HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY WEDNESDAY NOVEMBER 26TH 2014. NEXT UPDATE THURSDAY NOVEMBER 27TH 08:00 THE CURRENT GENERAL SITUATION . A slack pressure area across the UK will slowly give way to a freshening SE flow tomorrow and Friday MODELS-2 WEEK HEADLINE Becoming mostly dry with just a little rain chiefly in the North at times. Some frost and fog patches in variable temperatures. THE JET STREAM ENSEMBLE FORECAST The GFS Jet Stream Ensemble forecast shows the flow gradually strengthening over the Atlantic over the next week and crossing on a more direct West to East motion in the vicinity of the UK thereafter. GFS OPERATIONAL The GFS operational this morning shows disrupting Low pressure to the West of the UK by the weekend with a ridge from High pressure both to the East and to the West of the UK lying across Britain for the latter part of the weekend. Then the High to the West becomes the dominant feature moving into Southern Britain at times and lying just to the SW at others. A strong Westerly flow will lie across the North then with cloud and occasional rain in relatively milder air. The South close to the High pressure will see lighter winds and patchy frost and fog where clearer skies prevail. THE GFS PARALLEL RUN The GFS Parallel run is in unison with the operational in the first half of the period with the Atlantic High held slightly more out over the Ocean meaning once a few nights of chilly and potentially frosty conditions early next week a West or NW wind would bring rather cloudy winds for all with benign weather types developing when temperatures remain near average or perhaps a little above. A little rain is likely across the North from fronts passing by to the North whereas elsewhere would be mostly dry. Frost and fog would be limited in this arrangement as the UK would be covered in a lot of shallow cloud. the end of the run illustrates an attack from the North with colder and frosty weather likely should it evolve. THE GFS CONTROL. The GFS control run also follows the same basic pattern with High pressure to the SW of the UK looking the most likely option with time bringing rather cloudy and benign weather to all regions in temperatures generally settling close to normal after a few cold days early next week under a brief Northerly. THE GEFS ENSEMBLES. The GEFS Ensembles this morning show the most favoured point likely to be held in two weeks from now is the UK to be locked in a trough from Low pressure close to or over the North of the UK with the Jet flow quite well South with unsettled and at times chilly weather with rain at times and snow over Northern hills, though this brought about on a mostly Westerly flow. UKMO UKMO today shows a finger of High pressure lying across Central Britain at the weekend and start of next week. A large High is developing in the Atlantic with abroad Westerly flow across the North and a slacker easterly breeze over the far South. Many areas would become dry but probably rather cloudy with patchy frost and fog away from the windier North and far South. THE FAX CHARTS The Fax Charts support the models raw data well this morning with a freshening SE flow in a day or two gradually backing Easterly and dying down over the weekend. Complex troughs will gradually decay and move away from the UK as pressure rises later. GEM GEM this morning also shows High pressure dveloping over the Atlantic next week, although it is further away from the UK which opens the door to the North on this run with a shift towords cold North winds and a temporary burst of wintry showers and overnight frosts towards the end of next week. NAVGEM NAVGEM today maintains a ridge across the UK throughout this mornings run once the keen SE flow at the start of the weekend subsides. Dry weather would prevail for many with some frost and fog patches at times in locations where skies clear by night. ECM ECM this morning develops High pressure in from the West too next week and with the centre lying over the UK for a time the lack of a West flow rounding the North of the High is less influential giving all areas mist, fog and frost in abundance. Late in the run a small but vigorous Low to the SW does the UK a favour by preventing the High from collapsing South and allowing it to strengthen North through the Atlantic by Day 10 which would feed a brief cold Northerly down across the UK just outside the term of the run as Low pressure exits East away from the Northern Isles. THE ECM ENSEMBLES The Ensemble run shows strong support for much of the UK to be under quiet and anticyclonic conditions in 10 days time with much of the UK likely to have surface air pressure values in excess of 1020mbs. The centre of High pressure will be of paramount of importance as to what conditions will be experienced in any one place at the surface in terms of frost and fog amounts. NOTABLE TREND CHANGES FROM PREVIOUS RUNS There is a strong trend this morning for the UK to become under the influence of High pressure from the Atlantic in one shape or form from next week. MY THOUGHTS The models seem to be settling down in terms of agreement in that the UK is likely to become influenced by High pressure originating from the Atlantic next week. What is not in agreement is where that High pressure will eventually lie and it is this that will become important in ascertaining day to day conditions in any one place. The one constant is that there will be a lot of dry weather over the UK with only brief flirtations with fairly weak troughs giving a little rain at times chiefly to the North. Apart from that there is little agreed consensus on the resting place for the High with some output including ECM bringing the High across the UK meaning clear and cold conditions would develop with extensive frost and fog issues, slow to clear by day. There is also support for the High to lie or become close to SW Britain bringing an ever cloudy and benign WNW flow over the UK which means the air would infill with shallow cloud off the Atlantic and bring days of anticyclonic gloom but temperatures close to average with small diurnal variations. As usual the longer term models toys with bringing the occasional blast of chill down from the North later as the High relaxes and rebuilds North over the Atlantic but from past experience this just means a reset pattern once the following ridge topples over. The main hindrance of this High should it evolve as shown the Jet stream will be riding East to the North of the UK which will have the effect of suppressing the High South or SW and this theory has acquired some support from the ECM Ensemble 10 Day chart just released so I have to favour the least desirable option of it likely to be lying close to SW Britain with time and ensuring that no real notable weather of any kind affects the UK. There is of course a lot of water to pass under the bridge before the resting place of the Atlantic High is finally nailed as the block to the East has to subside cleanly first and the disrupted Low pressure down over Iberia in the short term behaves as anticipated currently. As a result I anticipate more shifts in forecast for the period of next week onward over the coming model runs as the synoptic pressure pattern changes. Source and credit ................ norton-radstockweather.co.uk/index.htm
Posted on: Wed, 26 Nov 2014 08:51:03 +0000
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