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What was up with Tuesday's tornado warning? A meteorologist explains

At 11:45 am on Tuesday, the National Weather Service (NWS) issued a tornado warning text alert to many San Diego County residents. The warning lasted for almost 30 minutes.

Tornadoes are very rare in Southern California said Brian Adams, a NWS meteorologist.

"We generally don’t issue very many tornado watches. Those are usually issued with a higher confidence that we’re going to see tornadic activity on a given day and that’s just really really rare around here,” Adams said.     


The last time a tornado warning was issued was during Hurricane Hilary last August.

Why it matters

On Tuesday morning, a "discrete storm" that was isolated from the main band of rain caught NWS meteorologists' attention.

“What happened over time is this storm continued to gain strength and also showed a few velocity signatures that (caused) us concern,” Adams said. "Eventually it got to a point where the winds looked like they were strong enough to where there was enough rotation in the storm to where we were concerned that there was some tornadic potential.”

Meteorologists projected a tornado could follow a path from National City through Lemon Grove, Spring Valley and toward El Cajon. That's why he said the NWS issued the warning.  

“It’s kind of a combination of how likely is it to occur versus how much lead time can we give people. So we have to anticipate to that if we think the storm is going to strengthen more and we’re showing signs that it could potentially produce a tornado at any minute, we have to get that warning out,” Adams said.       


Closer look

A tornado warning indicates the threat could be imminent.

To help explain the difference between a tornado watch and tornado warning, Adams used a cooking metaphor.

“The difference between a watch versus a warning is the watch includes the ingredients getting together," Adams said. "The warning means your food’s coming out of the oven or the event is basically imminent or it’s already occurring.”      

Adams said lots of people shared images of what’s known as a wall cloud which can look like a funnel. He said there was no confirmation of a tornado touching the ground in San Diego. 

Looking ahead

The first step to being prepared for potentially dangerous weather is having multiple ways to access and receive weather information, Adams said.

And the next time a tornado warning is issued Adams had this advice:

If you’re indoors, “The goal is to put as many walls between you and the thunderstorm that could be potentially producing a tornado,” Adams said.

If you're in a car, pull off to the side of the road and wait out the conditions. If you’re outdoors, find the lowest point like a ditch to shelter from flying debris.