The cyclone and atmospheric river that hit Northern California in late October caused exceptionally heavy rain and strong winds. But it also hit the California coast with epic ocean waves. During the storm, individual waves reached 60 feet from Washington to California, according to researchers at the Scripps Institute of Oceanography in San Diego.
For example, Buoy No. 29 Point Reyes, located at 1805 feet, 25 miles west of Point Reyes, recorded a significant wave 30.6 feet high on 25 October. This is the second largest excitement in 23 years of this buoy’s existence. data recording. Only in December 2015, in the year of El Niño, larger waves were recorded.
According to James Behrens, program manager for the Coastal Data Information Program (CDIP), the height of a significant wave is calculated by averaging the height of one-third of the largest wave over a 30-minute period. Typically, individual waves at a given station can rise to twice the average, and the Point Reyes buoy recorded a maximum single wave height of 50.5 feet.
To the north, buoy 179 off the coast of Astoria, Oregon, recorded significant wave heights up to 35 feet, with individual waves just over 60 feet. This became a record for a radio station that was connected to the network in 2011.
Later, as the storm subsided and the front settled on the California coast, Harvest Buoy # 71, 1,791 feet west of Conception Cape, recorded significant wave heights of almost 30 feet with a maximum individual wave height of 50 feet.
The deep low pressure system that generated these historically large and powerful waves seethed off the coast of Washington. It was part of a series of storms and atmospheric rivers that quickly hit the West Coast from October 19th to 24th. It underwent an explosive intensification called bomb cyclogenesis, which means that its central pressure dropped by at least 24 millibars (a measure of pressure) after 24 hours. Generally speaking, the lower the atmospheric pressure, the stronger the storm.
Mid-latitude or extratropical cyclones such as this are low pressure systems that typically occur between 30 and 60 degrees latitude in the Northern Hemisphere.
It was the second bomb cyclone to develop in this part of the East Pacific in a few days. When its central pressure dropped to 942.5 mbar on the morning of Sunday, October 24, it set a record for storms in this part of the ocean off the Pacific Northwest of the United States and was the equivalent of a Category 4 hurricane. The Saffir-Simpson Scale classifies hurricanes based on wind speed and central pressure. At the time, the storm was about 345 miles west of Aberdeen, Washington, and its winds hit Northern California and the Pacific Northwest.
The waves generated by the fierce storm were large, but forecasters were most impressed by the amount of wave energy rising to the beaches, according to the National Meteorological Service in Monterey. For example, they noted that the water flooded most of the beach in Carmel and rhythmically splashed against the sea wall. Similar scenes elsewhere suggest that the beaches were still in a summer configuration. In other words, they have not yet been formed by winter storms, therefore, they are not so steep and without significant protective sandbanks – they are completely unprepared for such a powerful explosion at the beginning of the season.
Satellite images show the classic comma-shaped system with deep low counterclockwise rotation off the coast of Washington State and a plume of moisture sweeping back towards the subtropical center of the Pacific Ocean. This formed the end of the comma. The remnants of Typhoon Namteun, which dissipated west of the international dateline of October 19, contributed to the formation of the plume.
This atmospheric river was the strongest to hit San Francisco since January 2017 and the fifth largest since 2000, according to the Center for Western Weather and Extreme Weather Events. It was the first highly atmospheric river to hit the region since February 2015 and the strongest weathered river in October to land in the Bay Area in 40 years. Heavy rain caused flooding and triggered several mud and debris landslides in Northern California.
The atmospheric river was like a fire hose trained in Central and Northern California, peaking in Category 5 strength near Point Reyes, hitting Marin and Sonoma Counties with its heaviest moisture transport around noon Sunday.
When the storm died down in Northern California on Monday, October 25th, the sound of drum rain was replaced by the roar of jet skis. Surfers from the Mavericks, a surf site south of San Francisco in Half Moon Bay, took up the challenge of the cyclone wave after the bomb. Surfline reported “victory conditions at sea,” the surfer language for big, ugly and stormy waves. The expression comes from the 1950s NBC television series of the same name about naval warfare during World War II.
Notably, CRIS includes the West Coast cyclone bombing last month on its Wave Watch page, along with the East Coast and Nor’ister hurricanes.
CRIS at the Scripps Institute of Oceanography at the University of California, San Diego operates more than 30 active buoys along the west coast with its partners and is part of a network of about 80 stations that also span the Atlantic Ocean and US Gulf coasts, as well as locations in the Caribbean. according to Behrens, program manager.
Behrens said his research team is studying wave data from buoys because erosional storms such as recent cyclones with bombs are “as powerful as hurricanes on the East Coast, and coastlines are taking the brunt.”