The Eyewall

Tropical Storm Bret is a feisty fellow this morning. It’s about as strong as you can get for a tropical storm before becoming a hurricane. Again, keep in mind that these 70 mph winds are in a small area, not over the entirety of the storm. Hazards such as heavy rain and rough surf will be bigger issues for most of the impacted islands. The good news is that Bret will likely peak in intensity soon before beginning a weakening trend leading to its demise this weekend. Behind Bret, Invest 93L was upgraded to Tropical Depression 4 overnight. It is currently no threat to land.

One-sentence summary

While the Atlantic is bustling with action, the main item to watch is Tropical Storm Bret which will impact the Lesser Antilles with heavy rain, rough seas, and gusty winds today before exiting into the Caribbean and dissipating this weekend.

Happening now: An August-like Atlantic with TS Bret and TD 4

It’s not often we have two Atlantic storms in June, let alone simultaneous ones, but these are not normal times. Here’s the latest.

TS Bret

Per the National Hurricane Center (NHC) discussion this morning, there were some pretty healthy winds measured overnight in Bret, but they were pretty isolated. Bret is trying to form an eye, but because of shear, that eye feature is displaced east of the surface center. In plain language: Bret is trying hard to fight the shear but it can only do so much. Here is a more annotated look at Bret’s structure this morning.

Anyway, the NHC has set the intensity to 70 mph, which again is in a small area. Bret’s biggest impacts to the islands will be via heavy rain and rough seas.

As of the 5 AM AST advisory:

Tropical Storm Warning (TS conditions likely within 36 hours): St. Lucia, Martinique, Dominica
Hurricane Watch (Hurricane conditions possible within 48 hours): St. Lucia
Tropical Storm Watch (TS conditions possible within 48 hours): Barbados, St. Vincent and the Grenadines

Expect Bret to pass near or make landfall on St. Lucia tonight. In terms of wind, the strongest winds will be along and north of where the center tracks, so St. Lucia and Martinique are likely to see the most gusty conditions and the best chance at sustained tropical storm force winds. The higher terrain of some of these islands will be most exposed to strong winds. Given Bret’s size, tropical storm force winds and gusts could extend from Barbados and St. Vincent north to Dominica. Most places will not see the 70 mph winds, however.

Rough seas will be the most widespread concern. They will continue to build today, with 8 to 11 foot seas expected as the storm approaches and passes in much of the central part of the island chain.

Rainfall may be the most serious concern with as much as 6 to 10 inches of rain, especially at higher terrain. The most likely islands to experience those higher end totals would be St. Lucia and St. Vincent. But I would not be shocked to see some higher end totals on Dominica, Barbados, or Martinique also. In general, 3 to 6 inches of rain will fall, but totals will ultimately vary.

Why are we confident that Bret will dissipate in the Caribbean? It will run into a face-ripping amount of wind shear. That’s never good for tropical systems, and Bret will be the next in a long line of storms to enter the Caribbean and not survive the trip.

So to summarize: We are mainly watching rough seas and heavy rain with Bret from Dominica south to Grenada, although a few areas will see some considerable winds, as Bret is a strong tropical storm.

Tropical Depression 4

Looking east of Bret, we have TD 4. This system does not look especially well-organized this morning, but it may do just enough in the next day or two to attain tropical storm status. The next name is Cindy.

The forecast for TD 4 is pretty straightforward. It will be more apt to turn northwest into a weakness between high pressure systems in the Atlantic, which should allow it to run head on into wind shear by Sunday or Monday.

Whatever the case, this system is currently no real threat to land.

The medium range (days 6-10): Beginning to settle down a bit

There is another wave trailing TD 4, but as of right now support for that to develop seems to have dropped off some. So at this point, we don’t expect anything meaningful in days six through ten.

Fantasyland (beyond day 10): Nothing of note

There is nothing of note out in the long-range. Hopefully after TD 4 (or Cindy) we get a couple weeks of quiet.

Good morning. Tropical Storm Bret continues to churn west in the Atlantic, working its way toward the Caribbean. It’s very clearly running into some challenges that are impeding it from strengthening a whole lot at this point, and it has about 24 to 36 hours left before those challenges get even more difficult to fend off.

One-sentence summary

Tropical Storm Bret, ragged as it looks this morning, could bring heavy rain and tropical storm conditions to several islands in the Lesser Antilles tomorrow before steadily weakening once it enters the Caribbean.

Happening now: Bret feeling the thorns of the rose

Besides Bret, we continue to watch Invest 93L, which has an 80 percent chance of developing over the next several days. More on that below. First, let’s walk through our main item.

Tropical Storm Bret

As of the 5 AM advisory, Bret is a moderately strong tropical storm with 60 mph winds. Tropical Storm Watches have been posted for Barbados, Dominica, Martinique, and St. Lucia. Those should be adjusted or expanded later today.

The environment around Bret is a bit tough right now. There is about 20 to 40 knots of westerly wind shear zipping across the northern quarter of Bret’s circulation. In the satellite loop above, you can see how ragged the northern half of Bret looks compared to the southern half, and that’s likely due to wind shear. On the northwestern side of Bret, there is a bit of dry air as well. Because of Bret’s size (it’s got a fairly large circulation), it can’t quite fend that off completely. In fact, Bret’s size may be working against it some, as it is being exposed to more adversity than a smaller storm might be.

So to summarize: Bret is an acceptable tropical storm by June standards for sure, but it is dealing with some dry air and a good bit of wind shear that will probably cap Bret’s intensity and trend it weaker as it moves into the Caribbean. An Air Force reserve hurricane hunter aircraft is expected to investigate Bret today to get a better idea of what’s happening out there.

