MEXICO CITY (AP) — Mexico's National Meteorological Service is increasing its forecast of the number of hurricanes and tropical storms expected to form in 2017 in the Atlantic and Pacific.

The service says warmer ocean temperatures have prompted it to raise its forecast of storm formation from 27 to 33.

It expects 18 to form in the Pacific, including five major hurricanes. Fifteen are expected to form in the Atlantic, including four major hurricanes.

The service said Thursday that 11 storms and hurricanes have already formed so far this year, with seven in the Pacific and four in the Atlantic.

The season got off to an unusually early start with a rare April tropical storm named Arlene, well before the official start of the Atlantic season on June 1.