Short range model discussion - into 2018

[knocker]

5 minutes ago, Evening Star said:

Can I ask where you find the visible satellite images?  Thanks.

http://www.sat.dundee.ac.uk/

[knocker]

The main wodge of rain, currently north of Manchester, will move into the North Sea this evening giving way to squally showers in northern Scotland where it will also become quite windy as the low pressure area tracks east. But through the night the line of rain associated with the front will track slowly south

[Dorsetbred]

1 hour ago, knocker said:

The main wodge of rain, currently north of Manchester, will move into the North Sea this evening giving way to squally showers in northern Scotland where it will also become quite windy as the low pressure area tracks east. But through the night the line of rain associated with the front will track slowly south

 

Not too much for folks in the south to get excited about rainfall wise in the south then, Knocker?

[knocker]

10 minutes ago, Dorsetbred said:

Not too much for folks in the south to get excited about rainfall wise in the south then, Knocker?

No Dorset

[knocker]

The ecm this evening curves TS Helene up into the central Atlantic where it phases with the trough ans eventually hitches a ride with the very intense upper low that has been ejected from northern canada. Well that's the current theory

[knocker]

A changeable but relatively quiet week, albeit still inclined to to a NW/SE split but with an invigorated vortex and the remnants of tropical storms in the mix the possibility of some wet and windy weather in the near future is becoming a favored option. But that's getting ahead of ourselves so the current NH profile and surface analysis at midnight.

The rain associated with the fronts is currently over northern England and Wales and this will move slowly south during the day tending to fizzle out as it goes. But the movement of the waving front and precipitation intensity is not straight forward and pulses of rain tend to run along it as it slows, and even trots north again for a  time, intensifying the rain once more. So the south/south east will remain dry whilst further north over west Scotland the squally showers will persist.

So during the evening and overnight the intensifying band of rain will move north for a while before once again tracking south and clearing the south coast by midday Wednesday. Meanwhile the blustery showers will continue, mainly over western Scotland but also some activity over N. Ireland and north west England. By the end of the day all of the UK is in the cooler air.

By Thursday we are in a N/S scenario with sunny interval and dry over much of England and Wales whilst further north, as low pressure skirts Scotland and the weakening cold front tracks south, blustery showers will again be the order of the day.

A very similar day on Friday with the showers moving a tad further south

Saturday will mostly be dry and fairly sunny with just a few showers still in the north west but by early evening rain will be approaching Ireland from the next frontal system.

And the NH profile at T120 and the onset of the shenanigans from the vortex and the TS remnants

Edited September 11, 2018 by knocker

[knocker]

Meanwhile with Florence stalling due to a lack of any steering mechanism such as an upper trough

 

Edited September 11, 2018 by knocker

[knocker]

The ecm has TS Helene drifting north and starting to engage with the Atlantic trough. The key to future movement may well be down the strength and direction of ridging to the east and thus wind and rain impacts on the UK and possible WAA

Edited September 11, 2018 by knocker

[SmartD]

Greetings- nice thread,hope you don't mind me butting in...David

As well as the tropical systems I think it's worth pointing out the conveyor belt of moisture affecting the NW UK. The pattern is just mobile enough to avoid very high accumulations over the Lakes and SW Scotland and the max in IVT (Integrated [water] Vapor Transport) is moving into the North Sea this morning. Radar accumulations suggest only ~50mm in 24hr in parts of the NW  rather than the 100mm+ totals associated with 'Atmospheric River' flooding events.

IR image

https://aviationweather.gov/satellite

MIMIC Total Precipitable Water

http://tropic.ssec.wisc.edu/real-time/mtpw2m/product.php?color_type=tpw_nrl_colors&layer=tpw&prod=natl&timespan=24hrs&anim=html5

IVT product courtesy Ben Moore, 

http://www.atmos.albany.edu/student/bmoore/natlantic_ivt.html

[knocker]

The 0900 UTC sat image illustrates quite well the low pressure to the NW and the trailing front. And the 0800 surface chart

 

[SmartD]

Blended WV & IR, GFS T+6 850hPa wind vectors (coloured by speed) and windspeed isotachs at 250 hPa valid 06 UTC.

