An urgent weather advisory has been announced for three states along the West Coast, as a powerful bomb cyclone is projected to bring hurricane-like conditions to the region. The National Weather Service (NWS) has warned residents in northern California, Oregon, and Washington of the potential for hurricane-force winds, devastating flooding, and significant snowfall in higher elevations this week.
Meteorologist Ryan Maue indicated that the central pressure of this bomb cyclone could plummet by nearly 70 millibars within a 24-hour timeframe, reaching levels comparable to a Category 4 hurricane. This intense storm is expected to generate wind gusts of up to 70 miles per hour and introduce a Category 5 atmospheric river, which may result in as much as 20 inches of rain in certain areas.
An atmospheric river is a narrow band of moisture that transports heat and humidity from tropical regions toward the poles. A Category 5 atmospheric river is particularly dangerous, leading to severe storm impacts upon landfall.
The storm's effects are anticipated to commence on Tuesday afternoon and could last throughout the week, possibly extending into the weekend. Residents in the affected areas are advised to seek shelter in interior rooms on the lowest floors of sturdy buildings and avoid traveling in cars or mobile homes.
The NWS forecasts that northern California and southwestern Oregon will experience the highest rainfall totals, raising concerns about flooding, rockslides, and mudslides. As the storm systems approach the West Coast, these states could see at least six inches of rain, with mountainous regions accumulating over 20 inches.
The influx of moisture into the mountains is likely to produce several feet of snow in the higher elevations, particularly in the Cascades and Siskiyou Mountains, potentially disrupting travel through mountain passes.
Winds are expected to pick up on Tuesday and continue into early Wednesday, with coastal regions of northern California, Oregon, and Washington facing gusts exceeding 60 to 70 mph. These high winds could lead to power outages and downed trees.
Bomb cyclones develop when a storm system rapidly intensifies, causing a significant drop in atmospheric pressure. For a storm to be classified as a bomb cyclone, it must lose at least 24 millibars of pressure in a 24-hour period. A loss of 70 millibars in such a short time frame is rare; for comparison, Hurricane Milton transformed from a Category 1 to a Category 5 hurricane by losing 84 millibars of pressure within 24 hours.
Following its peak on Wednesday, this storm may lead to lingering effects over the weekend, extending impacts further south into the Bay Area, Central Valley, and even parts of Southern California. Meteorologist Dalton Behringer from the NWS cautioned that while flooding may not be severe on Wednesday, worsening conditions could arise by Friday with a second wave of the storm, despite lower expected rainfall.
In Southern California, some rain is expected; however, it is unlikely to sufficiently alleviate wildfire risks for the remainder of the season. "While it won’t compare to the conditions in Northern California, any precipitation is beneficial," noted Bryan Lewis, a meteorologist in Oxnard. "However, it probably won't be enough to completely eliminate fire concerns."
The combination of the bomb cyclone and the atmospheric river is what amplifies the severity of this storm, according to the NWS. High-altitude areas in the mountains are forecasted to receive several inches of snow, marking the first significant storm of the season after a winter characterized by record rainfall across much of California.
Atmospheric rivers are elongated moisture channels that travel from tropical regions and are known for delivering heavy rainfall to the West Coast, accounting for 30% to 50% of the area’s annual precipitation. The "Pineapple Express" is a well-known atmospheric river that transports tropical moisture from Hawaii to the mainland.
A bomb cyclone arises when atmospheric pressure decreases by at least 24 millibars within 24 hours, often resulting from the collision of cold Arctic air with warm, moist tropical air. This week's storm is expected to create hazardous weather conditions, with the bomb cyclone contributing to strong winds and the atmospheric river bringing heavy rainfall. The NWS warns that some regions may experience between 10 to 20 inches of rain, while mountainous areas could see up to 3 feet of snow in higher elevations.
Zainab Y.
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