomaly is near or above record for this time of year in the Caribbean, an indicator of deep, rich, warm water in place for a storm to strengthen in. (Brian McNoldy)

The ocean heat content in the Caribbean is as strong as we’ve ever seen this time of year and prior to last year, the strongest we’ve ever seen. This is an indicator that there is a large reservoir of deep, warm water available for a tropical system to feast on. I often joke that the Caribbean is always supportive of big storms. This year, it’s supportive of big storms for longer.

We’ll continue to watch the positioning of the cold front. We’ll continue to watch the intensity of the trough. And hopefully we have a little bit more news to share on Monday or Tuesday. For now, continue monitoring this one, particularly in the Gulf and western Caribbean.

Next waves up

The next item on the docket is a tropical wave in the eastern Atlantic. This one has a low chance to develop over the next few days and would likely remain out to sea. The next wave emerging off Africa this weekend has perhaps a better shot to develop later next week in the eastern Atlantic. That too looks like it may remain out at sea.

One tropical wave is about to emerge off Africa. A slightly more robust wave is a few hundred miles east of there. These will emerge over the next 7 to 10 days. (EU METSAT)

Neither of these are a concern at the moment. Beyond that, we don’t have anything else of note to watch, which is good news.

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.