Jul 31, 2016

Hello Earl?

Earlier today, I posted ( Atlantic Tropics) about a tropical disturbance (97L)  moving quickly across the Caribbean Sea. Since then based on satellite and synoptic data the system has shown signs of much better organization.

The satellite "signature" itself is quite impressive. The system is taking on a much more circular appearance almost like that of a buzzsaw blade.

This is a sign that indicates that the system is developing outflow. Here is a schematic diagram of the air flow in a tropical cyclone's circulation
Image from: (From NOAA, Hurricane, Washington, DC: Superintendent of Documents, 1977)
Outflow is like a chimney, it ventilates the storm:  air currents move in at surface toward the center of the system, where they converge and rise up. As the air rises the moisture in it condenses releasing latent heat which lowers the air pressure. If this rising air wasn't ventilated from the top of the storm, the rising air would eventually cool and begin to sink. But with an outflow mechanism higher up over the storm this rising air is "removed" and allows the system to develop. The better the outflow aloft the greater the chance for the system to intensify and develop. There is a parodox of tropical system's and their intensification: the more air that is removed from the system aloft, the better the chance for the system to strengthen.

Based on the past few hours of satellite imagery I would not be surprised if 97L were at least a tropical depression come Monday. Time will tell. As of now the NHC is planning a possible aircraft reconnaissance mission for Tuesday afternoon but if recent satellite imagery continues to show better organization I wouldn't be surprised if an invest of it occurred sooner.