Matt Lanza

As we await the Atlantic’s awakening, a tropical wave without thunderstorms is what we’re watching

Headlines

  • The tropical wave in the Atlantic is unlikely to develop before at least Friday.
  • Development after Friday should be slow as it moves toward the Bahamas.
  • From there, numerous questions about which will determine if this system can up in the eastern Gulf or turn north off the Florida coast and where it goes from there.
  • Interests between eastern Louisiana and the Carolinas should check in on this again in a day or two.

A dry tropical wave for now

You hear the term “tropical wave” tossed around by meteorologists and others all hurricane season long. But what is it, exactly? By definition, a tropical wave is “an inverted trough (an elongated area of relatively low pressure) or cyclonic curvature maximum moving east to west across the tropics.” Nothing in that definition says thunderstorms or rain or anything like that. So, yes, in theory some tropical waves can be dry.

When we look at the central Atlantic today on the traditional satellite imagery, we don’t see a whole lot that’s perceptible. There’s a wave there, sure; you can see some cyclonic curvature. When you look at water vapor satellite imagery, you can see it even a bit better, but where you see browns, reds, and oranges, that indicates the presence of a lot of dry air. Use the slider below to toggle between a visible and water vapor image of the central Atlantic wave this afternoon.

Visible satellite imagery in black and white, and water vapor imagery with lots of red, orange, and brown indicating the presence of dry air in the central Atlantic. (weathernerds.org)

What does this tell us? It says that the tropical wave in the Atlantic is not going to develop anytime soon into a formal tropical entity. However, the presence of a tropical wave indicates that once it can shed some of this dry air, perhaps then we could see slow development. That may not be til Friday or the weekend.

Modeling continues to indicate the potential that the slow development noted above could occur as the wave comes west northwest toward the Bahamas or Turks and Caicos late this week or weekend. Clearly, it’s dealing with dry air and Saharan dust right now, but once it gets to the west, north of Puerto Rico by Thursday morning it will begin to likely increase moisture presence.

The overnight run of the European model shows this tropical wave adding moisture by the time we get to Thursday morning when its north of Puerto Rico. (Tropical Tidbits)

For the Lesser Antilles, Virgin Islands, and Puerto Rico, this system is unlikely to cause much heartburn. After Thursday, the system will continue to the west-northwest into the Bahamas. The overall atmospheric setup by Saturday as forecast by the European model is fairly complex, and as usual the ultimate path of this wave, depression, storm, whatever it is will be contingent on its strength as well as the exact location of these features. But at this point, I can count three big players: High pressure in the Atlantic, high pressure over Texas and the Plains, and a sharp trough of low pressure digging into the Ohio Valley and Appalachia.

Tropical wave over the Bahamas on Saturday will be steered west and northwest around high pressure in the Atlantic, tugged north by a sharp trough in the Eastern U.S., and likely slowed a bit by high pressure over Texas and the Plains. (Pivotal Weather)

The interplay that the Euro is “seeing” here right now appears to be that the wave slows on approach to Florida. It is being steered by the high to the east, but it slows as it runs into the influence of high pressure over Texas (the arrow pointing down) and also as it “feels” the trough over the Eastern U.S. trying to pull it north. It’s tough to speculate much on exactly what happens here. A weaker system would probably keep drifting west into the Gulf, whereas a stronger one would be more apt to turn northward in the Bahamas and possibly stay off the Florida coast. Most European ensemble members have supported this stronger idea, and you can see today’s 12z probabilities of a tropical depression from the ensemble favoring the “off the East Coast of Florida” idea.

The bulk of the European ensemble model guidance seems to favor a track of the tropical wave east of Florida, but sketchy beyond that as it comes north. (Weather Bell)

Beyond Florida, even in a faster turn scenario, all bets are off because the upper pattern may get a bit convoluted next week. An out to sea turn is not inevitable by any means in that scenario. Likewise, if a weaker storm sneaks under the trough and ends up in the eastern Gulf of Mexico, interests between Louisiana and the Florida Big Bend may be on notice too.

