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Old September 26th 12, 08:15 PM
Martin Gibbs Martin Gibbs is offline
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First recorded activity by Weather-Banter: Sep 2012
Location: Radstock Somerset UK
Posts: 6
Default 12z Model Output Summary 26/09/2012

Good evening. Here is the evening look at the 12zs from GFS, UKMO and ECM.


The pattern is agreed upon between the models between now and Sunday. The remains of this weeks monsoon depression will move away into Europe over the next 12 hours. A NW flow with a cold front embedded then moves down over the UK on Friday with a showery Westerly flow over the North on Saturday while a ridge of High pressure crosses the South. The following 48 hours see winds back to the WSW and freshen as new Low pressure moves East towards the North of Scotland spreading a trough East across all areas with rain for all, heaviest in the North.


GFS then moves towards the middle of next week with Low pressure situating close to Northern Scotland and a fresh to strong Westerly flow over the British Isles with showers and some longer periods of rain too. Later in the week a slider Low moves ESE across the South of Britain bringing a spell of quite heavy rain before clearing SE by Friday and leaving a cool, blustery and showery NW flow over Britain to start the weekend. FI is then shown to have Low pressure to the North and High to the SE with a West or Southwest flow continuing to bring alternating spells of cloudy breezy weather with some rain and brighter, drier but cooler spells.


The GFS Ensembles tonight continue to programme a return of near or just below average uppers along with changeable weather with occasional rain. However, rainfall amounts in general will be far less than recently experienced.


The Jet Stream currently troughed over the UK gradually weakens over the coming days before a new arm directs the flow on an eastward path across the Atlantic and the British isles as we move into next week.


UKMO for noon on Tuesday shows Low pressure just to the NW of Scotland and a fresh to strong WSW flow over Britain. Subject to any troughs straddling the South of the UK when and if persistent rain would occur the most likely scenario is for a sunshine and shower mix the majority of which would fall in the West and North.


ECM is not good news for those looking for dry weather. It shows a WSW flow over the UK next Tuesday with rain and showers almost anywhere. As we move through midweek and beyond Low pressure slides East over Central regions with heavy rain at frequent intervals here and severe gales over Southern England. Further North winds are much lighter but the air would be cool and unstable with the chance of showers, becoming wintry over Mountains and some frost at night should skies clear. The run ends with improvements from the South as the strong West winds push North along with the rain leaving Southern regions in breezy, rather cloudy but dry and milder conditions.


In Summary the models show that the weather remains changeable over the next few weeks. There is almost something for everybody tonight shown in the charts with a real cocktail of Autumn weather on offer over a period when almost anything could happen. The main common theme though is that the pattern of Low pressure to the North and High to the South offers spells of rain or showers and some drier and brighter spells too chiefly in the South.