Leaderboard

Best guess.

Hi everyone, just dropping in after a long break. I hope the variable summer weather (especially the thunderstorms) has kept everyone entertained. I must confess that I am finding all the forecast dithering over the fate of ex-hurricane Bertha rather baffling. Admittedly, forecasting potential storm tracks this time of year is somewhat difficult, owing to the lower jet speed. Yet, as I see it, the case for Bertha turning into quite a potent storm looks quite compelling. I notice that for at least 5 days, the GFS has consistently shown Bertha developing into an intense LP, keeping fairly close to the same track from run to run. That in itself suggests it is entirely possible that the track will be across England as it has been showing. That apart, the NHC, even when Bertha was still tropical, showed the expected track to be straight out into the Atlantic, south of 50N. The storm is currently very well placed to engage the jet off the E coast of Canada. There is always an abundance of very warm, moist air associated with these ex- tropical storms, which by itself increases the temperature gradient and favours substantial deepening. I think the ambivalence concerns whether Bertha will actually engage the jet or not. Well, as I said, the GFS hasn't had any doubts on that score. The latest MetO thinking gives a 60% probability of Bertha crossing S England, heading NE. Herein lies the greatest risk, I think, with a strong possibility of the storm developing a very tight gradient on its W and SW flank, as pressure rises sharply behind it. Not to mention copious amounts of rainfall, although with the likely speed of the system, that seems to preclude any significant rainfall issues. August storms of this kind are not that unusual, although this is pretty early in the month for one. Personally, I feel this storm could be quite notable, with the wind being the most potentially damaging feature. I shall watch with great interest how the situation develops and how the forecasts change in the next couple of days.

Some interesting convective potential showing on Sunday from GFS in association with the depression formed from ex-Bertha moving through. Strong jet aloft, veering wind profiles towards the surface with passage of low, 500mb dry air intrusion and several 100 j/kg CAPE in warm sector just ahead of cold front moving east = the recipe for severe thunderstorms. So potential for supercells bringing large hail, damaging convective gusts and even one or two tornadoes. Slp and jet + CAPE 12z Sun: relative humidity at 500hPa at 12z Sun - blue showing dry air intrusion - which will enhance convection: Lightning wizard wind shear and sig. tornado parameter charts at 09z and 12z Sun show the potential for rotating storms and tornadoes: However, I am only illustrating potential, rather than making an actual forecast, given uncertainty over the track of the low still. 12z ECM has the low tracking alot further south than GFS - through S England and exiting around the Wash, for example. Thus severe potential maybe confined to Sern England in this case.

Sigh, warnings were made and from some of the posts on here and news stories, some places got hit really badly. The weather warnings were well founded. There is no point trying to predict where showers will form and track as they tend to ebb and flow as opposed to organised bands of rain. That being said the imported rain never really took off this morning, though no models did well on that regard. That's the nature of showers, especially imported storms. Shall we leave this now and move on, looking forward to any pictures and videos that people got today As for the weather in my area, it chucked it down for a good 15 minutes, but I think we got away with the worst, as areas west of Cambridge found out.

The gods of rain dont seem to like Dronfield More torrential rain here now! this is amazing, Distant thunder also from the South, strikes being shown near Sutton in Ashfield also to the North near Sheffield What an evening this turned out to be!

Some serious flooding being reported here, Horns bridge area especially! Bottom of my garden is for the 4th time this year, like a river! Great little storm that was!

I detect the beginnings of the ol' north v south argument when it comes to storms. Please don't start that nonsense here.