So, to summarize:

  • Tropical development is not expected before Thursday or Friday at the earliest.
  • Development is likely to be slow, though with exceptionally warm waters, any risk of development should be treated with respect.
  • The best guidance we use favors a slowing in the Bahamas, followed by a turn north near or off the coast of Florida.
  • However, given the very high uncertainty with regard to the speed of development and the precise location of steering features, any track forecast is low confidence and interests between Louisiana and the Carolinas should continue to monitor this system’s progress.

Elsewhere, no further tropical development is expected before mid to late next week, but we continue to look toward mid-August as the Atlantic inflection point, and activity may begin apace by then.

Central Atlantic tropical wave and disturbance will take a minimalist approach to development this week

Headlines

  • A tropical disturbance and wave in the Atlantic may very slowly develop this week or next weekend as it comes west.
  • There is no imminent concern of rapid development or risks to land at this time.
  • Still, check back in on this through the week to ensure nothing has changed.
  • No other development risks are seen at this time.

Tropical wave in the dust

Rumors are swirling and hype is beginning around a tropical wave in the Atlantic that several models have shown developing into a system later this upcoming week or weekend. In fact, after my Friday post, the National Hurricane Center had it on their tropical outlook. Today, they’ve got chances bumped up to about 40 percent over the next 7 days.

A disturbance and approaching tropical wave may help trigger some development in the northern Caribbean or southwest Atlantic later in the upcoming week or next weekend. (NOAA NHC)

So what is it that we’re watching? Well, it’s this wave in the Atlantic, just southwest of the Cabo Verde Islands.

The Atlantic shows a tropical wave encased in dust to the west of the Cabo Verde Islands. This may slowly develop through the week. (College of DuPage)

Admittedly, this doesn’t look like much at all. It’s being choked by Saharan dust right now, and it has little to no thunderstorm activity surrounding it for the most part. In fact, the wave emerging off Africa to its east looks far more impressive, though that one is likely to fizzle in the coming days. Meanwhile, this wave will migrate westward. By Tuesday evening, it should be just east of the Leeward Islands, still unlikely to have developed much at all.

The tropical wave will approach the Leeward Islands Tuesday night or Wednesday, unlikely to be developed much, if at all. (Tropical Tidbits)

The system will still be essentially surrounded by dry air. It will also have to contend with a bit of wind shear. All in all, through Wednesday, it seems unlikely that this wave will develop much, and for the Lesser Antilles, Virgin Islands, and Puerto Rico this will not be one to create significant impacts.

Beyond midweek there will be a little less dry air and slightly more favorable atmospheric conditions for development as it approaches the area between the Bahamas and the Florida Straits. Through hour 144 (Friday night), about half of the European ensemble’s 51 members develop this system into a formal low pressure, and none do so significantly.

About half of the European ensemble’s 51 members develop this tropical wave by early next weekend between about Cuba and east of the Bahamas. None do so in major fashion. (Weathernerds.org)

So based on all this information we have, here’s what we can say about this tropical wave:

  • Development should be slow to occur and probably wouldn’t even begin until very late in the week, if not the weekend.
  • The wave should track generally harmlessly through the northeast Caribbean and end up somewhere between Cuba and east of the Bahamas by the weekend.
  • Dry air is likely going to play a significant role in the development (or lack of development) of this wave.
  • The 40 percent odds as posted by the NHC is a perfectly fine place to be right now.

Beyond the weekend, bets are off. We’ve seen some models track this toward the Southeast, some out to sea, and some not even develop the system at all. The GFS ensemble currently favors the latter outcome, with few to no ensemble members developing this. So for now, it’s just good to keep an eye on this one and wait and see. There’s clearly nothing here yet that is definitive, and there’s no reason to get too worked up about things right now. More to come.

Beyond this one, there are no specific signs of anything to follow. Perhaps after August 10th we’ll see our next potential candidate in the Atlantic.

