Storm discussion: including convective possibilities

[Coast]

Monday's storm action doesn't appear to be up to the same level as Friday/yesterday, but none the less. There looks like there could be some more moderate to strong winds and rain with a small chance of some more convective action:

What do you think?

[chapmanslade]

I agree, as well as later in the week.

The really big events are usually small scale rapid cyclogenesis spinning off a dominant low pressure. Next week looks windy from time to time but not really stormy in my opinion.

[Mondy]

I agree, as well as later in the week.

The really big events are usually small scale rapid cyclogenesis spinning off a dominant low pressure. Next week looks windy from time to time but not really stormy in my opinion.

Say that to the good folks of the Outer Hebrides!

[Cookie]

Say that to the good folks of the Outer Hebrides!

that's what I like to see, hope it comes off!!

[Zenarcher]

12z on NW charts,

Thursday 6am,

Thursday 6pm,

Thursday 9pm,

Friday 12am,

[dave48]

Is this the convective discussion too? Sorry if it's not, maybe a specific thread needs to be made but there are some interesting convective cells at the minute and certainly a small chance of some thunderstorms during the next 24 hours. Estofex have their forecast out now.

http://www.estofex.org/

[A.J]

I wasn't sure either. I thought the 'Atlantic Lows' thread was for discussing LP systems and their associated wind and rain, whereas the 'Convective Discussion' thread was for the potential of thunderstorms.

I agree that a seperate thread should be made so as not to have too many posts about different current or upcoming events.

Twas my fault, On friday I pm'd admin requesting to merge both threads during the weekend's event to discourage diluted posts, no doubt by tomorrow the storm thread will be back :winky:

[Cookie]

I was getting confused as well. the Atlantic lows thread used to be over here in this section of the forum but got moved to the seasonal area. so cant see why lows untill they become major be discussed over their.

Edited November 15, 2009 by cookie

[dave48]

Hopefully a mod will see this and lock and create new ones as appropriate.

Anyway as ESTOFEX say, small chance of some thunderstorms, level 1 probably not warranted despite the good shear values. Nothing from UKASF or UKWW as yet.

I have to say that this weekend was well forecasted in a convective sense, it was a difficult one in that there was this sort of overlap with the severe gusts, many of the convective forecasts include that because convective storms can obviously enhance them. All the main forecasters picked up on the tornado threat too, and that was obviously realised several locations. I suppose the other confusing thing is that you don't need hugely electrically active storms to get tornadoes and this weekend certainly reminded me of that. We saw the possible low topped supercell on saturday I think it was and that wasn't that electrically active.

So yes, a big thanks to everyone forecasting what was a very interesting few days, and continues to be an in interesting period.

[Somerset Squall]

Usually November's are dull, this one couldn't be further away from that!

[Roger J Smith]

Did you people see the Day after Tomorrow storms on the 12z GFS run slated for next weekend and middle of the following week?

Not too concerned yet, but this November set-up in general is conducive to major storm development, warm anomalies east and south, tight jet stream gradient from southwest, warm SST values in cyclogenesis zone ... not to mention December 2-4 will feature a perigeean full moon - northern max combo that gets even tighter on Dec 31 and Jan 30, 2010.

Are the big storms still on the 18z run?

I guess I can find out for myself. Off I go then.

[Hurricane Debby]

Morning all. Ding ding round two !!! Woken to a couple of flashes of lightning and long rumbles of thunder. Wind not too bad but peeing down. Wasn't expecting thunder I have to say ! Wheh heh !

[Tom Montalbano]

Morning HD,

Can confirm thunder here too in S.E.London, about 15 minutes ago. Thats now 3 days in 4 that thunders been heard in this area, not bad for mid-November. Heavy rain now , as well.

Regards,

Tom.

[Coast]

Hopefully a mod will see this and lock and create new ones as appropriate.

Differing opinions on that one Dave, some want a single thread covering all the current storms (convective, low pressure wind/rain, general Atlantic lows) others want specific threads for each element of the storm activity. I'll check with my colleagues this morning and see what the consensus is. :blink:

In the meantime, can I just highlight that ESTOFEX forecast for today:

Storm Forecast

Valid: Mon 16 Nov 2009 06:00 to Tue 17 Nov 2009 06:00 UTC

Issued: Sun 15 Nov 2009 22:22

Forecaster: SCHLENCZEK

A level 1 has been issued for Portugal and W Spain mainly for excessive rainfall and severe gusts and to a lesser extent for tornadoes.

SYNOPSIS

An upper longwave trough over the central N Atlantic will shift eastward during the period. Ahead of this trough, a 90 m/s jet streak stretches from extreme NW Iberia towards N Germany. In the vicinity of this jet streak, a developing surface low centred NW of Scotland will move northeastward. The cold front of this low will cross western France in the early morning and move eastward while weakening. Most showers and thunderstorms on Monday should be associated with the upper trough / cold front. Further upstream, a plume of warm and moist air is advected from the Canary Islands towards SW Iberia with cyclogenesis expected on Tuesday near the Bay of Biscay. An upper cold core over the Norwegian Sea will lead to unsettled conditions in parts of Scandinavia.

Most parts of southern Europe will see quiescent conditions on Monday and Tuesday as an upper ridge overspreads the western / central Mediterranean. Remnants of an upper trough over the E Mediterranean / Black Sea are forecast to shift eastward, leading to thunderstorms over the Black Sea and the E Mediterranean.

