Ex Ts Katia To Hit The UK - Chat Thread

[Zenarcher]

UKMO 12z is out for Sunday and Monday,

Very different to the GFS.

[Alpine glow]

Nice, not ever so far away from me then but a fair distance! So do you think the whole of Britain will feel the effects of this?

This was the size of Katia on 31 August from The International Space Station : http://www.youtube.com/watch?v=7Eoa19pRHiQ

A good forum about her progress that I have been watching since the birth: http://forums.accuweather.com/index.php?showtopic=27156&st=1060

[knightrider]

Been a long time since a major storm truely effected London and south-east, even the 07 storm didn't effect us that badly here compared with the south coast and futher west. The last real big 1 I can think of was in October 2002 so it would be nice if we get a proper blast from this like 80mph+ would be decent.

This was the size of Katia on 31 August from The International Space Station : http://www.youtube.com/watch?v=7Eoa19pRHiQ

A good forum about her progress that I have been watching since the birth: http://forums.accuwe...c=27156&st=1060

Blimey that is massive, looks like it would cover the whole of the UK pretty much if the centre of it where to cross the midlands. I remember them saying Irene was about 600 miles across.

[chionomaniac]

I cant say I remember this being on the news or anything, the last major storm to effect the south of the UK was the January 2007 storm and the last I can think of in Scotland that was like major storm/hurricane force was in 2005. But maybe I just didn't watch the news that day back in May lol Did it effect mainland Scotland or was it just the Shetland isles?

And I hope that red arrow on that last predicted track is wrong cause if the centre of it sweeps across the midlands like that suggests then southern England including London could be bombed by this lmao. I does look as if we are going to get a pretty windy day Sunday though before this is even due to arrive!

The red arrow has been added by Robbie and is not the predicted path of Katia.

If you could show me graphically, I am more likely to understand what you're on about, but I am guessing that as the weather is different in the Polars to the Tropics? What exactly will determine this Ex-Hurricane heading straight for the UK, as I thought the upper winds affect storms and what direction they move, in this case the JetStream?

In order for any hurricane to survive crossing the jet stream and become a strong extratropical depression there will have to be some kind of ongoing regenerative cyclogenesis occurring. Even with a clear understanding of this process it will be very difficult to predict the exact position and strength of Katia early next week.

[knightrider]

To be honest I think the suggestions of 80mph sustained winds with gusts over 100mph are abit exagerated anyway, that kind of event would only be expected to hit the UK about once a century, twice at the most. That would be on a par with the 1987 storm, infact worse in terms of sustained winds! According to the BBC weather website the storm is going to fizzle out before it reaches the UK and other websites I've read suggest gusts of 60-70mph so quite stormy yes but nothing exceptional.

[Alpine glow]

To be honest I think the suggestions of 80mph sustained winds with gusts over 100mph are abit exagerated anyway, that kind of event would only be expected to hit the UK about once a century, twice at the most. That would be on a par with the 1987 storm, infact worse in terms of sustained winds! According to the BBC weather website the storm is going to fizzle out before it reaches the UK and other websites I've read suggest gusts of 60-70mph so quite stormy yes but nothing exceptional.

If this was to become true, 60/70mph from a ExTS will be very exceptional. We are not just talking about gusts but sustained winds.

[chionomaniac]

The 12z GFS currently shows maximum development as an extratropical depression at T+102 some distance to the west of Ireland. From then on in the system is weakening as the temperature differentials start equalling out and the jet streak fades.

Let's see what the UKMO and ECM bring.

[knightrider]

If this was to become true, 60/70mph from a ExTS will be very exceptional. We are not just talking about gusts but sustained winds.

Well it said gusts of 60/70mph on this website I went on, but your right if it where to be sustained winds of that sort of strength then yes it would be exceptional and boardering on hurricane-force, I could imagine gusts of well over 100mph if that where to be the case!

