Models, teleconnections and nowcasting

[knocker]

Over the next couple of days the gfs has one of the above lows running along the Channel as a ridge edges in from the west

We are now entering the period where the gfs has been quite bullish of late as the subtropical highs amplify and the tpv restructures. I din't really want to get immersed in any detain fro a quick look at the medium termGEFS mean to illustrate the point

[knocker]

This morning's updated fax charts and some spot gust charts from the ecm

 

Edited February 28, 2020 by knocker

[knocker]

It can readily be seen why it's dangerous to look too far ahead by comparing the the NH gfs/ecm charts at t180. The latter goes on the develop another intense low that tracks east

 

[knocker]

The EC weeklies update is still looking at a better mid March, just not tat keen at the moment to rush to get there

[knocker]

This morning's fax and the 06 ecm not fully in agreement on the structure of the low Sat 12 > Sun 00

And the low currently gearing up south west of Ireland

Edited February 28, 2020 by knocker

[knocker]

Th movement of the low/fronts/rain this evening and overnight

Edited February 28, 2020 by knocker

[knocker]

The gfs has a complex energy distribution next week but it does illustrate the role played by cut off upper lows on occasion quite well

[knocker]

Although still no agreement on the re-alignment of the tpv and the amount of influence of the subtropical high in the eastern Atlantic, the ext anomalies are all on the same page. Thus the pattern change to a drier and more settled period that has been indicated of late does appear to be firming up.

Edited February 28, 2020 by knocker

[knocker]

The North Atlantic 850mb temp anomaly and surface analysis for midnight and the 0400 UK chart

The cold fronts and band of heavy rain are currently moving east across the country (already through west Wales and the south west) resulting in a cooler showery and windy day, particularly in western regions. But the low itself is drifting north east and further rain from the occlusion will effect norther regions during the afternoon and and it will become increasingly windy

Through this evening and overnight the low continues north east with the occlusion draped across southern Scotland and the slow movement of this will be a problem vis snow down to quite low levels. South of the front very strong winds in the north and the Midlands, with severe gales in places and frequent showers in the south

A similar scenario on Sunday with rain and Snow effecting Scotland with wintry showers and sunny intervals elsewhere with perhaps some more prolonged rain in the far south as a system scoots east across norther France. the winds easing slowly

The low continues to fill and drift north but the fronts still effect Scotland on Monday with further rain and snow whilst further south another day of wintry showers and sunny interval with the wind continuing to ease

Another day of sunshine and showers after a frosty start on Tuesday, the showers concentrated in the NW/W but further systems are approaching from the south west

A very slack gradient over the country by Wednesday but the low to the south west continues to approach and rain from the associated front will effect the south west by late afternoon

 

[knocker]

According  to the gfs the tpv continues to dominate over the next five days. not forgetting the day to day fluctuations that this entails. So continuing unsettled with a mixture of showers, sunny intervals with longer periods of rain thrown in with snow over higher ground in the north

[knocker]

At t144 the ecm has trough to the NW bringing some wintry weather to the north with another trough dropping into the western Atlantic

Twenty four hours later the latter is dominating mid Atlantic

But by t204 amplification of subtropical high zones forces the trough south east across the UK

 

Edited February 29, 2020 by knocker

[knocker]

A quite violent passing hail/rain shower just now

 

[knocker]

There would appear to be an increasing difference between the GEFS and EPS in the ext period, particularly concerning the tpv and Atlantic trough. Until this is sorted caution regarding any detail of the likely upcoming drier and more settled period is probably wise

[knocker]

The 0800 chart

[knocker]

1200 surface analysis and 1500 sat image

[knocker]

Just to note that with the passage of the cold front over Sat/Sun and then the next system to quickly to follow, further moderates rain in some western areas likely. But the ecm does differ from last night's Exeter update vis the latter

[knocker]

How far south does the font trail?

[knocker]

This evening's ecm, after the Sat/Sun cold front has two further systems tracking quickly through at the beginning of next week with more strong winds and rain

[knocker]

There are some major differences between the mean anomalies this evening so until these are sorted any meaningful discussion has to be put on hold.

Key areas

The structure of the tpv, in particular the regression of the Atlantic trough

And associated with this the amplification, or not, of the subtropical high zones in the eastern Pacific and western Atlantic

 

Edited March 5, 2020 by knocker

[knocker]

As has been noted recently the pattern change that had been indicated for a while has been put on hold and last night there was no agreement between the ext anomalies.That being the case I'm approaching the weeklies up date with some caution. But according to them the change has merely been delayed and starts to occur just outside of the ext range which o course comes as no surprise

19-26 March

The tpv has re=orientated with the retraction of the associated Atlantic trough allowing the subtropical high to amplify in the east to some extent and thus some easing of the upper flow. This would portend a much more settled picture, more so in the south, with temps varying around the average.

27-03

This trend continues in the following week and hopefully if this is correct, a much drier period iif not roasting hot. I suspect most would gladly live with that

[knocker]

And the beginning of next week isn't looking too clever at the moment with the tpv firmly in charge with further troughs dropping into the Atlantic from northern Canada. establishing a complex area area of low pressure over the NW Atlantic with frontal systems traversing the country bringing more rain and strong winds

 

Edited March 6, 2020 by knocker

[knocker]

Quite a complex frontal set up currently. Clearly it was that little occlusion that brought the line of heavy showers to these parts this morning/ Very unstable to around 10,000ft on the Camborne midday sounding with a marked change of airmass at 600mb

[knocker]

A quick glance at next week with the gfs. Essentially it's a story of a lobe of the tpv and two energy flows initially leading to some very mobile and changeable weather

 This is quite well illustrated Monday/Tuesday with front whipping through resulting in some heavy rain for a short time and very windy over the two days

No significant variation over the next three days with generally a W/NW showery flow, perhaps of snow over the higher ground in the north

Edited March 6, 2020 by knocker

[knocker]

Over the weekend the current upper trough will track east and disrupt, courtesy of the ridge to the east. But is quickly replaced by another that has dropped down from northern Canada And as can be seen this process continues in the western Atlantic as further troughs merge with another emanating from the eastern seaboard as the subtropical jet gets into the act

On to the detail

A frontal system associated with a complex area of low pressure to the north west is crossing the country. The warm front has almost passed the east coast leaving much of the country in the warm sector and thus typical warm sector conditions, quite mild but cloudy with perhaps the odd spot of drizzle. Brighter in the east at first.

But the waving cold front has already brought heavy rain to NW Scotland which will linger through the morning until by the middle of the afternoon the main belt of heavy rain arrives effecting N. Ireland and as far south as NW England

The cod front and belt of heavy rain  continue to move east/south east during the evening but should clear most areas by the early hours to be followed by frequent squally showers in the now strong surface wind, which could well include hail in the mix.

Sunday a windy day of sunshine and heavy showers which may at times coalesce to give longer periods of rain, courtesy of any troughs within the circulation

A brief overview of early next week. Suffice it to say the lobe of the tpv continues to dominate and frontal systems continue to track across the country and thus remaining unsettled

 

 

Edited March 7, 2020 by knocker

[knocker]

And are we continuing to lose the trough influence in the eastern Atlantic as the tpv slowly re-orientates?

NOAA not quite there yet but perhaps a suspicion?

Edited March 7, 2020 by knocker