Blogs

El Niño—the warm phase of ENSO, which is short for El Niño-Southern Oscillation—is still hanging on in the tropical Pacific, but signs are pointing to a quick transition to neutral conditions by the April–June period. There’s a 62% chance of La Niña getting the golden ticket by June–August. Stay tuned, because La Niña affects global climate patterns, including the Atlantic hurricane season and North American winter. Red carpet The sea surface temperature in the Niño-3.4 region of the tropical Pacific (our primary ENSO-monitoring region) was 1.6 °C (2.9 °F) above the long-term average (long-term = 1991–2020) in February, according to our most reliable dataset, ERSSTv5. This is still com…   Read article

We’ve talked about how the reversal of the west-to-east winds at 60 degrees North during a major sudden stratospheric warming sets up a feedback between large atmospheric waves and the winds, and how this results in the stratospheric wind changes being communicated down into the troposphere. But what does this mean for weather patterns down here after the polar vortex is disrupted? By taking the average of the surface temperature and atmospheric thickness for the 30 days after all the major sudden stratospheric warmings in the observational record, we can average out day-to-day variations in the weather and see more clearly what weather patterns related to major warmings look like. …   Read article

“It could be … it might be … it…!” Wait, is it? A homerun for the stratosphere? After a brief respite, the stratospheric polar vortex is expected to weaken again with potentially another major sudden stratospheric warming forecast to occur in the next week. But didn’t we just have a sudden stratospheric warming event?? Read on to find out what’s in the stratosphere’s line-up and how this double header fits in with typical stratosphere behavior. Loading the atmospheric bases  The atmospheric players have been positioning themselves again for another polar vortex disruption. First up, the current stratospheric conditions are primed for tropospheric wave activity because the polar vo…   Read article

On a brisk early February morning, all of us El Niño-Southern Oscillation (ENSO) forecasters emerged from our burrows and saw our shadows. That can mean only one thing: conditions are favorable for the development of La Niña within the next six months. Yes, the February ENSO Outlook officially announces that we are in a La Niña Watch, even while, at the current moment, the Pacific Ocean remains in an El Niño (this is simultaneous to the ongoing El Niño Advisory—here is an explainer to help sort it out). The outlook gives a 79% chance that El Niño will transition to ENSO-Neutral by the April–June period, and then a 55% chance the Pacific transitions into La Niña in June–August. Confused? I’ll…   Read article

With the occurrence of a major disruption to the polar vortex (or sudden stratospheric warming) on January 16 2023 [footnote 1], one of the first questions everyone asks is “How can a disruption way up in the Arctic stratosphere affect the winds and weather far below in the troposphere?”. A stratospheric traffic accident Scientists have a pretty good understanding of how a reversal of the winds ~19 miles above the Arctic influences the winds at lower altitudes, at least down to about the tropopause (the altitude where the troposphere transitions to the stratosphere, ~6-8 miles above earth’s surface at the poles). As we mentioned in this post, huge planetary-scale waves in the atmospher…   Read article