Wednesday 16th September
The narrow band of rain that passed over our area just after 09.00 on Tuesday morning had become fragmented on its journey and only produced very light drizzle and a few drops of light rain that did not even wet the pavement, thus recorded as a trace. As the morning progressed, the sun came out and by 14.33 the temperature had peaked at 21.7C, which was 2.7C above average. Due to the clear skies and cooler air stream the temperature dropped away to a low of 9.1C at 06.54, just after sunrise in Marlborough at 06.43. This low was 0.4C below average.
Wednesday arrived with glorious sunshine to start the day, however, it won’t last. Although there is a minor ridge of high pressure edging across the country, a large bank of cloud can be seen on the radar edging down from the northwest that will likely obliterate the sun for much of the day. Hopefully it might thin later in the afternoon to allow a little brightness to close the day. At 08.35 the first sign of cloud edging closer could be seen on the northwest horizon.
The air movement will be from the west for much of the day on Wednesday. This will mean the maximum temperature will likely be below average due to the cloud cover and cooler air stream. The forecast pressure charts indicate that a weather front is likely to arrive early Thursday morning, with a brief period of precipitation, but at the moment it is not thought it will produce prolonged heavy rain. As that cold front clears the rest of the day should bring sunny intervals. Friday, at the moment appears to be devoid of any weather fronts so a dry day with sunny intervals is likely but as evening approaches the forecast pressure charts indicate cloud and further weather fronts arriving as the ridge of high pressure gives way and the two depression to the northwest begin to dominate before the high pushes back again over the weekend that will see temperatures begin to return to around the September average.
What does the latest long-range (30-day) forecast show?
The latest Met Office long-range forecast suggests a generally changeable pattern through the remainder of September and into early October, there will also be spells of drier and more settled weather, especially in the south. Towards the end of September, high pressure may become more influential, bringing a greater chance of settled conditions for a time.
Temperatures are expected to be close to average overall through the remainder of September, with some rather warm days possible, before becoming slightly above average into early October.
At longer lead times, confidence inevitably decreases. As day-to-day weather variations become increasingly less predictable, forecasts focus on broader trends rather than specifics.
This is why long-range outlooks describe potential patterns and probabilities for a month or three-month period rather than exact conditions for a particular day or location.
What does this mean for the UK autumn?
The developing El Niño is expected to continue strengthening through autumn before reaching its peak during winter, and the Met Office will continue to monitor how it interacts with other climate drivers over the coming weeks and months.
Current evidence indicates an increased likelihood of wet, windy and potentially stormy conditions later this autumn and into early winter. This signal is reflected not only in our understanding of El Niño, but also in seasonal prediction models and other large-scale climate drivers.
However, while seasonal forecasts can identify shifts in the likelihood of particular weather patterns, they cannot determine exactly when or where individual weather events will occur.
This means we can assess the chances of a wetter, windier autumn and early winter overall, but it remains too early to identify any specific impacts for particular parts of the UK.