The storm that arrived to the Bay Area on Monday and will stay through Wednesday will have many of the features of the March 21 record-breaking "bomb cyclone," with heavy rain, high wind gusts, snow in the mountains and thunderstorms, according to the National Weather Service (NWS).
But unlike last week's storm, the worst of the incoming weather system will likely be to the north near the California-Oregon border, a National Weather Service meteorologist said on Monday, March 27.
This week's storm is predicted to still bring significant rain — between 1 inch to 1.25 inches in Palo Alto and up to 1.5 inches in the mountains. South winds of 15 to 30 mph and gusts up to 39 mph to 45 mph are predicted during the peak of the storm with up to 50 mph gusts in some higher peaks and ridges, according to the NWS Bay Area.
Most of the gusty wind will take place Tuesday between 7 a.m. and 1 p.m., Sarah McCorkle, a meteorologist with the NWS Bay Area, said on Monday.
"I will say it is looking to be another strong storm," with a low barometric pressure estimated at 985 millibars, which was similar to the March 21 storm, she said.
At 984.4 millibars, the March 21 storm had the lowest barometric pressure ever recorded for the month of March in the San Francisco Bay Area. The previous record was 990.2 mb on March 14, 1942, according to NWS data.
"The lowest ever recorded for SFO was 976.6 mb on Jan 27, 1960. Yup, we beat the monthly record, but not the all-time record," Brian Garcia, warning coordination meteorologist for the National Weather Service SF Bay Area/Monterey, said last week.
The March 21 storm was also a "bomb cyclone," a storm that grows rapidly in speed and intensity, Garcia said.
Bomb cyclones, or what meteorologists call "bombogenesis" and "explosive cyclogenesis," form when a cold air mass collides with a warm air mass under certain conditions such as over ocean water. Low pressure in the storm's center plummets, causing a sudden drop in barometric pressure of at least 24 millibars within 24 hours, according to the National Oceanic and Atmospheric Administration National Ocean Service.
"There's a potential for an impact of very strong winds around the area of low pressure," Garcia said.
The March 21 storm was unusual in that the low pressure had a very long drag down the coast and then looped back up through the Bay Area.
"If there was anything surprising, it's the track it took and how it circled back and rolled down the coast, up to the Bay Area and down the coast," he said.
Two low-pressure systems were very close, which is unusual for the Bay Area, he said. The "parent" low had a frontal boundary that developed a low onto itself, creating a double-barreled hook, which slammed the Bay Area, he said.
This time around, the eye of the very-low-pressure system will track over Oregon and northern California, McCorkle said. She couldn't say if it will become a bomb cyclone, however. In the Bay Area, by the time it passes over on late Wednesday, the barometric pressure should weaken, McCorkle said.
This week's storm is expected to produce thunderstorms, increased rainfall, lightning and the possibility of small hail on Wednesday for the entire Bay Area and Central Coast regions, the NSW said in a tweet on Monday afternoon.
More trees expected to topple over
Residents should expect that more trees will also topple, the NWS said.
Saturated soils and high winds contributed to many of the whole tree failures in Palo Alto and other surrounding communities during the past storms, city of Palo Alto spokespersonMeghan Horrigan-Taylor said in an email. Many trees that lost limbs had been weakened by years of drought and were not robust enough to survive the strong winds.
But Sabino Torres, owner of Mountain View Tree Service, which has a Palo Alto office, said trees that fell in high winds and heavy rain mostly toppled because they weren't maintained.
"Trimming is most important to prevent a tree from falling," he said.
A weakened tree, or one that has rot, are not the only ones that come crashing down.
"Excess branches prevent air circulation during a storm, especially in a big tree, and that's why the whole tree comes down," he said on Monday afternoon. "It's most important to keep the tree balanced."
Torres said he and his crews were kept busy seven days a week and late into the evening during the series of storms, and he expects more of the same during this week's predicted winds and rain.
"We're getting ready. It's supposed to be bad tomorrow. I'm hoping it's not bad," he said.
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