July 31, 2023 Outlook: Fish food

One-sentence summary

A pair of tropical systems have a chance to develop in the Atlantic, but both will scoot out to sea and not be a direct impact land.

Happening now: Invests 96L and 97L

As expected, the tropical wave in the middle of the Atlantic Ocean is on its way to potentially developing later today or tomorrow. This wave is now tagged Invest 96L. Meanwhile, off the North Carolina coast, we have Invest 97L, which is a vigorous area of thunderstorms with a lesser chance of developing in the next day or so.

Two areas to watch; neither is a threat to land. (NOAA/NHC)

Regardless of development, both systems will move out to sea, and neither is a threat to land. Even Bermuda should see only fringe effects at worst.

Why are we confident that both systems will turn out to sea? A quick look at the upper levels of the atmosphere shows that both systems have a pretty easy exit path away from land.

With high pressure west of the Azores, the clockwise flow around it should pull 96L north, then northeast and out to sea. 97L is already embedded in pretty fast flow off to the ENE, so it will rocket out to sea.

Invest 96L

The area we’ve been watching since last week out over the open Atlantic took on the Invest 96L tag over the weekend, meaning it became an area to investigate and we got some additional model data on it to look at. This really just confirmed what we already had confidence in, that this system was likely heading out to sea.

Puerto Rico and the Lesser Antilles are at the bottom left of this satellite image, while Invest 96L is on the right side. It’s heading out to sea, while some scattered clusters of thunderstorms impact the islands. (Weathernerds.org)

On satellite this morning, 96L doesn’t exactly look exciting, though I’ve seen worse looking storms upgraded, so we’ll see what the NHC finds in the next day or two. The 80% probability from the NHC seems perfectly fine here, because there’s a good chance it will develop, but it’s definitely not a guarantee. The ceiling on this system looks like lower-end tropical storm so not a huge deal. It will struggle due to wind shear and sinking air. It has about 3 or 4 days before it’s outta here.

Invest 97L

Admittedly, it’s 97L that looks most interesting this morning.

Invest 97L is hauling out to sea, with no risk to land. (Weathernerds.org)

There’s a hint of spin to it as it moves northeast, but this is more like a nor’easter than a tropical system in terms of how it’s developing (the formation process is being driven more by fronts and atmospheric dynamics than warm waters and heat). While that’s primarily a technicality, it’s all moot as this is heading out to sea. This could graze Bermuda with some thunderstorms as its trailing cool front approaches and stalls near the island. Aside from that? Not much to this.

The medium range (days 6 to 10): Pressing reset

A period of calm is expected to take control of most of the Atlantic basin this weekend and early next week, and we do not expect any storm activity as the atmosphere sort of presses the “reset” button. For the most part, this calm is expected to last into…

Fantasyland (beyond day 10): Still calm? Perhaps.

We don’t see anything of note right now on any modeling that indicates things will pick up at the end of the 10 to 14 day period. Last week, we were hinting at a potential ramp in activity for mid-August. Some of the support for a more conducive background state seems to have faded some, as the Pacific side heats up. There would be two primary ways to generate activity should that be the case, since an active Pacific generally means a quieter Atlantic. First, you’d have to watch close in for something, say, in the Gulf or just off the coast. Second, with a good bit of storminess ongoing in Africa, that could potentially get something to flare up in the far eastern Atlantic in time. But we have plenty of time to watch.

Early August and everything after

Which brings me to what I wanted to touch on more today. Where do storms usually form in the first third of August?

Historical storm origin points in early August. (NOAA/NHC)

The Gulf is a hotspot in early August, with numerous storms historically forming there. We also tend to see flare ups near the Lesser Antilles, as well as a peppering of storm origins across the Atlantic. So where do you look in early August? The Gulf, the Leeward & Windward Islands, and across the Atlantic.

We are entering the ramp up of hurricane season. Accumulated cyclone energy (ACE) for the season to date is quite high, thanks mostly to Hurricane Don. We’re over 16 units of ACE right now for 2023, which is almost twice as much as normal for the end of July. Remember, ACE is a stat that factors in the wind speed of tropical systems and for how long they maintain that intensity, and we sum it over the season (hence: accumulated). Far from perfect, but it gives you a sense of where the season compares to prior seasons in terms of activity.

