Dry environment not allowing deep convection for 93L

Dry air and cooler than normal SSTs are keeping deep convection to a minimum for 93L

Dry air and cooler than normal SSTs are keeping deep convection to a minimum for 93L

We have seen it a lot these past few years: dry air killing off deep convection within a developing Atlantic tropical cyclone. It appears that the same is happening with 93L today.

The dry air comes off of Africa as part of what is called the Saharan Air Layer. It can be very persistent and simply does not allow for the deep, tropical thunderstorms to develop and sustain themselves – the main process that drives a tropical cyclone.

In addition, cooler than normal sea surface temps along the path of 93L are not helping matters either.

I want to see if the system can gain any long-lasting thunderstorm activity before even beginning to worry about its potential impact on the Lesser Antilles or points beyond. Let’s see what happens overnight and go from there. If the dry air wins out, we may not have anything to track which is just fine with everyone I’m sure.

I will post more here tomorrow morning.

M. Sudduth 6pm ET July 29

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93L slowly getting better organized over the tropical Atlantic

A look at the various track guidance showing a potential threat to the northern Leeward Islands in the coming days

A look at the various track guidance showing a potential threat to the northern Leeward Islands in the coming days

Invest area 93L continues to get better organized, albeit slowly, as it tracks steadily off to the west. There is not a lot of deep convection or thunderstorm activity noted in satellite imagery. This may be due to the marginal sea surface temps coupled with the fairly dry air in place over the tropical Atlantic.

Computer models continue to indicate that this system will become a tropical depression and likely a tropical storm before the end of the week. How strong it gets remains to be seen. Water temps gradually warm the further west it tracks but the dry air and lack of deep convection could stall any rapid strengthening. It is interesting to note that some of the intensity guidance suggests this could become a hurricane while others actually weaken the system later in the forecast period. This just goes to show how little is really known about how tropical cyclones function, especially when it comes to intensity.

The track forecast seems fairly straight forward. Right now, the low pressure area is moving off towards the west at a steady pace. I see no reason for this to change much in the coming days. Eventually, it should begin to gain more latitude and begin tracking more to the west-northwest with time.

It looks as though the would-be tropical storm could impact portions of the Leeward Islands in about four days. The timing and strength, of course, is tough to call right now. I remain somewhat skeptical that this system will develop as much as some of the models indicate, only because this region of the Atlantic has been so hostile for development over the past year or two. Obviously, interests in the Lesser Antilles will need to keep a close watch on how things progress over the next few days.

In the longer term, the pattern over North America will likely dictate where this system ends up. A very strong trough of low pressure has carved itself out over the eastern parts of the United States, bringing much cooler conditions to a wide area of the country. Meanwhile, over the Atlantic, a fairly potent ridge of high pressure is in place which is currently helping to steer 93L westward.

There seems to be a growing number of computer models that indicate a more westward track beyond the five day time frame. If the deep trough lifts out and the Bermuda High builds back in sufficiently, then we could see a track farther west with a potential threat to the Southeast coast of the U.S. It is just too soon to know with any degree of certainty and a lot will depend on how strong the system ultimately becomes. Typically a weaker storm will move more west with the lower level flow while a deeper, more intense storm or hurricane would likely feel any weakness in the Bermuda High more and turn more north.

No matter how you look at it, the next five to ten days has the potential of being quite interesting for many people from the Caribbean to the East Coast of the United States. The best bet is to just keep up to date on the latest developments and react accordingly. With so much information out there these days available at your fingertips, it’s easy to get caught up in model mania. No matter what the computer models say now, we know they will change with time. This is a dynamic situation and we don’t even have a tropical depression yet – though it’s probably only a matter of time.

For now, we have several days before any potential impact to the Lesser Antilles. Let’s see what happens over the next 24 hours and whether or not 93L actually develops further. The rest will take care of itself. I’ll have another update early this evening.

M. Sudduth 8:45 AM ET July 29

 

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Bertha by mid-week? Seems likely at this point

NHC graphic showing potential path of developing system in the Atlantic, designated as 93L

NHC graphic showing potential path of developing system in the Atlantic, designated as 93L

The tropics are about to get active and this time, it could stick.

The NHC is monitoring a tropical wave, now designated as invest area 93L, far out in the deep tropics. While this region has been quite hostile up until now, it appears that the tables are about to turn and we will likely get the next named storm, Bertha, within a few days.

Global computer models are coming in to agreement that the tropical wave will develop steadily in the coming days as it moves generally west to west-northwest.

