Tropical Storm Hilary’s record-breaking assault on California and Nevada was allegedly cooked up by a combination of natural El Nino, climate change, a persistent heat dome over the central U.S., and other factors. Hot water and hot air were critical in swiftly developing Hilary and steering the storm on an unusual course that resulted in a deluge of rain in typically arid regions.
During a single weekend, areas that typically see ten months of rain were inundated with precipitation. Southern California’s mountains received nearly a foot of rain, shattering summertime records.
According to Kristen Corbosiero, an atmospheric scientist at the University of Albany, the circumstances around the storm were a “perfect situation” for its formation and strength.
Hilary originated in an area south of Baja California and west of Mexico, a region often responsible for the birth of many storms. However, the water in the storm’s birthplace was significantly warmer than usual, contributing to its rapid intensification. In just 24 hours, Hilary grew from a minimal system to a Category 4 hurricane.
Scientists attribute the abnormal warmth of the water to both the natural El Nino effects and the long-term climate change that has been breaking records for ocean heat.
However, the unusual route of the storm towards Southern California instead of the usual paths for Eastern Pacific storms, was due to a combination of factors. These include the hot air to the east and a low-pressure system to the west that pushed and pulled Hilary up into California.
Moreover, a large hot air mass sitting over the central United States prevented the storm from moving east. Some scientists believe these “stuck” weather patterns could be connected to global warming changes in the Arctic, though this theory remains a contentious topic in climate science.
MIT hurricane scientist Kerry Emanuel has suggested that storms like Hilary are more likely to occur now than they were 20 or 30 years ago. Emanuel’s computer models, which account for climate change and other factors, predict that the frequency of such storms has increased from a one-in-108-year event until 2010 to a one-in-30-year event today.
The role of climate change in enhancing hurricane activity in the region is an accepted fact among scientists. However, they also warn that it’s not solely climate change at work. As the warmer air holds more moisture, storms worldwide are becoming rainier.
With the Eastern Pacific hurricane basin expected to remain active for the next two to three weeks, climate experts are predicting more weather anomalies in the near future.