A quiet weekend for us, but some hints of development in the Atlantic next week

Headlines

  • Quiet for the next 5 days in the Atlantic.
  • Continuing to watch a potential tropical wave later next week in the Western Atlantic.

Watching the next wave

Hello from 35,000 feet! Just scoping out the atmosphere on my way back to the Gulf Coast. Anyway, let’s take a look at what’s doing in the tropics heading into another summer weekend

The National Hurricane Center has a clean outlook map for the next 7 days across the Atlantic. There has been some noise coming from some models for this wave in the far eastern Atlantic today.

A tropical wave in the far eastern Atlantic off Africa is getting some models enthused about tropical development later next week. (RadarScope)

The wave is currently in an atmosphere that is dominated by dust. Or at least the road in front of it is. As the wave approaches the Caribbean or southwest Atlantic later next week, it will have some dry air to fend off. The forecast from last night’s European model shows this rather well. I’m using this to illustrate what the environment may be like when it gets to that general location, not where I think it will specifically be or what it will exactly look like. So take this with a grain of salt. Or Saharan dust.

A look at where the eastern Atlantic wave could be next week, primarily focusing on the environment it’s in. Dry air and at least some wind shear will likely be in place. (Tropical Tidbits)

So yeah, this probably bears a bit of watching. But there is nothing to say that this will definitely develop into something yet. Ensemble support for this is growing somewhat, though again, no models really shoot this to the moon yet. Still, with a tropical wave in a marginally favorable environment in early August, I will at least continue to watch this.

Ensemble modeling from the Euro model earlier this morning shows lukewarm but meaningful support for something existing in the western Atlantic later next week. We will watch. (Weathernerds.org)

Outside of that, we continue to watch for the August increase. There are no other specific concerns we see at this time. Let’s check back in on this tomorrow or Sunday.

Signs of the Atlantic calm slowly breaking in early August

Headlines

  • Quiet tropics are expected to continue into the end of July.
  • Some signs of a potential tropical wave to monitor in the western Atlantic in early August.
  • More activity is expected to pick up in mid to late August.

Calm continues a little longer

The tropics continue to look pretty quiet over the next week or so, with no areas worth watching at this time.

Calendar flips into more action?

As we head into August, as we’ve been warning, it does look like the dam will begin to break, slowly at first but with perhaps more voracity as August progresses.

Yesterday afternoon’s week 2 and 3 outlook from the Climate Prediction Center do highlight the Atlantic for tropical potential north of 20 percent.

The week 2-3 tropical hazards outlook from the Climate Prediction Center highlight the western Atlantic and Caribbean through mid-August for possible development. (NOAA CPC)

This makes sense on a couple levels. As we noted the other day, it does look like a more favorable “background state” is on the way to the Atlantic basin. Additionally, there is some “buzz” in the modeling looking toward the Bahamas late next week or weekend. The Euro has been on this one for a bit, with the operational model guidance periodically showing something, including at midday today. The ensemble guidance is much less enthusiastic about this, as you can see from the 00z European EPS looking at the IQR difference map from Tomer Burg’s excellent site.

The Euro ensemble IQR difference, which indicates ensemble spread is pretty calm for later next week, with only about 5 or 6 of the 51 ensemble members even showing low pressure. (Tomer Burg)

This really lacks much support from elsewhere at this time. The GFS and its ensemble generally shows little in this region. Even the ICON (for now), which tends to overforecast in the tropics but nailed Beryl in the Gulf doesn’t have a particularly strong signal. That said, wind shear looks relatively modest next week. However, dry air may be in plentiful supply around the area with significant dust in the basin right now, which would limit development. I would say that I can understand modeling picking up on this area for possible development, but I do not necessarily think this merits significant concern at the moment. We’ve got some time, so let’s continue to watch for an uptick in showers and storms in the Bahamas late next week or weekend.

Elsewhere, we continue to see hints of more aggressive change later in August, with European weekly data now showing above normal tropical activity by late month. Not much else we can say at this point, except to make sure you’ve got your season preps complete or soon to be completed as we white knuckle our way into later August.