Sunday, 26 April 2015

Weather guide Monday 27th April to May Day Bank Holiday Monday 2015

Headline: Cool, sunny intervals and showers (possibly wet and windy Wednesday); frosty nights. Mostly dry and bright Friday into Saturday before the Bank Holiday turns more unsettled but milder.

Last weeks highlights

Much of last week was dry and rather warm with plentiful sunshine, a splendid spell of Summer-like weather across Wales, however it is still only April and clear skies and calm conditions by night meant fairly widespread frosts on many night up to Thursday. Sea breezes kept some coastal areas much cooler in spite of the sunshine, on Monday Aberporth only reached a chilly 12c cf. 15 to 17c inland.  Tuesday had another frosty start in many places, as low as -1.5c, at Llanwnnen, but then  was another sunny warm day, most places getting above 17c, with Porthmadog, North Wales, the warmest spot in the UK max 21.3c. Llanwnnen reached 21.1c (70f) on Tuesday making a massive diurnal (daily) temperature range of 22.6c and one the the greatest I have ever recorded. Sea breezes affected the coasts though and none more so than at Aberporth where the max was only 13.4c so almost 7c cooler than Llanwnnen just 18 miles away but crucially well inland.

Similar on Wednesday although the Midlands saw more cloud afternoon. The gradient (along the pressure isobars) ENE wind overrode the sea breeze effect so that even coasts experienced the warmth of up to 20c across WW as at Porthmadog, Llanwnnen and Pembrey, with even the oft-chilly Aberporth managing 19c! For much of Wales sunshine was virtually unbroken Monday to Thursday with largely clear blue skies giving an estimated 50 hours in these 4 days at Llanwnnen and being typical, so a very sunny spell.

The weather began to change Friday with much more cloud and a little rain over Wales, although still quite warm and mostly dry for the Midlands. An active cold front edged down Saturday pm turning it decidedly cold and wet over North Wales but still quite mild to the south of it, at 1600 BST it had dropped to just 4c on Anglesey while at Milford Haven, Pembs it was 15c. Although we have entered a more unsettled weather pattern this weekend, for much of Wales and the Midlands away from more northern parts there has been little rain, for most no more than a mm or two. So no matter what happens in the coming week a dry April is assured.

The week ahead

Fine and sunny this morning across WW and the NW Midlands, but cloudy for the rest of the Midlands. Sunday afternoon largely dry and most places will see sunny periods although the cloud and spits of rain may stick into this evening for the SE Midlands below Northampton to Stratford--upon-Avon. Cooler and fresher than of late, highs 11 to 13c with moderate north winds. Just the chance of a shower for North Wales late in the day, with a few showers skirting coastal WW overnight too otherwise dry.  Clear periods and light winds means a widespread air frost tonight, down as low as -2c in places, and one of the colder nights of April 2015.

With pressure low to our north through Monday and Tuesday we are in a cool, essentially showery NW flow of air which originated over the Arctic. Both days will see dry, sunny spells, but there will be some sharp showers about, these with hail in places and even some sleet or snow for the higher ground above about 400m (most likely Monday evening). Most of the Midlands dry and bright until well into Monday afternoon but a more defined line of showers looks set to track SE late Monday afternoon into the early evening, so most places eventually catch a shower or two. Cool highs on Monday of between 9 and 11c with a freshening WNW breeze afternoon. Breezy with showers dying out away from windward coasts on Monday night, a widespread ground frost inland, locally getting just below 0c. Tuesday and again a sunny spells and showers mixture, with perhaps a longer spell of rain during the afternoon which could end up quite cloudy. Chilly highs between 8 and 11c and a breezy day.

Clearing skies on Tuesday night means another widespread ground frost at least and locally even a touch of air frost as winds should decrease towards dawn.  Wednesday at best another sunny intervals and showers day, at worst it could turn out wet and windy as there is the potential for a new low to cross the UK at some stage during the day, although this scenario not set in stone as yet. Another cool day in any event no higher than 12 or 13c. Yet again Wednesday night could see a widespread ground frost developing once any rain or showers clear. Back to sunny spells and scattered showers for Thursday, lighter winds so not feeling too bad in the sun, highs between 11 and 13c though still below average for the end of April. Some places will no doubt miss Thursday's showers. Thursday night looks cold and frosty, -3c possible in places.

