ENSO: This year and next year

There’s an interesting behaviour in ENSO activity when we have an El Nino present during the hurricane season. What we tend to find is that – more often than not (at least based on 1950 onwards) – the following summer tends to lean towards a La Nina. If we take a look at the years since 1950 where we’ve had a prominent El Nino (ENSO 3.4 index of >1) in the months August-October:

• 9 years (circled dots) out of 15 have ended up with a La Nina
• 5 years out of 15 have ended up Neutral (neither La Nina or El Nino)
• Only 1 year has had an El Nino in the following summer.

Given the typical 12-18 month fluctuation of ENSO, this probably shouldn’t be too much of a surprise (but this flip-flop behaviour is less evident when a La Nina is present in a summer and only 6 out of 29 years flip back to El Nino).

Naturally this should alert us to the potential for a La Nina next summer, which might elevate Atlantic Hurricane activity. In a follow-up post we’ll take a quick look at how the Atlantic might be shaping for next year’s hurricane season but at least from an ENSO standpoint, we need to be well aware of what might be down the line next summer.