“Air, I should explain, becomes wind when it is agitated.”
~ Lucretius, ‘On the Nature of Things,’ (99 – c. 55 BC) Roman poet and philosopher

Wind … It does not have much substance – you cannot see it or hold it – but you can witness its force. It can dry your clothes in summer and chill you to the bone in winter. It is strong enough to carry sailing ships across the ocean and rip huge trees from the ground. It can transport and present the effects of a wildland fire burning 300 miles away. And one more thing – it can turn up and turn down the volume of freeway traffic.

One morning last week, we awakened to thickly filled smoky skies. The landscape took on an eerie orangish hue. Creepier yet, as the sun set it appeared as a red-orange orb. When dark, a scarlet full moon rose in the eastern skies. At first, I thought there was a fire in the nearby Angeles Forest. No; strong winds had blown smoke from faraway Sequoia National Park. On that day, in particular, erratic wind patterns blew from different directions at many levels in the atmosphere. The ever-changing wind maps kept the NWS meteorologists hopping, I’m sure!

You may also have noticed that sound levels are lower during the day than at night even though there may be more traffic traveling during the day. This occurs in areas where a nighttime temperature inversion occurs. An inversion causes temperatures of the atmosphere to increase with altitude in contrast to the normal decrease with altitude.

We live in a prime location for this to occur. Wind-blown fog, off the relatively nearby ocean, moves inland during the evening and early morning hours and collides with the San Gabriel Mountains. To make simple of the scientific: Sound is magnified when it becomes trapped under the fog layer. The direction of the wind also influences sound levels. I use the 210 Freeway as my example.

When the wind is blowing from the freeway toward you (downwind) sound level is higher. Conversely, you might notice that sound levels are lower when the wind is blowing away (upwind) from you and toward the freeway.

Shifting wind directions dictate the upcoming forecast. Weak to semi-moderate offshore winds will make for warm and dry weather over the weekend. With a shift in the winds – now onshore – a cooling trend is expected to usher in the first week of October.