It’s that time of the year again and everyone is wondering what UK summer 2024 will bring. Will it be a washout, will it be hot and dry, or will it be an average UK Summer 2024?
This year we see a shifting ENSO from El Niño to La Niña. This process is currently underway and by May we should be in what we call a neutral phase. The current signals (55-60%) probability then show us heading into a negative phase for June – August, taking us into a La Niña summer.
What is ENSO?
El Niño and La Niña are the warm and cool phases of a recurring climate pattern across the tropical Pacific—the El Niño-Southern Oscillation, or “ENSO” for short. The pattern shifts back and forth irregularly every two to seven years, bringing predictable shifts in ocean surface temperature and disrupting the wind and rainfall patterns across the tropics. These changes have a cascade of global side effects.
The 3 different phases of ENSO
- El Niño: A warming of the ocean surface, or above-average sea surface temperatures (SST), in the central and eastern tropical Pacific Ocean. Over Indonesia, rainfall tends to become reduced while rainfall increases over the tropical Pacific Ocean. The low-level surface winds, which normally blow from east to west along the equator (“easterly winds”), instead weaken or, in some cases, start blowing the other direction (from west to east or “westerly winds”).
- La Niña: A cooling of the ocean surface, or below-average sea surface temperatures (SST), in the central and eastern tropical Pacific Ocean. Over Indonesia, rainfall tends to increase while rainfall decreases over the central tropical Pacific Ocean. The normal easterly winds along the equator become even stronger.
- Neutral: Neither El Niño or La Niña. Often tropical Pacific SSTs are generally close to average. However, there are some instances when the ocean can look like it is in an El Niño or La Niña state, but the atmosphere is not playing along (or vice versa).
La Niña 2020-2023
The UK last experienced a La Niña phase lasting from 2020-2023, known as a “triple-dip” before we transitioned out of La Niña and into an El Niño phase during the winter period.
In 2022, many locations across the United Kingdom exceeded temperatures of more than 40 degrees Celsius.
The village of Coningsby in eastern England reached 40.3 degrees Celsius on July 19, 2022. That same day, temperatures at Heathrow and St James’s Park in London, as well as Pitsford, Northamptonshire, also recorded a maximum temperature of over 40 degrees Celsius. 2022 was the UK’s hottest year on record.
La Niña & UK Summer 2024
If we do see a La Niña phase for summer 2024, then I would certainly expect an increase of hotter spells affecting the United Kingdom. Globally we could also be looking at one of the highest average increases in temperatures.
I expect UK summer 2024 to be a “decent” summer, as I’ve eluded to many times on social media over the last few months. However, I expect it to start off as a bit of a slow burner, more especially June, with July and August the 2 months I would expect the warmest weather.
I also believe we’ll see a significant increase in thundery plumes bringing plenty of thunderstorms up from the near continent this coming Summer!
It is also worth noting that during a La Niña phase in Autumn and winter (if we can extend the phase through to the winter period), it will likely increase blocking in the Atlantic, promoting colder and drier weather across the UK.
Though lets get through summer first!
I will update my preliminary thoughts to a full month by month forecast in May.
Lewis