18th October 2011 - Convective/storm Discussion & Reports

[Coast]

ESTOFEX mention an area over Scotland and the North Sea today:

Storm Forecast

Valid: Tue 18 Oct 2011 06:00 to Wed 19 Oct 2011 06:00 UTC

Issued: Mon 17 Oct 2011 20:48

Forecaster: KOROSEC

No threat levels have been issued.

SYNOPSIS and DISCUSSION

The main feature today will be an intense deep upper trough located over NW Europe. There will be a small upper low crossing Black Sea during the forecast period. Stable conditions prevail across the rest of Europe.

... North Sea and surrounding areas ...

A deep trough, characterized by very cold mid-level temperatures will result in steep lapse rates, including the low levels. An intense cyclone will continue deepening while moving NE along the western Norwegian coast. Marginal instabilily will likely release with steep lapse rates over warm SSTs. Within rather marginal shear, widespread showers and isolated thunderstorms will likely form, staying sub-severe so no threat levels are needed.

UKASF map in line with the NW storm forecast for today:

Areas Affected:

SLGT: N Isles, N, W + SW Scotland, NW England, N + W Midlands, N Wales, Northern Ireland, NW Ireland

Synopsis:

Deepening upper low continues to migrate eastwards towards Scandinavia, with the trough axis located over the North Sea. With significantly cold air aloft, widespread convection is expected over seas.

Discussion:

Cold air aloft (T500's of -35C etc) atop warm SSTs will steepen lapse rates and generate a few hundred J/kg CAPE. As a result, numerous showers and a few thunderstorms will develop with ELTs as low as -50C locally. Due to the nature of coastal showers, lightning is possible throughout the period, regardless of daytime heating. Small, locally moderately-sized, hail is possible in many of the showers given the cold air aloft.

Weak DLS in areas of interest, but significant (>30kts) LLS would allow the potential for an isolated tornadic event, particularly across Northern Ireland and NW England where conditions will be most favourable.

Showers will persist well into the evening close to exposed coasts, but will die inland as daytime heating rapidly subsides.

SkyWarn still have the general forecast that's been up since Thursday. 21st OWS not showing anything but their UKMO interpretation shows:

KO index very messy, especially over France:

Shear:

Some convective precip in Northern England and Scotland:

Lapse rates:

Moderate amounts of CAPE, mainly confined to Western Scotland:

Looks like a low risk today with maybe some isolated thunderstorms in Western Scotland and the far North of England with those high lapse rates and marginal shear.

[Nick F]

Should be plenty of lively showers packing in across northern and western areas today, with hail, thunder and even sleet & snow over hills of the north. Please discuss and give your reports here.

Netweather storm forecast issued earlier this morning: http://www.netweathe...convective;sess=

A good weather site page for lightning detection using UKMO Atd: http://brunnur.vedur...ar/sf_na_1d.gif

[Backtrack]

Yep, already some sharp showers packing in over here.

Nothing thundery or containing hail yet, but then again we rarely do get storms from this type of setup.

Can always hope for some hail, which in Winter the Irish Sea NEVER fails to produce.

[Cheshire Freeze]

LOL same old story of recent years here ATM- winds too westerly meaning the showers are hitting north Cheshire and Manchester. I'm just glad this isn't a snow scenario!

[Backtrack]

LOL same old story of recent years here ATM- winds too westerly meaning the showers are hitting north Cheshire and Manchester. I'm just glad this isn't a snow scenario!

Damn that'd be good. Showers very frequent and heavy here.

[Cheshire Freeze]

Damn that'd be good. Showers very frequent and heavy here.

Haha wouldn't be good for here.....trust me.....been through that heartbreak too many times before. When you have 1-2cm of snow lying but there's almost a foot of snow just 15 miles up the road, it tends to make you feel a bit nauseous I can tell you.

[Backtrack]

Haha wouldn't be good for here.....trust me.....been through that heartbreak too many times before. When you have 1-2cm of snow lying but there's almost a foot of snow just 15 miles up the road, it tends to make you feel a bit nauseous I can tell you.

It's very rare the Irish Sea produces that amount of snow for me. For Manchester it's likely as the clouds are starting to rise before they hit the Pennines, meaning they get more snow than we do.

But if you look at the radar, there are some nice showers coming in from over Wales, and since the flow is so fast today due to the high winds, the hills aren't likely to kill them all off. You'll have a soaking soon, trust me.

[Cheshire Freeze]

It's very rare the Irish Sea produces that amount of snow for me. For Manchester it's likely as the clouds are starting to rise before they hit the Pennines, meaning they get more snow than we do.

But if you look at the radar, there are some nice showers coming in from over Wales, and since the flow is so fast today due to the high winds, the hills aren't likely to kill them all off. You'll have a soaking soon, trust me.

Haha. It's ok, I'm waiting for the winds to turn more NW'ly, though by that time the showers won't be as potent as the ridge starts to spread in. For what it's worth, I haven't seen a true Cheshire gap streamer for years and years- if this can set up in the right place during winter with cold enough air embedded, it can snow continuously for hours.......and the best bit?........Manchester tends to miss out

[Backtrack]

Haha. It's ok, I'm waiting for the winds to turn more NW'ly, though by that time the showers won't be as potent as the ridge starts to spread in. For what it's worth, I haven't seen a true Cheshire gap streamer for years and years- if this can set up in the right place during winter with cold enough air embedded, it can snow continuously for hours.......and the best bit?........Manchester tends to miss out

I would love that. Especially if Manchester missed out!

