On Sunday, Tropical Storm Hilary arrived in California, prompting the first ever tropical storm warnings in the state’s history.
In fact, Hilary was only one of three confirmed tropical systems that have made landfall in the history of the Golden State.
It’s almost needless to say that tropical cyclones are rare for this area, but why? How has California been able to avoid these systems for so long?
Well, it all follows the old basic sports analogy of “three strikes, you’re out.”
The first strike comes from cold ocean currents.
The California water currents act like a shield to help weaken or deter any approaching storm because they bring some very cold water from the Gulf of Alaska down the coastline.
This will lead us to strike number two: cold water temperatures.
That water off the West Coast is extremely cold.
Sea surface temperatures near the Pacific Northwest coast are normally in the 50s; these temperatures do slightly warm as we move towards California, but only into the 60s.
Which is way too cool to support any tropical development.
Normally, tropical systems need water temperature to be at least 80 degrees to power any significant storms.
And the final strike has to do with something called the trade winds.
These are the dominate or prevailing winds that exist in the upper portions of the atmosphere.
Since most of the tropical systems in the central pacific develop off the coast of Mexico, these trade winds help to push or steer these developing storms from the coastline out into the middle of the Pacific Ocean.
So, with the combination of cold sea surface temperatures, cold ocean currents and unfavorable wind speeds, hurricanes in California have three strikes against them.
That’s why it’s extremely hard, but not impossible, for hurricanes to come by this area.
