Sunday, 13 December 2015

Weather guide Monday 14th to Sunday 20th december 2015

Last weeks review: changeable and often mild; excessive rainfall Snowdonia

First regards the Cumbrian rain event of last weekend, it has been confirmed by the Met Office that a new UK record amount was recorded with 341.4mm falling at Honister in the Lake District in the 24 hour period to 1830 on Saturday 5th December. This event was caused by an 'atmospheric river' of extremely moist upper air that constantly fed off the Atlantic only to be released over the hills and rather than being a direct consequence of 'Storm Desmond' as widely portrayed.

Last Sunday was mostly overcast again with a little rain or drizzle in places, but many stayed dry, another very mild day (Hereford 15.0c, Trawsgoed 13.3c). Some clear intervals permitted the temperature to drop to 3.3c at Capel Curig Sunday teatime but a very mild night in most places, no lower than 11c on the south coast of Wales, there was a little rain in places. Exceptionally mild with sunny spells in many places on Monday, but a fresh to strong southerly. Warmest Gogerddan near Aberystwyth max 16.4c (UK date record) while it was the mildest December day in the 10 year record at Llanwnnen with a high of 13.9c (beating 13.6c in 2007). The mildest place in the Midlands was Newport, Salop 15.3c with Coventry (max 13.7c) having its mildest December day for 21 years. WW then had a wet evening, the front only giving a little rain for the Midlands overnight, another very mild night (min Milford Haven 11.7c).

Sunny intervals and blustery showers Tuesday, mostly over Wales where some were heavy with hail, mild but it cooled down afternoon (Wellesbourne 12.9c, Mumbles 12.0c). Clear with a touch of frost in places Tuesday night (Llanwnnen -0.2c, Shobdon +0.8c) but this had lifted well before dawn over WW as the breeze picked up. Mild Wednesday, rather cloudy for WW but decent sunny spells for the Midlands and a dry day by and large and it was windy with severe gales in exposed places across Wales (Milford Haven & Pembrey 12.2c, Shawbury 11.7c). Very mild again Wednesday night as most places stayed above 8c (Pembrey min 11.8c), wet for Mid and North Wales but the rain did not reach South Wales and the Midlands until morning.  Most of the rain cleared WW during the morning (Capel Curig 82mm in 24 hours to midday). Dull with mostly light rain on and off for the Midlands much of Thursday afternoon and it turned cooler for most places (Pembrey 12.2c, Pershore 11.0c).

Mild with a little rain Thursday night, although mostly dry Midlands (Shawbury 3.6c, Capel Curig 5.3c). Rain in places Friday morning, chiefly over Mid & South Wales, then a dry, bright afternoon for many but cooler than of late (Milford Haven 10.0c, Hereford 9.1c). Rather a widespread ground frost Friday night (air min Hereford & Llanwnnen 0.5c). Rain and strong winds then Saturday, a lot of rain much of WW, the rain more intermittent and generally light most of the Midlands. Very mild with many places getting above 12c eventually (Hereford 14.0c, Trawsgoed 13.2c) and with 92mm rain at Capel Curig falling in 12 hours on Saturday. Further mostly light rain fell on and off during Saturday night but with North Wales mostly dry at this stage.

The coming week: mild/ very mild and unsettled, further rain and wind at times, especially Wales

December is already shaping up to be another very wet month across Wales, none more so than at Capel Curig which has had almost 500mm (20 inches) in the first 13 days! In contrast much more modest totals over the Midlands with less than one inch (21mm) at Long Lawford so far. It has though been just about the mildest start to a December on record with mean temperatures more akin to late April. More very mild and at times wet weather in the coming week too so the buds and Daffodils will continue to be tricked into thinking its Spring! Another overcast day today (Sunday) but most of the main rain is clearing away north this afternoon with just a little residual drizzle left behind. Mild air once more behind this warm front with highs eventually this afternoon 8 to 11c for most, although a rather cold 6c max perhaps for Nottingham and light winds. A mild night with drizzle in places no lower than 5c.

Low pressure to the SW of Ireland Monday throws up a cold front pm with quite a wet afternoon across Wales, the rain reaching most of the Midlands by evening. Highs again 8 to 11c with quite a fresh southerly for WW. The main rain clears by midnight just with bits and pieces behind overnight and still mild. Tuesday morning could be mainly dry bar the odd spit, but active fronts arrive from the SW afternoon which will turn out wet and rather windy in many places. Very mild by the evening too as temperatures rise reaching 12 to 14c. Tuesday night sees further rain at times and winds could be strong to gale force but it stays exceptionally mild at above 10 or 11c all night.

The worst of the rain and strong winds should be clearing Wednesday morning but a lot of cloud still, very mild with bits and pieces of rain and drizzle through the day, another mucky mild day so typical of this December! Highs Wednesday though exceptionally mild widely at 13 to 15c. Exceptionally mild Wednesday night some spots may not get below 13c with nowhere lower than 10c, light rain and drizzle in places and rather windy. Thursday will see an active cold front coming through, although this may be a slow process and Wales in particular could get a thoroughly wet and windy day (potential for large rainfall amounts in places here), the rain band eventually crossing the Midlands as well. Another really mild day at 12 to 15c (highest Midlands). The cold front should have cleared though by midnight leaving just a few showers.

Timings impossible to rely on come the end of the week but Friday perhaps drier and calmer ahead of yet another low and it fronts that are inevitably set to bring their rain and strong winds - albeit perhaps not until after dark? Even if mostly dry, Friday sees a lot of cloud once more with any brightness at a premium as has been the case much of this dull December. Certainly another mild day maxima at least 10c. Next weekend looking disturbed with further spells of rain and strong winds, with the potential that fronts may stick over Wales giving the risk of further unwelcome deluges and flooding here. Mild or very mild still, highs 10 to 14c, with Saturday most likely to see the highest readings as during Sunday it may well cool down somewhat. Disturbed, often windy weather is likely to continue through to Christmas although with a less mild/ colder theme in which hill snow may be featuring from time to time though flooding and gale damage are likely to be the chief concerns.

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