Two tropical waves to monitor in the Atlantic

Satellite photo with invest areas 96L and 97L indicated

Satellite photo with invest areas 96L and 97L indicated (click to view full size)

We now have two areas to keep tabs on in the deep tropics. Both systems are far from land and really don’t have much of a future ahead of them due to limiting factors in the atmosphere.

The first, invest area 96L, is the eastern most tropical wave with a weak surface low associated with it. Overall, the system has become better organized since yesterday. The development of new convection or thunderstorm activity seems to be persisting though it is not very strong due to weak instability and overall upward motion in the region. This will likely keep 96L from strengthening too much in the coming days as it moves steadily westward over the open Atlantic.

Next we have area 97L which is moving a lot faster towards the west due to strong high pressure to its north. Convection is limited right now and the quick pace of movement will likely help to hinder additional development as the wave of low pressure continues westward.

It does appear that portions of the Leeward Islands will experience a period of squally weather as the tropical wave passes through this weekend. Interests in the region, especially boaters out in the open water, need to be aware of this system.

The fast movement of 97L means that what ever energy survives the coming days could end up in the western Caribbean early next week and while computer models are not indicating development there, we’ll have to watch to be sure. I still think it is just a little early to expect prolific development out of these tropical waves just yet. Give it another couple of weeks and things will probably be different and this makes sense considering the normal uptick in activity as we head in to August.

Meanwhile, the eastern Pacific refuses to shut down completely. We now have invest area 91E which is well on its way to developing well off the coast of Mexico. Fortunately, the steering pattern remains locked in for now and what ever manages to get going will move farther out in to the Pacific and not be an issue for Mexico.

I will have more here over the weekend.

M. Sudduth 11 AM ET July 29

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96L probably won’t develop and here’s why

Tropical weather watchers have had something to monitor for about 24 hours now with the designation of invest area 96L out in the far eastern Atlantic. While it is a sign of the changing pattern and move towards the climatological uptick in hurricane activity, I don’t think this particular system is, by itself, anything to be concerned with – at least not yet.

As I pointed out yesterday, water temperatures in the region of the MDR or Main Development Region are warm enough to support tropical storm formation. We have an area of energy, the tropical wave, entering the Atlantic from Africa and it would seem that all systems are go for this to develop. Let me explain, at least the way I see it, why this probably won’t happen.

Vertical instability or the ability of the atmosphere to produce convection is still somewhat below average in the deep tropics right now. This may be why 96L is not developing for the time being

Vertical instability or the ability of the atmosphere to produce convection is still somewhat below average in the deep tropics right now. This may be why 96L is not developing for the time being

Wind shear is low, water temps are warm, so why are we not seeing a marked increase in convection or thunderstorm activity with 96L? I believe it has to do with the overall instability of the atmosphere in the region. The air is still not quite moist enough in the mid levels and perhaps there is still a layer of warmer, more stable air present over the deep tropics. To put it in simple terms: the lack of instability seems to have a cap on thunderstorm development. This seems to have been an issue for development potential for the past several years, dating back most notably to 2013. However, last year, we saw hurricane Fred develop way out in the east Atlantic, almost in the same vicinity of where 96L is now. So what gives? Fred formed at the end of August, we’re only at the end of July. I think the additional time for the atmosphere to moisten up really does matter. Africa tends to contribute an incredible amount of dry, warm, particulate-laden (dust) air in to the MDR and this just takes time to mix out.

So what does this mean for 96L and the rest of the hurricane season? I believe that these recent robust tropical waves will progress westward with little fanfare, only to spring to life farther to the west where conditions are generally more favorable. Then, as the season evolves towards late August and in to September, the chances of one or two long-track hurricanes will go up. After all, the water temperature profile in the deep tropics is warmer than average just about everywhere. There is no abnormal cooling this year and no El Nino effects present. In short, it is only a matter of time and if these systems do in fact lay quiet as they work their way west before developing, then it could mean a very busy landfall season for the countries of the western Atlantic Basin – which of course includes the United States.

For now, 96L will be an interesting topic of conversation. In the longer term, I would be surprised if it developed further – but it won’t just disappear and we may have to deal with it later on when it reaches the western Atlantic. I guess time will tell – it always does.

I’ll have more this afternoon in my video discussion which is posted to our app, Hurricane Impact, and to our YouTube channel.