Another update in my blog after digesting the 12z output: http://www.netweather.tv/index.cgi?action=news;storyid=6068;sess= 2100 update 08/08/2014 Still the models disagree less than 48 hours away from when the centre of the depression formed from ex-Bertha makes landfall somewhere across the west of mainland UK on Sunday morning. 12z GFS takes the centre of the low up through the Irish Sea on Sunday morning and makes landfall across Cumbria around lunchtime before exiting over SE Scotland into the North Sea, the centre on land crossing circa 985mb, so fairly deep for the time of year. It shows wind gusts of 40-60mph over coasts and hills of SW England, Wales and northern England - perhaps more on the lee side of the Pennines and mountains of N Wales, plus funnel effect of valleys. 30-40mph gusts further south and east. Rainfall totals of 50mm+ across southern Ireland, 20-30mm max across Wales and N England. ECMWF, on the other hand, takes the low centre, a shallower feature, NE across S England, exiting The Wash into the N Sea around 995mb. Winds and rainfall totals less, but still appreciable to make Sunday a windy wash out across much of England and Wales. Met Office T+48 fax chart for noon Sunday is in between ECM and GFS tracks but closer to the ECM depth with 996mb, so perhaps this maybe the best compromise for the likely track for now. GFS indicates a convective element to this storm system, with instability and strong wind shear in the warm sector just ahead of the cold front sweeping east - so there is a risk of organised embedded storms, perhaps supercells, which could produce their own severe weather in the form of strong convective gusts, large hail and even a tornado or two ... I will look into this scenario in a storm forecast to be issued nearer the time.

Thunder and lightning for pretty much 6 hours. Crazy. Saw one last distant flash as I left Tesco recently.

Some pretty bad quality lightning stills, the last one is from a CG, couldnt manage to get the bolt when pausing the video.

Moving on, FAX chart for tomorrow Light to moderate west/south westerly. Looks a fine day, just the chance of catching an odd shower. Temperatures Look reasonable, 21-24C so a decent day overall. Sunday (subject to major change) Going to do the GFS/ECM and the FAX for this to give the options on the table. GFS Bertha deepens and tracks up the Western coasts of England and Wales before pushing across Southern Scotland. For us there would be a band of steady rain and strong winds (gusts around 40-45mph). This clears to showers in the afternoon, fairly warm (21-23C) ECM Shallow wave pushing East/North East across the south of the UK, winds light to moderate but the risk of significant rainfall totals. Temperatures could get quite high before the rain arrives. FAX Wet and breezy at this point with rain pushing through from late morning. Rain looks heavy so again local flooding could be an issue. Temperatures would struggle to reach the twenties here. As you can see, great uncertainty.

Well said CS, weather forecasting, even with super computers is incredibly difficult, even more so with showers rather than frontal rain. As an example, your old stamping ground has got wet today, areas west of me Fakenham to Lynn have been soaked, We've stayed totally dry, only about 15 minutes of sun all day, very murky, looked on several occasions that it was going to pelt down, rain?? Not a drop, but such is the nature of showers. We had a big(gish) storm here 2 nights ago, wasn't forecast ( as far as I know, I was just outside Stockholm hoping for a forecast Thunderstorm which never happened) but the family enjoyed it. Weather is weather, the people who stand in front of the cameras tell us what the models see, and when the models are wrong, so are they. I couldn't predict the weather as I'm not psychic, those that rely on technology can only report what the technology tells them. The weather in the last 3-4 months has been sufficiently "different" to make the models struggle. All the models rely on past data to predict the future, they need something similar in the past to predict the future, if its not there, any numerical model will only extrapolate what it can -- and the possinbility of getting it wrong increases. Final point, the models, as we know them, have only been about less than 10 years, all the talk of the wonderful storms of the 80's and 90's were before the models as we see them existed.

And again

One of the worst short range forecasts I think I've ever seen - how on earth could they manage to miss this amount of rain?

Well that was epic in terms of rainfall. Pleanty of thunder but no lightning.

fantasy island, where the outputs are very unreliable.... i prefer Forget It though ...lol.

