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Summer 2023 second update

Latest forecast signals and trends

18/05/2023

By Brian Gaze

This is the second update looking at what the seasonal weather prediction models are suggesting for summer 2023 in the UK, and some of the background signals which be impactful. It is not a forecast - that will be issued in late May. 

For more background information see Summer 2023 first look.

Seasonal model overview

A range of seasonal models are available. However it is important to remember that their skill level (accuracy) for the UK is low.

The notable things at this stage are:

i) All of the models seem to favour above average temperatures when taken over the 3 month summer period as a whole

ii) As is usually the case the rain signal is less clear. Updates issued earlier in the spring weakly favoured a drier than average season. That signal appears to have faded and there are suggestions of it being wetter than the norm in the south 

Anomalies masking the outcome

The anomalies in the table may not be telling the complete story. They are for the meteorological summer as a whole and there is a chance that extreme swings are cancelling each other out to an extent. For example, in recent summers there have been several intense bursts of heat despite rather mixed conditions dominating. 

ENSO conditions

The state of the El Niño Southern Oscillation (ENSO) has significant impact on temperature and rainfall patterns around the globe. Nonetheless its link to the UK summer is thought to be weak.

Latest forecasts suggest a transition from La Nina ENSO-neutral is expected in the next couple of months, with a greater than 90% chance of El Niño persisting into the Northern Hemisphere winter.

Analysis suggests that El Niño slightly increases the chance of extreme conditions in UK summers but it isn't generally thought to be one of the dominant drivers of the weather.

Atlantic Hurricane season

Several forecasts for the 2023 hurricane season have been issued. They are suggesting above average levels of activity. See Summer 2023 first look for more information. 

The predictions possibly favour an increased chance of settled weather in the UK during the late summer.

Recent summers.

See Summer 2023 first look

Summary

1) Seasonal models continue to suggest above average temperatures taken over the June, July and August period as a whole. The earlier signal for rainfall amounts to be below the average appears to have faded in the latest updates. 

2) ENSO conditions are not expected to be a major factor, although the transition to El Niño conditions may slightly increase the risk of extreme weather.

3) The 2023 Atlantic Hurricane season forecasts are fairly neutral in terms of the UK summer.

4) Recent climatology favours above average temperatures and an increased chance of hot spells.

A warmer than average summer remains favoured. Lower confidence is attached to rainfall levels, but the possibility of wet and potentially thundery periods is elevated.

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