August 30, 2009

The Arctic Oscillation (AO) refers to an atmospheric circulation pattern over the mid-to-high latitudes of the Northern Hemisphere. The most obvious reflection of the phase of this oscillation is the north-to-south location of the storm-steering, mid-latitude jet stream.

August 30, 2009

Over the span of days or weeks, the strength of surface air pressure over the North Atlantic seesaws between Iceland and the Azores Islands. The shifting pressure reflects changes in atmospheric circulation that have a big impact on mid-latitude weather in the U.S. and Europe. 

February 24, 2016

Where are my El Niño impacts?!

November 12, 2015

Warmer-than-average waters in the tropical Pacific are expected to reach their peak soon. How has El Niño affected global weather so far this year?

June 25, 2015

...but it's still a seasonal forecaster's best friend.

March 9, 2015

Guest blogger Dennis Hartmann makes the case that warm waters in the western tropical Pacific—part of the North Pacific Mode climate pattern—are behind the weird U.S. winter weather of the past two seasons.

December 31, 2014

Several times a year the MJO contributes to various extreme events in the United States, including Arctic air outbreaks during winter across the central and eastern portions of the country.

December 19, 2014

A first look at how we evaluate seasonal forecasts. How well do our eyes do?

August 1, 2014

How do changes in the equatorial Pacific Ocean impact places much farther away? The answer for the tropics, at least, lies in changes to the equator-wide atmospheric circulation called the Walker Circulation. 

July 10, 2014

Sea surface temperatures are up. So why haven't forecasters declared El Niño conditions? 

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