“A cut-off low is a weatherman’s woe.”
~ Dr. George Fischbeck KABC-TV, weatherman 1922-2015
Better known as just “Dr. George,” meteorologist Dr. George Fischbeck became an icon of the weather-world. He was both a respected scientist and a much-loved TV weatherman. Wearing thick black-rimmed glasses along with a bowtie he delivered his forecast with the demeanor of a science schoolteacher. The evening news was not complete without his joyful enthusiasm and explanation of his 500-millibar weather chart. One of his favorite weather phenomena was a “cutoff low.” Dr. George made this weather term one of common use. But what exactly does it mean?
It’s great to learn the scientific facts but even better to actually experience them. For two weeks, we’ve been sitting front row to a Picasso-like weather show. It all started with the crazy rain showers a week ago. While we received a disappointing and scant .20 inches, other areas in close proximity were battered by monsoon-like showers. Close on their heels followed the heat.
Heatwaves are common in October, although this one could not be categorized as typical. Like most during this time of the year, it was created and steered by Santa Ana winds. The difference was the hot air mass reached the coastline where it remained for several long days. History making temperatures were recorded. Yes, all the wacky, unbalanced weather is the product of a cutoff low.
Now for the science … At 18, 000 to 40,000 feet above the Earth’s surface, a tubular ribbon of high-speed wind – the jet stream – flows from the west to the east. In a wave-like pattern, a jet stream extends for thousands of miles. The jet stream is the main mechanism, driving storms off the Pacific Ocean and delivering them to California’s west coast. Occasionally an upper-level low-pressure system separates from the jet stream; a cutoff low is formed. It is notorious for being unpredictable, producing unsettled and sometimes surprising weather. Meteorologists often become just as crazy in trying to keep up with them. Why?
A cutoff low often moves in a slow and wobbly fashion. Its sense of direction and speed has been lost along the way. Sometimes it will remain stationary for days, or just turn around and head back to sea. Generally, as the jet stream shifts south, the cutoff low get picked up and pushed along, or it eventually weakens and dissipates.
Lingering until Friday, the low continues to spin offshore, ushering in lots of moisture; thunderstorms and showers are possible also. Mild temperatures, plus a chance for rain on Sunday, is the weekend forecast.
High pressure brings warmer but less humid conditions for next week. Perhaps the cooler days of fall have arrived.
Sue Kilpatrick is a
Crescenta Valley resident and
Official Skywarn Spotter for the
National Weather Service. Reach her at firstname.lastname@example.org.