Convective Weather General Discussion

[Jane Louise]

Altocumulus Castellanus here this morning, hoping maybe for some thunder later on

[Coast]

It still has a long way to come though, but that low in the Atlantic is looking angry later.

[Andy Bown]

Very disappointed with the amount of low cloud because that is preventing a good view of a very disturbed mid-level sky. When it does break fleetingly

I can see much Altocumulus, some Castellanus and even a few discreet towers with high bases.

[Coast]

Those of a 'desperate' disposition, may want to look away at this point.....

[Harry]

Yes, a lengthy quiet weather spell as upper ridge and high pressure dominate. At the moment, the early part of next week looks like it could hold potential for decent convective weather for some parts, with both the GFS (06Z) and ECM in good agreement at this stage on the upper trough an associated cold upper air over Iceland pushing south and east across the UK. Would likely bring heavy showers accompanied by hail, with perhaps a low chance of weak storms within the Pm air mass. However, given the air mass and decreasing solar input at this time of year, storms would struggle to develop despite cold upper air. Obviously, being this far out, significant changes should be expected.

A slight addendum to your post Weather09 if I may - this is the time of the year when coastal areas earn the bragging rights in terms of storms. Certainly last year in particular saw numerous nights of frequent thunderstorm activity across southern/southeastern coastal areas (no doubt elsewhere also, though this was what I witnessed). If I remember correctly, during late October and November last year, I witnessed several nights (including 3/4 nights in one week) of pretty decent lightning activity, despite crystal clear and cold nights.

The relatively warmer SSTs provide a fair degree of potential, while many inland areas (sometimes as little as 20-30 miles from the coast) will struggle to see sparks except in the distance.

[Stormyking]

I was referring to land-based convection, where sufficient solar input is needed for convection deep enough for lightning. But yes, places nearer to coasts are more favoured during this time of the year as SSTs are relatively warm and aid deeper convection given better moisture than compared with over land. Autumn last year was indeed pretty active near to southern and southeastern coasts, with also some night-time storms with hail pushing inland from the south across Kent in November.

It was pretty active here too on the Isle of Wight last year especially mid november and december had a few storms.

One particular storm that comes to my mind was on the 14th november or 15th last year, which turned out to be a supercell with amazing thunder, lightning, crazily heavy, severe winds.

There was aload of other days or nights in november where there was alot of lightning activity. Also I think it was one night in december around 21st or 22nd when we thunder and lightning all night neally, not all at once but it came in spells which also came with Sleet, rain and hail mixed in with few flakes of snow.

Edited October 11, 2010 by Stormyking

[TornadoJo]

Shall I mention the lovely supercell over my house last November 14th (producing a tornado over Benfleet) which I totally missed!!

*Craws up iton a tiny ball with embarrassment!*

[Paul Sherman]

Shall I mention the lovely supercell over my house last November 14th (producing a tornado over Benfleet) which I totally missed!!

*Craws up iton a tiny ball with embarrassment!*

Yes I wont forget your Birthday young lady!

Still my only Uk Tornado witnessed and a beauty it was (EF2) The Tornado was totally seperated from the FFD And in the clear air to the South of the Low Topped Supercell (20k Height) Just goes to show what 57f with Dew of 50f can do on a Saturday morning in Mid November LOL

Paul S

[Nick F]

Well, it's been a rather boring month so far convective/storm wise. So have been looking at a few past octobers for inspiration! Take October 2000 for example, seemed quite a lively month for severe weather! Taken from T A Harley:

The second wettest October in a century - equally as wet as 1987, but not as wet as 1903, with an average of 181 mm across England and Wales. Scotland and Northern Ireland were also wet, but not so extraordinarily so. It was an exceptional month. Parts of Sussex saw about 380 mm of rain. Exceptional flooding midmonth in the SE. Heavy rain affected Kent and East Sussex. 143.8 mm fell at Plumpton (Sussex) in 24 hours up to 6pm on the 12th, 120 mm of it in 12 hours, with many sites in the region recording more than 100 mm. The flooding particularly affected the rivers Uck and Ouse. Parts of Lewes had to be evacuated. A severe and damaging tornado hit Bognor Regis on Saturday 28th. A severe gale affected the south coast on the night of the 29-30th, with a central pressure of 950 mb over Yorkshire; this is a record low pressure for England. In its wake, there was even some snow - 4 cms in the early morning of the 30th on high ground in east Lancashire. Snow fell but did not settle across much of the north - only the second time that there was October snow or sleet since records began at Leeming (Yorks.). Six tornadoes touched down within minutes of each other along the Hampshire and Sussex coasts on the morning of the 30th, causing damage and even injury.Overall it was quite a sunny month in the east and north, but dull in the west and south. Average temperatures

http://www.personal.dundee.ac.uk/~taharley/british_weather_in_october.htm

[Coast]

I'm not sticking this one in the forecast thread because

1) It isn't strictly UK more offshore/North Sea

2) It stands pretty much on its own, without much support from other sources

3) This year has been so dire, I don't want to raise any expectations!!!!!