Accumulated cyclone energy through the end of July will be right around 16 units, which is a good bit above our normal of 9.6 on this date. (Colorado State University)

But, it’s important to note that we still have about 92 percent of hurricane season from an ACE standpoint still in front of us. It remains early. That said, by the end of August, we jump from today’s 8 percent of the season climatologically complete to 30 percent. We ramp things up in a big way after the first third of August. So, the fact that it’s looking fairly calm to start August is great news, but we’ve got a long way to go. Fingers crossed!

July 28, 2023 Outlook: Open Atlantic development chances plodding along

One-sentence summary

We continue to see the potential of a system developing in the open Atlantic heading into next week, but it will likely struggle through Monday or Tuesday and no land is threatened by this system.

Happening now: Tropical wave in the Atlantic no better organized today

Today’s National Hurricane Center outlook shows the wave in the Atlantic as having 60 percent odds of developing now, up from 40 percent yesterday.

Odds of development in the Atlantic are up to about 60 percent today as a disorganized tropical wave makes a go at things heading into next week. (NHC)

We are still a couple days away from this happening. If you look at satellite this morning, well, it’s not exactly organized, although it’s a lot more active looking than it has been the last couple days.

The Atlantic wave is disorganized this morning, but it has much more thunderstorm activity associated with it than it has the last couple mornings. It’s slowly working toward development. (Weathernerds.org)

Over the next 2 to 3 days, this wave should slowly organize. It will continue west-northwest and eventually turn more northwest and then north before getting to the islands. One very significant inhibiting factor for this system will likely be wind shear, which is extremely strong ahead of the wave and is expected to remain strong into this weekend.

The Atlantic system is expected to deal with good amounts of wind shear over the next 3 to 4 days (Saturday’s forecast shown here) which should stunt its growth to some extent. Shear may finally relax some next week, giving it space to grow. (Tropical Tidbits)

Wind shear will probably act to limit the system’s initial development through Monday. By the time the shear relaxes, the disturbance should be comfortably out at sea and away from land.

In summary, very, very slow organization is possible through Monday, but the wave will also begin to turn out to sea so that when it does have breathing room to possibly organize further it will be safely away from land.

Elsewhere, the NHC did re-tag the old Invest 95L in the far western Caribbean (heading toward the Pacific) and the upper level disturbance near Florida again this morning, but odds of any development are near zero at this time.

The medium range (days 6 to 10): Nothing new

For now, everything seems quiet looking next week. We’ll watch to see that open Atlantic wave likely turn north and northeast out to sea. Aside from that one system, there’s nothing we see on our radar that has much potential. We’re likely entering a brief period of calm now.

Fantasyland (beyond day 10): The calm before the storms, maybe

We start to scour the ensemble members this time of year for hints of activity. Remember that ensembles are just models run roughly 30 (GFS) to 50 (Euro) different times with initialization tweaks to give us a realistic spread in outcomes. As a meteorologist, you’re looking for any sort of hint of activity within that spread to try to hone in on something. We see nothing notable right now. As noted in yesterday’s post, we do expect things to pick up some around the 10th or so of August. That thinking has not changed.

We may post briefly to update the Atlantic system this weekend. On Monday, we’ll update the status of the season to date and talk more about early August.

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July 27, 2023 Outlook: Odds of the next Atlantic wave developing increase, but it may be destined for the open ocean

One-sentence summary

The odds of an eastern Atlantic tropical wave developing have increased to 40 percent today, but while it’s worth watching (especially in Bermuda), for now it seems most likely to turn away from the Caribbean and America.

Happening now: We’re still a few days away from the next Atlantic wave’s development window

If I showed you a satellite image of the Atlantic this morning, and I asked you to identify the area you would be most interested in monitoring for tropical development, I would assume that you’d pick the one near Florida.

The current view of the tropics on Thursday morning: Storms near Florida and lots of disjointed activity in the open Atlantic. (College of DuPage)

While that is certainly beefy looking, it’s being entirely driven by an upper-level low, not a surface-based system. Tropical development is unlikely to nil in that case. Though, this will hopefully do something to temper the outrageously warm water temperatures surrounding Florida right now. That said, modeling is actually latching onto the tropical wave located this morning around 30°W longitude. If we look at that on satellite, we’re probably all giving it the Larry David treatment.

