Hello everyone and happy Tuesday! As many of you already know, the Atlantic basin has been mostly quiet so far this year, with only three named storms so far. As we start to dive into this tropical discussion, we will get to see that we don’t expect any significant tropical activity over the next week or so, and discuss the reasons as to why.
Since there are no highlights in the NHC for the Atlantic currently, we will start with a look at the current tropical conditions, look at how the conditions progress in the model data, and then finish with the usual conclusions section to wrap everything up.
Current Tropical Conditions
Taking a look at the current IR image of the Atlantic, we can pick out 3 areas of organization out over the eastern tropical Atlantic. All of the circled disturbances are areas of thunderstorms activity that have moved off of the African coast. As we will see in the parameters that affect these areas of organization, development is unlikely to occur from these disturbances.
When we take a look at the current wind shear values across the tropics, we can see the highest shear values (40kts+) from the yellow and red colors. Just off the coast of Africa we can see some higher shear values, as well as in the Caribbean to the south of Cuba and to the north of the Lesser Antilles. As has been discussed many times before, wind shear prevents tropical systems from maintaining their vertical structure, leading to weakening and or preventing formation at all.
While there are pockets of areas with less wind shear that would be sufficient for tropical formation, when we look at the current relative humidity values it will gives us more insight into the lack of activity.
The main story: dry air, and a lot of it. Tropical systems need a sufficient moisture supply in order to maintain convection and strength. With such a large amount of dry air in much of the tropical Atlantic, there is little moisture in order for systems to become more organized and have the chance at formation.
Looking at sea surface temperatures, they are quite sufficient and warm enough for tropical activity. with much of tropical Atlantic above 26C (79F) which is enough to support any robust tropical system.
Model Prognosis
With current conditions not supportive of any tropical development, we will now take a look at how these variables will change over time, and if they will change in favor of development.
Taking a look at the average wind shear values over the next 5-9 days, we can see areas of higher shear in the Caribbean, where we have 40kt contours. Just off the coast of Africa, there is expected to be lower shear values with contours closer to 10kts. The shear off of the coast of Africa would be sufficient for tropical development however if the system were to travel into the Caribbean, it would encounter a high amount of shear and possibly be dismantled.
Taking a look at the progression of relative humidity we can see slight improvement over the next week or so into the abundance of dry air in the tropical Atlantic. There is still a dominating section of dry air expected to be into the eastern portions of the Atlantic, with improvements in the Caribbean as we begin to see higher relative humidity values next Wednesday. However, storms which may form in the Caribbean would have to overcome the intense wind shear present in the area, with storms off the coast of Africa encountering a big stretch of dry air moving westward.
Conclusions
Well there you have it, a shorter tropical discussion, however with quiet conditions all we can really focus on is explaining the reasons for the lack of any tropical activity. Mainly, the large amounts of Saharan dust as highlighted by the low relative humidity values continues to limit development. While wind shear continues to vary between high and low values depending on the location, the number one limiting factor currently is the lack of available moisture. In the future, we will have to see if storms can overcome this limiting factor, or begin to form in areas such as the Caribbean with higher moisture availability. We are beginning to approach the height of the Atlantic tropical season in late August and early September, so it is important to keep checking back and monitor for any substantial changes to the otherwise quiet weather.
