It is the 11th named storm of the 2017 Atlantic hurricane season.
Tropical Storm Jose formed Tuesday morning in the Atlantic Ocean, the National Hurricane Center said.
Katia was downgraded to a tropical storm from a hurricane when it was about 115 miles (185 km) northwest of Veracruz with sustained winds of 40 mph (65 km/h), the centre said in an advisory. A hurricane watch has been issued for the Mexican state of Veracruz by the Mexican government. It's still unclear how Irma will affect the United States, though Florida is bracing for a possible hit.
Katia is expected to produce total rain accumulations of 10 to 15 inches over northern Veracruz, eastern Hidalgo, and Puebla.
Katia is located about 200 miles east of Tampico, Mexico.
"This rainfall may cause life-threatening flash floods and mudslides, especially in areas of mountainous terrain", the Miami-based NHC said.
Katia is moving toward the west-southwest near 3 miles per hour (6 km/h) and this general motion is expected to continue until the system makes landfall within the hurricane warning area by early Saturday, Sept. 9.
At 7 a.m. CDT (8 a.m. EDT/1200 UTC) on September 8 the center of Hurricane Katia was located near 21.1 degrees north latitude and 95.6 degrees west longitude. Weather forecasters say that although Jose is not expected to make landfall, it will likely add misery to the already devastated island of Barbuda, which was destroyed by Irma this week.
A hurricane watch is in effect for Antigua and Barbuda, and a tropical storm watch is in effect for Anguilla, Montserrat, St Kitts and Nevis and Saba and St. Eustatius, according to the hurricane center.
Some strengthening of the storm is forecast during the next 48 hours before it reaches the Mexican coast late Friday night, or early Saturday.