The tropical wave that models have become fairly bullish on is rather disorganized at this time. Odds of development are near zero in the immediate term but increase to 40 percent over the next 3 to 7 days. (Weathernerds.org)

But! As we go through the next few days, this area is expected to consolidate some and become a little better organized. It will track generally west or west-northwest. Modeling insists it could develop. There is actually very good agreement between the GFS and European operational models and their ensembles (which are 30 to 50 different runs of the model with various initial tweaks) that this will develop, albeit not in a huge way. That aside, this is arguably the best agreement we’ve seen since Don formed. In my estimation, models have tended to be rather aggressive with development in the main development region (MDR) and Caribbean this year. So, while odds of development are on the increase and there’s good model agreement on this, we’ll see. Model odds of development over the next week are probably closer to 80 or 90 percent, but given recent struggles, the NHC estimate of 40 percent seems much more realistic to me.

Anyway, development of this system will likely be slow as it comes westward over the next 3 to 5 days.

The medium range (days 6 to 10): That tropical wave (should) swim with the fishes

One other thing that the models are in good agreement on right now is that whatever happens with this tropical wave, it is likely to turn northwest and north and eventually out to sea, missing the Caribbean and the U.S. Never say never, but that’s comforting for now. I would argue that there’s good reason to watch this if you are in Bermuda though just in case.

As the disturbance comes west, it should be able to split the gap in a weakness between two high pressure systems over the Atlantic, which should allow it to turn north and avoid most land. (Tropical Tidbits)

Beyond this wave, there’s nothing terribly exciting to focus on in the tropics through day ten.

Fantasyland (beyond day 10): All good for now

Quite frankly, it’s almost disturbingly quiet on the models right now out in the extended range. It does seem like we’re entering a briefly hostile background period in the Atlantic beginning around the first day of August. This is due to background activity associated with the Madden-Julian Oscillation and convectively coupled Kelvin waves. I won’t get into the heavy details here, but you can read and learn about the MJO and hurricanes and convectively coupled Kelvin waves here. Eric Blake at the NHC is a great forecaster, and this presentation that the WMO has online is really useful. All that to say that I would suspect that things pick back up again after August 10th or so.

July 26, 2023 outlook: August is nigh

One-sentence summary

There are a couple of areas that we’re watching, but overall things are fairly quiet for July with no imminent threats to land; however we’re now just six days away from August and at some point the switch is going to flip.

Happening now: Not too much, thankfully

We’re watching a (very) poorly defined area of thunderstorms near the Bahamas that Matt mentioned yesterday. However the odds are still stacked against this becoming something to worry about. So I want to talk a little bit more about climatology today.

We’re still about three weeks away from when we typically would expect the Atlantic tropics to come alive. This often happens around mid-August, when sea surface temperatures near their summer peak, wind shear reaches a nadir across much of the Atlantic, Caribbean and Gulf of Mexico areas we’re concerned about, and tropical lows move off the Africa coast with some regularity. This period is easily visible when we look at historical activity in the Atlantic, typically running from August 10 to around October 20.

Historical activity in the Atlantic basin. (National Hurricane Center)

The past offers no guarantee for what will happen in the year 2023, of course. Already sea surface temperatures are absolutely sizzling in the Atlantic and Gulf of Mexico, and are plenty warm to support the development and strengthening of tropical systems. We are also (see next item below) starting to see tropical waves moving off the coast of Africa with a bit more frequency.

What’s been holding us back so far this year has been El Niño, and its tendency to keep wind shear levels in the Atlantic above normal. We’re going to really need that pattern to hold on this summer, or else the Atlantic basin is likely going to explode with activity in about two or three weeks.

The medium range (days 6 to 10): A new contender emerges

As expected, the National Hurricane Center has started to track a tropical wave that recently moved off of Africa into the Atlantic Ocean. The global models are somewhat bullish on this system as it moves westward across the Atlantic Ocean, and it may develop into a tropical storm in five to seven days, or so.

This probably will be a fish storm. We’ll see. (National Hurricane Center)

The most likely scenario for this system, however, is that it curves to the north before threatening the Caribbean Sea or continental United States, but we’ll continue watching it all the same.

Fantasyland (beyond day 10): Happily quiet

There’s not much else out there, even in the fevered minds of the global models 10 days or later from now. That will change, so for now we’re embracing the quietude.