DAMAGING WINDS LIKELY FOR PACIFIC NORTHWEST

After Thursday’s deadly wind event across the region, winter continues to create a late-season comeback in terms of the active pattern for the Pacific Northwest.

The National Weather Service has prudently issued High Wind warnings for all of Puget Sound and for coastal sections of Washington State as of 7 PM local time Saturday.

 

Above, there’s a spattering of warnings draped across the region including the aforementioned high wind warning for most coastal sections of the region.

The Warning Details

* TIMING...FROM MID SUNDAY AFTERNOON THROUGH SUNDAY EVENING.

* WINDS...SOUTH WINDS WILL RISE SUNDAY AFTERNOON WITH THE

  STRONGEST WINDS...20 TO 40 MPH WITH GUSTS TO 70 MPH...EXPECTED

  LATE SUNDAY AFTERNOON AND EVENING. WINDS WILL SHIFT TO WEST TO

  SOUTHWEST EARLY SUNDAY EVENING. WINDS WILL GRADUALLY DIMINISH

  THROUGH LATE SUNDAY EVENING.

 

* IMPACTS...WIDESPREAD POWER OUTAGES AND DOWNED TREES ARE LIKELY.

  SOME DAMAGE TO BUILDINGS IS POSSIBLE. REMEMBER THAT FALLING

  TREES AND TREE LIMBS CAN CAUSE SERIOUS INJURY OR DEATH.

 

For us, what’s the implication of some of those gusts crossing into Canada?

70 miles per is the equivalent of over 110 km/h...

You’ll often hear meteorologists on air discuss ‘track-dependency’ and how those details are ironed out closer to the weather event. But the weather event is tomorrow?

Yeah, but this is still in flux and the subtle nuances and exact track is still yet to be determined and will not be able to predict with perfect precision.

Where’s our low now?

Let’s turn to space.

The wave of low pressure is just east of the 140 W line. Over the next 24 hours the innocuous low pressure wave will rapidly deepen in atmospheric pressure as it curls towards the tip of Washington State.

With the track of the low forecast to cross so close to the Lower Mainland wind will come in several directions depending on what quadrant of the low pressure you find yourself in.

I think it’ll go something like this, but check-in tomorrow as this could change:

SE winds of varying intensity for the morning hours can be expected, and it’ll especially gusty near Victoria and the Gulf Islands and portions of East Vancouver Island (40-70 km/h).

By mid-afternoon the low reaches peak intensity SW of Victoria.

Now, crossing the NW tip of Washington State, SE winds will increase in intensity to warning criteria for the Gulf Islands and the Victoria area. At this point, sustained winds may approach 40 knots (70 km/h) especially by the water. Expect outages to occur at this point. Easterly winds are occurring across the lower mainland but not damaging (30-50 km/h).

Western Sections of the Lower Mainland have dealt with SE winds between 40-60 km/h and it’s been particularly gusty for Tsawwassen and UBC throughout the day.

Canadian Model Simulation: SE Wind Portion

Courtesy: WeatherBell

Courtesy: WeatherBell

Now, here’s where things get a little chaotic and complicated.

With the abrupt passage of the strong area of low pressure (980-985mb), winds will barrel down the Juan De Fuca strait out of the WSW at storm force (>50 knots) intensity early in the evening. Victoria is mildly protected, but southern sections of the Capital Regional District including Sooke, Metchosin, Colwood, Esquimalt, and Oak Bay are at the highest risk of outages.

Courtesy: WeatherBell

Courtesy: WeatherBell

As the low pressure system crosses the Lower Mainland winds will be swirling and damaging southerly winds are possible in the right quadrant of the low as it tracks inland (see above). Unfortunately, this would put the Fraser Valley under fire for a portion of the evening.

Isolated power outages are also possible further inland into parts of the Interior as the low crosses the southern portion of the province pre-dawn Monday.

The westerly surge will be abrupt and sudden for Vancouver in the evening; watch for tree damage around Stanley Park, UBC, and Delta & even parts of the North Shore as we head later into the evening.

SW Winds will ease overnight, but at this point thousands of power outages have likely occurred.

The ground is relatively saturated with the recent rains. Tidal surge is not anticipated to be as significant as last Thursday’s system.

Stay safe and send updates to #BCstorm and @weathernetwor

SIGNIFICANT BC STORM: March 9th-10th

It’s happening.

Intense pressure drops are already being recorded west of Oregon Wednesday morning. A classic wind storm is on the way for parts of British Columbia.

Take a look:

The purples off the western fringes of North America signify pressure drops in excess of 1mb/hr. This will continue to intensify throughout the afternoon.

Before I go any further, let’s briefly analyze the past before diving into the future.

The upper air pattern over the past 48 hours represents a major meridional pattern. A meridional jet stream often means active weather for the British Columbia coast.

