Hurricane Irwin gathered strength in the eastern Pacific off the Mexican coast, while nearby Tropical Storm Jova threatens to grow larger by tomorrow, according to the U.S. National Hurricane Center.

Both Irwin and Jova are forecast to turn toward Mexico and strike the west coast sometime next week.

Irwin, a Category 1 hurricane, is 925 miles  southwest of the southern tip of Baja California with winds of 85 miles per hour, up from 80 mph earlier today. Jova, 684 miles east of Irwin, has winds of 60 mph, up from 50.

“Jova is expected to become a hurricane by tomorrow and could continue to strengthen after that time,” the center said in an advisory at 11 a.m. East Coast time. A storm is classified a hurricane when top winds reach 74 mph.

Jova may grow into a Category 3 storm with winds of 115 mph capable of causing “devastating damage” including crushing poorly built homes, snapping trees and disrupting power and water supplies for days, according to the hurricane center. Irwin may reach a weaker Category 2 peak with winds of 105 mph.

Some weather models show Jova reaching Category 4 strength, according to a hurricane center forecast analysis.

“The one that will have the biggest impact will be Jova,” said Jim Rouiller, a meteorologist with Planalytics Inc. in Berwyn, Pennsylvania. “Landslides and widespread flooding will be the main concern. Irwin will reinforce the flooding. There will be some very intense flooding scenarios as we go through next week.”

Irwin will weaken while moving through cooler water churned up by Jova, and wind shear will tear at its structure, Rouiller said.

In the Atlantic, Hurricane Philippe, a Category 1 storm, weakened as it moved east-northeast at 16 mph, according to the hurricane center. The system’s top winds dropped to 85 mph, down from 90 mph earlier, and Philippe poses no threat to land.