September’s reputation as the busiest tropical month is taking shape as we observe four areas of interest and the potential of a developing tropical system.

Let’s start with Investing – AL99: Showers and thunderstorms are more organized in association with a non-tropical low pressure system a few hundred miles east of North Carolina, and current satellite data shows the system producing near-storm force winds. This system could take on some tropical or subtropical characteristics over the next day or two while moving generally north-northeastward and remaining off the coast of the northeastern United States. Once the low pressure system moves over cooler waters early Saturday, no further development is expected.

The probability of occurrence within 48 hours and 7 days is 30 percent.

Showers and thunderstorms continue to develop in the northwestern Gulf of Mexico in association with an extensive low pressure system interacting with a weak frontal boundary over the northwestern Gulf of Mexico. Upper-level winds are expected to become less conducive to development through Friday night and Saturday as another frontal boundary approaches the system. Although development is unlikely, heavy rains are expected over parts of the northern Gulf Coast over the next few days.

The probability of occurrence within 48 hours and 7 days is 10 percent.

In the southwestern Gulf of Mexico, shower and thunderstorm activity associated with a westward-moving tropical wave remain disorganized over the western Caribbean. The system is not expected to develop in Belize and the Yucatan Peninsula until early Friday. Gradual development is possible late weekend and early next week after the system emerges over the southwestern Gulf of Mexico.

The probability of occurrence within 48 hours is 0 percent. The probability of occurrence within 7 days is 20 percent.

Closer to the Caribbean, another tropical wave located a few hundred miles east of the Leeward Islands is producing limited rain and thunderstorm activity. Strong upper-level winds are expected to inhibit the development of this system over the next few days as it moves west-northwestward at 10 to 15 mph. Environmental conditions may become more favorable for slow development early next week as the system moves across the southwestern Atlantic.

The probability of occurrence within 48 hours is 0 percent. The probability of occurrence within 7 days is 10 percent.

Deep in the Atlantic: An elongated low pressure system over the eastern tropical Atlantic is producing limited shower activity. As long as the system is barely moving, no development is expected this weekend. Slow development seems possible early next week as the disturbance slowly moves northwestward.

The probability of occurrence within 48 hours is 0 percent. The probability of occurrence within 7 days is 20 percent.