DISCUSSION

... SE Ireland, Irish Sea, British Channel, SW North Sea...

A few hundred J/kg of CAPE are forecast along the northern parts of the cold front and also near the upper cold core of the surface low near Scotland. A narrow multicell line may develop along the cold front in a strongly sheared environment (DLS around 30 m/s, LLS around 15 m/s) and an isolated severe gust cannot be ruled out. A strong gradient flow may allow some strong / severe gusts in the wake of the cold front which are mostly non-convective. Overall threat is too marginal for a level 1.

Carol said on the BBC Breakfast forecast there had already been reports of a thunderstorm in Hants and Debby's post above confirms that the storm have risen early this fine Monday morning!

Nothing from TORRO or UKASF this morning so far, general charts showing:

More fun and games today then. A nice active month and still more to come?

[Lewis]

Good morning all,

A fairly active week ahead thanks to a very active Atlantic!

This morning there's a small little system zipping across England and Wales, it's nothing major, just a small system pushing across the South and as it push's further North with the Center to the north over Scotland, the winds will pick up with gusts for a time around the 45-50mph mark across parts of N England.

As we look ahead to this coming Thursday we are looking at another fairly large system pushing from the West. As it stands I doubt it will be as "severe for the areas that do get the strongest winds" as the low pressure according to the current charts is not as deep to the one that battered parts of the South over weekend, although its fairly significant enough to warrant any warnings of high winds, I expect the winds to top 70mph possible 75-80mph in the western isles, with 45-65mph winds elsewhere.

It will bring with it some fairly heavy rainfall for the Western Isles, Mainly NW England, Wales and possibly the SW of England. Other areas including N England, may get some fairly hefty rainfall later in the day during Thursday night into Friday morning.

Convective potential is there once again with these type of systems, they will be a fair amount of instability around, so don't rule out the odd thunderstorm or even tornado.

Temps will be above normal for this time of the year during Thursday/Friday, with max temps around 14-15°c.

Temps over night will even struggle to get to single figures due to the strong wind, with temps averaging around the 10-11°c mark.

The precipitation is hard to forecast this far out, with another LP close by, it's hard to work out the exact flow, although the more likely scenario is for the precipitation to push East from the West and later in the day it may track more N/NE.

All-in-all I'm certainly looking forward to another active week, with the attention moving further North this week. Still at this stage, there is no sign of a Northerly insertion, and I don't think we should be looking for one to at least around the middle part of December.

Lewis

Edited November 16, 2009 by Storm Force Lewis

[Lewis]

Gusts of 64mph down south and a lot of 56-59mph gusts down south, looks like this little LP is deepening rather unexpected by the GFS.

Could get windy up here later!!

[Roger J Smith]

06z GFS suggesting an intense storm for Ireland on Saturday. The pattern is such that the windy gradients from late Wednesday through Friday would be more of a constant moderate gale in many parts without really strong gusts or convection along fronts, more of a rain and drizzle potential, but this Saturday low if it came off would bring 100 mph gusts or worse to west coast of Ireland and these would spread in some form into western Scotland too. We've seen the GFS offer up these intense storms at 96-120h before, then found them downgraded, however, this constant pumping up of strong southerly winds and the raging jet across the Azores have me concerned that sooner or later, this pattern will reload into another severe windstorm and possibly one as intense as the GFS wants to create here.

As the last such offering was fairly accurate on intensity but shifted more towards the UK in terms of eventual track after day five, I would be concerned about the potential here for this to hit the UK as well as or rather than Ireland.

[TonyH]

Thunder and one flash of lightning half hour ago to the ESE, first one had the flash and was 2 miles away.

Over 150mm for the first half of November.

[Lynxus]

Its currently windier here now than it was on friday!

Some VERY black clouds passing by.

I see the metoffice have warnings out for thurs & fri.

Could be interesting.

[Coast]

I see the metoffice have warnings out for thurs & fri. Could be interesting.

I really shouldn't do this to myself, this early in the week as well!!!

[Lewis]

Highest gust today 25.9mph

[Lynxus]

LOL Coast, You love it really.

I do agree though.. Im not reading too much into it yet. I will just be disappointed.

[Tom Lynch]

OK well we did the crossing overnight in Friday 13th and was triffle wild but I got my head down and only got told off once for going out on deck(by my wife) I took the necesary precations against being seasick. 2 lagers, 1 John Smiths, 2 seasickness tablets , a 3 course meal and a bottle of red wine. It worked well and I didn't have a problem. Saw some lovely cloud structures whilst driving through France on saturday am. Right now sat watching out onto the Atlantic whilst a heavy sea mist is drifting in. been changable for the past few days cold front, warm front and troughs. Wndering i worth heading down towards the Spanish borders and see if the mountains can produce something worth watching.

Roll on the plains.

Tom

[dogs32]

Torrentail rain for Wales tomorrow expected according to Alex Deacon..

Could cause some problems later with already sodden ground

Edited November 16, 2009 by dogs32

[Nick F]

I know it's one run, and it's one model being looked at but I think alot of people should be keeping an eye on this system should it develop in the way the GFS is showing.

Large divergence between the 'big three' models from the 12z output for Saturday and Sunday, ECM has a much shallower feature tracking NE across Ireland to Scotland, while UKMO has a slow moving low wallowing to the SW of Ireland both days.

So the jury's out for now ... until we get nearer in time, probably Weds-Thurs the models might have a better handle - though GFS seems quite persistent, but it maybe overdeepening its dartboard lows!