The map below is very bizarre in terms of having such an anomalous  powerful upper low over Mexico. The NWS for Portland has recently confirmed that the jet streak (region of fast moving air) over parts of Portland was likely the strongest recorded for that particular station.

 


The calm region above the jet stream above is a NE Pacific trough which has been hampering the region over the past several days and will suppress the storm track towards Vancouver Island and Haida Gwaii as it slowly digs SE over the next 36 hours

How can a system go from a weak open wave of low pressure to a damaging low pressure system?

Picture this: an innocuous trough and bundle of upper level vorticity (lift and instability) is harmlessly drifting west.

This is the barrel of gas.

A super-charged jet stream can be described as a lit match just waiting to fuel any disturbance that interacts with the powerful upper level winds; consequently, providing the divergence aloft and necessary ingredients  to create a powerful low pressure system.

Boom. Explosive cyclogenesis is likely.

Below, a map early Wednesday morning showing the main parent low in the Gulf of Alaska and our benign open wave of low pressure  

To this roughly 24 hours later:

 

A formidable low west of Solander Island off the NW tip of Vancouver Island early Thursday AM—perhaps approaching 960 mb of atmospheric pressure by early tomorrow AM. Climatology says lows really can’t get fall below 960 mb in this part of the world:

Map above shows the approximate return interval for a storm of this magnitude for Southern B.C with about a 1 in 10 year occurrence for NW tip of the Island, but more frequent lower pressures for the Lower Mainland.

TIMING: Use The Weather Network app to look at hourly forecasts in terms of precipitation intensity and wind gusts but a general foreseeable weather threats go something like this:

WINDS

Strong SE winds pick up this afternoon and persist into the evening. Highlighted regions (with the exclamation mark) below where gusts 70-90 km/h may be possible.

A wider crop encompassing all of Vancouver Island lies below.

Comox & Campbell River, this particular model showing SUSTAINED winds of 45 knots, so local gusts to hurricane force through Thursday AM cannot be ruled out especially for this region, but models have some disagreement here.

Notice the storm force region NW of Johnstone Strait?

It’s the only red on the map below. I’ll give a friendly heads up to Port Hardy and Port McNeill to prepare for outages. Tofino has a high confidence to see very strong winds, but Port Alberni is a little more complex and complicated.

By 6-8 am local time the strong associated cold/occluded front races ashore—this puts the Lower Mainland at greatest risk for power outages early tomorrow morning. The part of the storm we have to pay particular close attention to houses the highest pressure gradients—or the back-bent occlusion/ trough that wraps itself around the low pressure system. In rare cases, this can form the ‘poisonous tail of the back-bent occlusion,’ or also simply referred to as a sting jet.

Exposed coastal sections look for winds 60-80 km/h through early tomorrow morning, with some gusts locally higher. Gusts inland may exceed 70+ km/h even into parts of the Fraser Valley such as Abbotsford and Metro Vancouver as well. Our Canadian model below highlights strong southerly winds sustained at 40+ km/h for much of the Lower Mainland:

RAIN

·        Heaviest rain includes the mountainous regions of Vancouver Island and Coastal Mountains including North Shore and Squamish—watch the Comox Valley for localized flooding with high tide tomorrow AM. A boil water advisory is in effect for this region due to recent heavy rainfall and increased levels of turbidity (cloudiness of water).

·        24 hour rain totals for some parts of Vancouver Island will approach 100 mm (see below)

 

·        Yes, this is an atmospheric river stemming from Hawaii, so a Pineapple Express term could be used without hesitation. The yellow area below signals where the moisture river is originating from.

 

COASTAL FLOODING/HIGH SURF

·        BC Storm Surge Forecast Centre shows potential for localized flooding in the yellow regions as the vigorous low pressure system is coinciding with an early Thursday AM high tide at roughly 6am local time. The expected surge plus high tide to be about 50 cm below some extremes recorded, but high enough to toss driftwood into local parks and highways immediately adjacent to Georgia Strait. With that said, drive with caution early tomorrow morning.


MOUNTAIN SNOW

·        Fresh pow alert. We’ll see a spike in freezing levels late this afternoon through pre-dawn Thursday, but primarily a snow event for most ski hills.

·        Look, you won’t believe these 24 snow totals:

 

 

Mt. Washington: 50-80 cm above 1200 metres. Offchance, some highest slopes record 100 cm with this single event on Vancouver Island

Whister: 30-50 cm above 1600 metres

Grouse/Cypress/Seymour: lower snow totals with rain mixing in Thursday: Locally, up to 10-20 cm possible at highest elevations, but rain will hamper totals

Live Blog will be active through tomorrow for BC as this is anticipated to be one of the more impactful winter storms this season.

Stay safe and send photos, videos and tag @weathernetwork and #BCstorm in your tweets.