Two confirmed tornadoes have happened in SLO
By John Lindsey
San Luis Obispo Tribune
Sunday, April 24, 2011 The past few weeks have seen a marked increase in the number of tornadoes east of the Rocky Mountains. Around 245 tornadoes were reported last week, with North Carolina probably being the hardest hit.
April and May historically have the greatest occurrence of these violent storms. Tornadoes nearly always develop from thunderstorms, especially from a class of thunderstorms known as supercells.
This type of thunderstorm can be seen over the Central Plains when warm and moist air moving northward in the lower to mid-levels of the atmosphere from the Gulf of Mexico runs into cold air moving southward from Canada.
When this occurs, the warm and less dense air is forced up by the advancing mass of colder and denser air.
As this air rises thousands of feet into the sky, it cools and releases tremendous amounts of latent heat. This condition keeps the air rising inside the cloud, triggering thunderstorms.
These convective storms can contain areas of organized rotation a few miles up in the atmosphere. If the conditions are right, these thunderstorms can spin out tornadoes.
Even though a greater number of tornadoes occur east of the Rocky Mountains during the spring, California is not completely immune from these violently rotating columns of air.
There have been two occurrences of confirmed tornadoes in San Luis Obispo.
The first happened April 7, 1926, when a Pacific storm came in from the west and produced lightning.
The lightning struck large oil tanks along Tank Farm Road. Altogether, more than 5 million gallons of oil burned over five days.
It was reported that burning oil made it all the way to Avila Beach by way of San Luis Obispo Creek.
Intense heat from these fires produced hundreds of fire whirls — many of them showed characteristics of true tornadoes.
One of the fire tornados traveled 1,000 yards, picked up a house and carried it 150 feet, killing the two occupants inside.
The other confirmed tornado that hit San Luis Obispo occurred on the morning of May 5, 1998. At the time, I was living in a neighborhood near Cal Poly where it touched down.
About 5:40 a.m., the rain became heavy and the wind caused my windows to vibrate. I thought it was a train at first.
My anemometer — a device to measure wind force — was fluctuating from 60 to 70 mph, and the power lines around my home began to arc.
Tree branches were breaking, and then I saw debris rotating in a counterclockwise direction — clear evidence that a tornado was occurring.
My anemometer reached 86 mph! I called 911 to report the activity. To say that she sounded a bit skeptical would be an understatement.
But later, the National Weather Service indeed confirmed a low-level tornado happened in the area.
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