Invest 95L in the east-central Atlantic is expected to develop this week as it heads toward the northeastern Caribbean islands

Less than a week after the Atlantic notched its two most powerful hurricanes so far this hurricane season – Category 4 Franklin and Category 4 Idalia, which struck Florida last Wednesday – another disturbance is poised to become a powerful, long-track hurricane by later this week as it heads westward. The northeastern Caribbean islands, including Puerto Rico and the U.S. Virgin Islands, should closely monitor the progress of the system this week.

For now, the disturbance – designated Invest 95L by the National Hurricane Center on Saturday – is still in its infancy. Though the large disturbance has all the hallmarks of a strong September tropical wave, including a pronounced turning of mid-level winds, storminess remains scattered around its periphery. It’ll take some time for thunderstorms to coalesce but once they do – likely by mid to late week – forecast models show a ripe environment ahead for steady strengthening. Most intensity guidance suggests a Category 3 or stronger hurricane by the weekend.

Invest 95L or future Lee will travel generally west-northwest this week under high-pressure steering to its north. The two big questions this week for the northeastern Caribbean islands are where the low-pressure center forms and how quickly it pulls together.

Caption: Low pressure tracks for Invest 95L from the European ensemble modeling system through Sunday evening (September 10, 2023). Although models suggest a path just north of the islands, until the system has a defined circulation, model forecasts will remain more uncertain than usual, especially this far out. Credit: Weathernerds.org. (Weathernerds.org.)

Though the overall model consensus, for now, keeps the circulation of future Lee just north of the islands this weekend into early next week, until we have a defined circulation center, the forecast is too uncertain to make any definitive calls on potential impacts to the islands. Residents and visitors from the Dominican Republic eastward to the Leeward Islands should carefully follow the forecasts this week given the potential strength and close path of the system. We’ll have more details in the days ahead.

As far as any threat to the mainland U.S. down the line, it’s far too early to speculate. If the system even makes it this far west, it would be beyond a week out, so we have plenty of time to watch. Don’t bother getting caught up in the long-range forecasts at this stage.

Gert, Katia, and another wave to come

The low-pressure system that was once Hurricane Idalia is now a non-tropical frontal low in the north-central Atlantic. Tropical Storm Gert – which regenerated over the central Atlantic last Friday – is being absorbed by this larger frontal low today.

Meanwhile, in the far east Atlantic, Tropical Storm Katia – upgraded on Saturday – already hit its peak and is barely hanging on now as a tropical depression. The system is expected to unravel over the open Atlantic over the coming days.

Another disturbance forecast to move off Africa tomorrow into Wednesday has a moderate chance of becoming a tropical depression later this week as it heads northwestward.

Atlantic disturbance may become formidable hurricane this week

Caribbean islands monitor Invest 95L in east-central Atlantic

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Michael Lowry