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Storm & Convective Forecast Issued 2015-04-25 08:57:09 Valid: 25/04/2015 0600z to 26/04/2015 0600z THERE IS A RISK OF THUNDERSTORMS FORECAST Synopsis Low pressure system NW of Iberia will advect a modestly moist airmass across southern Britain during Saturday, ahead of a weakening cold front pushing south, expected to lie E-W across central Wales - Midlands - Lincs by 18z. Convergence zone south of the cold front may support locally heavy and thundery showeres across parts of southern England. ... S ENGLAND, SE WALES, MIDLANDS, E ANGLIA .... Fairly steep lapse rates and moist airmass across southern Britain south of southward moving cold front will create an unstable airmass with surface heating in the above areas today. Wind convergence zone is forecast by models to develop from Cornwall/Devon, through Gloucestershire, S Midlands, and up towards The Wash/Cambs this afternoon, shifting slowly south with time, and will be the focus for the development of heavy showers and a few thunderstorms. Vertical wind shear will be rather weak, so no severe weather is anticipated. Showers/t-storms are likely to be slow-moving ... So bringing a risk of localised flooding. Light winds aloft and surface covergence will be conducive for funnel clouds or even an isolated brief weak tornado. This evening and overnight, UKMET surface analysis indicates frontagenesis ahead of the weakening cold front arriving across southern England overnight, this new cold front forming, surface convergence along south coast ahead of front and increasing vorticity aloft with arrival of left exit region of a jet streak moving NE from Bay of Biscay may support further heavy showers and thunderstorms for a time this evening and overnight across southern coastal counties of England - before the cold front clears out into the English Channel Sunday morning. This overnight convection is also supported by ECMWF and HIRLAM. Forecast also here: http://www.netweather.tv/index.cgi?action=convective;sess=6ebcf3fb1a7d2b0d7d4eaec501002939

Erm......

Something to look forward to hopefully, the Gfs 12z shows warm weather returning from the south later in low res with temperatures into the 70's F. One of the things I like looking out for from late spring and throughout the summer is the 564 dam line and I'm hoping we will see plenty of it close to the UK in the next 4-5 months.

I'm certainly not... snow is a miserable pain in the backside at this time of the year. Hurry back lovely southerlies and that lovely tropical air!

The Gfs 00z shows almost a repeat of the unseasonably cool weather next week during week 2 as well...ie. very unsettled and rather cold with sunshine and showers, wintry on hills and not just on hills and occasional bouts of persistent rain and strong winds, however, it's not cool or cold all the time with the south having low teens celsius a few times in the week ahead and next weekend becomes warmer with temps into the 60's F so it would feel pleasant, especially in the strong sunshine.

Interesting differences today in the anomaly suggestions for the 6-10 day outlook from yesterday, today from NOAA also similar. That is the worst of any cold looks to finish in the 5-9 day time scale. Not so on the EC-GFS version, although they are not consistent in this or with each other. Overall they show the colder north of west flow at 500mb continues with a fairly marked trough over and just east of the UK. I wonder which suite will be nearer the mark come the first 2-3 days in May? The cold pattern change about to start was predicted by the synoptic models first, that is before the anomaly charts which is quite unusual. So interesting model watching for a week or so to come.

Regarding the Bank Holiday Weekend. Winds look light on the latest GFS 12z so temperatures in the low teens would feel pleasant in the strong early May sunshine. The very cold uppers being held at bay to the north. Its an improvement on last nights GFS 12z thats for sure which had a northerly gale and rain off the north sea.

A very pleasant afternoon after the early morning light rain cleared, reaching a high of 18c in the sunshine. It's clouded over this evening and started raining at 19.30'ish. Looking at the rainfall radar the band of rain is moving E/NE, so it looks like the rain will be falling here for some hours to come. Cloud building 19.00 Rainfall radar 19.30

Only a few weeks left to go now. I know I can't wait and I'm all ready to go.