Water temps are okay for development but are certainly not running above normal in the region. This might keep the system from developing faster, we’ll see. The presence of dry air all across the deep tropics may also inhibit development even though there are indications that this pattern is about to let up some.

The track appears to be generally westward with a gradual bend to the west-northwest with time. Keeping this in mind, interests in the Lesser Antilles should be monitoring this feature closely. The NHC’s five day outlook graphic suggests a path towards the islands. After that point, it is just too soon to even begin speculating on where this might end up. We know the drill by now: it could turn north and eventually away from the United States or it could continue west enough to eventually affect land somewhere after a potential encounter with the Caribbean islands.

One thing that interests me quite a bit is the fact that, if this system develops, it would be several weeks ahead of the usual time frame that we look this far east. It would also signify a change in the overall hostile pattern for the deep tropics. In short, this could indicate that we are in for a different hurricane season than originally forecast. The El Nino failed to develop thus far and now that we are seeing development in the deep tropics, it may be that the forecast of a below average season is in jeopardy. I do not want to put too much in to this but considering just how hostile the region between Africa and the Caribbean has been for the past year at least, I do wonder if we are seeing a change that could lead to more long-track systems that do not fall apart.

The rest of the Atlantic Basin is quiet as we start the week. I see nothing to worry about anywhere outside of 93L.

In the east Pacific, things remain quite busy with weakening TS Hernan moving away from the Mexican coastline. Other areas to monitor dot the Pacific but none pose any significant threat to land right now.

I will post another update on 93L later this evening after more information comes out from the global models and the NHC.

M. Sudduth 9:27 AM ET July 28

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Slowly but surely, it looks as though development potential is there

The GFS model showing a tropical cyclone approaching the Lesser Antilles in about five days. How strong it could be remains to be seen.

The GFS model showing a tropical cyclone approaching the Lesser Antilles in about five days. How strong it could be remains to be seen.

A tropical wave over the eastern Atlantic continues to move westward without much convection or organization associated with it. Dry air and a general lack of upward motion in the atmosphere are keeping the system in check for now.

Despite the lack of organized thunderstorms, the NHC has increased the potential for development over the next five days to 40%. This is due to the fact that the overall environmental conditions are expected to improve in the favor of gradual development of this system.

So far, there is not a lot of global computer model support for the area. This is not too uncommon over the deep tropics when marginal conditions are in place. The GFS model seems to have the most consistency, showing a gradually developing tropical storm moving towards the Lesser Antilles within a week. Whether or not this actually happens remains to be seen but we are heading in to a more favorable time period and as such, interests in the region should keep an eye on this system.

It will be very interesting to see if this tropical wave actually develops. If it does, considering it is still only late July, then it will show me that the deep tropics are not quite as hostile as we’ve seen in recent weeks and even dating back to last year. The plethora of dry air dominating the tropical Atlantic tends to make me skeptical about any significant development but time will tell, that much is for certain.

In the east Pacific, tropical storm Hernan, which formed yesterday, is gaining strength and could become a hurricane before it moves over cooler water and begins to weaken. It poses no threat to mainland Mexico as its track is away from land.

I will have more here tomorrow morning.

M. Sudduth 2:25 PM ET July 27

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Deep tropics the place to watch this coming week

Tropical wave over the far eastern Atlantic has potential to develop next week

Tropical wave over the far eastern Atlantic has potential to develop next week

It’s not much to look at now, but the NHC has mentioned a tropical wave over the far eastern Atlantic that has some potential for development over the next few days.

Right now, the environment is not very suitable for anything to get going but that may change as indicated by some of the global computer models. A more favorable upward motion pattern, coupled with less dry air (perhaps) just might allow for a tropical low and eventually a depression to develop. It is close enough to August that this scenario seems plausible, especially considering the fact that TD2 formed within this general region just a few days ago. Even though that depression literally dried up, it is still a sign that this part of the deep tropics is becoming more and more favorable.

On the other hand, there has been an overwhelming amount of dry air across this region for a good part of the hurricane season to date. If this pattern does not ease up, it will be extremely difficult to believe that much will come out of the area south of 20N between Africa and the Lesser Antilles. All it takes is a few weeks of less hostile conditions and the lid could come off but for now, I am skeptical of seeing much – we’ll see what happens in the coming days.

Elsewhere, the Atlantic Basin is quiet this weekend.

In the east Pacific, things remain very busy with several systems on the map this morning. However, none pose any threat to land areas and that looks to remain the case over the next several days at least.

I’ll have more here tomorrow.

M. Sudduth 11 AM ET July 26

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