Invest 97L Designated, but Development Odds Dwindling

A stable tropical Atlantic continues to cap organized storminess

The disturbance that rolled off the coast of Africa over the weekend was designated Invest 97L by the National Hurricane Center late yesterday morning. Despite a favorable positioning within a broader region of background spin and rich tropical moisture known as the monsoon trough, the system is struggling to organize. Thunderstorms in the area have largely waned since yesterday and forecast models in the short term have trended weaker, leading NHC to lower development odds for the week ahead.

The big story across the eastern tropical Atlantic so far this season has been the very stable atmosphere, keeping a lid on storminess that tries to bubble up and organize. While some modest northeasterly wind shear may be playing a role in stunting 97L’s organization, model guidance suggests the sinking motions from a stable Atlantic are also staving off persistent storminess.

Vertical instability across the tropical Atlantic. The solid black line indicates typical instability and the blue line shows instability so far in 2022, averaged over a 7-day period. The blue dots are instability readings every 6 hours so far in 2022. The atmosphere is much more stable than average so far this hurricane season, which suppresses thunderstorm activity. Credit: Chris Slocum/NOAA/CIRA.

The window for development with Invest 97L will be short-lived and, by the weekend, as it detaches itself from the umbilical cord of moisture and spin of the deep, tropical Atlantic, increasingly hostile wind shear will deliver a final blow to future development.

As we discussed in yesterday’s newsletter, a weaker system may move farther south and closer to the northernmost islands of the Caribbean over the weekend into early next week. This could enhance showers and thunderstorms for Puerto Rico and the U.S. Virgin Islands by Sunday into early next week.

We don’t expect any tropical threats to South Florida in the week ahead, with even a break in the typically widespread coverage of afternoon storms courtesy of drier Saharan air moving into the area by tomorrow.