Hurricane Hilary Strikes Mexico and Poses Threat of Heavy Rainfall and Flooding in Southern California
Tropical Storm Hilary made landfall on Mexico’s Baja peninsula and has now begun to lash Southern California with strong winds and heavy rain. Forecasters are issuing warnings of a potentially historic amount of rainfall, which could lead to dangerous flooding. In response, California’s governor has declared a state of emergency, urging people in high-risk areas such as Catalina Island to evacuate. Similarly, Nevada’s governor has also declared a state of emergency.
Hurricane scientist Nick Grondin explains that this storm, combined with the El Niño climate pattern and a persistent heat dome over a significant portion of the country, has the potential to bring flash flooding, wind damage, and mudslides to the U.S. Southwest.
It is uncommon for tropical storms to hit the Southwest region of the United States. California has only experienced one confirmed tropical storm landfall back in September 1939, known as the Long Beach Tropical Storm, which caused extensive damage amounting to around $2 million at the time. In 1858, a hurricane came close to making landfall, causing significant damage to San Diego with its powerful winds.
However, the Southwest region does frequently experience the remnants of tropical cyclones, which are storms that continue even after the initial tropical cyclone loses its surface circulation. These remnants are more common than many people realize. In fact, a study conducted in 2011 discovered that an average of 3.1 remnant systems from tropical cyclones affected the U.S. Southwest each year from 1992 to 2005, indicating the frequency of such events.
Last year, Hurricane Kay took a similar track to Hurricane Hilary and brought substantial rainfall to Southern California and Arizona. Back in 1997, Hurricane Nora made landfall in Mexico’s Baja California and continued moving north, resulting in tropical storm-force winds hitting California and widespread flooding that caused hundreds of millions of dollars in damage, specifically affecting fruit trees and agriculture.
This particular storm is particularly unusual due to the El Niño climate pattern, which is showing signs of strengthening in the Pacific. Additionally, the heat dome over a significant portion of the United States is another contributing factor. Typically, Southern California’s waters are much cooler than the minimum temperature of 80 degrees Fahrenheit that hurricanes require to maintain their intensity. However, with Hurricane Hilary already intensifying over warm water to the south and its fast movement, forecasters believe it may be able to sustain itself even in cooler waters.
The influence of the heat dome is an interesting aspect to consider. Meteorology researcher Kimberly Wood highlights the presence of a ridge or high-pressure system in the central U.S., which is a common characteristic of storms that impact the southwestern United States. When a high-pressure system like the heat dome covers a significant portion of the country, it causes air to be pushed down and warm up substantially. Simultaneously, a low-pressure system over the Pacific Ocean with counterclockwise winds will accelerate the northward movement of Hurricane Hilary, enhancing its impact on California.
The primary concern during this storm is the threat of tropical storm-force winds, as indicated by the National Hurricane Center’s issuance of the first-ever tropical storm watch for Southern California. However, water-related issues such as flash flooding and mudslides are generally the primary risks associated with tropical storms. In California, the presence of mountains can amplify rainfall, leading to dangerous flash flooding and even mudslides, particularly in areas that are still recovering from recent wildfires.
Even dry areas can experience heavy downpours that trigger flash flooding. Death Valley, for example, is expected to receive more rain from Hurricane Hilary than its average annual rainfall. Due to this forecast, Death Valley National Park has closed its visitor centers and campgrounds while warning of potential flash flooding until August 22.
It is essential to note that this is an evolving situation, and forecasts can change. The effects of the storm are expected to extend far north, with a moderate risk of flooding projected across large parts of Southern California, southern Nevada, and far-western Arizona, along with a high risk of flooding for regions east of San Diego.
Individuals in the path of Hurricane Hilary should stay updated with information from local weather offices, including the National Weather Service in the United States and Servicio Meteorológico Nacional in Mexico.
In conclusion, the arrival of Hurricane Hilary in Mexico and its subsequent impact on Southern California has raised concerns about the possibility of historic rainfall and flooding. The combination of the El Niño climate pattern and the presence of a heat dome over the United States has created a unique weather system that could lead to severe consequences. Although tropical storms are uncommon in the Southwest, the region frequently experiences the remnants of tropical cyclones. As the situation continues to develop, it is crucial for residents to stay informed and take necessary precautions to ensure their safety.
