6 comments on “Jetstreams over Australia.

  1. Late May2019
    the AAO has just had a strong dip in the negative direction. Past obs’ have shown the sub polar jet meanders with a strong negative trend.
    and the sub polar belt expands to the north.
    I have been surprised that the polar belt hasn’t contracted as far nth as l would have expected.
    Looking for a possible reason why.
    Here is a snap of the 200hpa , stratosphere jets.
    It is a 124hr forecast but shows a 4 nodal wave pattern for the sub polar jet.
    Nice and wavy as you would expect from the strong neg ‘ direction of the AAO
    but look at the sub tropical jet…… Very zonal (straight) and contracted south.
    I suspect the sub tropical jet is inhibiting the northern expansion of the sub polar jet
    This keeps the cold well south and prevents cut off lows upper troughs breaking off and migrating north

    What driver controls the sub tropical jet?

  2. There has been a period of time where sub polar jetstream has been well south in amplitude and weak in velocity. Lets say from at least June 2019 until July 2019
    See my stratospheric warming thread
    The Sub polar jet is described in literature as being stronger and further north in the winter bit this has not been the case so far. An anomaly
    The sub tropical jet has been very zonal,, straight for the same time.
    This pattern may be starting to change..21st July 2019
    noticing some undulations forming in the sub tropical jet .200hpa layer


    and signs of the sub polar jet streaks re emerging but still contracted well south

  3. 2nd August 2019
    Still noting that the polar vortex temp’ anomalies warm/cold poolzm10to 70hpa
    are still strong and the sub polar jet still responding with weak jets and lacking formation.
    The AAO going strongly neg’ this week appears not to change the strength of the sub polar jet but the forecast this week suggests the sub tropical jet will strengthen in speed and become more zonal

    https://weathercycles.files.wordpress.com/2019/08/2nd-auguzt-2819-jetztream.jpg?resize=438%2C438

  4. 31st Aug 2019
    A moderate meridonal (wavy)flow of both the polar and sub polar jet. But that isn’t going to help rain enhancement as a stalled weak high pressure area over most of Australia persists this week.

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