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Rhybuddion

Iau 27 Tachwedd Cyhoeddwyd am 11:52

Rhybuddion DU

Rhybudd Tywydd

Cyhoeddwyd gan y Swyddfa Dywydd

Mae'r cynnwys hwn ar gael yn Saesneg yn unig.

Thursday 27th November, 2014

Currently no warnings in force.

Rhybudd Llifogydd

Rhybudd gan Asiantaeth yr Amgylchedd neu gan SEPA yn yr Alban a Chyfoeth Naturiol Cymru yng Nghymru

Mae'r cynnwys hwn ar gael yn Saesneg yn unig.

Thursday 27 November

There are no flood warnings in force anywhere in the United Kingdom.

Ynglŷn â Rhybuddion Tywydd y Swyddfa Dywydd

Mae BBC Tywydd yn darparu dau fath o rybudd tywydd gan y Swyddfa Dywydd: Rhybuddion a Rhybuddion Cynnar.

Bydd Rhybuddion yn cael eu cyhoeddi pan disgwylir tywydd garw o fewn y 24 awr nesaf.

Bydd Rhybuddion Cynnar yn cael eu cyhoeddi mwy na 24 awr cyn tywydd garw.

Mae yna dri chategori o ddigwyddiad: Coch, Ambr a Melyn – y mwyaf difrifol yw Coch.

Mae Rhybudd a Rhybudd Cynnar yr un lliw yr un mor ddifrifol â’i gilydd ond eu bod wedi eu darogan i gyrraedd ar adegau gwahanol. Felly, y gwahaniaeth rhwng Rhybudd Coch a Rhybudd Coch Cynnar yw amseriad y digwyddiad.

Pan mae rhybudd mewn grym, ceir gwybodaeth lawn yn Rhybuddion Tywydd y Swyddfa Dywydd (dolen allanol Saesneg).

Ynglŷn â Rhybuddion Llifogydd

Mae’r rhybuddion llifogydd yn cael eu cyhoeddi gan Asiantaeth yr Amgylchedd, Scottish Environment Protection Agency a Chyfoeth Naturiol Cymru, a’u hanfon at Ganolfan Dywydd y BBC. Yna rydyn ni'n cyhoeddi crynodeb o rybuddion wedi eu seilio ar y wybodaeth ddiweddaraf sydd ar gael. Pan mae rhybuddion llifogydd difrifol yn cael eu rhyddhau, bydd rhain yn cael pwyslais ar ddarllediadau teledu.

Dysgwch mwy am Rybuddion Llifogydd

Mae yna nifer o ffyrdd y gallwch chi ddarganfod os yw eich ardal chi mewn perygl o lifogydd. Mae Asiantaeth yr Amgylchedd, Scottish Environment Protection Agency a Chyfoeth Naturiol Cymru yn diweddaru eu rhybuddion 24 awr y dydd trwy rif Floodline.

Floodline - 0345 988 1188

Rhagolwg Misol

Llun 24 Tachwedd Cyhoeddwyd am 10:00

Rhagolwg Misol

Mae'r cynnwys hwn ar gael yn Saesneg yn unig.

Crynodeb
A cold chapter starts a mild story

The first two weeks of November continued the unsettled theme of much of October, and not much has changed in the past week with colder interludes relatively limited. Many of you will have noticed that we started this new week on a rather crisp, frosty note, and in fact Monday morning was one of the coldest of autumn so far. This is not a sign of things to come however; while we are expecting a few relatively chillier days initially, by the end of this week it's likely to be on the mild side once again.

Thanks to a rather wandering jet stream the weather that we have had recently hasn't all arrived with gusto from the Atlantic, and on Tuesday this week we'll be watching a weather system bringing rain into the UK from the south. As we head into December though, there are signs that the jet stream should start to straighten itself out again, allowing Atlantic low pressure systems to make more determined progress past the UK. A straighter jet stream will depend on how developments in the upper atmosphere pan out this week, but one thing looks likely: there are no strong signals for snow other than over the mountain tops.

Llun 24 Tachwedd—Sul 30 Tachwedd
Scrapers at the ready

For much of the UK on Monday it will be dry and sunny after a frosty start, although morning fog may take time to clear from some spots. A relatively weak weather front will bring cloud and some rain into Northern Ireland and then western Scotland through the day. This front will come to rest on Monday night over southern Scotland and northern England. Elsewhere, it will turn frosty again under clear spells with fog patches reforming.