[knocker]

The high res. MODIS at 1300 with the rain currently fizzling out on the front leaving the band of cloud but the next pulse is due this evening Breezy with showers still across N. Ireland and Scotland

.

[knocker]

Further to the above and looking at the latest updates it appears that the distribution and intensity of the rain that apparently has been causing one or two headaches is down to an upper cold front swinging in from the south west and following behind the established front with the rain finally not clearing the south until lunchtime tomorrow.

[knocker]

Further trough ejections from the vortex, north of the blocking HP, is crucial to the following evolution

[knocker]

The ecm merges Helene with the developing Atlantic upper trough, which backs the jet stream and initiates height rises to the east resulting in Helene continuing to track NNE west of Ireland.

[knocker]

And apart from anything else flooding is going to be a problem with Florence

[knocker]

The medium term outlook will be influenced to some extent by the travels of TS Helene but prior to that a fairly mixed bag with nothing seriously drastic and once again tending towards a N/S bias.So on to the detail,  and as usual starting with the NH profile and the surface analysis at midnight.

As mentioned yesterday evening the next band of rain, perhaps heavy at times, associated with the upper cold front on the chart above, is currently over south Wales and the Midlands (shows quite clearly on the 0300 WV image)

And will slowly track south east behind the weakening surface front, not clearing the Kent until the afternoon. So cloudy with rain south of this whilst clearer and cooler air to the north but with frequent squally showers over N. Ireland and Scotland where the occlusion and low pressure to the north west is in close proximity

With the fronts finally out of the way it will be a clear night over much of England and Wales, thus probably a cool start to the day on Thursday with a few fog patches, but these will clear quickly  to give a pretty fine day. But further north the aforementioned occlusion and low pressure is still in fairly close attendance so a continuation of the blustery showers. But during the day but more persistant rain associated with the next frontal system will arrive  over N. Ireland and western Scotland by 1700.

The rain will spread east and then south east overnight and through Friday following the cold front whilst the south remains dry with perhaps the odd shower in western regions.

The north/south bias theme is epitomized over the weekend as a complex low pressure system moves east on the quite strong jet

and this and associated fronts bring rain and strengthening winds to the north on Saturday which track south during Sunday leaving the latter quite dry on both days and relatively warm on Sunday.

And on to the NH profile at T120 where quite a lot is happening with Florence going ashore south of the block, another trough being ejected from the vortex north of it and Helene entering the fray.

 

 

Edited September 12, 2018 by knocker

[knocker]

As a forerunner to what is potentially a wet and windy period for the western half of the UK quite a wet and breezy Sunday in the north

 

[knocker]

And the wave and tidal surges with Florence

[knocker]

The 0900 UTC geostationary image

[knocker]

Getting there. Modis at 1140 UTC

[knocker]

The cloud and any rain will clear the south east this evening (some ac but clear sky to the north west here now)

1500 UTC

resulting in a clear night and a touch of ground frost in some places. A continuation of the blustery showers over Scotland shorthly giving way to more persistent rain, fragmenting,  as the front tracks south east during the night.

[knocker]

Slightly outside the remit of this thread but the ecm this evening is running Helene straight across the UK. Looking at gusts around 80kts along the west coast

 

Edited September 12, 2018 by knocker

[knocker]

It's apparent that there are two jet streaks around the upper trough. Is Helene getting a boost near the right exit of the easterly one? Any thoughts anyone?

[SmartD]

1 hour ago, knocker said:

It's apparent that there are two jet streaks around the upper trough. Is Helene getting a boost near the right exit of the easterly one? ...

Did you mean right entrance?. This solution for Helene resembles ex-Debbie (1961), ex-Gordon (2006) and ex-Ophelia (2017) all of which produced damaging winds over Ireland/western UK. At the estimated time of transition the storms were near the right entrance of a meridional jet streak on the flank of a trough. Composite anomalies for the 3 cases from the NNRP.