Short range model discussion - into 2018

[knocker]

A different, and more simplified perspective , of the complex low to the south west and associated fronts as they meander north over the UK from the 1500 geostationary.

[knocker]

Note the difference in temps N/S at 1500

[knocker]

I was hoping to pop down the country park early tomorrow before the rain from the low en route up the Channel gets going but I suspect that's off the table.

 

[chrisbell-nottheweatherman]

3 hours ago, knocker said:

A different, and more simplified perspective , of the complex low to the south west and associated fronts as they meander north over the UK from the 1500 geostationary.

That's simplified?

[knocker]

Changes continue this evening with the anomalies. Now an Aleutian ridge and trough in the SW United States and still the dual vortex lobes over Ellesmere Island and NE Canada. Thus a dual upper flow across North America exiting the south east seaboard as a strong westerly jet.

Meanwhile the block has transformed and moved east in the form of a ridge orientated Scandinavia to southern Greenland resulting in the eastern Atlantic trough becoming negatively tilted and slipping south with the aforementioned jet doing the same.

All of this leaves the UK in a very slack low pressure area with little or no lateral movement portending an unsettled period but the detail liable to be a little tricky to sort. Temps again variable but not a million miles away from average generally.

[knocker]

The key features in the short term continue to be the block in the Labrador Sea area, and the upper trough to the west of the UK being 'topped' up by energy exiting the eastern seaboard/

Thus over today and tomorrow the surface low associated with the trough tracks ENE up the Channel.

The fronts associated with the low bring patchy rain into the south west early this morning whilst at the same time rain associated with yesterdays fronts finally clears northern Scotland. This patchy rain will spread north and east during the day and overnight with eastern England and Scotland staying dry. Temps not bad but still depressed in northern Scotland.

Through Monday as the low continues east along the Channel further outbreaks of rain, some heavy, will affect mainly southern England and Wales and by 00 Tuesday the low is in the southern North sea.

Tuesday will be the best day of the week with a transient ridge bringing a dry ,quiet, day to all but by evening the upper low/trough to the west has been 'topped' up and, to risk an understatement, the associated surface area of low pressure is somewhat complex with low centres dotted around all over the place.

One of these centres then proceeds to deepen quite rapidly with a strong low level jet running to the south of it and tracks clowly north east to be 957mb south west of Ireland with the associated front already impacting the south west by 1800 Wednesday

The front does struggle north east across the country  overnight Wednesday through Thursday but eastward movement of the low ceases and it drifts north to be west of Ireland as the pattern change gets underway involving amplification east and west which diverts the energy even further south and constrains any eastbound movement. A good place to leave it.

Edited March 11, 2018 by knocker

[knocker]

Satellite at 0430 showing the cloud and rain still affecting the SE and approaching same in the SW

[knocker]

The ecm not dissimilar to the GFS with the west-east movement constrained. And the 850mb temp anomaly and contours

[knocker]

Satellite at 0930 bout the time the rain started here. Already at Culdrose at 0900

[knocker]

Cracking 1145 high res. MODIS and the midday geostationary for a broader view which shows the low to the SW and the trailing occlusion very well (Images courtesy Dundee Satellite Receiving Station). And the 1200 surface analysis. Very little rain down here this morning with a lot of Ac.As.

[knocker]

A belt of rain will move northwards through Wales and England this evening and overnight with showers creeping into the south later, No frost in the morning but nippy in Scotland,

[knocker]

Just to reiterate in what is likely to be an unsettled and windy week that Tuesday looks like being not a bad day with a transient ridge between systems.

 

[knocker]

A quick look at mid week with this evening's ecm.

At 1200 Wednesday the deep low 962mb is west of southern Ireland with the front orientated N/S just to the west of Cornwall. Not precisely the same as the latest fax

By 1200 Thursday the front has fragmented as it traverses the UK, bringing some very unsettled weather, under pressure from the amplification of high pressure to the west and north east which grind the trough to a halt. At the same time initiating a strong south easterly over the north of the UK with possible gales.

