The so-called bomb cyclone is a fact of life along the east coast. These rapidly-developing storms are infamous for bringing Atlantic Canada some of the worst weather fall and winter have to offer, with heavy snow and lashing winds. When flow from the warm Gulf Stream and cold air flooding down from northern Quebec and Hudson Bay collide, a vigorous nor'easter is often the result. The Eastern Seaboard is perfectly arranged to support these kinds of explosive systems, dubbed 'weather bombs' when the central pressure lowers by at least 24 millibars in 24 hours.
So the weather bomb that's developed off the coast of Oregon and California has forecasters across North America sitting up and taking notice.
Check out this graphic of a surface low well off the coast of Oregon (1015 millibars) will strengthen rapidly as it drops 37 millibars within 18 hours to a 978 millibar surface low. The term "Bombogenesis" is used when a surface low drops at least 24 MB in 24 hours or less.NWS Los Angeles on Twitter
There are several eye-catching things about this system -- one that will play a leading role in North American weather this week -- but its location and track are perhaps the weirdest.
Intense west coast storms are typically the product of Gulf of Alaska low pressure centres or atmospheric rivers (like the Pineapple Express) that funnel tropical moisture toward the coast. This low is very much 'doing its own thing,' strengthening as it moves northwest to southeast. The driving force here is the unusually intense jet stream, which is both very strong and diving very far south just off the western coast of the continent.
Don't this every day (or every lifetime). https://t.co/UavLCsrdI2Tyler Hamilton on Twitter
With Arctic high pressure seeping down through British Columbia and the Pacific Northwest and the jet in this position, the atmosphere is primed for an historic storm.
And it's not just the track that's rare.
The central pressure is expected to be the lowest on record along the northern coast of California when the storm comes ashore late Tuesday.
Pressure continues to drop at the office on Woodley Island in Eureka. And yes, we will be adjusting the scale on the chart soon. #cawxNWS Eureka on Twitter
The tight pressure gradient between this strong low and the Arctic high pressure off to its northeast will serve to drive punishing winds, as well. Hurricane-force wind warnings were in effect Tuesday offshore along the California and Oregon coasts as winds were expected to exceed 160 km/h. Even closer to the coast, winds the strength of a high-end Category 1 hurricane will batter NorCal through Tuesday night.
Waves towering higher than 10 metres are also expected, and more than a metre of snow is likely to fall over the mountains of Northern California and the Sierra Nevada.
While this storm will pack a wallop across the Western U.S. through one of the busiest travel times of the year, it'll play a role in weather north of the border, too.
It's this low moving through California and into the Great Basin that drives the next round of heavy snow for southern Alberta, which will pick up Wednesday and Thursday.
As energy from the system continues its trek across the continent, it is also expected to have impacts to Ontario by the weekend, meaning the potential for the first widespread wintry mix event is on the table for southern Ontario and Quebec.