MEXICO CITY — Tropical Storm Lidia formed off Mexico’s Pacific coast Wednesday as authorities warned the Baja California Peninsula to prepare for high winds, heavy rain and a dangerous storm surge along a shore that includes the twin resort cities of Los Cabos.

A new tropical storm, Irma, also formed far out in the eastern Atlantic but forecasters said it did not pose an immediate threat to land.

The U.S. National Hurricane Center said Lidia was expected to approach the southern tip of Baja California on Thursday night. It said some strengthening was expected and the storm “still has the opportunity to be near hurricane strength” before landfall.

Mexican authorities posted a tropical storm warning for the southern part of the Baja peninsula. A hurricane watch also was issued.

Lidia had maximum sustained winds of 40 mph (65 kph) Wednesday night. Its center was about 160 miles (255 kilometers) south-southeast of the peninsula’s tip Wednesday evening and it was heading north-northwest at 7 mph (11 kph).

The hurricane center said the storm was dumping heavy rains over southwestern Mexico and could produce total accumulations of as much as 8 to 12 inches across much of Baja California Sur state and western Jalisco, threatening flash floods and landslides.

Tropical Storm Irma formed over the far eastern Atlantic Ocean and was predicted to become a hurricane Thursday. It was on a general path that could bring it near the eastern entrance to the Caribbean Sea by early next week.

Irma’s center was about 545 miles (875 kilometers) west of the Cape Verde Islands. Maximum sustained winds were 65 mph (100 kph) with higher gusts. It was heading west at 12 mph (19 kph), and no coastal watches or warnings were in effect.