2023-09-03 08:38:41
On its way to southern California, Hilary transformed from a Category 1 hurricane to a tropical storm with minimum winds of 63 km/h, a transition that took place before making landfall early Sunday morning north of the Baja Peninsula. California, in Mexico. At 8 a.m. Monday, Hilary was categorized as a “post-tropical cyclone” and was well inland, 185 kilometers northwest, in Elko, the heart of Nevada, at a brisk pace of 39 km/h, maintaining maximum winds. sustained of 56 km / h.
This is a new record in the history of climate in this part of the world: the National Hurricane Center issued a tropical storm warning for the first time in southern California. The state governor, Gavin Newsom, declared a state of emergency and stressed that it was an extraordinary weather phenomenon in Los Angeles, a city versed in natural disasters such as forest fires and seismic activity. During a press conference, Mayor Karen Bass referred to the storm as an “unprecedented weather event.” San Diego Mayor Todd Gloria also expressed concern regarding power outages stemming from high winds and the imminent threat of flooding and landslides in the area.
On Sunday night, Southern California experienced the precursor effects of Storm Hilary, aggressive torrential rains. Some areas of Palm Springs, a city with an arid climate, received an accumulation of more than two inches of rain, that is, in just six hours they absorbed the amount of water equivalent to the precipitation of six months.
As the day progressed, a cascade of records was broken, with notable cases in downtown Los Angeles, Burbank and Palmdale. The Los Angeles Weather Service documented an excess of 8.5 inches of rain on Mount Wilson in the Angeles National Forest. In other words, during the downpour more than 21.59 cm of water was collected per square meter. Beverly Hills recorded 4.8 inches, and downtown LA a buildup of almost 3 inches.
In the San Diego area, the storm dumped more than 6 inches of rain on Mount Laguna, with strong 85 mph winds near Big Black Mountain. And while the news was running flood warnings, a magnitude 5.1 earthquake reverberated in and around North LA that same Sunday followingnoon.
The impact of ‘Hilary’
The storm’s impact extended to Nevada and Arizona. Evacuation orders have been issued in parts of Lake Mead National Park in Arizona, urging residents to move to higher ground due to possible flooding. Nevada Governor Joe Lombardo declared a state of emergency. In a few hours on Death Valley Sunday morning, Death Valley, one of the driest and hottest places on the planet, experienced triple its typical August rainfall: Within an hour the area received almost a month’s worth of rain .
Southern California authorities advised the population to avoid driving, due to the risk of flooding, landslides, debris accumulation and sudden torrents. To further complicate matters, scars from persistent wildfires in recent years have left surfaces prone to rapid flow of water and debris. The National Weather Service noted that scorched earth can repel water just as effectively as pavement, causing sudden landslides that can wash away houses in their wake.
More than 7 million people were affected by the storm this Sunday. Hundreds of roads and train tracks cut. Navigation was suspended and more than 1,000 flights were canceled and another 4,900 suffered delays.
An unprecedented phenomenon
“A tropical system like this in southern California is a rare phenomenon, in fact, it’s barely unprecedented on record,” Greg Postel, Weather Channel hurricane and storm specialist told CNN. California has been safe from hurricanes thanks to three natural barriers. The first is the cold ocean current that flows along the Pacific coast, stripping storms of their tropical heat and further weakening them. Second, an east-west wind pattern prevents storms from colliding with the mainland, pushing them out to sea where they dissipate.
Finally, atmospheric subsidence, a downward flow of air over California that compresses storms before they can form and contributes to the region’s characteristic marine layer. These three factors combined have preserved the state from hurricanes for at least 165 years. However, this week the National Weather Service has had to issue “tropical” flood warnings from Santa Barbara, California to Flagstaff, Arizona.
Cyclone generation and feeding requires a sustained ocean surface water temperature of greater than 26°C, which is very rare off the California coast. However, global warming suffered by the planet is causing alterations.
2023, among the warmest years
The average global surface temperature last July was 1.12 degrees Celsius above average, making it the warmest July in the National Oceanic and Atmospheric Administration’s 174-year history. 2023 ranks among the five warmest years on record, and may well become the warmest year on record, with a global temperature of 1.03°C above the 20th century average of 13.8°C. And this has also brought with it another new record: The highest temperature of the ocean surface in 174 years was recorded with an anomaly of 0.99 degrees Celsius above average. The average sea surface temperature has risen 0.83 degrees Celsius since 1901.
Coupled with the warming of the seawater surface, the convergence of two other exceptional weather conditions has brought down the easterly wind broom that was dragging the storms out into the Pacific, away from California. A high pressure ridge in the central United States has generated extreme heat in the region that, together with the persistent depression of low pressures off the West coast, have transformed the east-west winds into a South-North flow. , inviting Hilary to penetrate southern California.
Jayme Laber, a hydrologist at the National Weather Service in Oxnard, explained that these conditions will drag more and more tropical systems towards this region of the planet. The Tropic of Cancer is located approximately 23.5 degrees north of the Equator; Tropical Storm Hilary has reached Los Angeles, which is approximately 34.05 degrees north, more than 2,200 kilometers above this parallel.
Southern California normally receives less than 1/10 inch of rain on average in August. Hilary has dropped between 2 and 4 inches of precipitation in just a few hours. As the world warms, rising ocean surface temperatures provide more fuel to intensify these storms. Consequently, the prospect of a warmer world casts a shadow over the future, opening up the possibility of more recurrent, active, and powerful hurricanes.
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