Well Van, what a difference a week makes, but thanks to modern day weather prediction we saw this change coming 7-10 days in advance. On a post back on October 9th, I discussed the potential for a fairly significant mid-week storm for the BC coast this week.
Some of our most advanced forecasting guidance caught on to this potential storm event back on the evening of October 8th, or over 192 hours in advance. Wind gusts near the headlands of Vancouver Island will gust over hurricane force Thursday (tomorrow) evening, especially over Brooks Peninsula. I'll often check Solander Island weather conditions during strong wind events, as these unmanned weather station often reports the strongest winds.
Don't worry, it's uninhabited.
Here is a look at some advanced ensemble forecasting output generated on October 8th showing the immense amount of time before tomorrow's storm.
Rain totals over the next 120 hours will be quite significant for the B.C coast, with communities such as Tofino and Bella Bella receiving in excess of 200 mm over the next 5 or 6 days, as shown below:
A stationary low is currently churning in the Gulf of Alaska, but the real weather story will be a strengthening front and developing low pressure system tracking in from the southwest bringing a skirt alert to most exposed coastal sections around southern British Columbia. Communities such as Comox and Campbell River should prepare for very isolated power outages Thursday evening as sustained winds will be between 30-40 knots over Georgia Strait with higher gusts possible (70-90 km/hr)
The developing low does an excellent job at drawing some subtropical moisture out of the lower latitudes, which is adding to the amount of rainfall forecasted for Tofino and other coastal locations. Precipitable Water may sound like a tricky foreign concept or just more weather jargon, but think of it like this: Imagine wringing out the clouds/atmosphere (like a towel). The amount of moisture that falls to the surface can be quantified as precipitable water. Typically regions with higher precipitable water values receive higher amounts of precipitation.
The BC Storm Surge Forecasting Program model indicates very modest increases in sea heights of about 30 cm for southern BC, fairly non-significant. Potent west coast lows can wreak havoc along portions of the coast especially when they hit during high tide. The March 12th, 2012 storm is a great example of a deep low pressure system hitting during high tide.
Thankfully this low pressure system is much weaker and will bring modest changes in sea heights to coastal regions of B.C
On the weekend, the remnant energy from Typhoon Vonfong will arrive on coastal B.C bringing another bout of gusty winds and heavy rains.
Sound like a broken record, yet?
Tropical Storm Ana (Yes, it's an A because we've already been through the alphabet once in the eastern Pacific) is forecasted to gradually strengthen and become a weak hurricane as it tracks closer to the Hawaiian Islands. Hurricane watches will be likely be issued later tonight or tomorrow for portions of Hawaii, and all islands will at least be directly affected by this storm.
Heavy, flooding rains will be the greatest threat, mainly because the system will be a slow mover. It will take in excess of 48 hours to clear the Hawaiian Island Chain.
As far as landfalls are concerned in Hawaii, they're truly few and far between. After doing some digging only Hurricanes Dot of 1959 and Iniki in 1992 have made direct landfalls. Current model consensus, including the National Hurricane Centre's preferred path indicates the storm is most likely to skirt just south of Hawaii. In fact, the Big Island has never had a hurricane make landfall See for yourself (Courtesy Meteorologist Mark Nelson):
How much rain is forecasted with this system?
After Ana weakens and begins to turn NW it will eventually become extra-tropical and re-intensify down the road. The latest GFS run (18Z on Wednesday) suggests it may attempt one of the greatest squeeze plays of all time, sneaking between 2 significant high pressure systems - Don't bet the farm, though.