In an unprecedented meteorological event, Tropical Storm Hilary has left a trail of destruction in California and Nevada, setting new records in the process. The storm’s unusual trajectory was influenced by a combination of factors including a natural El Nino, human-induced climate change, and a persistent heat dome over the nation’s midsection. Experts suggest that the exceptional warmth of both air and water played a key role in the rapid intensification of Hilary, steering it on a path that resulted in 10 months’ worth of rain being dumped in a single weekend on regions typically known for their dry conditions.

"Hilary’s unusual path can only be understood when we trace back to its genesis," explains Kristen Corbosiero, an atmospheric scientist at the University of Albany specializing in Pacific hurricanes. The storm was born in an area to the south of Baja California and west of Mexico, a region known for being one of the most active birthing places for tropical cyclones. However, the water there was unusually warm, about 3.5 to 5 degrees Fahrenheit hotter than normal at the surface. This extra heat, serving as fuel for the storm, resulted in Hilary rapidly intensifying to a Category 4 hurricane in just 24 hours, a phenomenon that scientists have been observing more frequently in recent years.

The Recipe For Tropical Storm Hilary’s Record-Breaking Impact

A unique blend of natural and human-induced factors, including an El Nino event, climate change and an unyielding heat dome over the U.S., are responsible for Tropical Storm Hilary’s unprecedented impact on California and Nevada.

The Perfect Storm

The storm’s extraordinary path can be traced back to its formation south of Baja California and west of Mexico. This region is one of the most active birthing places for tropical cyclones, according to Kristen Corbosiero, an atmospheric scientist at the University of Albany. The unusually warm waters, about 3.5 to 5 degrees Fahrenheit hotter than normal, fueled Hilary’s rapid intensification. Within 24 hours, the storm’s wind speed escalated by 75 mph, transforming it from a tropical depression to a Category 4 hurricane.

The Role of Climate Change and El Nino

Climate change and El Nino both contributed to the warmer waters that supercharged Hilary. El Nino is a natural occurrence involving the warming of parts of the equatorial Pacific, which alters weather patterns globally. Meanwhile, long-term climate change has been shattering heat records in the oceans’ depths. These factors, combined with the lack of crosswinds, provided ideal conditions for Hilary’s explosive development.

The Unusual Path to California

Normally, the cold coastal waters of California and Baja California, coupled with the state’s dry, downward-moving atmosphere, would deter a hurricane like Hilary. However, Hilary’s strength and size allowed it to maintain its destructive power, even after encountering the cold waters. The usual east-to-west winds also failed to push Hilary away from the coast. Instead, a combination of hot air to the east and a low-pressure system to the west steered Hilary towards California.

The Stalled Weather Pattern

Another factor in Hilary’s unusual path was a large, immovable mass of hot air over the central U.S., which effectively blocked the storm from turning east. Some scientists, such as Jennifer Francis from the Woodwell Climate Research Institute, theorize that this type of stuck weather pattern is becoming more common due to global warming-induced changes in the Arctic. However, this idea remains one of the most debated topics in mainstream climate science.

The Increasing Probability of Extreme Weather Events

MIT hurricane scientist Kerry Emanuel has calculated that the likelihood of a storm like Hilary hitting Los Angeles has increased from a one-in-108-year chance to a one-in-30-year chance, factoring in climate change and other factors. "Hilary was substantially more probable today than it would have been 20 or 30 years ago," Emanuel said. Furthermore, when storms like Hilary do hit, they are likely to be rainier due to the warmer air’s ability to hold more moisture.

Takeaways

The case of Tropical Storm Hilary serves as a stark reminder of our changing climate’s power to amplify extreme weather events. While understanding the exact contributions of natural phenomena like El Nino and human-induced climate change is complex, it’s clear that we need to prepare for an increased likelihood of such devastating storms in the future. It also underscores the importance of ongoing research in climate science to better predict and mitigate the impacts of these events.