[Iceberg]

I noticed that Chino, It might well be that GFS mixes out the +10 850's a bit too quickly. Interesting that UKMO makes more of the secondary low that flows further sough on the tails of ex-Katia and then merges with it, GFS makes an attempt but never quite engages it (presumably as it mixes out the warmer air quicker).

ECM will be interesting as always.

A few things to watch IMO.

1. the exact position of the low prior to Katia as this will help set up the directional flow for ex-katia.

2. the position and intensity of ex-katia.

3. the strength and position of both the 300 and 500 jets.

4. the development of the post ex-Katia low.

5. when full development to a baroclinic low occurs, sooner and the low will fill, later and it will deepen more.

Lots more but a few points for 5.

[Robbie Garrett]

The red arrow has been added by Robbie and is not the predicted path of Katia.

In order for any hurricane to survive crossing the jet stream and become a strong extratropical depression there will have to be some kind of ongoing regenerative cyclogenesis occurring. Even with a clear understanding of this process it will be very difficult to predict the exact position and strength of Katia early next week.

hahah, sorry! I still think it will happen though.

It's just anyones guess at the moment, it could go anywhere.

[knightrider]

I know this is abit off topic but Peter Cockroft our local weather forecaster just hinted at some pretty nasty winds arriving at the weekend, steady winds of 25mph with stronger gusts and heavy rain so could be looking at some Gales. Maybe it could be the 1st signs of Katia rolling in off the Atlantic, with had storms like this in the past where the winds are quite strong in the days leading upto the main event then things go abit mad lol I'm thinking Sunday onwards could get very interesting indeed.

[summer blizzard]

some of you are amplifying the effect too much. while katia will produce hurricane force gusts in excess of 75mph, extratropical storms do not have symetrical cores and as a result sustained winds will be around 50mph, below hurricane force.

[chionomaniac]

I noticed that Chino, It might well be that GFS mixes out the +10 850's a bit too quickly. Interesting that UKMO makes more of the secondary low that flows further sough on the tails of ex-Katia and then merges with it, GFS makes an attempt but never quite engages it (presumably as it mixes out the warmer air quicker).

ECM will be interesting as always.

A few things to watch IMO.

1. the exact position of the low prior to Katia as this will help set up the directional flow for ex-katia.

2. the position and intensity of ex-katia.

3. the strength and position of both the 300 and 500 jets.

4. the development of the post ex-Katia low.

5. when full development to a baroclinic low occurs, sooner and the low will fill, later and it will deepen more.

Lots more but a few points for 5.

It is good to be able to monitor how an ex hurricane that doesn't make land fall tracks towards us. In my eyes the UKMO keeps the intensity of an existing depression to the NW at T+72. The already diminished Katia then enters the fray as a secondary to this and combines completely with this by T+120. So two very different scenarios on offer already.

[Nick F]

Not sure if UKMO global may run at a lower res, hence has been less deep that GFS and ECM over recent runs with ex-Katia as it approaches Nern UK.

[knightrider]

some of you are amplifying the effect too much. while katia will produce hurricane force gusts in excess of 75mph, extratropical storms do not have symetrical cores and as a result sustained winds will be around 50mph, below hurricane force.

Very true, even some of the biggest european windstorms with had here in the UK like the 1987 storm and the Burn's Day storm in 1990 only produced sustained winds of 50-60mph max in the worst effected areas, maybe slighly more out at sea but on land generally anything with sustained winds over 40mph here is quite unusual. Gusts are normally a little over double the strength of sustained winds until you get to the top end of hurricane's where the sustained winds are around 150mph with gusts rarely reaching over 200mph. So if we where to get sustained speeds of 40mph then winds gusting upwards of 80mph with 90+ possible can be expected which lets face it by our standards is very rare!

[chionomaniac]

It is good to be able to monitor how an ex hurricane that doesn't make land fall tracks towards us. In my eyes the UKMO keeps the intensity of an existing depression to the NW at T+72. The already diminished Katia then enters the fray as a secondary to this and combines completely with this by T+120. So two very different scenarios on offer already.

And ECM looks very similar to the GFS at T+96.