Storm & Convective Forecast Issued 2014-08-08 10:44:01 Valid: 08/08/2014 1100z to 09/08/2014 0600z THERE IS A RISK OF THUNDERSTORMS FORECAST Synopsis Large upper low sits to the W/N of the UK, driving a deeply cyclonic SWly flow across the UK, parent surface low is slow moving to the NW of British Isles with a surface trough moving NE across SE Uk developing into an area of low pressure, an unstable airmass develops across central, eastern and northern areas. ... SE ENGLAND, MIDLANDS, N & E ENGLAND, S/W SCOTLAND ... Warm air advection at lower levels and increasingly cooler mid-level air overspreading from the west from upper low – will create an unstable airmass to surface heating across the above areas. Heavy showers and thunderstorms are likely to develop as a result, with t-storms already across Yorks and Lincs. Thunderstorms will become more widespread through the day. Fairly strong SWly will allow some storm organisation into clusters/multicells, capable of producing localised high rainfall totals leading to flash flooding, hail of up to 1-2cm in diameter, frequent lightning and strong wind gusts. These storms should clear away east later in the evening. ... IRELAND/N IRELAND ... Steep lapse rates here on the edge of upper low and its cold pool, combined with some weak surface heating and forcing from occluded fronts moving in from the west, will support scattered t-storms today, storms capable of producing hail, gusty winds and localised flooding

Well ECM ensembles are finally seeing the bigger picture and only 10% no longer have Bertha to the SW at T48. Now the main variable is how intense it is and there are breezy members and gale force with ones in between. By T96 Bertha mixes with the core low in the trough and the new low deepens (again variations on that theme). By D5 the new low is filling at different rates according to its members. ECM's track of the low Sunday: 6am noon 6pm It is in line with GFS, in that again certain parts of the SE will escape the rain. GEFS offer similar variety with regard to Bertha, maybe slightly more have a weakening feature as it approaches the UK. The GEM op also made little of Bertha, but like the rogue GFS run a day or so ago, this was likely to happen at one point as there remains a cluster showing this. Currently about 30% of GEM's 0z support the op, 70% support the GEM control: UKMO have struggled with Bertha and this morning the Fax looks like it weakens Bertha as it crosses the Channel/South coast: Not sure this has much support anymore, yesterday this was showing up as an option, but today most have UK impact around SW crossing NE. Assuming we have reached some sort of consensus (based on ensembles) then UKMO and ECM have been disappointing in their guidance whilst GEM and GFS have been very consistent. Tonights runs should clarify this finally. Afterwards it looks like there is no clear consistent sign of a return to higher pressure. ECM's warm D10 chart last night is now a distant memory. ECM mean at D10: Similar to GEM mean: and also GFS mean: I suspect the greater impact Bertha has on our mid latitude location the longer our weather will be sourced from a cooler direction.

The Met Office have warnings out to "be aware" and at this stage that is exactly what the general public need to be. There is still uncertainty about it's track and so the Met Office are right to put out yellow warnings, even if it ends up heading down the channel and bears little effect on the UK. If this does happen then the Met Office were not wrong (i am sure we will get somebody posting this fact at some place across the forum) as the warning to be aware would have still been valid. It may only be 2 days away but the system is still a thousand miles away in the Atlantic, another 24 hours and we should have a much better grasp on its path. 1976 (great year, it was the year i was born ) welcome to the forum. I wouldn't be packing up any holidays yet, if the storm heads on the northern track (i.e. affecting a swathe of the UK) then I would expect the met office to issue Amber warnings - this is the point where you would need to consider packing up and heading off. This in addition to any warnings from valid forecasters on netweather. By valid forecaster I mean a proper alert issued from one of the netweather forecasters not somebody ramping up one run of one model on the general forum.

I must confess that I am finding all the forecast dithering over the fate of ex-hurricane Bertha rather baffling. Admittedly, forecasting potential storm tracks this time of year is somewhat difficult, owing to the lower jet speed. Yet, as I see it, the case for Bertha turning into quite a potent storm looks quite compelling. For an ex met observer I find this a rather surprising comment. The immense technical problem this kind of thing throws up has yet to be solved in any computer model. So 'dithering' is hardly the right word I would say. Uncertainty, yes, and perfectly understandable. This morning the 3 main models are still no in agreement although returning to basics may be called for if they still have not got very close agreement by the 12z output this afternoon. At least the models now have a good fix on its position since it turned into an ex tropical storm over the last 12 hours, so surface and upper air details should become less problematical from now on.

