75ºF

Norcross: Tropics are calm, but keep an eye on the Caribbean

A look at the satellite on Monday, Sept. 28, 2020.
A look at the satellite on Monday, Sept. 28, 2020.

As sure as September will give way to October, our attention will shift from the eastern Atlantic to the western Caribbean as we watch for possible tropical development. And sure enough, the upcoming weather pattern is the type we watch carefully.

In a general sense, the mechanics are simple. An area of low pressure often forms over or near Central America this time of year. It often extends into the western Caribbean and south into the Pacific. If it’s well developed, it’s called the Central American Gyre — a gyre being a large circulation.

For a variety of reasons, one or more circulations sometimes form within that broad area.

When a dip in the jet stream comes along over the Southeast U.S., it can sometimes act like a scoop to pull one of those circulations north. It’s a question of timing. Is there a scoop at the same time there’s a sufficiently developed system?

Currently, a weak tropical disturbance is moving from east to west through the Caribbean. When it gets near the Mexican or Central American coast in the next few days – in the vicinity of the general low-pressure area that’s already there – it appears that atmospheric conditions will become more conducive for a circulation to try to develop.

At the same time, a sharp dip in the jet stream and its attendant cold front will dip into the Gulf and across South Florida.  That dip will tap into tropical moisture and increase the likelihood of heavy rain across the southern Florida peninsula and the Keys.

There is some possibility that the jet stream dip will pull the weak circulation north late in the week or over the weekend, but that doesn’t appear to be the most likely scenario. Instead, just moisture is more likely to stream north, while the disturbance is left in the western Caribbean or near Mexico.

If the disturbance survives, a subsequent dip in the jet stream might bring it north in some shape or fashion next week, but it’s too early to know.

For now, we just stay aware that hurricane season is still in full effect, and the western Caribbean is where it appears the action is most likely to be.


About the Author: