Sunday, 3 January 2016

Weather guide Monday 4th to Sunday 10th January 2016

Last fortnights review: mostly very mild or mild; unsettled, further heavy rainfalls Wales

Sunday 20th December hail and thunder in the showers, much of Midlands missed the showers, at least sunny intervals! (mildest Pershore College 12.9c, Nottingham 3.2 hrs sun, lightning sferics Carmarthen Bay, Brynamman/ Black Mountain, Nottingham).

Monday 21st surprised by a ground frost here, min 2.1c, soon went with cloud and rain. Shobdon also had a ground frost (air min 3.7c). Spell of rain followed by welcome sunny spells (Shobdon 13.3c, Trawsgoed 12.6c).

Tuesday 22nd very mild indeed once more, cloudy with rain or drizzle at times, even the Midlands saw some quite heavy rain (Capel Curig 62.6mm, Nottingham 10mm; Wellesbourne 14.4c, Trawsgoed 13.3c). Showers evening with thunder NW Wales 

Wednesday 23rd less mild, sunny spells and a few showers (Milford Haven 11.7c, Hereford 10.8c were evening max).  Named storm Eva then gave a wet, windy night across Wales.

Christmas Eve very mild night up to 13c places. Squally band of rain moved east through the day, further heavy rain in places, cleared to sun and showers in colder air, enough for snow over high ground, also thunder for a few (Pershore 12.1c, Pembrey 11.9c). Ground frost in places overnight but gone by morning.

Christmas Day a chilly start became very mild with some rain especially North Wales (Hereford 14.8c, Trawsgoed 13.5c), mildest Christmas day in Coventry since 1902

Boxing Day 173mm rain in 24 hrs to midday at Capel Curig; exceptionally mild night, most places above 12c, new record min Llanwnnen 12.1c. Exceptionally mild day, extremely wet over NW Wales, rain at times rest of Wales, mostly dry Midlands (Shawbury 15.0c, Trawsgoed 13.9c). Some heavy rain for parts of the Midlands overnight as WW dried up (Pershore 15.6mm) and Capel Curig ended up getting 254mm (10 inches) in 48 hours.

Sunday 27th another very mild cloudy day, some rain or drizzle (Hereford 13.8c, Trawsgoed 13.6c).

Monday 28th very mild and mostly dry, some rain over WW, especially evening 

Tuesday 29th very mild, dry, sunny Midlands, cloud and some sun WW, rain arriving here evening, max 10 to 12c. Even milder overnight with strong to gale winds associated with named Storm Frank, heavy rain WW

Wednesday 30th 33.6mm rain in 24 hrs to 0900 made 29th Llanwnnen's wettest day of 2015, it turned out rather wet in most places during the day, a very mild start cooled pm (Pershore 13.8c). Thunder and hail in the showers in places during Wednesday night which was much cooler than of late (air min Llanwnnen 2.8c)

New Years Eve was one of the cooler days of an extremely mild month as many failed to reach 10c (Mumbles 10.9c, Pershore 10.6c). Squally prolonged showers with hail and again thunder affected Wales, dry and sunny at least to midday Midlands but heavy showers arrived during the afternoon (thunder reported Coventry). Temperatures then fell below freezing in some rural places to see in the New Year.

New Years Day widespread frost was quite a novelty (Shawbury -2.8c, Llanwnnen -2.4c)! More rain at times eventually to greet New Year though, some of this heavy over Wales later. Chilly in the breeze but became milder overnight (Milford Haven 10.3c, Nottingham max 5.2c by 1800). Some further showery rain at times Friday night.

Saturday 2nd January rather with showery rain in places and mild (Trawsgoed 12.8c, Pershore 10.4c, Shobdon 17mm).

December 2015 review: remarkably mild, a true record breaker! Huge West to East rainfall contrast

What a month! Unprecedented December mildness (verging on 'warmth' at times) particularly during a 4 day spell mid month when many records were broken, with another unprecedented mild spell around Boxing Day. Most places mean temperatures were 4 to 6c above average, the months highest reading across our regions being 15.9c at Pershore around dawn 19th! Nights perhaps more incredibly mild, more akin to July nights on occasion as some places did not drop below 13c. The Central England Temperature (CET) December record was absolutely shattered with a mean of 9.7c (average of maximum + minimim) or 5.1c above average, this series goes back to 1659! The previous record belonged to December's 1934 and 1974 both having mean temperatures of 8.1c. This suggests a hypothetical return period for December 2015's warmth of over 1000 years (provided Anthropogenic Global Warming is not taking place of course..). Perhaps the greatest perspective on this incredible month is the fact that it was milder than any previous March, all but one November, only 7 April's and even one May from the past three and a half centuries!!

Stark west to east rainfall differences with WW having an exceptionally wet month, most of the West Midlands was very wet, while for parts of the eastern Midlands it was not a great deal above average. Capel Curig was wettest in the UK and must have had well over 1000mm although we wont know for sure as the station failed to report over the final few days of the month. This compares with just 69.1mm at Long Lawford. Here at Llanwnnen with 340.3mm it was comfortably the wettest month I have recorded in the 10 year record (beating 309.4mm Nov 2009) and looking through the historical record only January 1974 was wetter (381mm at the closest station back then, Alltyblaca, 1 mile away).

