Tropical Update: Invest 91L Likely to Develop; Three Other Areas of Interest to Monitor

A broad area of low pressure has developed along the tropical wave we have been monitoring in the eastern Atlantic. It has been designated Invest 91L.

Invest 91L will track generally west to west-northwest over at least the next 5 days. The National Hurricane Center is giving it a high (70 percent) chance of developing into a tropical cyclone (TC) over the next 5 days. However, dry air, an uptick in wind shear from a tropical upper tropospheric trough (TUTT), and a broad/elongated center should keep it from organizing too quickly.

Looking at the latest model guidance, the ECMWF, GFS, UKMET, and CMC develop Invest 91L into at least a tropical depression by Thursday/Friday as it approaches the northern Lesser Antilles and Greater Antilles. Right now most model guidance keeps Invest 91L north of the Lesser and Greater Antilles.

Frame from today’s 12z ECMWF valid at 12z Friday. Invest 91L can be seen as a tropical storm passing to the northeast of the Lesser Antilles. (Tropical Tidbits)

Both deterministic and ensemble guidance suggests Invest 91L will track into the southwest Atlantic/vicinity of the Bahamas In about 7 – 10 days. But it is too early to know if Invest 91L will pose a threat to the U.S. or not. The latest model guidance indicates that a trough may erode the eastern flank of a subtropical ridge allowing for a stall and/or recurve into the Atlantic.

If Invest 91L does develop and end up in the southwest Atlantic/vicinity of the Bahamas late this week/early next week it could find more favorable environmental conditions.

For now Invest 91L is not a concern for the U.S., but it does warrant attention over the coming days.

In addition to Invest 91L the NHC is monitoring 3 other areas of interest. All have a low chance of development.

The area in the Caribbean seems unlikely to develop. While the GFS and GEFS continue to develop it into a TC mid to late this week in the northwest Caribbean with a track into the Gulf, there is no longer any support for development from the EPS or any other model guidance. This strongly indicates that development is unlikely.

The other two areas of interest are not an imminent development threat (one is a tropical wave still over Africa) or an issue for any land masses.

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Caleb Carmichael
Caleb Carmichael

Caleb is the owner of Gulf Coast Storm Center. He is currently an undergraduate student at Mississippi State University majoring in geoscience with a concentration in broadcast and operational meteorology. While not yet a meteorologist, Caleb has been providing weather updates, news, and analysis for the Gulf Coast since 2014.

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