Short range model discussion - into 2018

[knocker]

The high res. MODIS at 1150 UTC. A few 'waves' around in the westerly flow.

https://earth.nullschool.net/#current/wind/surface/level/orthographic=-3.74,54.00,3000/loc=5.727,47.244

[knocker]

Quite a warm and dry airmass creeping into the south west at midday. Not much sign of that front

And after a clear night the cold front arriving in the north west by morning

 

Edited August 27, 2018 by knocker

[knocker]

It might be interesting to see how the ecm handles the evolution of this subsidiary vortex lobe that has tacked east from N. Canada

[knocker]

So far developing the low in the baroclinic zone around NE North America

and tracking it east where it becomes absorbed by the aforementioned major trough to the north which is digging south

Edited August 27, 2018 by knocker

[knocker]

Last evening’s EPS mean 500mb short range anomaly indicating some retrogression of the trough to the north west that would tend to back the upper flow a tad further west and thus facilitate  the Azore’s HP ridging north east and the influence of high pressure over the UK albeit still tending towards a N/S split to some extent. Temps would then rise a little from just below average to just above but perhaps with a fair bit of regional and diurnal spread and generally quite dry. This should become apparent on the overlap at the end of the short range if the prognosis is on the money.

Back to the here and now and not a bad day in prospect in most areas with some early morning Sc tending to break up during the day so a fair bit of sunshine and feeling quite warm in the light winds. But during the afternoon a band of rain from the front associated with the low south of Iceland will edge into N. Ireland and western Scotland and progress slowly south east.

Apart from the cold front continuing to track south east overnight and through Wednesday, weakening en route, a further complication is the thundery outbreak (mentioned in earlier posts) over France that is likely to track north east during the early hours of Wednesday and impact the south east. Apparently there is still uncertainty about the detail of this. Behind the front in the north cooler and showery weather.

By Thursday the weakening front is away to the south east and a ridge quickly builds over the UK portending a not unpleasant day with broken cloud and sunny intervals with temps around average. But it worth noting here (as mentioned last evening) the arrival of another lobe of the vortex over southern Greenland with a lot of energy flowing east to the south of it.

Thus by Friday the pressure on the ridge is slowly taking it's toll and although another pretty good day is on the cards with again broken cloud and sunny intervals after a chilly start, cloud and some rain will arrive in the north west from a plethora of fronts associated with the deep surface low in the Denmark straits.

And on Saturday the aforementioned fronts will track south eastwards down the country, weakening against the ridge as they go, so probably only light, patchy rain and staying dry and quite warm in the far south.

And so to the NH profile at T120 and to the question posed yesterday evening, are we going to get agreement on the evolution of the developing Atlantic trough?

 

[knocker]

A fair bit of cloud on the 0600 sat image and 0500 chart. no doubt much of it Sc under the inversion at the moment

[knocker]

This morning's fax charts for tomorrow and the Arome in the early hours

 

[knocker]

The ecm and gfs still disagreeing on the evolution from here. It essentially boils down to promoting the ridge north east or the low pressure north. Not a huge adjustment needed for them both to agree

[knocker]

The 0900 UTC geostationary

[knocker]

A fairly clear night in many areas but the weakening cold front will continue to track south east along with cloud and some patchy rain before fizzling out.

At the other end of the country a batch of thundery showers associated with the shallow low and fronts tracking north east from Biscay will effect the south/ south east

[knocker]

Quite a good depiction of the cold front and convective activity in Biscay on the 1800 sat image

[knocker]

The gfs disrupts the Atlantic trough and forms another cut off upper low just after T120. The ecm doesn't.

But it does, still, form a low in the baroclinic zone off the coast of north east N. America and run it north east on the jet to eventually bring some wet conditions to western regions of the UK by midday Sunday.

[knocker]

The NH profile at midnight

which translates to this surface analysis and WV image at 0300 UTC\

which leads on to the unfolding picture today of the cold front continuing to track south east with some patchy rain that eventually fizzles out leaving just a cloudy scenario whilst the wodge of cloud over France indicating a fair amount of thundery activity, which is currently introducing some showers in the south east, will track north east over the next few hours with some storms just impinging on the SE. Behind the cold front much cooler air and some showers, mainly along NW coasts.