A frosty dawn to Friday but some decent sunny spells during the day as a ridge of high pressure edges into the west, this should have the effect of dampening down any showers that may develop, and although there is likely to be a few knocking about for many places quite a nice, dry and bright day. Still quite cool on Friday though maxima 12 to 15c but with only light breezes. Another widespread frost likely again Friday night with largely clear skies expected. A chance that a tenuous ridge is over the UK during Saturday, so just about another mostly dry and bright day, however indications are that low pressure and rain fronts to our SW will be edging in later in the day.

Unfortunately, pressure looks set to fall as we progress through the Bank Holiday weekend with low pressure centred to our west, at least this does draw up milder (if sometimes moist) south to SW winds so frost concerns should have alleviated by then. Details impossible with no clear signal, but Sunday and Monday likely to see some spells of wet weather, but no real washout is anticipated, and at times it could well be dry, bright and mild. The latest GFS output in fact keeps the Midlands largely dry on Sunday and Monday but I feel this unreliable so prepare for some rain at some stage over the holiday period.

Sunday, 19 April 2015

Weather guide Monday 20th to Sunday 26th April 2015

Headline: Dry and quite warm with sunny spells; turning cooler and unsettled from Friday (belated April showers!)

Last week's highlights

Last week was completely dry (Monday onward) almost everywhere, and it was often rather warm for April, particularly for inland Wales and the West Midlands with several sunny days. There were a few slight frosts or at least ground frosts in many inland places: 

Some rain for most places for a times last Sunday, this cleared to give a widespread air frost inland, lowest at Shawbury, Shropshire -2.7c, but temperatures soon recovered with the strong April sunshine and 18.2c was attained at Pershore.  Unseanable heat flirted with southern England midweek, France getting temperatures above 30c and SE England 25c recorded in places. Nearer home Hereford and Coleshill reached a warm 20.3c on Tuesday with sunny skies, but much cooler along the south coast of Wales where Pembrey managed just 11.7c and was presumably plagued by sea mist. NW Wales was also quite cool Tuesday, a maximum of just 10.7c at Capel Curig, while at Llanwnnen it was a gloriously sunny afternoon with a respectable high of 16.3c.  A similarly very pleasant day for many areas Wednesday, quite high temperatures for the Midlands, widely above 19c, best being 20.8c Pershore and 20.6c Little Rissington, NW Wales dull and quite cool however with highs of just 10c or so. 

An east to NE breeze meant West Wales (WW) was favoured for warmth and sunshine Thursday onwards, with Thursday itself 19.4c at Llanwnnen - this after a dawn ground frost. Still much cooler for many western and northern coasts though, just 12c the best at Aberporth due to the breeze off a still cold sea, and also a cool though bright day on Anglesey. Again with the NE breeze WW continued to fare better on Friday being reasonably bright and warm while much of the Midlands kept a lot of cloud and subsequently supressed temperatures. Maxima on Friday illustrate the favourabilty of WW in a NE flow during Spring with Llanwnnen reaching 17.6c cf. just 11.8c at Coventry. The Cardigan Bay coast even managed 17c Friday with the breeze off land and WW was the warmest part of the country. Sunny for all Saturday (an unbroken 13 hours for some places) and rather warm for WW and the Marches, but nearer average (14c) over the Central and East Midlands with that cool ENE wind.

The week ahead

More fine and quite warm weather to come this week, temperatures pushing 21c (70f) for some areas midweek but the weather is set to breakdown from Friday with an unsettled weekend as the more traditional April showers arrive belatedly for the end of the month! Risk of ground frost for many nights this week given clear periods as winds fall generally light. 