I think I might watch Twister tonight, been a while

Unusual to see you in here BW, but welcome ^ On the doorstep seems to be convective in nature with some heavier pulses. Edit: I can't remember the last time we had meaningful rainfall

Very quiet in here, despite much more variety in the charts compared to recent weeks - probably a sign no-one likes what is on offer... but we have done very well these past 3 weeks.. I said its a preety tall order for synoptics as we have seen much of this month sustaining themselves beyond 3 weeks. What are the charts showing - a very different picture, sustained cool weather especially in the north, showery airstream, but some decent sunny conditions especially in the south. Notable cold nights in the north, plenty of frost about. Uncertainty regarding bank holiday weekend, but at this range, in a word it doesn't look particularly warm, indeed could be a real chilly one.

lol talk about cherry picking, also that's 15 days away

Sun been out warming things up nicely here in the south lock that heat in, get the colder air moving south to bump into it and hey presto hopefully we will get some storms later

Indeed, radar image showing some convective rainfall breaking out up north though, although no sparks so far. Looking briefly worldwide, some eye opening storms across SE USA and off of the SE coast of Aus at the moment - the activity from the SE Aus storms in particular is impressive for storms over the seas.

Does look increasingly better for later on this evening and into the night

9.6c to the 24th 2.0c above the 61 to 90 average 1.5c above the 81 to 10 average

The highest 24 hr minimum of the year so far last night at 8.0c, and the highest since Dec' 18th last year.

A glance at this mornings ECM 0z mean shows a move away from the very unseasonable cold that we were predicted to get. A northerly flow doesnt really have time to establish at the end of the week before the next low moves in off the Atlantic ushering up slightly milder air. The ECM op indicates we could get a brief spell of settled and cool weather at the weekend, but not overly cold due to the very cold uppers not managing to make their way south. Night frosts could still occur though.

re my past 1136 last night This morning and ECMWF is more like NOAA 6-10 again but with some fairly small differences. GFS has changed yet again, this time with a fairly marked vortex NE of the UK. I would bet on the NOAA 6-10 being nearer the mark=a more W'ly flow http://www.cpc.noaa.gov/products/predictions/610day/500mb.php This would still leave the UK in a relatively cold 500mb flow

