Matt Lanza

Tropical wave bound for the Caribbean in no hurry to put itself together

Headlines

  • Model support for tropical development in the Caribbean has fallen off a bit since yesterday, but the wave that moves through there next week does still bear watching.
  • Low pressure in the Gulf of Mexico continues to serve up locally heavy rain on the Texas coast, where totals are approaching 10 inches or more.
  • Additional rain or localized flooding is likely through the week, shifting south a bit toward Corpus Christi as the week progresses. Tropical development, if any, would be slow and still on the lower end of intensity.

The little Caribbean wave that may or may not

Something funny has happened with hurricane season this year. Storms early on tended to outperform model expectations. Systems since mid-August that have shown in modeling are tending to look more lackluster longer. And indeed, the tropical wave we’ve been discussing that will pass through the Caribbean this week is following that pattern. Yesterday, the National Hurricane Center boosted development odds to 50 percent, only to back it down later to 40 percent. We’re still there today, but model trends in the last 24 hours have pulled back even more.

Tropical development probabilities are hovering around 40 percent with the tropical wave that will emerge in the Caribbean this week, and that may even be a bit generous. (NOAA NHC)

On satellite, this tropical wave remains nothing impressive. Yes, it has thunderstorms with it, and there will definitely be some heavy rain moving into the Lesser Antilles early this week, but any development is non-existent at this point.

The tropical wave just east of the Lesser Antilles remains poorly organized this afternoon. (Weathernerds.org)

And, look, that’s what we expected. We’ve been saying most of the last week that this was not going to be quick to develop, and so far that seems to be playing out. Yesterday we noted the inflection point that this system would hit in the western Caribbean when the atmosphere got a little less hostile to tropical development. We also noted that there was a distinct split in the European model ensembles with a bunch staying weak and going west toward Mexico or Central America and some that strengthened and turned northward. Indeed that continues today, but if the split was 60/40 yesterday, it’s 80/20 or even 90/10 today!

European ensemble members strongly support a weaker, more south and west track of the Caribbean wave after next weekend. There are a still a handful of stronger, farther north outcomes, but trends in the last 24 hours have been to back down on those. (StormVista)

The first thing many of you will say is “Oh, you said Beryl was supposed to do that too and look what happened!” That’s an understandable reaction. The difference this time around is 1.) this system is in no hurry to develop whereas Beryl was a Category 5 hurricane in the Caribbean, 2.) there is no real model support from models like the ICON or AIFS (AI version of the Euro) or even the GFS, and 3.) We have a cold front sitting off the Gulf Coast as this one approaches the western Caribbean. So this is a fundamentally different setup than in Beryl. We are going to continue to keep tabs on this obviously, but the message since yesterday has been to back down somewhat on development odds. There’s just something hindering development in the Atlantic basin right now. I think we continue to see generally sinking air in the western Atlantic in the background and overall more stability in the atmosphere than had been expected this season. This may now continue into mid-September.

Texas coast tallying nearly double digit rains

We’ve seen an additional 3 to 5 inches of rain since yesterday between Baytown, just east of Houston down to the Bolivar Peninsula and out to about High Island, bringing totals since Thursday up to about 6 to 12 inches of rain along the coast and just inland for portions of Texas. The highest officially measured total I’ve seen is 9.17″ at JB’s Seafood in Crystal Beach, where I believe Jefferson County has a gauge.

Radar estimates of rainfall since Thursday show 7 to 11 inches over a good portion of coastal Texas between the Bolivar Peninsula and Sabine Pass. (RadarScope)

Overall, models snuffed this one out well, though they were a bit overzealous inland. In the meantime, surface low pressure continues swirling today about 50 to 75 miles southeast of Galveston. It remains very disorganized.

A late morning surface analysis shows low pressure sitting off the Texas coast. It remains weak and disorganized. (NOAA WPC)

The low is expected to continue drifting offshore of Galveston for a few more days. It may eventually trend southward with time, closer to Corpus Christi. All the while there will remain a low chance it develops a little. But rapid intensification or strong organization is not expected with this system. Rainfall over the next 5 days looks to be on the order of 3 to 6 inches between Corpus Christi and Sabine Pass, with locally higher and lower amounts. A localized flash flooding risk remains very much in play for these areas.

Anywhere from 3 to 6 inches of additional rain is possible on the Texas coast between Corpus Christi and Sabine Pass over the next few days. (Pivotal Weather)

Thankfully, the rain has mostly been coming at a pace that is manageable. It’s just adding up in these locations over time. And that can lead to localized flooding eventually. For Houston, Beaumont, and Lake Charles, this is mostly a non-event with just passing showers or storms in the cards over the next several days. The stalled front in interior Texas may focus rainfall through the week in drier parts of the state.

Elsewhere, no tropical development of note is expected, and certainly no land impacts are expected over the next week.

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.