Weather Watch

SLO County to get prime view of Perseids meteor shower

Despite a waxing gibbous moon, NASA says this year’s Perseids meteor shower display will be one of the most spectacular in decades for shooting-star seekers for a couple of reasons.

The moon will set before the predawn hours Friday and Saturday, the expected peak of the meteor shower associated with the comet Swift-Tuttle. Perhaps more intriguing, Jupiter’s gravity has pulled the middle of the debris field from Swift-Tuttle closer to the Earth’s path around the sun.

As travelers on planet Earth, we orbit the sun at about 67,000 mph. At this point in our annual journey, our planet is blasting through the stream of debris that lies along the orbit of the comet Swift-Tuttle, which circles the sun about every 130 years. The comet’s most recent appearance occurred in December 1992.

Most comets, like Swift-Tuttle, are made of dust, small rocky particles and frozen gases that turn into giant glowing spheres with tails that stretch for millions of miles as they near the sun and accelerate like a slingshot. They are often referred to as “dirty snowballs” that return back to their popsicle state when they move away from the sun.

Because the remains from this comet are moving in an opposite direction to Earth’s orbit, its small bits and fragments slam into the Earth’s upper-atmosphere at a combined velocity of 130,000 mph. At speeds like this, even the most minuscule bits of debris can produce beautiful meteor showers to light the night sky.

This month’s meteor showers take the name Perseids because of their apparent origin in the constellation Perseus. The Perseids are one of the most dependable and brightest of the annual meteor showers.

Normally in August, those who look toward the heavens after midnight see 90 to 100 meteors per hour. This year, the yield could be double that during the predawn hours of Friday and Saturday with 200 meteors per hour. In fact, sky watchers have already seen numerous meteors at the darkest hours before dawn.

To get the best view of these showers in San Luis Obispo County, you need to move inland away from the marine layer and light-polluted urban areas. Look toward the northeast, because the Perseids full splendor is reserved for places with dark skies. From my experience, your eyes may take as long as half an hour to adapt to the darkness.

Like the Southern Hemisphere swells that reach the Central Coast, these meteor showers tend to arrive in groups with lulls in between. In the past, I’ve had to wait up to an hour to spot my first meteor, but for weather geeks, it’s worth it. I’ll be out in the early morning hours with my camera on top of my tripod with hopes of capturing a Perseid.

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On Saturday, Aug. 27, the San Luis Obispo County Early Warning System sirens and the Reverse 911 System will be tested. These systems may be used for any local emergency. The sirens will sound at noon and again at 12:30 p.m. for three to five minutes. During these tests, no action is required on the part of the public. If you hear sirens at any other time, tune to a local radio or television station for emergency announcements. This message is from the County Office of Emergency Services and PG&E.

John Lindsey is PG&E’s Diablo Canyon nuclear power plant marine meteorologist and a media relations representative. Email him at pgeweather@pge.com or follow him on Twitter @PGE_John for weather and other useful information.

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