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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Some thoughts on TD7

Wide Atlantic Tracking map showing TD 7

Wide Atlantic Tracking map showing TD 7

We now have TD7 in the tropical Atlantic and it is forecast to become a tropical storm as it passes through the Lesser Antilles and in to the Caribbean Sea. The path looks very similar to Ernesto’s though TD7 has formed quite a bit farther to the east than Ernesto.

It is interesting that once again, the global models, namely the GFS and ECMWF, do very little with the depression while the less “sophisticated” statistical intensity models make it a moderate to strong tropical storm. As I mentioned in this mornings video blog for our app, there seems to be a lack of vertical instability across the Atlantic Basin again this season and this is perhaps putting a literal lid on things. We saw this time after time last season and ended up with a lot of named storms but not many intense ones overall.

Never the less, we’ll be tracking yet another tropical cyclone in to the eastern Caribbean over the next few days and since it is on the maps, we need to take it seriously- just in case the global models have missed some piece of info that would otherwise make TD7 something more than they depict it.

Note that the fast motion of the depression is also something that needs to be considered. When they move fast, like we saw with Ernesto, they tend to outrun their own deep convection and lose organization. It will be another interesting duel between the dynamic models and the statistical models as we track TD 7 steadily westward. I’ll have more tomorrow morning.

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