The extended range forecast, which includes the monthly and seasonal forecasts, can at times provide an insight into weather patterns in the months ahead. However, they should not be used for specific planning purposes as they have generally low skill compared with the 10-day forecast. This is because forecasts beyond one week become increasingly uncertain due to the chaotic nature of the atmosphere. Further information can be found here Monthly and seasonal forecast explained.
Images: Shutterstock/gabriel12. Met Éireann HQ during Storm Emma 2018
MONTHLY FORECAST, ISSUED TUESDAY 19 SEPTEMBER 2023
Week 1 (Monday 25 September to Sunday 01 October)
A mild south-westerly airflow is expected to dominate during Week 1, generated by high pressure over mainland Europe and low pressure in the Atlantic, so mean air temperatures will likely be above average throughout the country. Weather fronts from the west will still likely encroach leading to above average rainfall over much of the western half of the country. Further east, it is expected to be drier. Rainfall accumulations are the most likely hazard.
Week 2 (Monday 02 October to Sunday 08 October)
Week 2 has a similar setup signalled as in Week 1 though the high pressure over Europe will possibly decline slightly. Mean air temperatures are signalled to remain above normal throughout the country and the western half of the country will likely see continued above average rainfall amounts. The eastern half of the country will more likely have normal amounts of rainfall or less. Running rainfall accumulations will need to be monitored in this setup for possible impacts.
Week 3 (Monday 09 October to Sunday 15 October)
For Week 3, there are no signs for high pressure or low pressure to dominate as the high pressure over Europe is set to decline. This would likely mean changeable conditions. Mean air temperatures will likely be around normal for the time of year. Parts of the southwestern half of the country are signalled to be drier than normal, with more normal rainfall amounts expected elsewhere.
Week 4 (Monday 16 October to Sunday 22 October)
There is no strong signal for Week 4 with further changeable conditions expected with a mix of settled and unsettled periods likely. Mean air temperatures and rainfall amounts will likely be around normal for much of the country with some areas seeing below average rainfall amounts, most likely in the south.
SEASONAL OUTLOOK FOR OCTOBER, NOVEMBER AND DECEMBER (OND)
The signal from the C3S seasonal models for Ireland during the OND period is for above average temperatures to continue with higher than average rainfall likely across Ireland.
Above average temperatures are very likely for Ireland during the OND period, though the likelihood decreases slightly as the period progresses. Mean temperatures are expected to be between 0.5 and 1.0 °C above average nationwide through each of the months.
Wetter than normal conditions are likely across Ireland during OND.
The sea surface temperatures around Irish coasts and over the Atlantic are expected to remain well above average during OND, trending 0.5 to 2.0°C degrees higher than normal.