28 replies to this topic

[Robbie Garrett]

So what happened?

[Candice]

Simple really, the MCS didn't want a holiday in the UK

[Victor Meldrew]

Forecasters got it badly wrong. Mainly the met office a highly payed organisation that has trouble looking at the latest readings and updating them for the customers. But don't tell everyone that because some people are so far stuck up the meto's backside they'd twist it around to make it seem that they can do no wrong. Why even in the early hours the forecasts still went for " torrential rain and alot of lightning " by next day not one person at the met says anything, it would make me feel so much better if THEY the pro's explained why it went wrong or would could be improved to stop the epic fail from happening again.

Sorry that should say " what could be improved "

[Mesocyclonic]

This was posted by Matt D over at UKww:

----

A glance at the 00z (1AM BST) soundings for Trappes (Paris) and Herstmonceux (Sussex) is quite revealing, demonstrating why N France received so many active storms overnight and why Sussex did not. As can be seen on the (modified) Trappes ascent, there is a warm nose of temps at ~850mb followed by steep lapse rates between there and 500mb. I have analysed a most unstable, elevated CAPE situation which demonstates the HUGE amount of CAPE available to a parcel of air rising from the 850mb plume. The boundary layer (lowest 1km or ~150mb) near Paris was already much cooler by 00z (probably cooled by rain/outflow from earlier storms) and storms were therefore decoupled from the boundary layer. However, this did not prevent storms forming and persisting as they were growing from out of the plume above. This situation does happen in the UK too, explaining how we (sometimes!!) get active overnight storms.

Now looking at Herstmonseux, Sussex - a sounding which is likely to be quite typical of an ascent over SE England. For an appreciable storm risk we really needed to advect some of the warm 850mb plume in from the south to generate the necessary instability to maintain storm cells that were travelling up from France. There is a very slight warm bulge at 850mb but it is very insignificant compared with the Trappes ascent and crucially we don't have those steep lapse rates between 850mb and 500mb to help create that store of elevated CAPE.

It was always going to be a knife edge scenario last night as the very unstable air was sneaking right past the far SE of the UK and there was a small risk (accounted for in my forecast) that some of this instability could get advected over the far SE for a time. It is far easier to predict thunderstorms when all the forecast parameters are 'red lining' and the only thing that can go wrong is that the storms are slightly less numerous or active than you forecast.

The position of the UK relative to the Atlantic and France/Spain often means we are clipped by the edges of these plumes and a slight shift west or east in the plume can make a HUGE amount of difference to the weather experienced and forecast success.

The extensive (and largely unforecast 12 hrs before) raft of elevated thunderstorms that affected the SE and East Anglia on Tuesday 28th June this year is an example where the plume was slower to clear than forecast, with an approaching upper trough rapidly destabilising it creating many thunderstorms over a short time period.

[Robbie Garrett]

Interesting read, so far - clearly shows that you cannot forecast 'accurately' all you can do is take a educated guess at what these things do.

All well and said, but I agree the MetOffice was slow to update last night and should created a better website of showing us why things didn't go to plan.

[SNOW_JOKE]

Not the first time the models have been a letdown this year. Who can forget the infamous Midlands/Lincolnshire 3000kj setup when everything was perfectly corresponding to a significant thundery breakdown, happening in these parts ahead of a CF axis'ed to the North. In the end it turned out the CF was the provider of the day, and everyone who set out hoping to see some 'great plains' style of storms retreated home empty handed.

Its just one of those things you have to take as a storm-chaser or even if your just interested in the weather. As Matt D's post proves all it takes is one elevated parcel of CAPE that was progged by models to shift or even dissipate with capping, and its watching the light show on the laptop instead while outside you could be seeing stars and satellites.

[pottyprof]

It's was a difficult situation to forecast for and therefore it was best to go for the worse case forecast. Better that way than to not have plans in place.

[Victor Meldrew]

pottyprof, on 23 August 2011 - 12:21 , said:

It's was a difficult situation to forecast for and therefore it was best to go for the worse case forecast. Better that way than to not have plans in place.