M. Sudduth 9:45 AM ET July 28

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Tropical wave in far eastern Atlantic worth watching

Tropical wave, designated at invest 96L,. moving off the coast of Africa

Tropical wave, designated as invest 96L, moving off the coast of Africa

It is late July and the tropics are beginning to shows signs of life. After several weeks of a very busy east Pacific, the tables are slowly turning and it won’t too be long before the Atlantic begins producing storms and hurricanes.

Right now the focus is on a strong tropical wave emerging from the west coast of Africa. The National Hurricane Center has designated it as invest area 96L – the first step in the process of watching for potential development. In this case, the potential for additional development is rather low, only 20% out to five days. However, it is the fact that we have something of interest entering the so-called MDR or Main Development Region that makes this situation interesting.

Climatology suggests that while development is possible this early in the season in the tropical Atlantic, it doesn’t happen too often. Dry mid-level air, typically associated with Saharan Air Layer outbreaks off of Africa, usually squash development potential until later in August. That may be what we see in this situation though it doesn’t mean the tropical wave will vanish.

Water temps, outlined in green here, are warm enough in the far eastern Atlantic to support development

Water temps, outlined in green here, are warm enough in the far eastern Atlantic to support development. The contour lines show temperatures of the sea surface in degrees Celsius and typically anything above 26C is warm enough to support tropical storms and hurricanes

Water temps are warm enough in the region off the African coast and overall, upper level winds are generally favorable.

Some long range models suggest that the wave of energy will wait until it reaches the western Atlantic before developing. We have seen this time and again in recent years as the MDR has seemed to be rather hostile for seedling storms to take root.

Right now, it is a topic of conversation for tropical weather watchers and TV meteorologists. Whether or not 96L becomes more of a story later on remains to be seen. It is certainly a sign that we are getting closer to the prime time of the Atlantic hurricane season and with so much warm water waiting in the western regions of the basin, it’s only a matter of time in my opinion – which makes sense considering the time of year we are in and where we are headed climatologically speaking.

Meanwhile, the east Pacific remains fairly busy with tropical storm Frank dying out well to the west of the Baja peninsula where cooler water and a more stable air mass awaits.

The NHC has outlined an additional area of interest farther to the southeast of Frank that has some potential for development over the next five days. No worries for Mexico, however, as anything that does manage to get going will move generally west to west-northwest out in to the open Pacific.

I will have more on 96L in my video discussion later today and a full blog post again tomorrow morning.

M. Sudduth 11AM ET July 27

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96L: defying the odds, could become “Danny”

Satellite photo showing the position of 96L in the tropical Atlantic

Satellite photo showing the position of 96L in the tropical Atlantic

Despite being surrounded by an impressive plume of Saharan air or SAL, the vigorous tropical wave and associated low pressure area, also known as 96L, continues to get better organized.

Latest satellite images show more deep convection developing along with classic banding “arms” indicating that the low pressure area continues to strengthen over the warm tropical waters of the east Atlantic.

I was not convinced as of yesterday that 96L would amount to much but this morning, my tune is changing somewhat. It seems as though conditions are not quite as hostile as I thought and it looks as though the system has a chance of becoming a tropical storm before too long.

Upper ocean heat content is decent along the path of 96L as it moves west to west-northwest

Upper ocean heat content is decent along the path of 96L as it moves west to west-northwest

If we look at sea surface temperatures and more importantly, upper ocean heat content, we see that 96L is moving over fairly warm water with decent heat content. In other words, the warm water is not just at the surface, it extends down in the ocean for several dozen meters if not more. This allows sufficient moisture to be drawn in to the developing low as it stirs up the ocean’s surface, essentially bringing up more warm water. In addition, the farther west it travels, the warmer the water becomes.

Wind shear is not an issue either right now as it looks like a well-established bubble of high pressure in the upper atmosphere is allowing deep thunderstorms to develop and rise vertically, not being blown off in one direction by shearing winds. If this pattern holds, it will only aid in the development of 96L in to a tropical depression and eventually a tropical storm.

GFS ensemble tracks indicating a general track towards the NE Caribbean and eventually, the southwest Atlantic

GFS ensemble tracks indicating a general track towards the NE Caribbean and eventually, the southwest Atlantic

Let’s say it does go on to develop in to a named storm. If so, it will be “Danny”. The computer models generally agree that it will move west-northwest with time towards the northeast Caribbean Sea. In a way, this could spell great news for the region which has seen little in the way of rain over the past few months. As long as the would-be storm doesn’t get too strong, it could be a huge benefit rain-wise for parts of the Caribbean. It is still way too soon to know for sure about the future track but it looks as though a general west to west-northwest path will continue for the next few days.