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 08:00 ON SATURDAY APRIL 25TH 2015. THE CURRENT GENERAL SITUATION A trough of Low pressure will move South across the UK slowly today and tomorrow followed by a cold and unstable NNW flow http://www.wetterzentrale.de/pics/Rtavn001.gif MODELS-2 WEEK HEADLINE Becoming unsettled and changeable with bright spells and showers, heavy and wintry on hills in the North for a time. Local night frosts still possible. THE GFS JET STREAM ENSEMBLE FORECAST TheSouthern arm of the Jet is strongest at the moment lying near Spain . This extends North to lie across Southern parts of the UK for much of the period undulating North and South at times in association with a Low pressure trough near the UK. http://www.netweather.tv/index.cgi?action=jetstream GFS OPERATIONAL The GFS Operational this morning shows Low pressure and cool conditions affecting the UK weather for much of the coming week as a Northerly flow establishes tomorrow. then through the week this slowly backs Westerly and a ridge follows across the UK by next weekend. Through week 2 changeable weather returns with rain and showers borne off the Atlantic maintaining the cool theme with rain or showers at times. http://www.wetterzentrale.de/pics/Rtavn1441.gif http://www.wetterzentrale.de/pics/Rtavn3841.gif THE GFS CONTROL The GFS Control run follows a similar pattern to the operational today though it does build High pressure strongly across the UK at the very end of the run with rain and showers dying out then to be replaced by dry and more settled conditions. THE GFS CLUSTERS The GFS clusters today show no clear message this morning with a mix of options offered to lie across the UK in two weeks time, ranging from westerly winds and rain at times from off the Atlantic to dry and fine weather under a ridge over the South or to the West of the UK. http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=372&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD= UKMO UKMO this morning shows a showery cool West or NW flow early this week followed by an active depression moving East across the UK Wednesday with rain for all followed by a more showery and still cool NW flow late in the week as the Low slowly moves away East over Europe. http://www.wetterzentrale.de/pics/Rukm1441.gif THE FAX CHARTS The theme of the Fax charts this morning is to weaken the Northerly feed of cold air quite quickly in the first half of next week with an active Low pregrammed to move in from the West or SW on Wednesday http://www.weathercharts.org/ukmomslp.htm#t120. GEM GEM this morning shows quite a changeable pattern through the next 10 days as the cold NW flow early in the week is replaced by Low pressure around midweek with rain for all and a ridge at the weekend with a dry and fine interlude for most. the pattern still looks changeable and unsettled with further rain towards the West and SW at the end of the period. http://www.wetterzentrale.de/pics/Rgem2401.gif NAVGEM NAVGEM shows changeable and showery conditions for the most part but with a more sustained period of rain midweek as a Low moves East. Then a large Low pressure over the Eastern Atlantic drives cloud and rain North and East across the UK at the end of the period. http://www.wetterzentrale.de/pics/Rnvg1681.gif. ECM ECM this morning shows an unstable outlook with Low pressure never far from the British Isles over the next 10 days. Showers or rain at times remains the focus of the model with all areas at risk with temperatures no better than average and often rather cool. http://www.wetterzentrale.de/pics/Recm2401.gif ECM 10 DAY MEAN(12z) The ECM 10 Day Mean Chart from last night shows a Low pressure belt lying across the Atlantic and the UK maintaining the risk of showers or rain at times 10 days from now. http://www.wetterzentrale.de/pics/Reem2401.gif NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trends this morning show a common theme of Low pressure driven weather with centres close to or over the UK. 31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKM & ECM The current verification statistics for the past 31 days shows ECM leading the way at 3 days with 97.3 pts followed by UKM at 96.8 pts and GFS at 96.1. At 5 days ECM ties at 88.4 pts over UKMO also at 88.4 pts and GFS at 86.0. At 8 days ECM remains the leader with 62.4 pts over GFS's 58.4 pts. Then at Day 10 ECM retains superiority at 47.0 pts over GFS at 42.0. http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day3_PMSL_MSL_G2NHX.png http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day5_PMSL_MSL_G2NHX.png http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day8_PMSL_MSL_G2NHX.png http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day10_PMSL_MSL_G2NHX.prig MY THOUGHTS The High pressure dominated weather of late has gone for the time being and in it's place we look like moving into an unstable flow with rain or showers and some very cool weather for a time especially across the North early next week when some snow showers are possible on the hills and some unwanted night frosts too more widely. Then as we look to the latter end of the week there is strong support for a new Low to move East across the UK giving all areas a period of more prolonged rain together with strong winds and followed by more cool and showery weather late in the week. By next weekend there is some support from some models that pressure may recover for a time with a dry and brighter interlude across the UK as ridge looks as though it may cross the UK from the West but then in the longer outlook models it looks like any rise in pressure will be shortlived as further Low pressure moves into the UK from the West or SW with further rain and showers at times to end the forecast period. While temperatures never look like being particularly warm with a lot of cool air aloft dictating the changeable nature of the weather sunshine between the showers will feel pleasant enough and coupled with the occasional rainfall will aid the growing process. So in a nutshell a changeable spell of weather to come over the two weeks for all areas with some rain and showers and temperatures near or a little below normal but still with the unwelcome risk of occasional night frosts where skies clear and winds fall light. Next update from 08:00 Sunday April 26th 2015

A bit of rain overnight has been replaced with bright blue arctic skies with fantastic visibilities and a peppering of snow showers to the north in their true winter colours of grey and yellow clouds. Currently 3c with a fresh cap of snow on the Cawdor hills down to about 1200 feet. If the sky looks as wintry as it does today then the next two days may be quite exceptional for the time of year. Cows and calves still in at night although they did not want to come in on the last two warm days but we will have no problems tonight. Young Mr. Norththernlights took home a load of silage bales from a neighbouring farm last night and there is more concentrate feed on the way in case we have to keep the cattle in till May

