Not much going on in the tropics since Arthur earlier this month. This is typical for July which is usually a very quiet month in the Atlantic Basin.
In fact, we did not have any tropical waves to flare up worth mentioning until yesterday when the NHC issued an outlook for one in the central Atlantic. It rolled off of Africa a few days ago and has a low pressure area associated with it at the surface. Water temps are warm and overall, environmental conditions are generally favorable for development right now. However, this is likely only temporary as it looks as though conditions will not be so great for development as the week wears on. It’s just too early in the season yet for robust Cape Verde tropical waves to get going this far east. We’re still looking at another month or so before that happens.
The presence of this system does remind us of what could lie ahead. As I mentioned, July is usually not very active, especially in the deep tropics. Once we get in to mid to late August, conditions change and we begin to see more and more active tropical waves moving west from Africa. At that point, it will come down to upper level winds and, perhaps more importantly, instability in the atmosphere. If the mid-levels of the atmosphere are too dry with lower humidity value than usual, then the tropical waves will struggle to develop deep convection and will remain weak. On the other hand, if moisture levels are where they should be or are above average, then we would likely see a very busy August and September.
I believe that much will depend on the situation with the El Nino which was forecast to be coming on quite strong by August. As it turns out, there is barely any El Nino to talk about, especially in the central regions of the tropical Pacific. It just never made it and what warming there was has all but vanished. However, the water just west of South America, extending westward for several hundred miles, is still quite warm compared to normal. This could have just enough negative influence on the Atlantic side to help keep the peak months of August-October quieter than normal.
One thing I will be watching for is how much, if any, cooling takes place in this region of the Pacific. There are indications that we could see a considerable drop off in the surface temperatures of this area and if this happens, I suppose it could remove at least a portion of the negative influence for the Atlantic Basin. It’s just so complicated and hard to tell if one puzzle piece really makes that big of a difference considering how the other pieces fit together and interact with each other.
For me, the tropical wave that the NHC is talking about this morning is a sign that we are approaching the peak months of August-October. Thus it is a good time to remind you to be aware and prepared. Arthur was an interesting event in that it was so early in the season and it did not fall apart at landfall – instead, it continued to strengthen despite its close proximity to the North Carolina coast. If that is the way things will go this season, it won’t matter much if tropical waves develop far out in the Atlantic. What matters are the ones that would do so close to land, leaving little time to react. We’ll see how things shape up over the coming weeks but August is just around the corner and from there on, at least from a climatological perspective, the season should become more active. Time will tell just how active, that is the only certainty at this point.
I’ll have another blog post here tomorrow morning.
M. Sudduth 10:24 AM ET July 21