The unsettled weather with possible gales continues through Friday as the trough takes on a distinctly negative tilt.

The 850mb temp anomaly and contours

 

 

Edited March 11, 2018 by knocker

[knocker]

The 2100 analysis and satellite

[knocker]

Quite an interesting few days ahead, if not particularly appetizing, as a pattern change gets underway in the NH.

Today and this evening.

Cloudy for much of England and Wakes with outbreaks of showery rain in many areas, particularly central and eastern England where outbreaks could be quite heavy,, as the low continues it's journey eastwards to be 984mb in the London area by 1800. Scotland should see the best of the weather with a fair bit of sun and to a lesser extent N. Ireland and the south west although cloud and drizzle may affect them late on from the occlusion nudging in from the west.

Overnight the showery rain will continue to move east and by Tuesday morning will only be affecting the far south east whilst the occlusion nudges a tad further east also.

By 1200 on Tuesday the low has lost it's identity over northern Germany and a transient ridge builds over the UK portending a dry and fairly pleasant day for most. But the west of the UK a large complex upper low has formed with the not unfamiliar block in the Labrador Sea and the sub tropical jet exiting Florida creating the ideal environment for yet another Nor'easter, All of this boils down to a complex large surface low pressure area with a myriad of centres dotted about just to the west of the UK

By 1200 Wednesday one of these lows has deepened quickly with the 160kt jet running south of it and during the day it drifts NNE to be 959mb adjacent to SW Ireland by 00 Thursday with rain and the associated front already impacting N.Ireland, Wales and the south west.

But during Thursday the aforementioned pattern change gets underway with high pressure beginning to surge to the north east and the west resulting in the trough realigning with a negative tilt and the the surface front over the UK struggling to make any headway east and duly fragments.

So by 00 Saturday the stage is once more set as the UK sits at the interlace between the two energy systems, the trough with the warmer air to the west and the colder high pressure block to the east.This is of course according to the GFS And just to add last night's fax for 1200 Friday

 

 

 

 

Edited March 12, 2018 by knocker

[knocker]

Very sparse 0500 chart but what there is shows a fair bit of rain

[knocker]

Satellite and surface chart at 0600

[knocker]

Given that the GFS and ecm diverged quite early this morning a quick early glance at the gfs 0600 det, run and it is still at odds leading up to the weekend

The GFS surface and charts for 00 Friday and Saturday and the 500mb and 850mb anomaly 

The ecm for 00 Saturday

clearly this pattern change is causing some problems

[knocker]

The high res. MODIS at 1100 illustrating most of the UK under the expected cloud cover with just the west of Scotland escaping.(Image courtesy Dundee Satellite Receiving Station) A lot of rain around

 

[knocker]

The GEFS 0600 0-5 temp anomaly

 

[knocker]

The 1200 geostationary (courtesy DSRS) which, apart from the mess over the UK, does show the low south of Iceland and occlusion quite well. And the 1200 surface analysis. Perhaps the low nipped east a tad quicker than expected?

 

[knocker]

Time to relax and enjoy a relaxing day tomorrow before the defibrillators get whipped into action at the end of the week as the transient ridge promises a reasonable day.

In fact Wednesday may well be not a bad day either for most to start with but heavy rain and strong southerly winds will slowly take over as the front associated with the major trough to the west struggles east.

A similar story on Thursday although the strong winds will abate apart from the north east.

Still unsettled on Friday but changes are afoot with the trough to the west becoming negatively tilted (forcing the jet south as Interitus mentioned earlier in a much more detailed and complex post ) whilst the high cell amplifies in the north east.

 

 

[knocker]

The 1800 surface chart

[knocker]

The ecm evolution this evening is quite intriguing, It forms a small upper low over Denmark at T108 and develops it and tracks it west to be over south east England by T120 where it is still intensifying and phasing with the main trough. Will this key development repeat at midnight.

Edited March 12, 2018 by knocker

[Timmytour]

Love this thread and your running commentary Knocker. Thank you your observations are much appreciated