Through Tuesday and Wednesday it will be cloudier and feeling chilly, with many parts away from the northwest of the UK seeing some rain thanks to a weather system moving northwards across the country. Northwest UK will escape much of the rain through midweek.

Much of the country on Thursday will be drier and brighter again, although a new weather front will be starting to push into the far west later, bringing increasing cloud and strengthening winds. This front will bring outbreaks of rain and strong winds across the west on Friday, but will also draw mild air northwards ahead of it. This will lead to a less chilly end to the week, especially in the east where the dry and bright weather should last through Friday. However the southerly winds will reach gale or severe gale force at times in the west and northwest.

Into the weekend, the rain and strong winds will push slowly eastwards, although with southeastern areas not expected to see much rainfall. Nights will be milder too, with the frost risk much lower than at the start of this week.

Llun 1 Rhagfyr—Sul 7 Rhagfyr
A more determined jet stream

As discussed here earlier this month, at this time of year changeable weather is not unusual. As the northern hemisphere's temperature patterns adjust more noticeably, it causes the jet stream to become more active and thus exert more of an influence over the British Isles. Each time an Atlantic low crosses the UK, colder air from northern latitudes is given the opportunity to dig down behind the departing low. So even if the average signal from computer models is for westerly winds, that can easily mask short interludes with winds from a more northerly direction.

As the jet stream starts to try and straighten out and take a more directly eastward route across the Atlantic, it will help to drive spells of occasionally heavy rain across the country, with gales in exposure at times. The milder conditions associated with the wind and rain will be interspersed with sunnier, showery and colder weather, as the wind switches around before the next weather system arrives. Some wintry showers over the mountains in the north are possible during the colder interludes, as well as frost and fog, but averaged out it looks like the first week of December will see temperatures close to normal for the time of year.

Llun 8 Rhagfyr—Sul 21 Rhagfyr
Snow joke, there'll be little

At the time of writing there is no strong signal for any particular weather pattern to dominate during this period. Currently, the most likely scenario is for a continuation of unsettled and, at times, windy weather, especially in western parts of the UK, with eastern parts seeing the best of any dry weather. Temperatures are generally expected to remain around, or a little above, average for the time of year, although there will still likely be a chance of some frost and fog in places by night. This presently looks more likely across northern areas, where there is also a chance of some snow on higher ground.

Wythnos nesaf

The most important monthly outlook of the year? A first glimpse at whether it'll be a white Christmas...

Rhagolygu Misol
Mae'r tywydd y tu hwnt i'r wythnos i ddod yn herio hyd yn oed yr arbenigwr tywydd mwyaf profiadol. Mae modelau rhagolwg rhifiadol y tywydd o'r Swyddfa Dywydd a'r Ganolfan Ewropeaidd ar gyfer Rhagolygon Tywydd Ystod-Canolig (ECMWF) yn cael eu rhedeg nifer o weithiau'r mis (a'r tymor) i ddod, er mwyn creu darlun o'r tebygoliaeth o'r gwahanol fathau o dywydd fydd yn effeithio'r DU.

Diweddariad nesaf am 10:00, Llun 1 Rhagfyr

Crynodeb

Iau 27 Tachwedd Cyhoeddwyd am 15:42

Crynodeb

Mae'r cynnwys hwn ar gael yn Saesneg yn unig.

Remaining cloudy and murky for many overnight with patchy rain.
This Evening and Tonight

Many parts will remain cloudy with extensive low cloud giving hill fog and patchy drizzly rain. However, rain will become increasingly confined to northeastern parts. Transient fog patches to low levels are possible where clearer breaks develop. Windy in southwest.

Friday

Largely cloudy with further patchy drizzly rain likely, especially northeastern parts. Bright/sunny spells in extreme west and perhaps later the south. Breezy generally, with strong, gusty, winds in the southwest.

Outlook for Saturday to Monday

Northern parts cloudy with occasional rain. Southern parts very mild on Saturday with sunshine, before overnight fog lingers into Sunday leading to a colder day. Rain pushing southeast on Monday.

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Rhagolwg UK Diweddarwyd 16:47, Iau 27 Tach Mae’r fideo yma ar gael yn Saesneg yn unig.