We always do well from the Irish Sea though. Take last winter for example. We had around 8 inches of snow in about 3-4 hours from a band that appeared out of no where!

Streamers are absolutely brilliant, although it tends to be North of here that gets them.

According to the GFS the flow should switch around 18:00, but by that time solar heating has died off and it's no fun to go outside and enjoy the rain

Move further North.

Edited October 18, 2011 by Backtrack

[Cheshire Freeze]

Move further North.

Don't tempt me any more than I already am, it would solve a lot of weather related stress lol

[SP1986]

I remember well, as here there was barely an inch. I can testify it was deeper elsewhere though, they got a fair few inches in Birkenhead, it was said to be deep down the coast towards Ellesmere Port too.

[Backtrack]

Don't tempt me any more than I already am, it would solve a lot of weather related stress lol

The minute you move Crewe will get battered by blizzards of epic proportions and where you move to, rain.

A shower really took off then, thought it was hail but it was just very large rain drops. Looks like walking the dog is going to have to wait. Cannot be bothered getting too wet. I wonder if a streamer can set itself up today? Would be interesting!

I remember well, as here there was barely an inch. I can testify it was deeper elsewhere though, they got a fair few inches in Birkenhead, it was said to be deep down the coast towards Ellesmere Port too.

Doh! It was much deeper than that here I assure you. You do seem to miss out a lot Stephen.

[Stuart]

yep some sharp showers here to

Areas Affected:

SLGT: N Isles, N, W + SW Scotland, NW England, N + W Midlands, N Wales, Northern Ireland, NW Ireland

Synopsis:

Deepening upper low continues to migrate eastwards towards Scandinavia, with the trough axis located over the North Sea. With significantly cold air aloft, widespread convection is expected over seas.

Discussion:Cold air aloft (T500's of -35C etc) atop warm SSTs will steepen lapse rates and generate a few hundred J/kg CAPE. As a result, numerous showers and a few thunderstorms will develop with ELTs as low as -50C locally. Due to the nature of coastal showers, lightning is possible throughout the period, regardless of daytime heating. Small, locally moderately-sized, hail is possible in many of the showers given the cold air aloft.

Weak DLS in areas of interest, but significant (>30kts) LLS would allow the potential for an isolated tornadic event, particularly across Northern Ireland and NW England where conditions will be most favourable.

Showers will persist well into the evening close to exposed coasts, but will die inland as daytime heating rapidly subsides.

http://www.ukasf.co.uk/storm-forecasts/132

Edited October 18, 2011 by Stuart

[Backtrack]

Talk about convective. just got caught in 2 torrential hail bursts. Temperature dropped to 6.9C, winds 30mph, the windchill is almost at freezing.

That dog walk hurt!

[Cheshire Freeze]

Winds seem to be shifting slightly now, edging more NW'ly as the afternoon progresses. It can be seen on latest radar images that there appears to be less 'ganging' up of showers around the Liverpool Bay area now which is symptomatic of a wind shift. There may be a lull in shower activity for a short while but should pick up again with more spreading down towards the Midlands as we head towards evening.

[gottolovethisweather]

Talk about convective. just got caught in 2 torrential hail bursts. Temperature dropped to 6.9C, winds 30mph, the windchill is almost at freezing.

That dog walk hurt!

Thanks for the weather report Backtrack. Having read several of the last few posts, I thought this was the CreweCold and Backtrack only thread. Marvellous entertainment however.

My weather btw is crystal clear blue skies, 9.8c and 77% humidity from down here in Newbury. No sign of any convection here and most probably unlikely.

Cheers

gottolovethisweather

[Lancashire Lass]

Lots of heavy showers and hail so far today.

Thanks for the weather report Backtrack. Having read several of the last few posts, I thought this was the CreweCold and Backtrack only thread. Marvellous entertainment however.

My weather btw is crystal clear blue skies, 9.8c and 77% humidity from down here in Newbury. No sign of any convection here and most probably unlikely.

Cheers

gottolovethisweather

Wait till you see them in action in the NW regional thread

You never did eat those socks backtrack.

[Terminal Moraine]

A mainly sunny and windy day so far with just one short shower at 1145 g.m.t.

Current temp' is 8.3c and maximum gust so far, 53 mph W during the shower.

[Cheshire Freeze]

Nowt going on here, just partly cloudy and breezy. Seems a bit quiet on the showers front at the minute.

[Backtrack]

No probs I enjoy giving weather reports

As for the NW regional threads. -rubs hands together- oh yes, bring them on

The socks? Dammit I was hoping everyone had forgotten, keep it secret

Back on topic and the temperature is up to 10.5C, the wind is increasing in strength, but the rain showers have been less frequent, although when they do arrive, they are very heavy and they allow the winds to increase further. No thunder or lightning observed today and no further hail after what I reported this morning..

I want winter back, I'd have about 6-8 inches of snow by now

[sunny scunny]

A brief heavy shower has just passed through here, which was very unexpected.

[Andy Bown]

Been quite fascinating to have a number of showers all day on a streamer running from the Bristol Channel, across the Mendips and approximately

2 miles W-SW-S of my location - until half an hour ago when one was a few miles futher N and came right over giving a sharp downpour.

I'm wondering if the streamer will shift this evening and overnight to run over a different zone of the area, I certainly expect one to continue to some

extent right through the night as that more often than not happens in this set up.