Great plan with only two minor drawbacks. 1. We would die 2. We would die I thought that the drawback was so big that it had to be mentioned twice

Well I ended up seeing a storm in the end as I chased that line of storms this evening from around Alfreton to Mansfield and beyond just before it started to die away. I didn't see a lot of lightning, but a few bright flashes evident as I was driving. The main thing about it was the rainfall and how dark it was. Considering it was only around 7:30pm it was like dusk and the rainfall was incredible. I can well believe the kind of rainfall amounts that have been reported as it was coming down in absolute torrents with visibility very poor on the A38 around Sutton, despite traffic only moving at around 30-40mph.

Both the Boulder and SIDC sunspot numbers are calculated from the observations of teams of volunteers all over the world (often amateurs), who take their telescopes, go into their back gardens and count every spot they can see. You can actually volunteer to do this yourself and make a contribution to solar science! Each observer has an adjustment factor to account for the capability of their telescope etc, and in the case of the International Sunspot Number (the SIDC one), it is all calibrated to a reference station in Locarno in Switzerland. There's a wealth of information here to allay any fears: http://sidc.oma.be/silso/faq-page There is an ongoing initiative to make the sunspot historic record as accurate as it possibly can be: http://ssnworkshop.wikia.com/wiki/Home The SIDC site is very cool, because you can see the current estimate for the day's sunspot number change as the observations come in: http://sidc.oma.be/silso/eisnplot

http://forum.netweather.tv/topic/80662-south-east-england-east-anglia-central-southern-england-regional-weather-chat/?p=3020078 Don't let the mods see you say that, they'll give you one of those cool warning points

If you think Milankovitch cycles can have no influence over 10,000 years, the you need to re-read the link you provided. You dismiss numerous reconstructions as having too many holes and assumptions, without being able to name any. hat's nt very sceptical There are studies that have looked at my last point, here's a few. http://onlinelibrary.wiley.com/doi/10.1029/2009JD011800/abstract https://ams.confex.com/ams/Annual2006/techprogram/paper_100737.htm http://www.nature.com/nature/journal/v410/n6826/abs/410355a0.html If you think you can dismiss inconvenient data by repeating the AGW denial meme "So how has that been working out for them the last 15+ years then", then you are far from being a sceptic. I'll respond to your posts in future when you learn to have an informed, or at least an adult, discussion about the climate.

The track of Bertha is still undecided by the models. The differences in them are still large but lets take a look at what the GFS, ECM and UKMO say in a quick map I've made below showing their tracks, The GFS seems keen on keeping it to the North while the UKMO goes for it tracking across the very far South and the ECM is in between them. So what do the other models say? Both the JMA and GEM models show something similar to the UKMO, they track it along the far South as well. NAVGEM agrees with the ECM. It would seem the UKMO has good support behind it from the other models. The ECM has some support but the GFS at the moment doesn't have much backing it. Now lets take a look at what the GFS, ECM and UKMO show. GFS 0z run has the low tracking across Southern Ireland and into Northern England. It brings wind gusts of 35 to 45mph but in exposed places over 50mph would be likely. It also brings heavy rain to Ireland, Wales and England. GFS 06z run has the low tracking a bit more further North than the earlier 0z run. This puts the wind speeds up a lot more with 50 to 60mph gusts for Southern Ireland and Wales. Northern England gets something slightly lower around 45 to 55mph gusts. Heavy rain moves over the whole country through out the day but its Ireland that see's the worse. ECM 0z shows the low at 9am to the South of Wales with winds around 35 to 50mph for the South West of England, By 12pm the low is now over the Midlands and strong winds of 30 to 45mph move across Southern England. 3pm the low has moved up to Northern England which moves the strong winds to Eastern England now at 25 to 40mph. UKMO 0z shows probably the least windiest out of the three. It shows gusts over 20mph for most places near the low as it passes by. But it does show either heavy rain showers or heavy rain affecting almost everywhere in the UK during Sunday. Overall the track of Bertha is still undecided between the models at the moment where the ECM or UKMO places the track of Bertha seems the most likely. The GFS and ECM show us that if it does track further North heavy rain and very strong winds will be a big issue for many however if it does track a lot more further South like the UKMO does the wind won't be much of a problem at all but either way they all agree on heavy rain will be a issue.