After a touch of frost in places (-0.7c here at Llanwnnen) and a bright start, Sunday afternoon sees plenty of cloud but with some sunny intervals (especially for Pembrokeshire). Just the chance of a light shower affecting parts of the Midlands this afternoon but essentially another dry if rather cloudy day. A rather cool day, maxima 11 to 13c although 15c for brighter parts of WW, with a light or moderate NE breeze. High pressure centred over northern UK through to midweek so a dry picture and with winds perhaps turning more ESE we should be seeing decent sunny spells raising temperatures into the warm category:

Skies may clear on Sunday night leading to a widespread ground frost and touch of air frost locally. Still some troublesome areas of cloud knocking about during Monday but most areas should see some sunny spells, with the best of the sunshine over WW, highs between 15 and 18c and dependent on sun amounts with fairly light east breezes. Clear breaks on Monday night with local frost, minima generally 1 to 4c. Hopeful that Tuesday sees more widespread decent sunshine amounts and be reasonably warm (max 17 to 19c), although with an east breeze temperatures still somewhat restricted for the East Midlands (max 14 or 15c). Once more with clear periods expected, a widespread ground frost cannot be ruled out for Tuesday night, down close to 0c in places.

Winds should have more of a SE tendency about them by Wednesday and such subtle shifts as this may profoundly affect the weather. A SE flow would waft in warmer air from off the near Continent, so we should all get a warm fairly sunny day and highs of 18 to 21c, however some models still keep a North Sea influence (ENE breeze) and subsequently inhibited temperatures over the Midlands (max say 15 or 16c), with some areas of cloud too, although once more West is Best!  Perhaps less of a frost risk for Wednesday night with the anticipated slightly warmer airmass over us. High pressure declines by Thursday but still a legacy ridge across most of the UK means another largely dry and fine day. Decent sunny spells are expected with temperatures reaching 18 to 20c, just the slight chance of a few showers later in the day especially for more southern parts.

Changes afoot from Friday to cooler and unsettled weather as pressure drops across the UK. Hard to detail this breakdown but we may well see quite a deep trough of low pressure form over the UK during next Friday into the weekend bringing showers or longer spells of rain and lower temperatures. The low could deepen sufficiently, and as shown by some of the models, to give a spell of particularly wet and windy weather at some stage during Friday or Saturday. After this spell of rain the weekend looks like being cool and showery but with dry, sunny intervals and with the wind shifting into the NW expect some heavy hail showers and chilly winds. Any clear spells by night means a continued risk of ground frost, perhaps more especially on Saturday night when locally temperatures could potentially drop below zero should the wind fall light. The cool and unsettled theme could then last into the start of May!

Sunday, 12 April 2015

Weather guide Monday 13th to Sunday 19th April 2015

Headline: Mostly dry with sunny spells; very warm mid week with thundery shower risk

March 2015 summary

March continued the trend of very average weather thus far in 2015, both temperatures and rainfall close to the norm, some areas were quite dry though and most places were sunny. Once again a month that lacked extremes, nothing colder than -5c or higher than 13c here at Llanwnnen, a limited range. Some rainfall totals:

Capel Curig, Snowdonia c. 192mm
Trawsgoed, Ceredigion c. 95mm
Llanwnnen, Ceredigion 72.6mm 87%
Aberporth, Ceredigion 54mm
Pembrey Sands, Carms 58.0mm
Llanelli, Carms 77.2mm
Milford Haven, Pembs 69.4mm
Long Lawford, Rugby 28.5mm 67%
Church Lawford, Rugby c. 34mm
Bablake School, Coventry 46.2mm 97%
Coleshill, Warks 52.4mm
Hereford 45.6mm
Little Rissington, Cotswolds c.32mm

Last fortnight's highlights

A windy, unsettled end to March with gales and heavy showers, wind gusts of over 40mph almost everwhere, highest being 97mph at  the exposed location of Capel Curig. April came in cool and turned somewhat damp, much of West Wales (WW) below 10c max on Wed 1st. The rest of the turn of month week saw rather cool to average temperatures at best, frost though largely absent. Rain at times the Thursday night and for Good Friday, especially wet over Pembrokeshire where some places had close on an inch.