As far as intensity goes, this is tricky. Warm water temps and light winds aloft should allow 96L to become our next tropical storm. However, this is where I am skeptical; knowing how hostile conditions have been in the deep tropics for some time now. On the other hand, I also know the limitations of intensity forecasting and realize that anything can happen within reason. It is not completely out of the question that this system becomes a hurricane at some point. It’s also probably fair to say it has just as good a chance of being a weak tropical storm at best. We are simply going to have to wait it out and see what happens.

Fortunately, what ever becomes of 96L will be within range of reconnaissance aircraft in a few days. It won’t be long before we see the NHC task recon to fly out and investigate the system as it closes in on the Caribbean later in the week. Until then, we’ll rely on satellite and possible ship data to determine what the strength of 96L is.

I will have an in-depth discussion on my video blog to be posted this afternoon. It will be accessible via our YouTube channel and in our app, Hurricane Impact for iOS and Android devices. I’ll also post a link to it on our Facebook and Twitter.

M. Sudduth 6:45 AM ET August 18

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It’s mid-August, do you know where your hurricanes are?

Sea surface temperature anomalies showing the El Niño in the Pacific. Notice how much warmer the Pacific is than the Atlantic

Sea surface temperature anomalies showing the El Niño in the Pacific. Notice how much warmer the Pacific is than the Atlantic

Normally we would have had a hurricane by now in the Atlantic Basin. Normally.

This year is far from normal.

First of all, El Niño is in full swing along a vast stretch of the tropical Pacific. This abnormal warming of both the surface and subsurface waters has created all kinds of weather havoc with more to come. Luckily for those of us in the Atlantic, El Niño is typically a big bully to developing hurricanes.

Second up – wind shear and lots of it. Strong upper level winds blowing across the deep tropics, especially coming through the Caribbean, has done its job of keeping fledgling hurricanes from taking flight. This too is a common occurrence during El Niño years.

Saharan Air Layer still holding on in the tropical Atlantic

Saharan Air Layer still holding on in the tropical Atlantic

Third culprit – dry, sinking air. A lot is often made of African dust and the Saharan Air Layer but I think it sometimes gets more attention than it deserves. There have been quite a few impressive outbreaks of dry, warm air spewing off the Sahara in recent weeks and months but it is the overall pattern of dry, sinking air that has really put a lid, literally, on tropical development in the Atlantic. Any why not? With all of the warm water in the Pacific, the upward motion has been focused there while the Atlantic, though warmer than perhaps some had expected, is still out of balance and thus the non-rising nature to the atmosphere. This lack of general upward motion has been a serious impediment to development this season.

Now enter 96L in to the picture. What about its chances?

NHC 5-day Graphical Tropical Weather Outlook showing 96L and its potential development/track area

NHC 5-day Graphical Tropical Weather Outlook showing 96L and its potential development/track area

The National Hurricane Center is giving it a high chance of becoming a tropical depression sometime this week. After all, it’s mid-August, water temps are plenty warm and we have a well developed tropical wave and surface low moving across the deep tropics. It seems like it would be all systems go, right? Maybe but probably not – at least not this time.

Conditions for development are marginal right now though the water is warm, there’s no doubt about that. But warm water alone is not enough. The environmental conditions needed to produce deep, tropical convection just seems to be lacking once again in the tropical Atlantic. This was predicted very well in advance of the season by models such as the ECMWF seasonal forecast. In other words, it’s no surprise that we’re seeing such little activity. That being said, there is at least a chance that 96L makes it to become a tropical storm over the open Atlantic. If so, its name will be Danny.

Recent intensity plots for 96L

Recent intensity plots for 96L

Some of the intensity models indicate that 96L will become a tropical storm and eventually a hurricane. I just have a hard time seeing this considering the hostile environment ahead of the system. Never the less, we have something to watch now and as August comes to a close in a couple of weeks, we may have even more to watch. For now, the hurricanes have been shut out completely this season in the Atlantic and it looks to remain that way for the time being. We shall see.

Check out my video blog which will cover all of these topics and more – I’ll have it posted later this afternoon.

M. Sudduth 6:00 AM ET August 17

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