Almost constant loud thunder here and few flashes has been rumbling for last 45 minutes so slow moving But no rain at all may I add

Met currently show the centre off the Channel Isles at 12z Sunday tracking NE to exit the east coast just south of the Wash, see Fax links below, http://www.weathercharts.org/ukmomslp.htm#t72 these charts will be updated through the day and into tomorrow so worth bookmarking to see how any changes show for the same times as on the output between 0500 and the current T+72 chart for 00z Monday. We can all try and beat Exeter but at the end of the day the most probable centre position and depth is going to come from one of these charts. Whether the current output or updates today or tomorrow will be the closes we can look back later on Monday to find out. Will GFS be a better guide than Met or ECMWF, no one knows at the moment, the next update on video from the senior man should be interesting. Remember the charts shown with UK Met stamp on them are NOT necessarily all UK Met. I suspect that at least one shown yesterday was the GFS output. A very interesting period for weather fans to watch.

John have you had a go on the Pin the tail on Bertha in the forum http://forum.netweather.tv/topic/81104-competition-pin-the-tail-on-the-bertha/

If the warming during the 20th century had been due to increased solar activity, it would have had a certain warming signature, such as days warmer than night, a warmer stratosphere, etc. Instead we see the opposite, which is what's expected from an enhanced greenhouse warming (so we're seeing a bottom up warming, rather than a top down warming). Mike, the authors of the paper did a questions and answers on RealClimate, you might want to have a look http://www.realclimate.org/index.php/archives/2013/03/response-by-marcott-et-al/

We can do it I know we can! I am guessing looking at the models that we should see near 50 mph wind gusts here which is more like 70 mph - 80 mph in Winter.

Met Office â€@metoffice 29s Graphic showing potential tracks of ex #Bertha for Sunday http://bit.ly/1pGdvRP

just a reminder that this thread is for convective/storm discussion.....to have a general moan about storms or lack of please post in the following thread... http://forum.netweather.tv/topic/80928-no-storms-hate-storms-post-your-storm-related-moans-and-groans-here/ cheers

Cell near st Neots looked like it was developing supercell characteristics, definite rotation as I went by on the train.

"Netweather Forum in blowing something out of propotion shocker"Never!

OMG! This rain is sooooo heavy!!!! Cant remember the last time i saw anything like this!

BIg edit -Direct Lighting hit not more than 2 meters from me and much swearing

When I last saw the forecast at 7pmish they showed precipitation covering south east england, heavy bursts with possible thunder. It was due to arrive about 5am! I woke up, looked outside and it was dry and sunny, it's now partly cloudy and sunny spells and very humid still no rain. And you lot think the beeb and met do a good job? Seriously

The 06 GFS Midnight Sunday low 987mb centred over Cork with moderate rain stretching into Wales and SW. Midday Sunday 984mb north Irish Sea. Midnight Monday 984mb east of Wick with strong westerly winds over the UK Summary Damp and windy

Just for a bit of fun, we have a competition - pin the tail on the Bertha - NW Extra subscriptions for the winners http://forum.netweather.tv/topic/81104-competition-pin-the-tail-on-the-bertha/

It's interesting that they haven't issued a wind warning.

