Nuri's Fury: A Ticking Time Bomb

After the drenching rains of October, some relative tranquility is just around the corner, Van. But, first a recap of a significant rain event earlier this week. A subtropical plume of moisture was aimed at the South Coast like a fire hose; consequently, flooding became an issue by Monday evening.

But was this event predictable? During my briefing shift Thursday evening, I encouraged Kim Macdonald to send a tweet. With some hesitation, Kim sent out this: 

Van, this is exciting, as synoptic scale weather events are beginning to become predictable 5-7 days in advance with long range pattern recognition and temperature trends predictable up to two weeks.

Take a look below at the 24 hour rainfall prediction by the WRF-GFS for 24 hour rainfall totals. Any shaded area in black could realistically expect localized flooding as those amounts are in excess of 60 mm. 

Predicted precipitation amounts by the UW-GFS (4 am Monday to 4 am-Tuesday). Note the Olympic Rain shadow in the upper left hand corner, and heavier rains over the Olympic mountains. These fluctuations are primarily driven by topography 

Predicted precipitation amounts by the UW-GFS (4 am Monday to 4 am-Tuesday). Note the Olympic Rain shadow in the upper left hand corner, and heavier rains over the Olympic mountains. These fluctuations are primarily driven by topography 

Recently, the coach of the New England Patroits, Bill Belichick made some controversial statements about weather forecast accuracy.

But were his comments merited?

Operational forecast skill has seen significant improvement over the past several decades.

Folks, these aren't your grandmother's forecasts from the 1960's. In fact, a 3 day forecast in 2014 is about as accurate as a 1 day forecast from the late early 1980's.

Comparison of 36 hour forecast accuracy (blue) and 72 hour forecast accuracy (red). Steady improvements mainly due to faster processing power and advancements in computer technology

Comparison of 36 hour forecast accuracy (blue) and 72 hour forecast accuracy (red). Steady improvements mainly due to faster processing power and advancements in computer technology

Nuri's Fury

  • Super Typhoon Nuri will undergo a slow weakening process and a transition to an extra-tropical cyclone is a lock as the system begins to recurve towards the Bering Sea
  • The atmospheric dynamics will be extremely favourable for the system to rapidly intensify and 'bomb out' as Nuri enters the right rear entrance of an extremely powerful jet streak
Ex-Nuri may deepen to as low as 920 mb as it reaches the lowest pressure seen in the Bering Sea for some years, but will it be record-breaking? 

Ex-Nuri may deepen to as low as 920 mb as it reaches the lowest pressure seen in the Bering Sea for some years, but will it be record-breaking? 

  • For simplicity, think of a jet streak as jet fuel for a weather system, or a region that promotes the development of cyclogenesis (the birth of a low pressure system)
    • the jet streak modeled below is an incredible 215 knots or 400 km/hr
      • Don't worry, you'd likely to be able to stand up during those winds as the air is very thin at those altitudes
    • Jet streaks also mould the troughs and ridges in the atmosphere and help shape the Rossby Waves that circle the globe, and can often amplify a jet stream to become more meriodional
      • In 6-10 days, cooler air will filter into Eastern Canada, thanks in part by the influence of typhoon Nuri and the associated powerful jet streak that will amplify the downstream pattern
Jet streaks above 200-210 knots are relatively rare, and Typhoon Nuri couldn't enter a more favourable environment for rapid intensification 

Jet streaks above 200-210 knots are relatively rare, and Typhoon Nuri couldn't enter a more favourable environment for rapid intensification 

Ear-Popping Pressure Drop

Often when meteorologists measure storms a 1 bergeron drop in pressure (24mb) in 24 hours indicates a very significant intensification process. Ex-Nuri is about to attempt 2X this. 

  • Typhoon Nuri is forecasted to undergo an astounding 57 mb pressure drop in 24 short hours or well over 2 bergerons

Gigantic Waves

The American Wave model (WW3) has consistently predicted wave heights in excess of 50 feet (or 15 metres) over the past several runs. That's significant wave height or roughly the 1/3 largest waves one might encounter at sea. It's entirely possibly that one may encounter a wave roughly 2x the significant wave height, or in this case over 100 feet or 30 metres

The American Wave model (WW3) has consistently predicted wave heights in excess of 50 feet (or 15 metres) over the past several runs. That's significant wave height or roughly the 1/3 largest waves one might encounter at sea. It's entirely possibly that one may encounter a wave roughly 2x the significant wave height, or in this case over 100 feet or 30 metres

Back At Home, Van

As a small child growing up on Vancouver Island, my family and I became accustomed to the vile southeast winds that could accompany a juicy, Pacific Low. It's one of the main reasons I fell in love with weather

We called them South'easters. 

South'easter

noun

1.

wind or storm from the southeast.

So, lets get some West Coast pride, B.C. and name these storms. The East
Coast takes immense pride in their prolific Nor'easter's, so it's time to show them the power of a real storm (shhh, don't tell them I said that).

Long Ranger

  • A couple more *garden variety lows will impact the South Coast over the next several days, with stronger winds located around Haida Gwaii (Wind warnings in effect)
  • Things look to calm down as a significant upper level ridge develops over B.C, bringing above seasonal temperatures, although it's likely systems will still under cut the ridge during the medium range.
  • Depending on the strength of the offshore flow, this may be a recipe for an abundance of low cloud/fog, and stratus. Fogcouver, anyone?

*As I wrote garden variety I had a quick look at some newer model runs including the NAM-MM5, and it's especially bullish on bringing strong westerly winds to #YVR tomorrow afternoon...I'll keep a close eye on this. 

Let's hope this is an outlier because with the soils being as saturated as they are and winds coming from an atypical direction, there's the possibility this could be sufficient to cause localized power cuts. 

Model simulation for Thursday afternoon, showing gusty westerly winds developing as low crosses Vancouver Island

Model simulation for Thursday afternoon, showing gusty westerly winds developing as low crosses Vancouver Island

The ensemble forecasts are mostly agreeing that temperatures in B.C will flourish, while the east will Freeze. Drawn below is an exaggerated jet stream (yellow):

Very high probability B.C will experience above seasonal temperatures, along with portions of the Maritimes. Ontario, not so much...

Very high probability B.C will experience above seasonal temperatures, along with portions of the Maritimes. Ontario, not so much...

Van, I give you permission to send the photo below to all your friends in the east.

The latest and greatest update to the American weather model indicates temperatures may be in excess of 10-15C below normal. for portions of North America. Snowpack is also well above normal for some portions of the North, and when this pattern develops, a semi-permanent high pressure system over Greenland will continue to advect cool air into Eastern Canada. 

Welcome to Fall, Canada.