HURRICANE WEEK: Could ENSO Explain the rest of the 2022 Hurricane Season?


Climatology is a vital resource to meteorologists. It provides us a basis of what can be expected based on trends through the past decades. It is how we know what the average temperature is each day, it explains how changes in our atmosphere result in weather changes, it also can hold a key to forecasting hurricane season.Climate teleconnections are large scale, recurring and persistent atmospheric patterns that have been linked to variability in weather patterns. 

Typical influence of El Niño on Pacific and Atlantic seasonal hurricane activity. Map by NOAA, based on originals by Gerry Bell.

One of the most well known is the El Niño-Southern Oscillation (ENSO), also known as El Niño and La Niña. This climate teleconnection is a key part in forecasting hurricane seasons. Typically, during an El Niño year, the shear in the atmosphere increases over the Atlantic Basin leading to lower chances for tropical development and often below average seasons.

Typical influence of El Niño on Pacific and Atlantic seasonal hurricane activity. Map by NOAA, based on originals by Gerry Bell.

La Niña on the other hand reduces that shear and leads to above-average seasons in the Atlantic Basin. 

National Centers for Environmental Information

ENSO is measured in multiple regions in the Pacific. In these regions we monitor the departure from normal sea-surface temperatures. Typically if the water temperature is -0.05°C to -0.9°C below average, it is classified as a weak La Niña, -1.0°C to -1.4°C is moderate La Niña, and anything below -1.5°C is a strong one. On the other hand, +0.5°C to +0.9°C is a weak El Niño, +1.0°C to 1.4°C is moderate, and 1.5°C is a strong El Niño. 

Figure provided by the International Research Institute (IRI) for Climate and Society (updated 19 July 2022)

In 2022, we are experiencing a weak to moderate La Niña. Sea-surface temperatures in Nino 3.4 region remain between -0.9°c and -1.1°C. Recently another upwelling event occurred leading to another push of cooler water leading to the surface. This is expected to keep us in a weak to moderate La Niña through the end of the year. However, models try to weaken the phase closer towards neutral by December-February. 

If we take a look back in recorded history at similar setups, several years show a close trend. The years of 1956, 1964, 1971, and 2000 all had a similar phase trend. Especially the years 1964 and 1971. Both of these years were also similar in that the season really did not pick up until late August into September. Though these trends may not play out and we may see something completely different, they give us the best indication of what the rest of the season could bring us. At this rate, if the season plays out like these, we can expect a closer to average season. As we approach the month of September, we have to keep an extra close eye because we know from climatology that this is the time of the year that the season amplifies. 


Tags: El NinoENSOhurricane seasonHurricane Week


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