autumn weather 2012, fall El Nino, Arctic Oscillation, hot Atlantic, storms | The Old Farmer's Almanac

The Fight for Fall

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The US and Canada are in for a real battle this autumn.

Think of it as a battle of the heavyweights. In the north corner of the ring, it’s the Arctic Oscillation. Its punishing blows can knock you out cold. In the west corner lurks the El Niño. Don’t let the name, which means “little boy”, fool you. He can come roaring out with a cold punch to the South and hot and heavy in the North.

The El Niño is weak but may pack a warm punch later. SOURCE: NASA Earth Observatory

Oh, and just to make the battle even more interesting – in the east corner is the hot Atlantic. This battler has been the past champion, dominating the ring, baking the US with scorching hot temperatures. The champion is not going to give up easily.

On Saturday, September 22, the opening bell rang and autumn starts. The battle to see which forces shape this fall’s weather will begin. In short, the hot dry summer is finally dragging to a close and a stormier fall is about to begin.

Let’s pretend that there is a ringside announcer. He is sizing up Round 1 – the opening week of autumn.

  • The Champion, the hot Atlantic still controls the ring. The US is still warm and dry, but it looks like he is getting tired. Some cooler temperatures are entering the South.
  • The cold Arctic Oscillation is entering the ring. Those winds that trap polar air north are weakening and some cooler air is surging into the Great Lakes and the Midwest. Already we are seeing snowflakes over the Great Lakes. The AO won’t do much this round, but he is shaping up to be a real contender. This winter will be colder than last winter.

Last year had a warm positive Arctic Oscillation, but this year a negative AO may bring in the cold. SOURCE: NOAA

  • The El Niño has not officially begun. (Scientists wait a number of weeks for temperatures in the tropical Pacific to remain warmer than 0.9˚F before they officially declare an El Niño has begun.) We are seeing only a few small blows from the “little boy”. He’s bringing some rain to Texas and the Southern Plains. Expect him to start growing stronger and peaking in November and December.

Expect an epic battle and a very messy fall. The warm waters of the two oceans will clash with cold winds from the north. It’s hard to know which weather factor will triumph. However, if the US gets some rain and cooler temperatures, we will all be the winners.