Short range model discussion - into 2018

[knocker]

Excellent 1240 UTC MODIS (courtesy DSRS) with the front over Ireland and the low cloud that hasn't shifted from here all day

[knocker]

The band of cloud and patchy light rain currently over N. Ireland and western Scotland will track south east this evening, tonight and through tomorrow leaving clearer weather in it's wake so central southern Areas will tend to cloudy and much cooler than today.  And depressed temps applies particularly along north east coastal areas with the onshore wind as the high establishes to the west.

[knocker]

The gfs has the quite active front associated with the deep trough in the Greenland/Iceland area tracking east and impinging on the north west over the weekend as it hits the buffers of the block. Apart from introducing some patchy rain in the area it initiates a fair temp spread on Sunday

 

[knocker]

The 1800 geostationary with the front easing south east and thick fog over Cornwall

[knocker]

The ecm is not without interest at the end of the short range. It is looking at some disruption at the base of the upper trough to the west which could well activate some instability around the low pressure in the western Med and push this north towards the UK.

[knocker]

Today marks the transition to a different airmass once the cold front, currently the north Midlands, clears the south coast by this evening. This is not a problem as high pressure will still dominate so a spell of sunny and dry for most, albeit with a marked diurnal temp range with some ground, and even air frost possible.

So today very much a north/south split with N. Ireland and Scotland and northern England clear and sunny, after a cool start, whilst central southern, south west England and Wales, cloudy with patchy light rain as the front moves south before clearing this evening. Temps will be much cooler than of late, particularly along eastern coasts where an onshore wind will prevail thanks to the high pressure building to the west.

With the high cell safely esconced over the UK tonight will be clear and quite chilly leading to a pleasantly warm and sunny day tomorrow.with the usual caveat vis the east coast.

Very similar on Friday although a decaying front could bring some cloud and possible some light rain the N. Ireland and north west Scotland and more cheer along the east coast as the high cell adjusts and snips the onshore wind.

generally another fine and sunny day on Saturday but changes are afoot to the west where the surface features associated with the deep Atlantic trough are pushing east against the block resulting in the wind picking up in N. Ireland and western Scotland accompanied by cloud.

Edited May 16, 2018 by knocker

[knocker]

The above post is incomplete as suddenly I cannot upload images.

[knocker]

Just to finish if possible.

The fronts track further east by Sunday bringing some patchy rain to N. Ireland and western Scotland with strengthening winds whilst the rest of the country enjoys another warm and sunny day.

All of this fits quite neatly into the overall NH pattern as depicted by the short term anomalies

 

 

[knocker]

Satellite at 0500 and 0400 surface chart

[knocker]

This morning's 0600 UTC geostationary

[knocker]

The ecm perhaps looking to disrupt the base of the Atlantic trough and engage the low pressure in the western Mediterranean perhaps a tad more more than the gfs at the end of the short range and thus more likely to bring some instability north into the south. Just a thought.

Edited May 16, 2018 by knocker

[knocker]

The 0900 geostationary showing the southern half of the UK under cloud and also cloud at the base of the high cell south west of Ireland

 

 

Edited May 16, 2018 by knocker

[knocker]

Great overhead high res. MODIS at 1330 UTC (courtesy Dundee Satellite Receiving Station)

[knocker]

The gfs seems to be taking a closer look at the evolution in the latter stages of the short range

At midday Sunday it starts to deconstruct the Atlantic trough and split the Azores ridge with quite an active front along the quite marked airmass boundary. This front is orientated SW/NE and is developing a little wave whilst already impacting N. Ireland and western Scotland

By 12 Monday the wave has tracked north to be over western Ireland which and by so doing has temporarily curtailed the Azores ridging north east and and at the same time perhaps activated some instability to the south which may move north.

The ecm has been toying with something not completely dissimilar

Edited May 16, 2018 by knocker

[knocker]

The ecm is on the same page as the gfs and has the front and wave over Ireland 12 Monday, with rain into N. Ireland and Scotland, which also temporarily blocks the ridge whilst promoting some instability to the south. Not particularly looking like amounting to much at this stage.

Edited May 16, 2018 by knocker

[knocker]

Today is the beginning of a period of quiet and pleasant spell of weather for all, with the odd exception. dominated by high pressure, so waffle can be kept to a minimum. Although it is worth remembering how impressive the cold trough, and the east bound energy south of it, is as it makes the odd dent in the block. But of course the resilience of the block augmented by the ridging Azores high pressure is equally, if not more so, impressive..

The decaying front finally cleared to the south last evening leading to clear night. This will continue today with plenty of sunshine and temps quite respectable albeit east and south east coasts may be a tad cooler with the onshore breeze. Some cloud may bubble up of western Scotland and the north west as the day progresses.

