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No More El Yawño
February 9, 1998
By Mark Hoover
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I'm sitting in front of a deck of cards, but I'm not the dealer. I have to play what I'm dealt, and it's been a while since I've seen a face card. Each day, I wonder if I'll be eating dinner at home, or three time zones from here. I got both the jokers in the deck this weekend. Our original planned flight into the jetstream from Alaska is out, and now the flight from Portland has been cancelled too, thanks to the vagaries of El Niño. Researchers are scrambling their schedules to keep up with the suddenly wild storm season on the west coast, and redeploying their instruments and planes on very short notice. (Very few of them seem to notice how much this inconveniences cyber-correspondents.)

There's a lesson here. In the midlatitudes, the only predictable aspect of an El Niño winter is that day-to-day, it can be very unpredictable. The recent "regime change" of the southern jetstream - its change of location - is the main reason storms have been punishing California. In weather systems, states can be persistent, but when they change, they can change suddenly and dramatically. Forecasters like to use "persistence" as a tool of prediction. The idea is that on a gross scale, weather tends to be the same for long periods. If there's drought today, there'll probably be more drought tomorrow. But forecasters drop persistence like a wormy apple when they recognize a regime change coming on, knowing that a whole new set of conditions is now likely to establish its own persistence.

Californians joked for two months this winter about "El Yawño," the threat that never materialized...until last week. The latest forecast says another bad storm will hit Wednesday. Nobody's joking now. Suddenly and dramatically, the jetstream has taken up its new residence, and odds are that there are more storms in store for the west coast. South of the equator, you can see the same thing happening in Peru.

There may be a flip side to all this. The NORPEX researchers are going to extend the jetstream investigations they've been conducting, but they're going to concentrate their resources in Hawaii. We may yet get to take that jetstream flight, at the end of this month, after we return from the tropics. But it won't be from'll be from Honolulu. As soon as I see the next card, I'll show it to you. It'll either be Aloha...or ha-ha.

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