El Niño’s role in the tropics and how it could impact weather patterns this winter season

While peak hurricane season is officially underway, what's happening across the global tropics looks completely out of balance. Looking into the Pacific, storm activity has been relentless.

We've seen multiple named storms tracking near or south of the Hawaiian Islands, and now most notably, Hurricane Lala, that's brought heavy tropical downpours, major flooding, dangerous surf, high winds, and unfortunately, loss of property.

There have already been 8 named storms in the East Pacific this season, with 6 being tropical storms and 2 being hurricanes, one of which was major.

Compare that to the North Atlantic, and it's a completely different story. There have only been 3 named storms, all of which were tropical storms. No hurricanes have been recorded so far for the Atlantic season.

This is all caused by what is known as El Niño. This is part of a climate pattern known as El Niño Southern Oscillation, or ENSO, in the Pacific that can impact weather across the globe. Specifically, in the El Niño phase, the trade winds that are usually blowing from the east to the west across the equator, moving warm water in the same direction with them, start to weaken. So, instead of cooler waters persisting near the Americas, warmer water returns as it is pushed back east toward the West Coast.

For the tropics, this presents lower levels of wind shear in the Pacific on average, while in the Atlantic, higher amounts of wind shear are present. Wind shear, simply put, is the change in wind speed and direction with height, and any sort of tropical system is very sensitive to this component. Higher amounts of wind shear mean there's a lower chance for disturbances to be able to organize into tropical storms or hurricanes.

This impact from El Niño can be seen in the numbers, as the Pacific has had the majority of this activity so far, where wind shear has been lower, while the Atlantic has been practically muted.

And it looks like this is set to continue to have impacts on the tropics throughout the rest of the season. Furthermore, it is forecasted to strengthen, hence why there is a 90% chance of reaching a very strong category. That would mean anomalies of +2 degrees Celsius or more heading into the fall and winter.

So, although this is a short-term impact on the tropics, long-term impacts could be seen across all of the United States.

More specifically, when El Niño is present during the winter season, a drier, warmer footprint is often observed across the Central and Northern United States, while a cooler, wetter pattern is typically seen across some of the Southern United States.

The difference with this setup, though, is the fact that because this El Niño cycle is expected to be so strong, the impacts it has on the overall weather pattern could be amplified. It will be important to monitor how this oscillation evolves as the next seasons approach to understand how weather might act in Central Missouri.