But a dodged bullet to the NW by T+120.

Edited September 7, 2011 by chionomaniac

[Liam J]

We only have to go back to January 2005 for the last event which brought near hurricane force winds to Cumbria, sustained winds of 73mph and a top gust of 101mph at st bees head and Great Dun Fell in Cumbria recorded a scary 97mph mean speed with a gust of 127mph!!

I will never forget that night and the damage the next day - large mature trees snapped off and forests flattened in the Lake District National Park, also extensive roof damage and chimney stacks toppled.

http://www.metoffice.gov.uk/climate/uk/interesting/jan2005wind/

[knightrider]

We only have to go back to January 2005 for the last event which brought near hurricane force winds to Cumbria, sustained winds of 73mph and a top gust of 101mph at st bees head and Great Dun Fell in Cumbria recorded a scary 97mph mean speed with a gust of 127mph!!

I will never forget that night and the damage the next day - large mature trees snapped off and forests flattened in the Lake District National Park, also extensive roof damage and chimney stacks toppled.

http://www.metoffice...ng/jan2005wind/

Yes there's no denying that was bad although I imagine the 97mph mean speed was recorded at a high altitude or am I wrong there? I do remember reading about this storm though and reports of gusts regularly over 100mph and quite a few reports of gusts over 120mph.

[Nick F]

T+120 ECM centre of ex-Katia between Eire and Iceland, so strongest winds over N Ireland and NW Scotland - long way off still and wouldn't take too much of a shift south for those high winds to affect a larger area of the Britsh Isles.

[knightrider]

I would say that storm was on a par with 1987 down south lol

[Andy Bown]

I know this is abit off topic but Peter Cockroft our local weather forecaster just hinted at some pretty nasty winds arriving at the weekend, steady winds of 25mph with stronger gusts and heavy rain so could be looking at some Gales. Maybe it could be the 1st signs of Katia rolling in off the Atlantic, with had storms like this in the past where the winds are quite strong in the days leading upto the main event then things go abit mad lol I'm thinking Sunday onwards could get very interesting indeed.

Wrong LOW, 'Katia' will not arrive (if at all over the BI) until Monday.

[Liam J]

Yes there's no denying that was bad although I imagine the 97mph mean speed was recorded at a high altitude or am I wrong there? I do remember reading about this storm though and reports of gusts regularly over 100mph and quite a few reports of gusts over 120mph.

Yes Great Dun Fell is 848m ASL but a 97mph sustained is a very impressive wind speed and well into hurricane force 12!!

[knightrider]

Wrong LOW, 'Katia' will not arrive (if at all over the BI) until Monday.

Yes I know that but the energy that Katia is producing could spawn depressions either side of it, I remember the October 2000 storm a low preassure arrived over the UK in the 2 days before it and we had gusts of 45-50mph regularly on the Saturday and Sunday before the the storm itself hit during the night on Sunday into Monday when gusts in excess of 90mph where reported.

Yes Great Dun Fell is 848m ASL but a 97mph sustained is a very impressive wind speed and well into hurricane force 12!!

Yes 97 sustained is about the equivelent of a category 2.

[Ruislipredbee]

Some of the runs from the states have this crossing the Atlantic straight in to Ireland into the west country across Middle England which would be the worst storm for 300 years.

This could be bad but my feeling it will run into the west of Scotland equally as bad but saving the more build up population centres of the uk.

[knightrider]

Some of the runs from the states have this crossing the Atlantic straight in to Ireland into the west country across Middle England which would be the worst storm for 300 years.

This could be bad but my feeling it will run into the west of Scotland equally as bad but saving the more build up population centres of the uk.

Worst storm in 300 years lol I doubt that, assuming that Katia will weaken slightly before it reaches us as do most tail end of hurricane's/ex tropical storms then this will be bad maybe the worst for a decade but not 300 years, even if it hit with the same power it's producing at the moment it wouldn't be any worse then 1987 so worst in 24 years maybe but cant see it being the worst for 300 years!