October 25, 2010

What is That Little Girl Doing to the Weather?

This broad-strokes weather prediction for the upcoming winter by meteorologist Art Horn suggests that much of the northern United States and Canada (and China and Europe) are in for a cold winter.

This La Niña appears to be special, at least so far. It is well on its way to being the strongest of these events since the super La Nina of 1955-1956. During that powerful La Niña that lasted two years, the global average temperature fell nearly one degree Fahrenheit from 1953 to 1956.


For the last year, the world has been dealing with the warming effects of a strong El Niño. The El Niño [sic] warms the ocean waters of the tropical Pacific Ocean and in turn heats the atmosphere. Western Russia melted under a record heat wave this summer, after freezing from record cold last winter. Many parts of the southern United States had record heat this summer, but also shivered under record cold last winter. The persistence of the jetstream to blow in patterns that changed very little for long periods of time contributed to these extremes of temperature. This locked in jetstream wind pattern enhances temperature anomalies by restricting the exchange of air flow from one place to another. What would be hot becomes very hot, and what would be cold becomes very cold.

It is common for the jetstream to behave this way when the sun is in the solar minimum, such as it has been for the last three years. We are emerging from the minimum, but the sunspot numbers are continuing to be very low. Some solar experts say this next sunspot maximum may be one of the weakest in 200 years. As a result, the tendency for the jetstream to blow over parts of the Earth with little month-to-month variability may continue this year. That would result in continued extremes of temperature. The difference would be this time cold areas would be even colder due to the oncoming super La Nina and the falling global temperature.

He is suggesting much late-winter snow in the western United States, but I suspect that such snow will mainly be a Northern Rockies event. The NOAA Climate Prediction Center suggests a warmer, drier winter for the Southwest, so if that is true, we will be worrying about water, as usual.

All weather, like politics, is local.

1 comment:

Darrell said...

I daresay it'll depend on where the jet stream lies this winter.