After a clear, chilly, night resulting in a ground frost in some places tomorrow will be another warm and sunny day with temps a little above average. The odd exception as mentioned earlier, will be N. Ireland and north west Scotland which will be cloudy with some patchy rain from a front loitering in the vicinity.

After a clear night Saturday will be sunny and warm for all although worth noting that the center of the ridge has shifted into the North Sea under pressure from the aforementioned energy.

By 1200 Sunday the trough to the west has deconstructed to some extent which impacts the Azores ridging north east and facilitates the movement of the front(s) east bringing cloud and rain to N. Ireland and the north west with also freshening winds Conversely this also allows the high pressure to the east to ridge south west thus the rest of the UK will continue to bask in warm sunshine.

Although Monday will be another warm and sunny day for many areas there will be cloud and patchy rain to the north and west courtesy of the front hanging around and there could well be the odd thundery shower in the south drifting north from the low pressure area to the south

But the deconstruction of the trough does promote the low pressure and instability from the south according to the gfs

 

Edited May 17, 2018 by knocker

[knocker]

Quite cool in the north at 0500 UTC

[knocker]

The 0600 UTC geostationary  A fair bit of high Sc here

[knocker]

The ecm not dissimilar to the gfs

 

[knocker]

The UKMO has the upper trough down through Ireland at T120 which temporarily severs the HP connection before it deconstructs

 

[knocker]

As previously mentioned the Atlantic trough starts to deconstruct by 1200 Sunday when there is an active front orientated SW/NE along the strong thermal gradient. There is some very cold air in the trough denoting it's origin. The front is bringing cloud and patchy rain to N. Ireland and Scotland whilst elsewhere benefits with another warm , sunny day,. from the high pressure to the north  east ridging south west

The front is still lingering around the north west on Monday but the deconstruction has continued with a cut off upper low giving a boost to the low pressure over Iberia and this then tends to track north thus squeezing the ridge,and initiating a brisk E/SE wind and maybe some showers in the south. Still another pleasant day in most areas.

Edited May 17, 2018 by knocker

[knocker]

There is quite an interesting band of cloud adjacent to Cornwall on the 15 and 18 geostationary sat images relating to I no not what. Perhaps an upper trough as we had some very thick Ci here early afternoon which was around 23, 000 feet according to the sounding

 

[johnholmes]

but the deconstruction has continued 

Am I the only one on here that wonders what deconstruction of a trough actually means?

Can you explain please K?

 

 

Edited May 17, 2018 by johnholmes

[knocker]

5 hours ago, johnholmes said:

but the deconstruction has continued 

Am I the only one on here that wonders what deconstruction of a trough actually means?

Can you explain please K?

 

 

I mere lo use it, rightly or wrongly John, to denote when the axis of an upper trough has 'split or become 'deformed' under some form of external pressure, often as the result of a major block within the  general pattern'. Resulting, as in the current scenario, you often get cut off upper lows escaping along the path of least resistance towards other low pressure areas when the prime energy path is diverted.

Edited May 18, 2018 by knocker

[knocker]

Not surprisingly the overnight NH pattern is much as expected with the key players remaining the Greenland trough, the Scandinavian ridge and low pressure in the western Mediterranean. Thus the srong westerly upper flow diverges in mid Atlantic courtesy the block The 250mb wind field might help clarify what I was waffling about above. On the other hand it might not

Today after a cool and clear night virtually everywhere will have another warm and sunny day. The exception being the north west of Scotland where a front is still hanging around thus cloud and some patchy rain. East Anglian coasts may be a tad cooler but the winds are lighter than yesterday.

After another clear and quite chilly night in places and then tomorrow will be warm and sunny just about everywhere, the front eventually drifts away from north west Scotland. Temps a little higher than today but a little lower around some coasts if the odd sea breeze kicks in. But by 00 Sunday fronts associated with the deep low near Iceland have tracked east and introduced cloud and rain, with a strengthening south west wind, into N. Ireland and the western Isles.

Overnight and through Sunday the front stalls to the west as it hits the buffers of the high cell to the east ridging south west into the UK thus whilst most of the UK has another warm and sunny day N. Ireland and western Scotland will continue to experience cloud and patchy rain. Another consequence of this is the major upper trough to the west comes under extra pressure as the Bermuda high begins to amplify north east

By Monday the pressure on the upper trough has resulted in a cut off low slipping south east to merge with the low pressure over the western Mediterranean  The upshot of all this on the surface is a continuation of cloud and rain in N. Ireland and western Scotland whilst elsewhere it will be a very warm day with a risk of some heavy showers in the south

By Tuesday the front has moved a tad east so cloud and some patchy rain in western areas but it is another very warm day with distinct possibility of thundery showers developing in the south

The rainfall distribution tends to illustrate this scenario.

Edited May 18, 2018 by knocker