Tropical Depression 4 has weakened and is no longer a tropical cyclone according to the National Hurricane Center (NHC). The system is now an open wave, but still has convection associated with the wave. The appearance on visible satellite imagery is not impressive at the moment, and Firsthand Weather is not expecting tropical cyclone development with this system for now.
Visible Satellite Imagery (Remnants of TD 4)
The next wave worth monitoring is is off of the western African coast. This wave is supported by numerical guidance to potentially undergo tropical development this upcoming week.
Visible Satellite Imagery (New Tropical Wave)
So why is this tropical wave seeing support from numerical guidance? The wave is in an environment that is conducive for slow tropical cyclone development. The latest vorticity map shows the tropical wave is beginning to show some environmental spin. This is needed for tropicalgenesis.
Current 850mp Vorticity Map (University of Wisconsin)
The latest numerical guidance is indicating this vocticity will continue to increase and become more symmetrical with time as the wave moves towards the WNW. The latest GFS (12Z) shows the environmental spin becoming well-defined by Wednesday.
Future (Wednesday) 850mp Vorticity Map (Tropical Tidbits)
This looks plausible based on the current atmospheric conditions the wave is encountering. The wave is in a moist environment with low environmental shear. Numerical guidance indicates the environmental will remain relatively favorable for organization over the next several days.
Current Environmental Wind Shear Map (University of Wisconsin)
Saharan Air Layer Map (University of Wisconsin)
As the tropical wave moves towards the WNW, the system needs to be monitored as tropical cyclone development is plausible. The general WNW motion is likely due to the strong ridge north of the system. This would potentially place the Lesser Antilles in a favorable geographical area to see impacts by the upcoming weekend. The latest GFS (12Z) shows the wave developing into a tropical cyclone, impacting the islands, and moving into the Caribbean by the weekend.
Future (Saturday) 850mp Vorticity Map (Tropical Tidbits)
It is too early to determine the strength and final movement of this system, but Firsthand Weather will continue to monitor this evolving forecast. Keep checking back for updates.