Storm Forecast

Valid: Tue 19 Oct 2010 06:00 to Wed 20 Oct 2010 06:00 UTC

Issued: Mon 18 Oct 2010 19:20

Forecaster: KOROSEC

A level 1 was issued for North sea and coastal areas of Netherlands, NW Germany and parts of Denmark mainly for funnel clouds and non-mesocyclonic tornadoes (waterspouts).

SYNOPSIS

Between the two persisting upper ridges, one over eastern Atlantic and another over western Russia, a deep polar trough spreads SE-wards towards central Europe and Scandinavia. Accompanied by this powerful trough, a strong surface pressure with an attendant surface cold front moves across North sea in the early morning hours of Tuesday where front continues racing towards the Alps during the forecast period. More to the south, a filling robust upper low slowly moves towards ENE and merges with the coming polar trough by Wednesday morning. Another strong cold front serves as a focus for severe convective storms over Aegean sea and western Turkey, continueing from the nighttime activity.

DISCUSSION

North sea and coastal areas of Netherlands, NW Germany and parts of Denmark

Behind the rapidly SE-wards moving strong surface cold front, polar airmass will be spreading across the North sea and coastal areas of Netherlands, extreme NW Germany and Denmark. Models release a marginal instability once the steep lapse rates overspread the still warm SSTs there. Given the low EL temperatures, CAPE will be tied in the lowest levels and combined with steep LL lapse rates and weak shear (although surface winds will be quite strong from the NW), shallow convection is likely within the maritime airmass. A couple of funnel clouds or waterspouts could occur in these conditions as well. However, a marginal level 1 threat area has been placed over parts where the potential for some spout type tornadoes or some strong gusts seems maximized.

[Stuart]

i cant see much happing this time of the year we all ways got next year to look Forwoad to

[Nick F]

GFS builds some CAPE across central and eastern England mid-afternoon, we've got a trough/occluded front moving south across NW England and into N Midlands atm, which is creating a line of sharp showers into central areas - so might get some hail and a crack of thunder - especially given rather steep lapse rates across central UK, also another front further NE moving down the east coast.

[Nick F]

Have issued a storm forecast for this afternoon, though thunder and lightning will probably be isolated - could see some hail in the showers, given the steep lapse rates:

http://www.netweather.tv/index.cgi?action=convective;sess=

[Andy Bown]

Goodness me, something of interest convection wise (!!!) and several showers in the region with core rain rates around

50mm-75mm per hour!

[conor123]

Had a violent hailstorm here 40 minutes ago but i was still in college with a poor view so missed out, and typically now ive finished the action is clearing southwards :lol:

[Nick F]

Some sferics popping up across SE Midlands and Nern Home Counties recently, showers/storms seem to be organising into bands as pool of colder upper air spreads south.

Should be some good photogenic skies this afternoon with the crisp, clear arctic air, shame I’m stuck in the office.

[Lewis]

just had a very very heavy shower here in East Hull giving 4-5mm of rain in a space of 5-8 mins. Couple of rumbles of thunder thrown in too.

[Paul Sherman]

Well it took 11 months and 5 days but finally today witnessed my first Uk Bolt of Lightning in 2010

Some brief Hail as well on the leading edge at 1615pm here at SS9

Paul S

[TornadoJo]

Well my BF alled me at 4.30 to tell me he'd beenworking in Clacton all day where they had a few bits of thunder and lightening. There was aslo Hail in Basildon around this time.

And where am I? At work in W12 *sulk*

Jo

-x-

[Paul Sherman]

Lol @ Jo

Reports of a Possible Tornado about 1 Mile to my east as well near Rochford at 415pm over on Ukww

http://www.ukweatherworld.co.uk/forum/forums/thread-view.asp?tid=39537&posts=5

Well if there was the bloody kids distracted me.......Doh!

Paul S

[Noctilucid]

Evening all.

Flash of lighting from a shower approaching from the Northwest here just SW of Heathrow.

Edited October 19, 2010 by Free Three

[Kentish Kiwi]

Flash of lightning and rumble of thunder with moderate heavy showers, very dark skies though. Was amazed to see all the convection/showers on the radar when I logged on a few minutes ago I had no idea any of it was about...

[Kris T]

Flash of lightning and rumble of thunder here in Croydon 5 minutes ago! Very happy! :-)

[Costa Del Fal]

Very heavy thunderstorm like rain here this afternoon. About 4 hours ago the stream in the woodland here would have been rather low. Now its totally FLOODED!

[Coast]

3) This year has been so dire, I don't want to raise any expectations!!!!!

I need to say that more often!!!! :lol: