Weather in the Foothills

“Don’t knock the weather; nine-tenths of the people couldn’t start a conversation if it didn’t change once in a while.” ~ Frank McKinney Hubbard, 1868-1930, American journalist, humorist and cartoonist

The words “summer” and “hot,” based on where you live, are synonymous. Merriam (and Webster, too) give the meaning “…suggesting a particular quality…” It’s doubtful if in 1831 the East Coast publishers could imagine their definitions being used to explain Southern California where summer is hot.

In recent years, TV weather reporters and meteorologists have turned scientific, using terms straight off their Meteorology 101 notes. The once heard, “It’s going to rain tomorrow” is now “A low-pressure system has split into a cut-off low. While heading south it will tap into tropical moisture fed atmospheric river. Along the foothills orographic lift will enhance precipitation amounts.” Please repeat … What’s it all mean?

Here are just a few, but frequently used, terms:

Catalina Eddy. Local name for a cutoff low. A detached part of the system, which spins around and around, off our coast. The behavior is unpredictable with heavy rain possible.

Pineapple Express: A type of atmospheric river as moisture capable of bringing heavy rain is transported from the Hawaiian Islands to the California coastline and inland.

The Doppler: Named for Austrian physicist Christian Doppler. Uses radar to track storm movement and intensity.

Low Pressure: Air in a low-pressure area rises and cools as it ascends. Clouds form and temperatures drop, making for storm development and rain.

High-pressure: Air in a high-pressure area compresses and warms as it descends. The warming prevents the formation of clouds, leaving the sky clear with warm temperatures. When a high-pressure ridge is off the West Coast, it blocks incoming storms from the Pacific Ocean. Those over the Four Corners cause heat, low humidity and frequently Santa Anas.

Orographic Lift: As wind hits a mountain, it is forced to rise. The air cools and moisture condenses forming rain and snow. Our San Gabriel Mountains make for the perfect scenario.

Inside-slider: A storm that drops directly down from the north to the south and turns inland at Point Conception. Not much rain here. Most Pacific storms come off the Pacific Ocean and move west to east.

Partly Cloudy/Partly Sunny: According to the National Weather Service, both terms refer to opaque cloud coverage of three-eighths to five-eighths.

Onshore Flow: A wind pattern bringing cooler air and fog inland.

Offshore Flow: A wind pattern bringing warm and dry air off the desert. Often turn into Santa Ana winds.

Heat Wave: At least two days with temperatures above historical average.

Jet Stream: Intense winds blowing west to east at the highest reach of the atmosphere. During the summer they remain far north and typically in the winter they drop south. These “rivers of air” transport weather conditions; for us, it means winter storms –hopefully!

Back to the simple weather … High pressure over the region will keep the mercury hoovering around the 100 degrees point. Watch for the fluffy white thunderheads over the mountains – the icons of summer – in the southwest.

Sue Kilpatrick is a Crescenta Valley
resident and Official Skywarn Spotter for the
National Weather Service Reach her at suelkilpatrick@gmail.com.