10:45 p.m. Update: Tropical Depression 19 (TD19) has formed according to the National Hurricane Center.
Though November is just around the corner, and the conditions across these regions are gradually becoming hostile toward tropical cyclone formation, a disturbance south of Cuba (99L) is being monitored for possible development.
If it becomes a tropical depression, it will be referred to as TD-19. The National Hurricane Center (NHC) gives this disturbance 70 percent odds of doing so. Should it become a tropical storm, its name will be Richard. Even if this system does not develop, heavy rains are possible over Jamaica and the Cayman Islands over the next several days as this system tends to meander around its current position.
In the satellite presentation (shown to the right), this disjointed-looking system appears to be taking a beating from high-altitude westerly winds.
These high-level winds, shown by the long arrows coming into the western Caribbean in the image above, are blowing aside the main thunderstorm activity and isolating 99L's low-level swirl. In a healthy system, the storms would sit atop the near-surface vortex. But in this case, they're currently more than 100 miles to its east.
If that is not enough, these upper-level westerlies are extremely dry, as indicated by the orange tint in the water-vapor imagery shown to the right.
As long as these dry and windy conditions near 99L persist, there will be no significant development. The high winds will shear the system apart, and the ingestion of this dry air will act to unwind any potential spinup.
However, there are some indications that by the weekend the environmental flow will relax a bit. Indeed, some of the models suggest 99L will become a hurricane in roughly the same place it is located now in less than 48 hours. I am not so bullish on this idea, but we will be watching.