Wed. Aug 22nd, 2018

Weather Forecast Post – Cool and possible showers coming Saturday?

  • Vancouver Island Inland Sections Forecast - SPECIAL AIR QUALITY STATEMENT IN EFFECT
    Issued: 9:31 PM PDT Tuesday 21 August 2018

    Forecast Issued 4:00 PM PDT Tuesday 21 August 2018 - Tuesday night: Partly cloudy. Widespread smoke. Low 12. Wednesday: A mix of sun and cloud. Widespread smoke becoming local smoke near noon. High 31. Humidex 34. UV index 7 or high. Wednesday night: Partly cloudy. Local smoke. Low 12. Thursday: Cloudy with 30 percent chance of showers. High 23. Thursday night: Cloudy periods with 30 percent chance of showers. Low 12. Friday: A mix of sun and cloud. High 22. Friday night: Cloudy with 60 percent chance of showers. Low 12. Saturday: Cloudy with 60 percent chance of showers. High 20. Saturday night: Cloudy with 30 percent chance of showers. Low 13. Sunday: Cloudy with 30 percent chance of showers. High 18. Sunday night: Cloudy with 30 percent chance of showers. Low 11. Monday: A mix of sun and cloud. High 20.

  • Current Conditions
    Temperature
    18.4° C
    -1.4 ° C/hr
    Barometer
    101.45 kPa
    0.0
    Wind
    N/A 0.0 km/h
    gusting 0.0 km/h
    Humidity
    62 %
    Rain Rate
    0.0 mm/hr
    Wind Chill
    18.4° C
    Heat Index
    18.4° C
    Dewpoint
    11.0° C
    UV
    0.0
    Solar
    0 W/m2
    Last Updated: 0:10:00 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
    05:45
    Moon Phase
    Waxing gibbous (85% full)
    Civil Set
    20:56
    Day Length
    13:22:01
    Day High
    18.8° C @ 00:00 Tdy.
    Day Low
    18.4° C @ 00:09 Tdy.
    Day High Rain Rate
    0.0mm/hr00:00
    Day High Barometer
    101.45 kPa @ 00:00 Tdy.
    Day Low Barometer
    101.45 kPa @ 00:00 Tdy.
    Day Low Windchill
    18.4° C @ 00:09 Tdy.
    Day High Heat Index
    18.8° C @ 00:00 Tdy.
    Day High Wind Gust
    S 0.0km/h @ 00:05 Tdy.
    Day High Solar Radiation
    0W/m2 @ 00:00 Tdy.
    Day High UV Index
    0.0 @ 00:00 Tdy.

Before doing the fire post, I wanted to get back to a regular weather forecast post.  There is a definite shift in the weather coming that could have important implications for our fire.

Smoke Keeps Heat at Bay Again

Where it not for the smoke, we would have had continued on our >30º C weather all weekend and through today and tomorrow.  Here is what the forecast says we should get to for a high this afternoon.

wa_tsfc.24.0000-6

The Valley is into the 90ºF/33ºC range.  However, we will *not* get there with this smoke.  Our high will likely be in the 25-28ºC.

Assuming the smoke continues to affect us, we can expect the same situation  on Thursday.

Friday pattern shift brings wind first, then moisture.

The jet stream is finally changing.  Here it is this morning looking all bent out of shape and split over and above but mainly  looping high to the north allowing us to heat right up. (Anywhere there isn’t smoke)

300j.15.0000

Now here it is on Friday evening.

300j.75.0000-2Notice it is strengthening considerably (thicker and with deeper colours) and it is possibly diving to the south of us.  This has the ability to drive cooler air from the north our way and drive a few more disturbances as well.

There is one small issue with this pattern change for our fire, and that is wind.

wssfc.75.0000

This will be of concern to the firefighters of course.

By Saturday though, the jet stream has bent again, directing a small flow north, and that means moisture.

300j.93.0000

 

Look what happens to our precipitation picture that day:

wa_pcp24.96.0000Rain across the south Island!  Not much, 8mm in this image between Friday and Saturday 5PM.  But it is a lot better than nothing.  And temperatures will only reach into the low 20s.  With smoke, it might again be less than that.

We get maybe a tiny bit, 2mm more Saturday through Sunday evening.  Not enough to make any difference.

wa_pcp24.120.0000-3

It then dries out again and will become unstable as the Jetstream doesn’t really seem to know what to do.

300j.141.0000Notice there is still a split happening with bits going into north Alberta and others going into eastern Washington and Idaho.    Whether the jet decides to go above or below us will be the difference between heat and cool.  And if it decides to blast right overtop, we will probably end up with rain.  At this point it is hard to say what will happen.  And really that is a good thing because for weeks it has been in a huge and stationary loop overtop of us which is why we have had such persistent hot weather.

If you want to know what might be causing this unusual pattern and the drought conditions it has resulted in, check out this article from Rutgers University on the Jet Stream, Arctic heat, and climate change. “More evidence for link between wavy jet stream and extreme weather, Rutgers study finds”

Numerical models confirm uncertainty.

Looking at the super-long range forecast, we can clearly see the uncertainty in the models as to whether we go back to a regime of high pressure, high jet stream, high temperature, or low, low, low.

Screen Shot 2015-07-08 at 7.46.49 AM

This is the thickness which is a good analog for whether the jet stream is above or below us.  Notice right now (on the left) it is quite high and it gradually declines through Friday and Saturday.

We then start to see the models and uncertainties come in.  There is pretty good agreement through about Tuesday next week but by Wednesday notice the dark and light shades of purple start to stretch.

At this point from that chart I’d line toward going back to a warm and dry regime by Friday/Saturday next week but we will see.  That is a long way out.