The cold front clears by the evening leaving all of the UK in the cooler air and with the cloud clearing and light winds as the ridge becomes established quite a chilly start to Thursday, with maybe a ground frost in places,.but then a pleasant day with plenty of sunny intervals with the odd shower in western regions.

A not dissimilar day on Friday, perhaps a tad warmer, but there may well be some regional variations vis cloud amounts depending on the precise orientation of the high cell.

But as can be seen on the above surface analysis there is plenty of activity still to the west in the Atlantic with sundry waves forming and running north east on the jet and then north as they hit the block. Thus the associated fronts only tend to impact the NW/W of the UK with cloud and patchy rain in these regions whilst the S/SE remains dry and quite sunny and becoming warmer by Sunday.

And the NH profile at T120 with some quite significant upstream ridging

Edited August 29, 2018 by knocker

[knocker]

The Arome this morning vis convective activity in the south east

[knocker]

Quite an impressive 0600 sat image.

The overriding feature of this morning's runs as high pressure becomes more influential is the dry outlook

[Badgers01]

On 28/08/2018 at 07:41, knocker said:

This morning's fax charts for tomorrow and the Arome in the early hours

 

Seems a good fit with this mornings heavy rain in the SE.

[knocker]

[knocker]

Quite a good depiction of the showery airstream behind the cold front on the 0900 sat image.

[knocker]

The high res. MODIS at 1130 UTC

[knocker]

The fronts associated with the low in Denmark Straits tend to hit the buffer of the ridge over the weekend leading to a NW/SE split with cloud and some rain favoring the former. But the regional temp variations are not that straightforward probably due to variation in cloud amounts,

Edited August 29, 2018 by knocker

[knocker]

Last night’s EPS anomalies tend to put in context where the evolution in the Atlantic and Europe has been indicated for a few days. A slight adjustment of the orientation of the low/vortex complex over the Pole/N. Canada/ Greenland,  ridging in NE/N Europe with strong positive anomalies ad low pressure to the south/south and west of the UK all facilitates ridging from the Atlantic into northern Europe and portends a fairly lengthy period of settled and dry weather for most of the UK. Still a lot of energy exiting the NE of N. America, north of the high pressure in the south east, but it backs south westerly in mid Atlantic and mainly swings north of the UK, courtesy of the block, but may still impact the north and thus tending to a NW/SE split.

The orientation of the surface high cell will likely determine the cloud and temp distribution as well as the diurnal spread of the latter.

In the meantime, with high pressure becoming influential overnight, most of yesterdays cloud and showers will have gone resulting in quite a cool morning in many places with a ground frost possible in the usual spots in the north.

But it will become quite a pleasant day with a fair bit of sunshine, more particularly in the east, as cloud will pop up in the west with maybe the odd shower.Temps around average, perhaps a tad below

 

The showers and cloud will tend to dissipate overnight heralding another cool morning on Friday and then a similar day to today, perhaps a tad warmer, The one proviso being that fronts, associated with the deep low in the Denmark Straits, have edged east and may bring some cloud and patchy rain to the far south west.

The story of the weekend is essentially the aforementioned fronts struggling against the blocking ridge. Thus on saturday cloud and patchy rain will effect NW and W areas whilst further east it will be sunnier and quite warm.

A not dissimilar story on Sunday with a complex area of low pressure to the north west and north and the fronts battling to move slowly south east over the UK

On Monday the fronts are still traversing the country so to the north west more cloud and possible some light rain in places whilst again to the south east sunnier and getting a tad warmer.

And the NH profile at T120 is not a million miles from where we came in

Edited August 30, 2018 by knocker

[knocker]

And the tropical system forming near the Cape Verde Islands around now

[knocker]

A fair bit of cloud around on the 0600 sat image. Total cover down here of Ac and Cs which is no great surprise looking at the midnight sounding although the earlier Sc has gone/

And not a bad illustration of the N/S divide by Mon/Tues on the ecm

[knocker]

Not part of the remit of this thread but the EPS anomalies in the later range are not looking at any significant changes to my earlier comment

 

[knocker]

This morning's fax update is not pushing the fronts as far east on Sunday