Hurricane Lorena, which was weakening in the Pacific the morning of Sept. 4, is expected to bring heavy rainfall to parts of Arizona and New Mexico, forecasters said.

Former Hurricane Lorena weakened back down to a tropical storm the morning of Sept. 4 but is still poised to bring heavy rainfall and the chance of flash flooding to parts of the Southwestern United States, forecasters said.

Lorena, which made its brief stint as a hurricane after forming on Sept. 3, is expected to have the greatest impact to land in the Baja California Sur and Sonora, Mexico, regions through Sept. 5. Bands of heavy rainfall from Lorena could bring 4 to 8 inches of rainfall Sept. 4 and 5, with totals topping out at about 15 inches from the storm. Flash flooding and mudslides are a risk, the National Hurricane Center said.

In the U.S., 1 to 3 inches of rain are expected across portions of Arizona and New Mexico, with some isolated totals of 5 inches, bringing a chance of isolated to scattered flash flooding, forecasters said.

As of 10 a.m. ET, Tropical Storm Lorena was located 125 miles west-southwest of Cabo San Lazaro, Mexico, and about 500 miles from the Mexico-Arizona border. It was moving northwest with winds of 70 mph and is expected to make a northward turn later Sept. 4. It will move parallel to the west coast of the Baja California peninsula and could move closer to the west-central coast of the peninsula as it weakens on Sept. 5.

"Although Lorena is forecast to rapidly weaken, abundant moisture will continue to stream northeastward away from the cyclone," the National Hurricane Center said on Sept. 4.

What are the chances of flash flooding in the Southwest?

The extreme southeastern corner of California and much of the southern half of Arizona have at least a 15% of rainfall that could produce flash flooding through the morning of Friday, Sept. 5, according to the Weather Prediction Center.

Because Lorena's track has slowed down, the plume of deeper moisture is expected to remain across northern Mexico, said John Glueck, a meteorologist with the weather service in Tucson.

"At this time, we are still looking at some isolated heavy showers on Friday," Glueck said.

A broader area across California, Nevada, Utah and New Mexico is forecast to have at least a 5% chance of heavy rain. The southeastern corner of Arizona and southwestern corner of New Mexico face similar chances for heavy rain on Sept. 6, the prediction center said, with a smaller chance of heavy rain extending up into Washington state.

Lorena to rapidly weaken as it threatens Mexico

Tropical Storm Lorena is expected to continue its rapid weakening before degenerating further into a remnant low by Sept. 6, the hurricane center said.

Tropical storm warnings are in place along the west coast of Baja California Sur from Puerto Cortes to Punta Eugenia. Tropical storm watches along the east coast of the peninsula were cancelled.

Lorena's tropical storm-force winds extended 70 miles, forecasters said.

Forecasters also eyeing Hurricane Kiko for impacts to Hawaii

Another system in the Pacific, Hurricane Kiko, was headed toward the Hawaiian Islands from the east as a major Category 4 cyclone as of the morning of Sept. 4 ET.

Kiko was still well off the coast of Hawaii, chugging along at a speed of under 10 mph, the hurricane center said. It was moving west and a turn to the west-northwest is expected as Kiko picks up speed on its approach to the islands. It will remain a major storm through Sept. 5 before gradually weakening through the weekend and then rapidly weakening before it reaches near Hawaii.

Hurricane Kiko is expected to pass close to the Hawaiian Islands and possibly make a rare landfall, according to AccuWeather. Regardless of whether it makes a direct hit, Kiko could drive damaging 40-50 mph wind gusts along the windward side of Big Island, Maui and Oahu, toppling trees and power lines, the outlet reported.

"People across Hawaii should be prepared for several inches of rain and gusty winds from Kiko next week," said Alex DaSilva, AccuWeather's lead hurricane expert. "There is a possible scenario that Kiko could bring strong winds and little rain, which could increase the risk of wildfires.”

See the storms brewing in the Pacific

How do hurricanes form?

Hurricanes are born in the tropics, above warm water. Clusters of thunderstorms can develop over the ocean when water temperatures exceed 80 degrees Fahrenheit. If conditions are right, the clusters swirl into a storm known as a tropical wave or tropical depression.

A tropical depression becomes a named tropical storm once its sustained wind speeds reaches 39 miles per hour. When its winds reach 74 mph, the storm officially becomes a hurricane.

Prepare now for hurricanes

Delaying potentially lifesaving preparations could mean waiting until it’s too late. "Get your disaster supplies while the shelves are still stocked, and get that insurance checkup early, as flood insurance requires a 30-day waiting period," the National Oceanic and Atmospheric Administration recommends.

  • Develop an evacuation plan: If you are at risk from hurricanes, you need an evacuation plan. Now is the time to begin planning where you would go and how you would get there.
  • Assemble disaster supplies: Whether you’re evacuating or sheltering-in-place, you’re going to need supplies not just to get through the storm but for the potentially lengthy aftermath, NOAA said.
  • Get an insurance checkup and document your possessions: Contact your insurance company or agent now and ask for an insurance check-up to make sure you have enough insurance to repair or even replace your home and/or belongings. Remember, home and renters insurance doesn’t cover flooding, so you’ll need a separate policy for it. Flood insurance is available through your company, agent, or the National Flood Insurance Program. Act now, as flood insurance requires a 30-day waiting period.
  • Create a family communication plan: NOAA said to take the time now to write down your hurricane plan, and share it with your family. Determine family meeting places, and make sure to include an out-of-town location in case of evacuation.
  • Strengthen your home: Now is the time to improve your home’s ability to withstand hurricane impacts. Trim trees; install storm shutters, accordion shutters, and/or impact glass; seal outside wall openings.

This article originally appeared on USA TODAY: Tropical Storm Lorena weakens but threatens rain, flooding in the Southwest

Reporting by Jeanine Santucci and Dinah Voyles Pulver, USA TODAY / USA TODAY

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