But in the last few years even the simplist of weather forecasts have been difficult for the top end pros. For example forecasting a sunny day clear blue skies and you get 3 days of cloud across the south east corner

[pottyprof]

Victor Meldrew, on 23 August 2011 - 12:24 , said:

But in the last few years even the simplist of weather forecasts have been difficult for the top end pros. For example forecasting a sunny day clear blue skies and you get 3 days of cloud across the south east corner

True. There does seem to be an over reliance on computer models rather than using the forecasting skills of experienced forecasters.

Perhaps someone could shed some light as to if this is the case or not?

[Coast]

I don't think any one thing 'went wrong' as such for the thunderstorm forecasts, I just think a lot of indications were 'out' and the finely balanced potential (such as it was) was only for a very small strip of land anyway. I am surprised more places didn't get the torrential rain that was being touted, although Eastbourne has had 20.6mm today so far.

[johnholmes]

There is another thread about this and I'll put my pennorth in there if anyone wishes to read it as I am one of those mentioned in the other thread as being ex Met.
Just to comment on last night they got it wrong simple as that why then you best ask them not me? A clue is the item above about the Trappes and Herstmanceaux ascents.
But I'll attempt a constructive comment on the other thread later today.

[Sprites]

Worse things happen at sea, and Ipswich town... lol

[Lauren]

I blame Terrorists.

[Robbie Garrett]

Lool, some fantastic replies. But we cannot all blame the MetO as everyone mearly almost said last night we was going to get a severe thunderstorm.

Looking at Frenchie yesterday, we almost did - but it decayed over the channel and stayed there for quite a few hours.

Something is very wrong with the climate, either if that's normal 'Climate Change' or this rubbish theory behind 'Global Warming' - we should investigate?

[Solar Sausage]

I blame the parents!

[Harry]

Robbie Garrett, on 23 August 2011 - 17:33 , said:

Lool, some fantastic replies. But we cannot all blame the MetO as everyone mearly almost said last night we was going to get a severe thunderstorm.

Looking at Frenchie yesterday, we almost did - but it decayed over the channel and stayed there for quite a few hours.

Something is very wrong with the climate, either if that's normal 'Climate Change' or this rubbish theory behind 'Global Warming' - we should investigate?

As we've discussed before...the Atlantic has been considerably quieter in the past few years (unlike the 90s) and IMO we need a +NAO, high octane Atlantic if we are going to improve our chances of seeing storms.

The last few years have been primarily -NAO and accordingly weather systems weaker. This IMO (emphasise this is just my opinion and I have little scientific evidence to back it up, just theory) is what has contributed to a less typical distribution of storms but furthermore, fewer storms generally.

+NAO is associated with stronger pressure systems, which if you think about it means our chances of storms increases. It means depressions and anticyclones are more pronounced, meaning wind distribution between to two areas tends to be stronger! If you picture a pronounced, strong depression in the atlantic moving towards a strong, pronounced anticyclone to our East, it helps provide two things which we have lacked of late - one, is a deeper fetch of winds...a large depression is likely to draw in much cooler winds on the western flank and much deeper, warmer winds on the East (with the anticyclone doing the opposite). This means we have greater potential for heightened lapse rates, bigger differences between the moisture (which has been pumped out of the Med/N Africa and the cooler drier air fed from the polar regions), bigger differences between temperature.

Most critically, it enables us to have a more N-S orientated plume than the weaker SW to NE as we've been seeing. The prevailing wind at our latitude is a SW'erly...unless you have synoptics strong enough to drive, in particular storm cells and warm, moist air, in a northerly direction, they will be influenced to a greater degree by the prevailing SW to NE winds, particularly those which often blow through the Channel (which funnily enough is orientated towards WSW to ENE, narrowing at the eastern tip)...this may help explain why our storms once nearing the channel are both falling apart and/or flinging NE'wards.

IMO, the North Atlantic Oscillation is the biggest player in respect of our chances at bigger, night time thunderstorms. If we have a bitterly cold, snowy winter, it's more than likely we are at the mercy of a -NAO. A much milder, stormier winter, then we have +NAO! The last few years in particular have seen colder, more snowy winters, followed by generally mixed bag summers and reduced thunderstorm activity. The 90s were dominated by not only +NAO scenarios (8 out of the 10 years), but particularly strong +NAOs. Since the turn of the millennium, we've had fewer AND weaker +NAOs in relation to the 90s. I'm not suggesting at all that the NAO defines solely our chances - we've no doubt have cracking storms during -NAO years and hardly in +NAO years...however, the frequency of the 90s storms (and their intensity) compared with the 00s does strike me as somewhat suspicious....

