Weather in the Foothills

“Sharks have everything a scientist dreams of. They’re beautiful – God how beautiful they are! They’re like an impossibly perfect piece of machinery. They’re as graceful as any bird. They’re as mysterious as any animal on earth…”
~ Peter Benchley, “Jaws”

“Robin, stop the presses!” Temperatures sailed way beyond my predicted daytime highs of around 90 degrees. Mother Nature one upped me and pushed the mercury slightly over 100. As to be expected, a brush fire broke out in the rugged terrain of San Gabriel Canyon. Plumes of smoke were visible, as were thunderheads – cumulous nimbus clouds – further to the east. Both are signatures of summertime.

A new weather term was brought to my attention by the National Weather Service – “pyrocumulous clouds.” They are not recognized as a distinct cloud-type by the World Meteorological Organization, but categorized with other cumulus clouds. Nevertheless, they are unique.

Ordinary cumulus clouds are initiated by the sun and surface heat. On the other hand, pyrocumulus clouds are formed by an intense external heat source. The most common external heat source, especially in the western U.S., is forest fires. As the hot air mass –smoke – rises, cooling and condensation of water vapor from burning vegetation occur. These clouds continue to rise above the smoke. They are seen as dense bright white clouds billowing up to five miles above the smoke line. At this point, they become classified as pyrocumulonimbus clouds – a cumulus cloud fed by fire (a “fire cloud”) that is capable of a myriad of outcomes. The most ironic is the violent thunderstorms. Their heavy rains often extinguish the very fire from which they were created. Lightning can spark new fires downwind from the original one.

The biggest concern for firefighters during these storms is wind. Downdrafts can cause the fire to become erratic, suddenly changing direction. From a global perspective, these intense storms funnel pollutants high into the Earth’s stratosphere.

Warmer temperatures impact all creatures. As humans we can usually adjust to environmental change. Winter too cold? Throw on another blanket or head to Hawaii. Summer too hot? Set the thermostat lower or head to the beach. With the kids back at school, finding a quiet piece of sand is no problem. If the beach feels too lonely, one needs only go a short distance into the water to meet up with other swimmers. I suggest the YMCA as a safer alternative.

“Just when you thought it was safe to go back into the water.”A “Jaws II” tagline.

Great white shark attacks are on the rise, according to George Burgess, director of shark research at the Florida Museum of Natural History. There are a variety of possible reasons with no single one being the whole answer. The typically cold water off the California coast is 10 degrees warmer this year due to changes in wind patterns. The warm water attracts an abundance of sea life – schools of fish, sea mammals and even sea turtles. Following close behind are juvenile Great White sharks ready for a good seafood dinner. The mild water temperatures also attract more human swimmers. Here lies the potential problem.

Hungry sharks and human swimmers don’t mix well in a social setting. Interestingly enough, when a shark bites it is just taking a taste. The young sharks in our waters prefer fish. Sharks of Spielberg proportion are rare, but use caution when splashing in the waves.

The NOAA scientists agree that this summer’s weather is elusive. Desert and marine influences are sparring. A prediction of days in the upper 80s and nights around 60 degrees is my informed guess.

Not too bad, for August weather!
Sue Kilpatrick is a
Crescenta Valley resident and
Official Skywarn Spotter for the
National Weather Service. Reach her at