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Steady As It Goes : Tropics Update

Studying infrared satellites across the tropics from the Eastern Pacific Ocean to the Atlantic Ocean, at first glance we can see that it is relatively quiet. What I mean is that there are currently no waves in the Atlantic to discuss other than Tropical Storm Don out in the central Atlantic having no impact on land. For the eastern Pacific, there is a cluster of scattered showers and thunderstorms over south-southwest Mexico, according to National Hurricane Center there is 10% development in the next few days with no threat to the mainland.

We can study and view the Intertropical Convergence Zone nicely through the convective cooling that surrounds the Equator but as noted above, that’s pretty much all about the current tropical activity. Let’s look at the next two weeks of July for both basins to see what we’re going to tackle.

Looking over the Atlantic Ocean first, we see an anomalous ridge extending the Atlantic Ocean (indicated by the mean pressure above). This is your typical Azores subtropical ridge, currently “dominating” the tropics in terms of trade winds. A stronger ridge in this position exhibits one of two main forbidden components: 1.) Creates a surface divergence over the Atlantic, which is the exact opposite of what you would want for cyclic formation as this includes both shear and subduction air. 2.) Transmits dry air from higher latitudes, thus increasing stability. We can see this quite nicely by analyzing 700mb relative humidity, where orange and yellow show a 40% lower RH value. Putting these factors together, we have a situation where the tropics of the Atlantic remain quiet for the foreseeable future. A few days ago some computer models were trying to develop a wave off the coast of Africa and pass through the MDR, however, the computer models have been discontinued since then and for the reasons listed it makes sense.

When viewing the EPS tornado prediction verbatim, note that some members wave and try to move towards the Leeward Islands, but this shows that less than a few members do as more than 75% of the team members show little or no development over the next 10 days. To emphasize this point, take a look at GFS (mind you, this model can be quite “happy to trigger” showing “imaginary sticks”, and it is even showing a scarcity of tropical activity. In essence, we’ll be keeping quiet as we head into August, which is not surprising given the climate and El Nino playing a role in maintaining fairly high shear forces across the Caribbean.

When we look over the Eastern Pacific, the mean sea level pressures using anomalies show that the trade winds from the central Pacific ridge are also faster, but as we move towards Mexico and Central America, the pressures show a lower trend. Of course, we are likely to deal with an active ITCZ, but some waves may try to develop, especially as we head into August on this basin.

Currently, as Tropical Storm Calvin passes south of the Hawaiian Islands, another wave may attempt to develop somewhat over the eastern Pacific (from 100W to 115W longitude), although the probability is rather low. However, similar to the Atlantic, we also look likely to remain relatively calm in this basin with no tropical cyclones developing and bringing any kind of risk to landfall at this time.

As we head into August, we’ll have to watch verbatim for the wave of MJOs that will travel to the Eastern Pacific before crossing the Caribbean and then the major growing region (MDR) mid-month. As you may or may not know, the MJO can enhance and/or provide favorable atmospheric conditions for tropical cyclone formation with other factors, of course, by reducing wind shear and increasing relative humidity from the study. For now, we’ve remained silent, which is not surprising as stated earlier and looks like it will continue to do so as we move into August. Again, don’t let the current calm conditions fool you for the rest of the way as we’re not even at the climate “peak” when we catch the big waves east off Africa and just a general period of activity from August to October.

About the author

Armando Salvador

Hello! My name is Armando Salvadore and I am a Mississippi State graduate with a Bachelor of Professional Meteorology and an Activity Meteorologist working in the Private Sector. Stay tuned if you like technical, exotic, and general weather tweets! Also big on long-range forecasting as well! Twitter: @KaptMands


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