|Subtropical storm (SSHWS)|
On May 7, the NHC began monitoring a large extratropical cyclone developing off the coast of North Carolina. The NHC noted the possibility of it gaining tropical characteristics, giving it a 0% chance of development within 48 hours and a 20% chance of development in 5 days. Moving northeastward on a similar path to Hurricane Alex, the low eventually reached an area near the Canary Islands that was favorable for subtropical cyclogenesis.
On May 10, the NHC upped their development chances to 70% due to an eye forming and that the low was losing its frontal features, subsequently being designated Invest 91L. At 10:00AM on May 11, the NHC began issuing advisories on Subtropical Storm Bonnie, becoming the second named storm of the season. Bonnie would acquire peak winds of 65 mph on May 14, with little change in intensity over its path. On May 15, Bonnie weakened to a remnant low due to drier air. Bonnie then dissipated completely the next day.