Addendum (Sept 2016):

Crib Goch 1396mm could be the most in a month setting a new UK record monthly rainfall total. However it is indicated here that Llyn Llydaw, Gwynedd recorded 1436mm Oct 1909:

This  erroneous due to a faulty gauge though:

An attempt to place this into an appropriate historical context has revealed that the widely-quoted UK rainfall record for a calendar month, 1436mm in October 1909 at Llyn Llydaw Copper Mine on the eastern flank of Snowdon, is erroneous. The page of errata at the beginning of the 1909 edition of British Rainfall requires the deletion of all previously published records in British Rainfall for Llyn Llydaw Intake and Llyn Llydaw Copper Mine, noting “…corrections made necessary by having accepted the records of two rain gauges of faulty construction.”

We therefore suggest that the Llyn Llydaw “record” for October 1909 be discarded as inaccurate, and that the more reliable assessment of 1430mm at Styhead for the calendar month of November 2009 take its place as – by some margin – the highest monthly rainfall total yet observed in the British Isles. We also suggest that, as records from this exceptionally wet spot are clearly of interest in determining the extremes of orographic rainfall, that consideration be given by the Environment Agency to supplementing the existing monthly gauge at Styhead with a tippingbucket logger to provide hourly and daily totals.

Philip Eden
Stephen Burt
Chilterns Observatory Trust

Some December rainfall totals:

Valley, Anglesey 252.6mm 279%
Crib Goch (713masl), Snowdonia 1396mm possible UK monthly record (added Sept 2016)
Capel Curig, Gwynedd well over 1000mm (no data last few days but 1100 to 1200mm most likely)
Trawsgoed c. 280mm
Llanwnnen 340.3mm 236%
Aberporth 203.4mm 213%
Pembrey, Carms 228.8mm 197%
Llanelli 222.2mm

Nottingham 90.2mm
Hereford 122.4mm 181%
Coventry 102.4mm
Long Lawford, Warks 69.1mm 123%
Dunchurch, Warks 71.6mm
Crick, Northants 120.4mm
Pershore, Worc 87.8mm 165%
Little Rissington, Glos 112.0mm 147%

And sunshine:

Valle 26.1 hours
Llanwnnen 24  hrs 63%
Aberporth 21.1 hrs 41%
Nottingham 35.1
Coventry 41.1

2015 review

For much of the year it looked like temperatures would end up around the average but the really mild November and then exceptionally mild December put paid to that and 2015 was another rather warm year, even though the Summer itself lacked any true hot spell bar the odd day.

Rainfall- wise, annual totals have varied from slightly below average over parts of the Midlands to rather to decidedly wet over NW Wales.

Some annual rainfall totals:

Llanwnnen 1453.2mm 110%
Coventry 721.4mm 104%
Long Lawford 608.4mm 95%

and sunshine:

Llanwnnen 1423 hrs 104%
Coventry 1558.1 hr 101%

The week ahead: unsettled, showers or longer spells of rain; rather mild to average temperatures

No let up in the unsettled weather in the coming week, showers or longer spells of rain, the Midlands more sheltered at times, even with a mostly dry day or two in places here, but expect further flooding as water tables are brimming over. With this mobile Atlantic driven set up, frost will be at a premium even though we will be in colder (nearer average) conditions much of this week. We have had 41 successive rain days (=/> 0.2mm)  here at Llanwnnen and I am not anticipating any dry days in the coming 7, indeed even at this very early stage we can expect January to end up another wet month in all districts.

Wet this Sunday morning, parts of WW have had an inch. Rain clears to bright intervals and showers this afternoon for WW but it remains cloudy with further spells of rain for most of the Midlands until dark, rather mild at 8 to 10c but quite a fresh SE veering SSW breeze. Some of the showers heavy with hail and possibly thunder this afternoon and evening for WW. Further showers for parts of WW tonight but becoming mostly dry for the Midlands this evening. A deep but flabby low slowly moves into Ireland during Monday so another unsettled day. Rather cloudy with showers or longer spells of rain, heavy with hail possible, however sunny intervals and just a few showers making it to the Midlands where many have a 95% dry day. Rather mild again with a moderate to fresh SSW breeze. Still a few showers for WW Monday night, dry over the Midlands where clear spells may lead to a ground frost locally.

By Tuesday the low with a central pressure around 980mbar has edged over to South Wales and SW England, in spite of this plenty of mostly dry and bright weather for the Midlands, with most of the showers over Wales, though even here they should be fewer and further between than was the case Monday. A cooler day as winds turn to between east and north but still up to the January average of 6 to 8c and only light to moderate winds. It becomes dry almost everywhere on Tuesday night and with clear spells there could well be a widespread ground frost and localised air frost as it touches 0c in a few spots. Mostly dry with some sunny spells Wednesday under a slight transient ridge but the next system is due to bring wet and windy weather to WW during the evening. Highs again average at 6 to 9c. It then turns wet and windy in all areas overnight, with gales in places. This feature Wednesday night has potential to bring damaging winds and flooding, and perhaps some hill snow for Snowdonia and the Peak District for a time.

The heavy rain should have cleared all but the East Midlands come dawn, colder fresh to strong westerlies bring showers and sunny intervals for Thursday, maxima 5 to 7c, some heavy showers with hail, and snow possible for high ground. Again the Midlands should be afforded shelter from the worst of the Thursdays showers and here some may manage a dry afternoon. If skies clear sufficiently and winds drop out enough then expect a frost to form Thursday night, however showers may continue for coasts and hills of WW. Remaining unsettled with further showers and more prolonged wet spells Friday and next weekend, temperatures average to quite mild with frost unlikely, max 6 to 10c.

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