ENSO climate transition

[Proud90sKid]

It is that time of the natural ENSO(El Nino Southern Oscillation) cycle again, which repeats every 2-7 years (but generally 3-5). And it is that time of year again (late boreal spring) when ENSO typically switches phases. Cooler than normal water is upwelling along the equatorial east Pacific and it is highly likely that in the next few weeks, either American(NWS/NOAA) or Australian meteorological agencies(BoM) will declare El Nino's official end. Likely both. Cooler than normal water is nearly certain to continue to upwell and will eventually result in stronger than normal equatorial trade winds, massive cooling of the waters off western South America, and a large westward shift in thunderstorm activity in the tropical Pacific, likely resulting in a La Nina(anti-El Nino pattern) forming by the end of the summer. ENSO is the most robust climate oscillation on Earth (within human life timescales) besides the annual seasons. Each phase generally lasts a year or so, with El Nino persisting for about a year, neutral often taking a year, and La Nina often taking 2 years. The mean period of the oscillation is therefore 4 years. No phase of ENSO can be called "normal" because there are more years with either El Nino or La Nina than there are "neutral" years due to it being an oscillation.

El Nino warms global temperatures after it peaks, including the tropical Atlantic(which is very anomalously warm at this time). It does this by discharging warm water hidden below the surface of the west Pacific and spreading it over a larger surface area and additionally by convectively warming the atmosphere. Meanwhile La Nina reduces vertical wind shear over the Atlantic and suppresses north Pacific tropical cyclone activity. Due to these factors, I expect a stronger than average hurricane season in the Atlantic. First year La Ninas often, but not always bring hyperactive tropical cyclone activity into the Atlantic basin. Hyperactive means both a large quantity and large intensity of storms.Second year La Ninas have the reduced wind shear but a cooler Atlantic and typically bring a lot of quantity but lack of quality so to speak. This year looks like it is going to be hyperactive given the warmth of the Atlantic and the changes in ENSO. Also, with the 2023 El Nino being pretty significantly strong and with global warming, I expect 2024 to be the warmest year on record globally.

[Ennui.]

This is really interesting information to have so thank you for sharing! Not looking forward to it being so warm though.

[Dawn.]

That really was interesting to read!