Jet stream giveth and taketh away

  • Vancouver Island Inland Sections Forecast - No watches or warnings in effect.

    Forecast Issued 4:00 PM PDT Saturday 21 July 2018 - Saturday night: Clear. Low 11. Sunday: Sunny. High 32. Humidex 34. UV index 8 or very high. Sunday night: Clear. Low 13. Monday: Sunny. High 34. Monday night: Clear. Low 14. Tuesday: Sunny. High 33. Tuesday night: Clear. Low 14. Wednesday: Sunny. High 32. Wednesday night: Clear. Low 14. Thursday: Sunny. High 28. Thursday night: Clear. Low 14. Friday: Sunny. High 27.

  • Current Conditions
    Temperature
    25.0° C
    -0.7 ° C/hr
    Barometer
    102.01 kPa
    0.0
    Wind
    SSW 16.8 km/h
    gusting 27.4 km/h
    Humidity
    45 %
    Rain Rate
    0.0 mm/hr
    Wind Chill
    25.0° C
    Heat Index
    25.0° C
    Dewpoint
    12.2° C
    UV
    1.2
    Solar
    283 W/m2
    Last Updated: 18:10:00 PDT
    Click to Refresh or See All Conditions
  • Day Almanac
    Day's Rain
    0.0 mm
    Day ET
    0.0 mm mm
    Rain Storm
    NotAvailable mm
    Civil Rise
    04:56
    Moon Phase
    First quarter (72% full)
    Civil Set
    21:54
    Day Length
    13:25:39
    Day High
    27.3° C @ 15:19 Tdy.
    Day Low
    12.3° C @ 06:21 Tdy.
    Day High Rain Rate
    0.0mm/hr00:00
    Day High Barometer
    102.13 kPa @ 08:59 Tdy.
    Day Low Barometer
    101.95 kPa @ 03:14 Tdy.
    Day Low Windchill
    12.3° C @ 06:21 Tdy.
    Day High Heat Index
    27.3° C @ 15:19 Tdy.
    Day High Wind Gust
    S 16.8km/h @ 18:10 Tdy.
    Day High Solar Radiation
    1062W/m2 @ 13:29 Tdy.
    Day High UV Index
    7.1 @ 13:26 Tdy.

It’s the height of the cold snap back East. I saw wind chills of -60F reported in the Midwest. New York City has set a new record low of -5F (-20C) for this day. It’s cold and here’s why.

The news has clung on to the words “Polar Vortex”. I think it’s kind of a silly term, not really based on anything other than it sounds great… Invoking memories of what of my favourite weather disaster movies, The Day After Tomorrow.

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But thankfully it’s not quite to the freeze-the-Statue-of-Liberty-solid level of seriousness.
The polar vortex isn’t some evil weather system hell bent on freezing Toronto solid… It’s more accurately, I think, really the jetstream itself as it is the jetstream that forms the boundary between warm southern air and cold northern air.

Right now, as it has been many times over the past few months, the jet is seriously kinked, and particularly over North America. It rises to the West of us, forming a big ridge that has kept us dry and reaching into Alaska, pulling Arctic air all the way from Siberia, over the Pole, and down deep into North America. Before it rises north again, sending storms to the UK and Europe and record warmth to the newly crowned World Junior Champions Finland.

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This will only last a little longer though. As is in evidence with our rain today, the jet is starting to shift East, pulling warmer and wetter air off the Pacific and finally breaking our drought.

You can see the warm patch of ocean off our coast here:

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That warm patch is both a cause and a symptom of our dry spell and now our warmth as the unusually warm area has been created by the strong ridge of high pressure that has dominated over the pacific in the past few weeks. And now it helps to reinforce and return to those conditions.

For now though, it is delivering relief. That relief will peak on the weekend when the jet nearly straightens completely and we get a big bout of rain and possibly wind.

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Those winds will travel across the continent and break the cold snap in the East.

But the relief may be short lived. It’s a very long way out, but the models are predicting a return to a big ridge here at home and a big trough in the East. Dry for us and cold for them again.

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It looks strong. One thing is for sure. We are a slave to the jetstream. And it is making its power over us felt this winter.