Mexico: Hurricane Hilary tracking north-northwestward off the Baja California Peninsula as of early Aug. 20 /update 4

Event

Hurricane Hilary has weakened into a Category 1 hurricane and is tracking north-northwestward just off the northwest coast of Baja California Sur State early Aug. 20. As of 02:00 PDT, the system's center of circulation was approximately 45 km (30 miles) south-southeast of Punta Eugenia, Baja California Sur State.

Forecast models indicate that the storm will move over Cedros Island in the coming hours. The system is then forecast to weaken before making landfall as a strong tropical storm over southern Ensenada Municipality in Baja California State early afternoon Aug. 20. After making landfall, Hilary is forecast to continue to weaken into a tropical depression as it tracks generally northward across northwestern Baja California State and then into southern California, US, late Aug. 20. The system is then expected to weaken further as it tracks northward across western Nevada before dissipating over far southeastern Oregon Aug. 21. Some uncertainty remains in the track and intensity forecast, and significant changes could occur over the coming hours.

As of early Aug. 20, authorities have issued the following coastal watches and warnings:

• Hurricane Warning: The Baja California Peninsula from Punta Abreojos to Cabo San Quintin.

• Hurricane Watch: The Baja California Peninsula north of Cabo San Quintin to Ensenada.

• Tropical Storm Warning: From San Evaristo northward on the east coast of the Baja California Peninsula; from Cabo San Quintin northward to the California/Mexico border and from Punta Abreojos southward to Santa Fe on the west coast of the Baja California Peninsula; mainland Mexico north of Guaymas, Sonora State; from the California/Mexico border north to Point Mugu; and Catalina Island.

Authorities will likely issue new warnings or update existing advisories throughout the system's progression in the coming hours and days.

Hurricane conditions are expected within the warning area early Aug. 20 and are possible in the watch area Aug. 20. Tropical-storm-force winds are occurring within the southern portion of the tropical storm warning area and will spread northward through Aug. 20. Tropical storm conditions are expected in southern California Aug. 20. Winds could be particularly strong and gusty in and near areas of elevated terrain. Higher gusts are likely well inland and will persist even after the system becomes post-tropical.

Rainfall totals of 7.5-15 cm (3-6 inches), with localized maximums of up to 25 cm (10 inches), are forecast across parts of the northern Baja California Peninsula through late Aug. 20. Flash and urban flooding is likely. Similar rainfall amounts are forecast in parts of southern California and southern Nevada; dangerous to catastrophic flooding is expected in these areas, Totoals of 2.5-7.5 cm (1-3 inches) are forecast across other parts of the western US. Localized, and in places significant, flash flooding is likely.

Storm surge could produce coastal flooding along the western Baja California Peninsula where the storm approaches the coast. Coastal flooding is possible along the northern coast of the Gulf of California Aug. 20-early Aug. 21. Large swells generated by Hilary, which are likely to cause life-threatening surf and rip current conditions, are forecast across Baja California Peninsula and southern California over the coming days. Tornadoes associated with the storm system are possible in the lower Colorado River Valley, Mojave Desert, and Imperial Valley regions Aug. 20.

Authorities opened 113 emergency shelters in Baja California Sur State and 80 in Baja California State ahead of the approach of the storm. Authorities have evacuated around 90 people from at-risk areas between Puerto Alcatraz and Cancun in Baja California Sur. The governor of Baja California State has advised citizens to shelter in place during the passage of the storm and nonessential public activities have been canceled throughout the state through Aug. 21. Authorities have reported one fatality in Mulege Municipality, Baja California Sur, after people were swept away by flood waters. Several roads have been made impassable by flooding and landslides in the state and at least 21 flights have been canceled at Los Cabos International Airport (SJD). One fatality was also reported in the El Quemadito community in Sinaloa State due to flooding following heavy rainfall associated with the passing of Hilary.

California Governor Gavin Newsom declared a state of emergency across southern parts of the state Aug. 19 due to the approach of the storm system. Authorities in Los Angeles County, California, have issued an evacuation advisory for Catalina Island; people on the island, especially those with medical conditions, are advised to evacuate. Prolonged utility outages are possible. San Bernardino County has issued an evacuation warning for the Oak Glen, Forest Falls, Mountain Home Village, Angelus Oaks, and Northeast Yucaipa regions due to the risk of flooding. Additional evacuations are possible as the storm approaches and weather conditions deteriorate. Southwest Airlines (WN) has canceled all flights at Palm Springs International Airport (PSP) through early Aug. 21. Hundreds of flights across southern California, including flights at San Diego International (SAN), Los Angeles International (LAX), Hollywood Burbank (BUR), and John Wayne (SNA) airports, have been canceled Aug. 20-21. Officials have canceled several sports events in parts of southern California over the weekend due to the anticipated severe weather brought by the storm. Authorities have closed parks and other facilities across southern California, including Joshua Tree National Park and Mojave National Preserve, through at least Aug. 22 in advance of the storm.

Sustained heavy rainfall could trigger flooding in low-lying areas and those with easily overwhelmed drainage systems. If weather conditions prove hazardous, localized evacuations, flash flooding, and landslides are possible.

The inclement weather could trigger localized business, transport, and utility disruptions and render some bridges or roadways impassable. Flight disruptions at regional airports and temporary closures of ports are also possible. Stagnant pools of water during and after flooding increase insect- and waterborne diseases, such as dengue fever, cholera, and malaria. Exposure to raw sewage and other hazardous materials mixed with floodwaters poses a serious health threat.

Advice

Activate contingency plans in areas where officials forecast tropical storm conditions. Heed any evacuation orders that may be issued. Use extreme caution in low-lying coastal areas and near streams, creeks, and other waterways due to the potential for severe flooding and storm surge. Stockpile water, batteries, and other essentials in advance. Charge battery-powered devices when electricity is available; restrict the use of cellular phones to emergencies only. Power down mobile devices when not in use. Keep important documents and necessary medications in waterproof containers. Observe strict food and water precautions, as municipalities could issue boil-water advisories following flooding events. Take precautions against insect- and waterborne diseases in the coming weeks.

Plan accordingly for protracted commercial, transport, and logistics disruptions in areas in the path of the storm, especially if vital infrastructure is damaged. Seek updated information on road conditions before driving or routing shipments through areas where flooding has occurred. Confirm flights before checking out of hotels or driving to the airport; clearing passenger backlogs may take several days in some locations.

Resources

US National Hurricane Center
Mexico National Meteorological Service (SMN)