Storm Hilary Causes Severe Flooding in California as Extreme Heat Warnings Affect US and Mexico
By Alice Fowle (MetDesk)
Mon 21 Aug 2023 09.34 BST
For the first time in 84 years, Southern California experienced the landfall of a tropical storm. Tropical Storm Hilary, with wind gusts reaching 130mph (210km/h) and an air pressure of 943mb, approached the Baja California peninsula as a category 4 hurricane before making landfall as a tropical storm in southern California on Sunday. It is worth mentioning that the last time a tropical storm hit southern California was in 1939, causing devastating floods and the loss of nearly 100 lives.
Tropical Storm Hilary led to California’s first-ever tropical storm warning, stretching from the Mexican border to just north of Los Angeles. Rainfall estimates suggest that southern California received between 70-150mm (3-6in) of rain, posing a serious threat of life-threatening flooding. Additionally, this amount of rain exceeds the average yearly rainfall in certain parts of California and Nevada.
President Joe Biden announced last week that the Federal Emergency Management Agency (FEMA) had deployed personnel and supplies across the affected region to respond to the crisis. The Mexican army also mobilized about 14,000 soldiers to Mexicali and the states of Baja California Sur, Jalisco, and Colima.
As Hilary progresses north-northwestwards through California, Nevada, Oregon, and Idaho, it is expected to weaken into a depression. However, heavy rain is still expected in these areas. Normally, central and southwest Idaho only receives about 15mm of rainfall in August, but cumulative totals of 30-50mm are possible over the next few days.
While Southern California battles flooding, other parts of the United States and Mexico are dealing with extreme heat warnings. The Midwest, central, and southern plains of the US have been put under excessive heat warnings as temperatures soar 5-10C above the climatological average. Over 65 million people were issued heat alerts last Friday, with many warnings extending into this week. Temperatures are expected to exceed 38C (100F) throughout the week, with some areas reaching as high as the low to mid-40Cs (104-112F).
In Europe, heat from northern Africa is moving up, affecting Spain, Portugal, Italy, and southern France. Southern areas of Spain and Portugal are expected to reach temperatures in the low 40Cs, while parts of Italy and southern France can expect temperatures around 40C. However, this heatwave is projected to subside over the weekend as low pressure brings cooler westerly winds.
The gradual weakening of Tropical Storm Hilary and the potential for further heavy rain, coupled with the extreme heat warnings in the US and Mexico, highlight the ongoing challenges posed by unpredictable weather patterns and the importance of preparedness and response measures.