Carlotta (2018)

A small tropical cyclone formed about 120 nautical miles (about 138 statute miles) south of Acapulco, Mexico on 14 June 2018 and remained very close to the southern coast of Mexico until it dissipated on 19 June. It strengthened to a tropical storm on 15 June, became nearly stationary just offshore on 16 June, reached its peak late on 16 into 17 June, then moved west-northwestward parallel to the coast, weakened to a depression on 17 June, and became a remnant low by 0000 UTC 19 June before dissipating offshore between Manzanillo and Zihuatanejo.

Carlotta did not make an inland, definitive landfall as a strong storm. It remained close to the coast and moved very near or just offshore of portions of the southern Mexican shoreline, particularly near Acapulco, between 16 and 17 June. Interaction with the nearby land during this period caused the center to weaken and become disorganized.

The storm’s maximum sustained winds were 55 knots (about 63 mph) at its peak around 0000 UTC 17 June, with a minimum central pressure of 997 millibars. At peak intensity Carlotta was equivalent to a moderate-strength tropical storm (below hurricane strength).

Observed storm surge and rainfall information is limited in the official record. An observing site at Acapulco International Airport reported a minimum pressure of 1006 mb and sustained winds to 28 kt with gusts to 40 kt on 17 June; the report notes Carlotta produced locally heavy rainfall over portions of southern Mexico but specific rainfall totals were not available in the report. No specific storm surge heights at named locations were provided.

There were no reports of damage or casualties associated with Carlotta in the official record. The greatest impacts would have been localized flooding and strong winds along the southern coast of Mexico near Acapulco and neighboring coastal areas.

Noteworthy items: the storm’s formation was not well predicted—forecasters raised the odds of development only within about one day of formation because global models did not signal genesis until shortly before it formed. Official track forecasts for Carlotta had larger-than-average errors early on because forecasts initially predicted an inland motion that did not occur, while official intensity forecasts performed reasonably well overall.