• Bryan Norcross

Atlantic systems showing some signs of development

The National Hurricane Center is continuing to call out 3 systems spread out across the tropical Atlantic. They are all related to a broad seasonal band of disturbed weather – the technical name is the monsoon trough. The broad disturbance can provide the moisture and the initial spin to get systems going.



The question is, what's going to happen when one or more of the systems organizes into a tropical depression or tropical storm. Computer forecast models are especially poor at forecasting the future track and intensity of developing systems, especially when there are other systems in the neighborhood. That's the situation we have here, so today's model forecasts are expected to change. Predictions bounce around like crazy.


Tropical Disturbance #1 is small but showing some signed of an organized rotation. It's heading toward the northern Caribbean islands as a moisture surge. It should arrive in the northeastern islands late tomorrow and then spread across Puerto Rico, the Dominican Republic, and Haiti through midweek. Forecasts show the moisture reaching Florida around next weekend.


If it's going to organize into a tropical depression, it's got challenges. The environment around the disturbance is clearly dry and dusty, making it hard for the thunderstorms to develop, and allowing the disturbance to strengthen. Also, the apparent track is right over the tall mountains of the northern Caribbean islands, which are always disruptive. Later in its life, the upper winds are forecast to become hostile.


For now, the expectation is that it will just be moisture surge bringing some gusty winds and tropical downpours to the islands, but we will have to watch it.



Tropical Disturbance #2 is showing some organization as well, and the National Hurricane Center is giving it a fair chance of developing. It's hot on the heels of Disturbance #1, which could inhibit both of them somewhat. The computer forecast models are no help. Some credible models organize it at times into a significant storm heading toward the islands while others dissipate the circulation. For now, the best evidence it that it will drift in the direction of the Caribbean.


It will also have dry air to contend with, although the upper winds appear somewhat supportive of development in the short term, unless it gets too close to Disturbance #1.


The current thinking is that Disturbance #2 will arrive in the southern to middle Caribbean islands about Wednesday.


If or when these disturbances organize into well-defined independent systems and not just tropical mush, the computer forecast models should settle down. Hopefully, we'll have a better idea of what the systems will do.


Tropical Disturbance #3 is a small almost-cloudless swirl near the Capo Verde Islands in the far eastern Atlantic. It now appears it will not develop. The steering currents favor pushing it northwest toward the open Atlantic. It will likely still affect the Cabo Verde Islands in the far eastern Atlantic with some gusty rain, however.


At this point, Disturbances #1 and #2 look like the ones to watch. We'll see if they can build any thunderstorms around the circulation and separate themselves from the broad area of disturbed weather, plus the dry, dusty air and other systems, which are reasonably close by.


It doesn't appear that anything will develop quickly.