From here, Bret’s track is pretty straightforward. Virtually all of the hurricane models and global models and ensembles are in good agreement that Bret will basically track due west or just north of due west into the Caribbean, somewhere between about Dominica and St. Vincent, and near or just north of Barbados. Because of Bret’s size, many of the Leeward and Windward Islands will experience heavy rain and some version of tropical storm conditions. Because of Bret’s speed, those conditions will probably pass relatively fast.

Virtually all models have Bret degenerating into a depression by Saturday. Its remnants should continue west toward Central America, bringing some locally heavy rain along the way.

Rain totals are expected to be on the order of 1 to 4 inches from Bret due to its speed and disorganization as it tracks through the islands. Max rain totals will probably occur somewhere between Martinique and Grenada. For Puerto Rico, the Virgin Islands, and Hispaniola minimal direct impacts are expected, though seas could be a bit choppy.

Invest 93L

Meanwhile, we continue to watch Invest 93L behind Bret.

It still needs a bit of work before we start seriously considering this for upgrade status to a depression. But, it’s certainly got a good bit of storms with it, which doesn’t hurt. At this point, 93L is expected to turn northwest as it comes west, passing north of the islands and out to sea. It too will likely have a window to develop before it hits wind shear that overwhelms it and leads to weakening. Something to keep tabs on but nothing to worry much over at this time.

The medium range (days 6-10): Ain’t no party like an MDR party

The main development region (MDR) of the tropical Atlantic is more on fire than Stockton & Malone in NBA Jam (though I was more of a Barkley/Majerle guy myself). Behind Bret and 93L lies another tropical wave that will make an effort to develop in the medium range. Whether it does or does not is TBD, but even the fact that we’re talking about three systems in late June in the deep tropics is virtually unheard of. This next wave may be a bit too far south to really get going, but we’ll see.

Fantasyland (beyond day 10): Some pattern shuffling in the U.S. & Atlantic?

At this time, we don’t believe any systems will become notable in the day 10 to 15 timeframe, but there may be a little reason to watch some things. The pattern in the Atlantic, as well as high pressure responsible for extreme heat over Texas and Mexico are helping to direct traffic either out to sea or toward Central America as weak disturbances. But once we get into the day 10 to 15 timeframe, the pattern may change some. We will detail what that means in the coming days, but to reiterate, we have nothing specific to watch beyond day 10 right now.

The National Hurricane Center began issuing advisories for Tropical Storm Bret on Monday, and we’re also tracking a second system not far behind that likely will also become a named storm. Both of these systems have formed in the “main development region” of the Atlantic where tropical systems often begin their lifetimes. However, the season for storm formation in the main development region typically does not kick off until August.

So what’s happening out there? Well, it’s blazing hot.

Ben Noll, a New Zealand meteorologist, noted on Monday that sea surface temperatures in the main development region are the warmest they’ve been on record for June. In fact, the seas are as warm now as they typically are in late August or September, when the Atlantic hurricane starts to peak. That’s one reason why we’re seeing a spate of early season activity.

A second chart from Ben is equally concerning, as it shows temperatures in this region presently exceeding those of the 2005 and 2010 Atlantic hurricane seasons, both of which produced frenetic activity. The 2005 season remains the most active year in my lifetime, and Gulf Coast residents will doubtlessly remember Katrina, Rita, and Wilma all reaching Category 5 status in the Gulf of Mexico.

Warm seas are not the only factor in storm formation, of course. This year, with El Niño in the Pacific, we can have some hope that wind shear will counteract the formation of storms. But worryingly, so far, warm seas appear to be winning out against El Niño. I have to say that I am starting to get mildly concerned about what is to come this year, particularly in August and September.

One-sentence summary

We’re tracking Tropical Storm Brett as well as Invest 93L, which has been given an 80 percent chance of developing this week into a depression or named storms in the coming days.

Happening now: The stage is set for Bret, with a possible encore

Here’s what we know about the two tropical systems out there.

Tropical Storm Bret

First of all, with apologies to fans of George Brett, this system has just one “t.” After forming on Monday the storm has changed little in intensity overnight, with sustained winds of 40 mph. This is likely due to some moderate wind shear nearby. Not enough to break the storm apart, but enough to keep its organization at bay.

The system has about three days to get its act together before shear is expected to increase, in which case Bret should start to weaken. At present the National Hurricane Center brings Bret to hurricane strength briefly, before winding it back down on Thursday night as it approaches the Lesser Antilles islands in the Caribbean Sea.

No one wants to see a tropical storm headed their way, and Bret is something that people in the Caribbean Islands, including Puerto Rico, the Dominican Republic, and Cuba will want to keep an eye on. Damaging winds and heavy rainfall are definitely possible with Bret later this week or weekend, although I don’t think we’re looking at a situation where this storm really blows up. My biggest concern is flooding, but it’s not really possible to say where the heaviest rain will occur. We should have a better handle on the overall threat tomorrow morning.

Invest 93L

Much like its predecessor, Bret, how well this tropical system gets organized is tied up with where it goes, with a better organized disturbance likely turning northwest before the Caribbean and a less organized one likely following 92L to the west and into the islands. For now the most likely outcome, I believe, is that this system turns north before reaching the Caribbean Sea. That would be best for all concerned, except maybe for the fish.

The medium range (days 6-10): And then there were three?

As Matt noted on Monday, there are some signs in the models that yet another disturbance will emerge off Africa soon, and that this may be something that could develop over the weekend or next week. However the models don’t appear too excited about this system becoming a big deal, likely due to a fairly uninviting environment overall for development. Certainly at The Eyewall we’re rooting for shear to have its day.

Fantasyland (beyond day 10): Possibly calmer to end June

After this present spate of activity, the overall tropics may turn a bit quieter to end the month and start July.

Hopefully?