Have a look at this chart depicting NAO below and draw your own conclusions....(if indeed there are any to be made)

Edited by Harry, 24 August 2011 - 09:49 .

[Coast]

Harry, on 24 August 2011 - 09:45 , said:

The 90s were dominated by not only +NAO scenarios (8 out of the 10 years), but particularly strong +NAOs. Since the turn of the millennium, we've had fewer AND weaker +NAOs in relation to the 90s. Have a look at this chart depicting NAO below and draw your own conclusions....

Interesting..... As a kid in the mid to late 60's (a period of sustained, negative NAO) I remember regular thunderstorms in the warmer months - both day and night. Now I may be wearing those rose tinted Ray-Bans, but my love of a good thunderstorm comes from those formative years and the fascination (if not then understanding) of how nature was so big! Just reading through the last couple of years of posts in this section of the forum, we really are struggling currently - is it like the 'odd' Winters and down to the jetstream position again?

[Nick F]

Harry, on 24 August 2011 - 09:45 , said:

IMO, the North Atlantic Oscillation is the biggest player in respect of our chances at bigger, night time thunderstorms. If we have a bitterly cold, snowy winter, it's more than likely we are at the mercy of a -NAO. A much milder, stormier winter, then we have +NAO! The last few years in particular have seen colder, more snowy winters, followed by generally mixed bag summers and reduced thunderstorm activity. The 90s were dominated by not only +NAO scenarios (8 out of the 10 years), but particularly strong +NAOs. Since the turn of the millennium, we've had fewer AND weaker +NAOs in relation to the 90s. I'm not suggesting at all that the NAO defines solely our chances - we've no doubt have cracking storms during -NAO years and hardly in +NAO years...however, the frequency of the 90s storms (and their intensity) compared with the 00s does strike me as somewhat suspicious....

Have a look at this chart depicting NAO below and draw your own conclusions....(if indeed there are any to be made)

But you could argue that some areas of Britain this year have had a fair bit of thundery activity, expecially NE England and probably some other areas too. While at the same time, for sake of keeping to the subject of the title of this thread, 'French Imports' appear to have drastically reduced in recent summers which coincides with a reduction of slow-moving troughs setting up just to our west and SW which allows those classic thundery Spanish Plumes to spread across the UK. This may bring a reduction of storms to the SE corner of the UK, but not necessarily to some other parts of the UK.

Not so sure that the NAO state has any role, though could be part of the reason, along with SSTs in the Atlantic - which can influence the tendency for a pressure/height pattern to develop each summer across W Europe. And generally teleconnections in the northern hemispehere may have an influence along with other cycles.

[Harry]

Coast, on 24 August 2011 - 09:52 , said:

Interesting..... As a kid in the mid to late 60's (a period of sustained, negative NAO) I remember regular thunderstorms in the warmer months - both day and night. Now I may be wearing those rose tinted Ray-Bans, but my love of a good thunderstorm comes from those formative years and the fascination (if not then understanding) of how nature was so big! Just reading through the last couple of years of posts in this section of the forum, we really are struggling currently - is it like the 'odd' Winters and down to the jetstream position again?

Linking your observations, Coast, with Nick F's above, the 60s (if that chart I posted was accurate) was a heavily -NAO period...interesting.

[Victor Meldrew]

Forecast for today FROM LAST NIGHT!

" Cloudy morning with the odd patchy light drizzle will clear by early afternoon with sunny spells "

We've got HEAVY SHOWERS, Nice one met office keep chucking the rubbish.

Even now it says A dull start for most places with a few showers likely but it should become mostly dry by the afternoon and the cloud should lift and break to give some warm sunny spells.

We had drizzle in the morning followed by some pretty hefty showers in the afternoon.

So if they struggle with french imports and struggle with the 12hr forecast we have no hope!

Edited by Victor Meldrew, 24 August 2011 - 13:08 .