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A friend told me of her storm experience on Monday, May 13, saying, “I heard the tornado warning come across on my phone and looked outside and said, ‘What the heck? The sky is totally clear!’”
Her disbelief changed to belief as the images from the storm damage started showing up on television and social media outlets.
That’s not the first time I’ve heard that story. People seem to think sunshine and puffy clouds mean there can’t be an imminent severe weather threat. Ironically, though, when the conditions are right, sunshine and puffy clouds are the precursors to towering cumulonimbus complete with hail, winds and tornadoes.
A few things to consider when looking at those happy little cumulus clouds on a warm day: What is the dew point? If it’s in the 60s or higher, there’s a good chance those clouds will continue to grow.
What is the temperature? The warmer it gets, the more energy the atmosphere has available to grow storm clouds. If the temperature passes a certain threshold, the atmosphere will destabilize, making that process easier.
Is there a front on its way or already nearby? Frontal boundaries are zones where two dissimilar air masses come together. They can be cold fronts, warm fronts, or stationary fronts, and any of the three can be a focus for developing storms. When cooler air collides with warmer air, the warm air is pushed higher into the atmosphere because warm air rises and cool air sinks. That rising motion is what we call “lift” and lift is required for storms.
Are the winds turning with height in the atmosphere? If the winds are going one direction near the surface and another direction above it, it’s possible there could be rotating storms. Veering winds — winds that turn clockwise with height — are often associated with the potential for severe weather, especially if they are strong.
As my friend observed, looking at the sky isn’t always a good indicator of what weather the day will bring. For that reason, meteorologists remind everyone to stay weather aware. How?
Keep up with the forecast on a daily basis. Local forecasts are widely available from the National Weather Service, local media, forecasting apps and private forecasters. There’s no good excuse not to know what the weather may do in the next few days.
Understand that on a day when storms are expected, breaks in the clouds can actually help them form by warming and destabilizing the atmosphere. Don’t let sunshine fool you into thinking the threat is over. Let the meteorologists make that determination.
Have a reliable way to receive storm alerts — a phone app, a NOAA weather radio, etc. — turned on and turned up when there is a chance for severe weather.
Niki Morock is a meteorologist who writes for frontporchweather.com, a website owned by The Wilson Times.