Unraveling the Mystery

California has gotten its first tropical storm watch ever. The last time a tropical storm hit California was in September of 1939 just after Hitler had started World War II. They didn't issue such watches in those days.

Major Hurricane Hilary in the Pacific is way stronger than low energy Hurricane Don in the Atlantic a few weeks ago; the latter spent only a few hours as a hurricane as it spun around aimlessly away from land.

Hilary will weaken from the current Category 4, but how much it will weaken is still not certain. If it maintains sustained winds of at least 74 MPH/119 KMH when it reaches California, then it will become California's first ever official hurricane.

Hurricane Hilary is expected to hit Southern California as a tropical storm, with a punch that could include flash flooding and significant amounts of rain, according to the National Hurricane Center.  A tropical storm watch for much of Southern California was issued Friday morning. The National Weather Service's San Diego outpost said this was the first time such an advisory had ever been issued for the region. 

As somebody who's been through half a dozen tropical cyclones on the East Coast, I would advise our California friends that rain is a bigger hazard than wind – in most cases. People in areas which have the potential for flooding should particularly remain on alert.

The 1939 storm, called El Cordonazo, became the first and only tropical storm to make landfall in the state in the 20th century, according to the National Weather Service. NWS says the storm, which was at one point a hurricane, originated off the southern coast of Central America before moving north and eventually coming ashore at San Pedro, California.  Resulting floods from the storm killed at least 45 people across the Southern California region and caused $2 million in damage to structures and crops, the weather service reports. Another 48 people were also killed at sea.

There were far fewer people in California in 1939 when El Cordonazo caused deadly flooding.

Here is the current forecast for rainfall potential.

Keep up with the track of Hurricane Hilary here. Southern California should begin to feel the effects of Hilary on Sunday afternoon. Monitor local emergency information and follow advisories.

And if you're wondering why this is happening...