"Advisories are being started on Tropical Storm Jose", reported the National Hurricane Center, which said Jose is following closely behind Irma.
The NHC said as a depression, Katia was blowing maximum sustained winds of almost 56 km per hour and should dissipate over the mountains of central eastern Mexico later on Saturday.
Hurricane Katia, the sixth hurricane of the 2017 season, is expected to make landfall in Mexico early Saturday morning.
There's no immediate threat to land from Jose, but meteorologists warned the storm's path could change, according to the National Hurricane Center.
Meanwhile, hurricane warnings were issued from Cabo Rojo to Laguna Verde in Mexico as Hurricane Katia takes aim on the nation's east coast.
Katia could bring a storm surge of 5-8 feet along the coast, the hurricane center said. Tropical-storm-force winds extend outward up to 45 miles (75 km) from the centre. Now the strongest hurricane ever recorded in the Atlantic, and packing 185-mile-per-hour winds, the storm has passed Puerto Rico and is now roiling through unusually warm waters to the immediate north of the Dominican Republic.
Hurricane Irma, which is Category 4, is on track to hit Florida after heading over parts of Cuba and the central Bahamas, according to the agency.
Hurricane Jose graduated from tropical storm status Wednesday afternoon when sustained winds picked up to 75 miles per hour. It's still unclear how Irma will affect the United States, though Florida is bracing for a possible hit.
For the first time since 2010, the Atlantic has three active hurricanes, two of which are expected to make landfall this weekend.