NOAA also predicting Bertha to deepen significantly thus take the more northerly track With the ECM now starting to come on board the channel runner idea doesn't look too likely now

Pretty much in agreement with supacell. Two features to spark of convection. A weak trough in the East. And low level wind convergence. Mid level lapse rates are moderate (condusive to convection but not strong convection). Convection seems unlikely to tap into the jet winds aloft and wind shear through the cloud is low to moderate (slightly better in the east). NMM suggests Strongest risk of a storm in Northern Ireland with a secondary area in the east of the country. Not quite sure how strong the convergence zone convection will be. Forecast SkewT's suggest a moderate risk of spout type tornadoes (very weak - more like wind devils). Poor instability , no dry air aloft and weak direction shear through the cloud suggest the possibility for severe convective activity is very low.

the latest met office surface pressure (as of 7:30 this morning) charts don't really make much of it: it's more like the UKMO did on some of it runs earlier this week. Similar to the GEM today as well which has gradually backed away froma significant event: But then there's the ECM at GFS....... This has been really interesting hasn't it? and there's still no consensus in the operational output! GEM fries the southeast again in FI:

I find this sentiment extremely perverse.

BBC and Met Office seem keen to break out thundery showers across the middle slice of the UK today, pushing east during the latter part of the day and clearing the east coast overnight. However, Estofex clearly not in agreement as only Ireland and Western Scotland in with a chance; the15% risk covers these areas, but I will come onto this shortly. NMM shows an increase in lapse rates this afternoon across a swathe of England: Lapse rates then increase over the SE quarter later this evening and first part of the night, although the NMM model has all precipitation moved off to the NE by this time. GFS and NMM agree on some 300-500j/kg of CAPE, so not a huge amount but should be enough to promote some storm activity this afternoon - GFS chart below: An interest for me is the existence of convergence zones, which could focus the heavy downpours. These are quite numerous across NW England this afternoon and then across N England and eventually NE England this evening, which ties in well with the Met Office prediction. Euro4 precipitation looks interesting, but will it be thundery? Estofex thoughts (or lack of) may be down to the fact that although there will be storms around they will not be especially electrically active as CAPE/instability is rather limited. What is not limited though is the amount of moisture, with some high PWAT levels this afternoon. Given this and the slow moving nature of showers this could mean a lot of water falling in some places over a space of time. My thoughts on today are that there will be some heavy showers and thunderstorms. It's hard to pin down a highest risk area but I would say draw a line from around west London to SW Scotland and anywhere east of this. As mentioned, storms that do occur will have the potential to produce torrential downpours and the combination of slow moving downpours and merging over convergence zones may lead to a risk of flooding. Storms could just about bring a risk of hail and CG lightning, although I think the risk of these is lower and today maybe more about rain than other storm aspects with only sporadic lightning.

Ya wrong, so wrong, it will be remnants of Bertha, even the Meto quote it as such, unless you think their chief forecaster doesn't know what he's talking about. The remains of hurricane Bertha, over the western side of the Atlantic on Thursday morning, will come steadily towards the UK. The transition from a tropical to an extra-tropical featureis a particularly hard one to forecast with confidence, and computer models continue to differ in thelocation and intensity of the resulting depression, which is expected to pass over, or close to, the UKfrom early on Sunday. There is the potential for widespread rainfall totals of more than 50 mm and coastal gusts of over60 mph, along with large waves. However, the system may pass harmlessly to the south of the country.or spread heavy rain even further north, and the public are advised to keep up to date with warnings.

I'd have thought to make that assertion MIA it would be necessary to compare apples with apples. Do we have decade figures for the 1990s and the first decade of the 2000s? Comparing 16 randomly chosen years with 7 thereafter feels a bit cherry-picky? The trend might well be true - which is very interesting, just need genuinely comparable evidence.

never mind feeling the effect of bertha, is anyone feeling the effects of the jet stream BOILING us