Y Tywydd Rhagolwg Estynedig
Mae'r cynnwys hwn ar gael yn Saesneg yn unig.
Extended Outlooks 1800 UTC Tue 23 Dec to 1800 UTC Fri 26 Dec Issued by the Met Office, on behalf on the Maritime and Coastguard Agency, at 212300 UTC
Tuesday evening, a trough lies across northern areas of Niton, from Sole to Irish Sea with high pressure across Fitzroy and Biscay. The rough will move southeast into the continent overnight and into Wednesday morning, leaving northwesterly flow across northern areas by midday, whilst the ridge of high pressure remains across the south. The high pressure strengthens during Wednesday night and spreads across all of Niton by midday Thursday, with central pressure 1038 in Sole. This high moves eastwards during Thursday night, allowing a deep Atlantic low to move across Portpatrick during Friday morning, affecting northern Niton. By midday Friday, the high will have positioned itself across the continent, central pressure 1042 over France, but remains extended across Fitzroy. Further north, southwesterly flow persists south of the deep low. Strong winds, occasionally gale force Tuesday evening and early Wednesday morning through east Sole, Plymouth and Portland. Gales or severe gales may return to northern areas during Friday afternoonGo to top of page
Tuesday evening, a low is centred 990 Faeroes with a trough running west-east through Tyne, Dogger and German Bight, with lowest pressure 1005. Meanwhile, high pressure lies over the continent. By midday Wednesday, the low over Faeroes will have moved south, located Cromarty 998 elongating to south Utsire with the same central pressure. The trough in the south will have moved into the continent. Overnight and into Thursday, the low will have continued southeastwards into the continent by midday, leaving northerly flow across Cullercoats with a ridge of high pressure beginning to build across the UK. This ridge transfers eastwards across Cullercoats overnight and into Friday morning. A vigorous Atlantic low will develop later Friday, affecting the Cullercoats area during the evening. Strong, occasionally gale force winds Tuesday evening through Thames, Dover and Wight, easing during Wednesday. Potential strong winds through central Cullercoats during Wednesday day, easing overnight. Widespread gales or severe gales may return during Friday eveningGo to top of page
Tuesday evening, a low is centred 990 Faeroes, influencing much of Portpatrick. This low will gradually move southwards overnight and during Wednesday morning, located Cromarty 998 by midday. A col will develop to the west of Portpatrick and move east Wednesday night, and then a ridge of high pressure will build from the south into southern areas of Portpatrick by midday Thursday. The high pressure will transfer northeastwards Thursday night, allowing a rapidly deepening area of low pressure to move east from the Atlantic into southern and western areas by midday Friday, with central pressure 989 at North 58 and West 20. This low is expected to continue eastwards and deepen during Friday evening. Gales possible across Southeast Iceland Tuesday evening, transferring to Faeroes and Bailey overnight and also affecting Rockall and Malin for a time. Then, later Friday, a risk of severe gales across most areas, perhaps reaching storm force in the westGo to top of page
Last Updated at 22:37 UTC on Sunday 21 December