Blogs

La Niña conditions persisted through February, but forecasters expect ENSO-neutral conditions to develop in the next month and persist through the Northern Hemisphere summer. ENSO La Niña is the cool phase of the El Niño/Southern Oscillation, or ENSO, a pattern of changes in the tropical Pacific Ocean and the atmospheric circulation over the tropical Pacific that persists for many months. La Niña’s signature is cooler-than-average surface water in the east-central tropical Pacific, stronger-than-average trade winds, more rain and clouds over Indonesia, and drier conditions over the central Pacific. El Niño is the opposite, with warmer-than-average surface water and weaker atmospheric c…   Read article

For much of this winter season, the polar vortex winds at 60°N have been racing around the stratospheric polar region. During February alone, these west-to-east winds were two times stronger than normal for that time of year. However, the latest forecasts suggest that the polar vortex is about to switch gears with a major vortex disruption to happen this weekend. Read on to find out why the polar vortex could be bottoming out early this season. Stratospheric pit stop At the time of writing this post, the polar stratospheric west-to-east winds are still speeding around the Arctic [footnote #1], but forecasts suggest they are not only going to come to a screeching halt by the weekend…   Read article

In the, roughly, 250 years of the ENSO Blog and our 3.4 million posts, we’ve discussed ad nauseum how complicated El Niño and La Niña are, and how difficult it is to forecast all of the ENSO nuances. Heck, I even wrote a three-part series 75 years ago that evaluated all of our seasonal forecasts (ok, it was 2014-2015 but it still feels that long ago). In a new paper, Azhar Ehsan, friend of the blog and a member of NOAA’s ENSO forecast team, and colleagues analyzed over 20 years’ worth of climate model forecasts of ENSO and found some interesting results. Why is this paper unique? Well, most seasonal forecasting evaluations focus on model hindcasts, which are forecasts run using past obser…   Read article

Because this is the Polar Vortex Blog, we would love to be able to tell you how the stratospheric polar vortex is doing super cool things that can explain how cold and snowy it’s been in many parts of the US this winter. But the truth is, in our opinion at least, while the stratosphere has been doing some interesting stretching and wobbling, there’s just not much evidence that this is really the main driver of our winter weather so far this year. Little typical communication between the stratosphere and troposphere As we have described before, one measure of “typical” downward coupling between the stratosphere and the troposphere are these plots showing the difference from average …   Read article

La Niña conditions continue, but forecasters estimate a 66% chance of a switch to neutral in March–May. This is looking like a weak and short La Niña. Also, while La Niña’s ocean conditions are currently weak, the atmospheric component is fairly strong. Today, I’ll cover current conditions, the forecast, and that mismatch between the ocean and atmosphere across the tropical Pacific Ocean. Live in the moment La Niña and its counterpart El Niño make up the El Niño/Southern Oscillation, or ENSO. La Niña’s characteristic cooler-than-average tropical Pacific surface water changes global atmospheric circulation in known ways, providing an early picture into potential upcoming temperature, ra…   Read article