A big improvement occurred over the Easter weekend to warmer, sunnier conditions and with a mostly fine and warm week just gone. This improvement first took effect over WW during the weekend, but all areas joined in by Easter Monday with plenty of warm sunshine, although some coastal areas were plagued by sea mist and fog. There were slight overnight frosts in places throughout last week - especially inland WW where Llanwnnen had a least a ground frost each night to Friday. Some mornings were foggy before the sun broke through, as was the case across Warwickshire both Monday and Tuesday mornings. Temperature-wise overall it has been a warm week for early April (at least by day) considering the average maxmum should be around 12c at this stage:

Monday saw temperatures reach 19.4c at Pershore (highest in UK), 19.0c Pembrey, with many places above 16c, however parts of Cardigan Bay much cooler with sea mist, Gogerddan, near Aberystwyth managing just 11.2c with Aberporth only marginally milder. On Tuesday several places topped 18c including 18.4c Llanwnnen and an unbroken 12 hours sunshine, with Wednesday and Thursday warm and mostly sunny again, 19.6c reached on both days at Llanwnnen - warmer than any official UK station, Porthmadog reached 18.7c Wednesday, while Trawsgoed hit 19c Thursday. Friday, the last day of the warm spell, saw temperatures widely above 18c, best of all being Pershore, Worc at 20.7c and Trawsgoed 20.3c; much cooler along the south Wales coast however due to a fresh onshore wind, max just 12.4c Milford Haven, Pembs. Some rain Friday night into Saturday but then a cooler and fresher day but largely dry with temperatures only a little below the mid April average.

The week ahead

Plenty more dry and at times warm weather once more this week - hopefully this good April will not dash hopes of a fine, warm Summer, as is often the case when the nice weather arrives too early! Not so good on Sunday though, an Irish low bringing strong to gale force wind for Wales with some rain or drizzle at times this afternoon, heaviest for Snowdonia, highs 11 or 12c. Windy for the Midlands Sunday afternoon and clouding over with a little rain possible later afternoon into the evening, maxima 13 to 15c here. Winds become light this evening and a dry night with clear spells and widespread ground frost and local air frost, -1c in places. High pressure close to southern England on Monday although weak fronts bringing quite a lot of cloud even some drizzle in places. However the sun should break through from time to time especially inland, but parts of the WW coast affected by low cloud and mist from off the Irish Sea. Highs Monday rather mild at 13 to 16c, although cooler for some western coasts. Mostly dry Monday night with no frost concerns.

A warm rather humid SSW flow across England and Wales on Tuesday, sunny spells and decent temperatures of 18 to 20c, although some coasts plagued by sea mist keeping it chilly, and a breezy day over much of WW.  A dry night follows. The warm air still in place for Wednesday although pressure will be falling off as a cold front edges across northern Britain. Sunny spells, light winds with temperatures likely to exceed the magic 21c (70f) in places! Highs in the 19 to 22c range, perhaps the odd 23c being recorded over the Midlands. Cooler in general though for Cardigan Bay and coastal NW Wales with again some sea fog lapping beaches. The warmth inland may set off some sharp showers afternoon with even an isolated thunderstorm or two knocking about by evening and rumbling into the night, especially further south. 

Thursday sees a weak front lying somewhere across southern Britain with a new (cooler) high building over northern parts and killing it off further. Areas of cloud, and perhaps a few vestigial showers, in association with the front should be breaking up to give sunny spells afternoon, a cooler day, highs closer to average at 13 to 15c but pleasant enough out of the breeze and shade. There is a ground frost risk for Thursday night but Friday another fine, dry day with sunny spells and temperatures at least up to average and possibly quite a warm feeling day.

Next weekend too looks like having high pressure in charge, quite pleasant and largely dry with sunny spells for most of us, WW perhaps most favoured for warmth as a NE breeze may keep it cooler at times into the East Midlands, but overall expect maxima in the 13 to 17c range. A continued risk of ground frost through the weekend as the ambient air may be quite cool.