Sunday, 27 September 2015

Weather guide Monday 28th September to Sunday 4th October 2015

Last weeks review: Rather cool and changeable; dry and sunny  from Friday with  ground frost

Last Sunday was cloudy and quite cool for most of WW, while there was some sunshine for the Midlands (mainly East) with temperatures nearer normal (Winterbourne, B'ham 17.9c, Valley 16.9c, Capel Curig 13.2c). Mild on Sunday night, rain at times for West Wales (WW) in particular (Llanwnnen 13.4mm), this lasting into Monday morning and progressing across the Midlands but cleared most parts by the end of the afternoon to sunny intervals. Maximum temperatures by day were rather cool to average (Hereford 17.6c, Milford Haven 16.4c, Swyddffynnon 14.2c).

Heavy showers and longer spells of rain during Monday night affected WW and parts of the South and West Midlands. Further heavy showers about during Tuesday, North Wales and Ceredigion caught successive downpours energised by and streaming off adjacent relatively warm seas.  Here at Llanwnnen 9mm fell in just one hour just before dawn Tuesday with a total 25mm in the 24 hours to 1800, while Swyddfynnon 15 miles to our NE was the wettest place in the UK receiving 29.2mm. A few of the more scattered showers over the East Midlands produced thunder in the afternoon. A cool and breezy day everywhere, most places not managing 16c (Pershore 17.2c, Capel Curig 12.4c).

A bright start to Wednesday for WW gave way to light rain or drizzle in the afternoon, some of which moved to the Midlands by evening after a fairly bright day here. Rather cool to average temperatures (Hereford 17.7c, Valley 16.3c). Just the odd passing shower Thursday which was a mostly  dry day with sunny spells and marked the end of the rather unsettled spell as pressure began to build. Temps rather cool to average once more (Coleshill & Hereford 17.1c, Llanwnnen, Milford Haven & Valley 16.0c, Capel Curig 13.2c).

Friday was a pleasant day with sunny spells temperatures around the late September average in most places (Pershore 18.1c, Milford Haven 17.8c, Aberporth 14.6c). Clear and cold Friday night with a widespread ground frost, the Season's first air frost here at Llanwnnen as it dropped to -0.4c before dawn. Some other low readings: Tirabad, Powys +0.1c, Capel Curig 1.0c, Trawsgoed 1.3c, Pembrey Sands 1.4c, Shobdon 0.6c. Saturday a lovely sunny and rather warm day with Ceredigion one of the warmest parts of the UK (Gogerddan 19.1c, Llanwnnen 19.0c, Trawsgoed 18.8c, Nottingham 17.9c, Aberdaron & Little Rissington 15.9c).

The week ahead: Dry and quite warm with sunny spells, particularly West Wales, often breezy; showers possible weekend

The cool and changeable September is redeeming itself with plentiful warm sunshine this weekend, with dry, mostly fine weather lasting through into the beginning of October it would seem, although the Midlands in particular may be seeing more in the way of cloud at times from midweek as the wind turns more to ENE. Another fairly widespread ground frost last night (Shobdon +0.5c, Llanwnnen  +0.6c), mist and fog in places too. Sunny again on Sunday, and it soon warm up, highs again of 16 to 19c this afternoon with a gentle SE breeze. Clear and rather cold again tonight, ground frost probably less of an issue and with any fog patches restricted to the Midlands, lows generally 3 to 6c.

The large anticyclone that will dominate our weather this week is over the North Sea on Monday with a central pressure of 1040mbar. Another dry and mostly sunny day, temperatures perhaps slightly higher at 17 to 20c, more of a breeze especially for SW Wales though. The breeze prevents frost and fog Monday night even though skies remains clear, no lower than 4c anywhere. The ESE breeze quite fresh during Tuesday, however another largely warm and sunny day, just the chance of some areas of cloud affecting the Midlands, highs 16 to 19c, best over SW Wales. Again too much breeze for frost or fog Tuesday night.

Pressure still high midweek at above 1030mbar across the UK, being centred near Scotland but with quite a squeeze in the isobars to its south over southern England and Wales. A pronounced and cooler east wind for Wednesday then, still plenty of rather warm sunshine expected for WW, but the Midlands may well see quite a lot of cloud and be feeling cool in  the wind. Maxima Wednesday ranging from 18c for Pembrokeshire to 14c for more cloudy parts of the Midlands. Similar for Thursday too, although the east wind may have eased and the Midlands may also be faring better again for sunny spells, highs 15 to 17c and so a little above the 1st October average.

Still high pressure dominates come Fridaylying across or close to northern UK, however the air might be cooler with a keen east to NE breeze feeding in areas of cloud and the odd light shower from the North Sea. Sunny spells most likely for Cardigan Bay on Friday, while parts of the Midlands has a rather cool cloudy day, highs in the 12 to 15c bracket but a long way out to know for sure and it could turn out a rather more pleasant day than this guide anticipates. Still no frost or frost risk in the latter part of the week due to the breeze and patchy cloud cover.

Pressure does decline over next weekend so we may be seeing a few showers about, however there is still relatively high pressure close to northern Britain and on the whole it looks to be a  mostly dry picture. A proportion of the model output does though bring in a shallow low from France with attendant showery rain for a time, but this scenario is largely unsupported and the predominantly dry weather should prevail with at least sunny intervals and just the outside chance of a shower. Maximum temperatures for the weekend expected  between 13 and 17c, around average for the start of October.

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