Tuesday Wind Risk
- Once we get through Monday's typical fall frontal system, the next wave of low pressure has strong potential to bring about decent winds; a developing surface low is forecast to track across Southern BC on Tuesday, with strong winds likely for some. The associated cold front slides across the Lower Mainland later on Tuesday with a pronounced wind direction shift to the WNW
- This low pressure system is expected to form off a wave of low pressure off Haida Gwaii, track across the northern half of Vancouver Island, and slide into SE BC by tomorrow evening; quite an unusual track. We'll check the upper level support to see if this makes any sense or if it's plausible
- Typical orographic enhancement (enhanced precipitation due to terrain) will give higher amounts of rain to the windward slopes including the North Shore, West Vancouver. The mountains in Washington State will take the brunt of the precipitation; yes, another 100 mm of rain is heading their way
- Soils remain saturated and stressed, meaning a landslide risk for portions of the Pacific Northwest still exists; subsequently, trees may be susceptible to strong winds. Unlike the August wind storm, trees have lost the majority of their canopies, which will result in less tree damage.
Victoria is looking particularly windy tomorrow; SW winds today but when they veer westerly and a surge of strong winds barrels down Juan De Fuca -- This could prove to be problematic
For those people who aren't fan of graphs, who would prefer to see the winds on a map, I have a solution:
One of Canada's highest resolution weather models has some insight.
Maps below highlight the sustained winds and don't factor in the gusts (roughly 1.5X sustained)
1) The SW Threat: Timing (Mid-Morning 9-11 AM PST)
2) The W or WNW Threat (early afternoon-evening)
- Unfortunately, this wind direction is Vancouver's Achilles heel. This is the very weakness that proved to be evident during such storms like the Hanukkah Eve windstorm of 2006. That storm will remain in a class of its own, since it produced compact pressure gradients around the South Coast. At this point it's perfectly reasonable to expect some 80-90 km/h gusts, especially following the frontal passage.
- There's an off-chance of some 100 km/h gusts in some exposed regions, so please adhere to the weather warnings issued over the next 24 hours by Environment Canada
This low will be in the process of strengthening, somewhat atypical over that location, with likley only a handful of proxies over the past 10 years.
Most extra-tropical cyclones come to BC to dissipate, not strengthen, as they track towards southern Alberta. The cold air advection on the back of the cyclone will have no trouble creating steeper lapse rates allowing some potent, locally damaging gusts tomorrow afternoon after the passage of the trailing cold front (see above)
Models are adamant in detecting an increase in strength of this low pressure system over the rough terrain in Central BC, as well as across the Rocky Mountains. This is most likely due to the strong forcing aloft.
LOW LEVEL JET (850hPa)
UPPER LEVEL JET (250 hPa)