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Summer 2020 weather

Forecast indicators


23/04/2018

What does summer 2020 have in store? The TWO summer forecast will be issued in late May but before then we will issue two updates taking a look at what the latest data is suggesting. 

By by simonwakefield [CC BY 2.0], via Wikimedia Commons

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.

Model Temperature Rain
GloSea (UKM) Close to or below average Near normal or above average
ECM Slightly above average in the south - slightly below in the north Below average
Meteo France No signal No signal
DWD Above average Slightly below average
CS3 Slightly above average Slightly below average weakly favoured
Beijing Climate Center Above average Below average
CanSIPS Slightly above average Slightly below average
CFSv2 Above average Close to average
Table 1: Forecast temperature and precipitation anomalies, June, July and August

 

The notable things at this stage are:

i) The output is mixed but most models favour close to or above average temperatures when taken over the 3 month summer period as a whole

ii) Most models are forecasting close to or below average levels of rain

Despite points i and ii, it is worth drawing attention to the GloSea model which seems to be favouring cooler temperatures and average to above average rainfall.

Below average temperatures over the three month period would be quite unusual and not consistent with recent climatology. 

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 hot and dry periods may be offset by cool and wet ones leading to a close to average outcome overall. 

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 there a 60% chance of ENSO remaining neutral for the Northern Hemisphere summer. Therefore ENSO is not expected to favour a particular outcome.

Atlantic Hurricane season

Several forecasts for the 2020 Hurricane Season have been issued. They are suggesting above average levels of activity. At this stage none of them go for an anomalously active or quiet season. 

Colorado State University is predicting 16 named storms, 8 hurricanes.

Accuweather is predicting 14 to 18 tropical storms of which 7 to 9 are forecast to become hurricanes. 

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

Summary

1) Seasonal models on balance suggest above average temperatures and below average rainfall levels taken over the June, July and August period taken as a whole.

2) ENSO neutral conditions are not expected to favour a particular outcome.

3) The latest 2020 Atlantic Hurricane season forecasts perhaps point to an increased chance of settled weather relative to the average in the late summer.

At this stage a warmer than average summer including some significant hot periods is favoured. Lower confidence is attached to rainfall levels, but a drier than average summer is weakly favoured.

The next update will be issued in mid-May.

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