Summer 2019 update 2

Latest indicators

21st May 2019

This is our second look at what the seasonal forecasting models and background signals are suggesting about the weather prospects for summer 2019. The first summer 2019 forecast indicators issued on 2nd May remain online to read. The TWO summer forecast will be issued in late May.

Fine weather in summer

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 Precipitation
GloSea (UKM) Above average No significant signal. Perhaps near to below normal
ECM Above average in the east. No signal in the west. Mainly no signal. Above average in the far north.
Meteo France Above average. More so in the east. Below average in the south.
DWD Above average. More so in the east. Above average in parts of the south. No signal elsewhere.
CS3 Above average in the east. No signal in the west. No signal
Beijing Climate Center Above average Below average
CanSIPS Above average Below average
CFSv2 Above average No signal
Table 1: Forecast temperature and precipitation anomalies, June, July and August

 

The notable things at this stage are:

i) Most models show temperatures above the average taken over the 3 month summer period as a whole. This is particularly true in eastern Britain.

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

Note: Since the first summer forecast indicators discussion the trend has been towards higher temperatures over the June, July and August period. 

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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 70% chance of El Nino lasting through the Northern Hemisphere summer. By the autumn the probability of it continuing falls to between 55% to 60%. Therefore ENSO is not expected to favour a particular outcome.

Note: The probabilities have increased since the first summer forecast indicators discussion.

Atlantic Hurricane season

Several forecasts for the 2019 Hurricane Season have been issued. They range from suggesting slightly below to slightly above levels of activity. At this stage none of them go for an anomalously active or quiet season. 

Colorado State University is predicting 13 named storms, 5 hurricanes and 2 major hurricanes.

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

Summary

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

2) El Nino is not expected to strongly favour a particular outcome.

3) The latest 2018 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 summer with above average temperatures is thought probable. The signal for rainfall is weak, but it is slightly in favour of drier than average conditions over the three month period.

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