How does La Nina influence extreme weather?

Question by Gas By Fannylight: How does La Nina influence extreme weather?
There is a massive cyclone about to hit the far north east coast of Australia, a region just north of where extensive flooding has occurred over the past two months. Cyclones are common in this area at this time of year, but this looks like it will be the worst one in a very long time. Is the current La Nina connected to these events and if so, how?

Best answer:

Answer by Microbots
Well, considering that Brazil has had major landslides and flood and the Northern Parts have had snow storms…

I think it’s just Climate Change (NOT GLOBAL WARMING) that is wrecking havoc. More intense weather patterns. e.g. Heat, Freeze, Water

Know better? Leave your own answer in the comments!

One Response to “How does La Nina influence extreme weather?”

  • UALog says:

    With an El Nino, you tend to get more stronger zonal flow with the upper jet (west to east).

    With a La Nina pattern, you tend to get more amplified flow pattern in the upper jet. In other words, the jet stream will tend to flow farther towards the polar region. As the jet stream flows over the top of the amplified ridge, it will tap into a much colder air mass than usual. Then the jet will head towards the tropics. When this flow reach the bottom of the amplified upper trough, it will be able to tap into a much warmer moist air before the jet will move towards the polar region once again.. So this process will result in a better chance that colder than normal air will meet up with warmer and very moist air. And you can guess what can happen what can happen when they meet up.

    One other item to note is that with a strongly amplified pattern, you would tend to have more blocking patterns. These blocking pattern will keep the general longwave troughs and ridges from shifting. Therefore, the pattern overall weather pattern wil be slow to change. Places that are in the wet like Australia and Brazil will see longer periods than usual periods of being in this wrest pattern. And in places where they have experience cold and snowy conditions will likely stay in this cold and snowy for a longer periods of time than usual.

    So with these larger ridges and troughs that is usually in place during a moderate to strong La Nina, you will get large areas of high pressure over the tropics in the southern hemisphere. And these areas will give ideal conditions for tropical Cyclones to develop and grow. And I think that is why you are seeing an extremely strong tropical cyclone .

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