Read that myself PJ and it certainly sounds promising .. However not so sure the words " dead cert" and Cfs should ever be used in the same sentence

The anomalies are in reasonable agreement at least at day ten but no real firming up on the evolution. They both have a trough NE Canada and another orientated SE into Scandinavia but the zonal flow is interrupted by developing HP south of Greenland. This is more noticeable on the GEFS. It will be interesting to keep an eye on this because the GEFS develops this idea in the ext. period with a linkage to the Azores HP which sets up ridging just to the west of the UK. The ECM is not so keen on this idea as yet or if ever. Charts weatherbell

Even so any clear sunny spells will still be pleasant ..

May Snow A trawl through the archives reveals that on 17th May 1955 was probably the most notable May snowfall on record. Much of England and Wales was affected by several hours of snow (Eden 1995), including two to three hours’ worth in the London area (Brazell, 1968). Coincidentally, the same date twenty years earlier in 1935 also saw England and Wales affected by widespread snow with some places, including theWirral and parts of Devon recording several inches of snow (Eden 1995). Incidentally, on 17th May 1935 snow also fell in the central Netherlands (Zwart 1985) and this is the latest in the season that snow has been observed here. May 8th 1943 saw snow falling over parts of northern Britain as a depression tracked eastwards across north Wales. The Isle of Man was among the worst hit places and in Douglas 15cms snow lay on the ground by the morning of the 9th (Pritchard 1997?), whilst virtually the whole of Scotland was affected, including falls of 7cms at Duntulm, Isle of Skye (Stirling 1997). Such is the fickleness of May weather that just a few days later temperatures reached 30C in Kent. Other notable instances of May snowfall include that of mid-May 1923, Scotland’s coldest May of the 20th century and the century’s second coldest May in England and Wales, whilst May 18th 1968 saw snow falling as far south as the Midlands. Meanwhile, a little more recently the Mays of 1979, 1981 and 1982 started with widespread wintry showers whilst May 13th 1993 saw several centimetres of snow settling over the higher ground in central Britain (Pritchard 1997?), including a fall of 30cm at Moor House in County Durham by the 14th (Stirling 1997). Stepping back into the nineteenth century Eden (1995) and Stirling (997) report widespread snow England between the 16th and 18th May 1891. Snow fell to depths of several inches in some places, including falls measured at 15cms deep in parts of the Midlands and East Anglia. A few days earlier on the 10th snow had fallen as far south as Bath and London (Stirling 1997). Meanwhile, Gordon Manley, writing in Weather in 1975 tells of snowfall in southern Britain on 22nd May 1867 and 27th May 1821 whilst Brazell (1968) mentions snow as having fallen in or close to the London area on 12th May 1816, ‘the year without a summer’. Moving into the eighteenth and late seventeenth centuries Manley (1975) raises the possibility of snow being observed on parts of the higher ground in Sussex on 12th June 1791. Early May snowfall was recorded in parts of the London area in 1770 whilst in 1698 a widespread deep snow was reported all over England on 3rd May (Brazell 1968). http://www.dandantheweatherman.com/Bereklauw/latesnow.html

That's the spirit frosty!, hate the vile northerly wind charts here at low level south, if I lived 300m+ north, I would be excited, so for me, bring on the warmth

This looks great, becoming very warm through early may on the Gfs 6z, I'm looking forward to hot summer plumes and Azores high's.

It's a been a pretty decent month. Looks like we're about to pay for it with a miserable couple of weeks coming up. Synoptics that would have been fantastic in Winter are now on our doorstep. Easterlies and Northerlies...yuch

Bored now!

Rest in pieces 'spring' 2015!... 15.5C Last sub 9C May in 1902. Last sub 10C May in 1996. Last sub 11C May in 2013.

Below is the May CET from 1659-2014 in blue, the 30 year average in red and the linear trend in black. The CET this month is likely to finish somewhere between 8.5 and 9.5C. The average May following an April within that range is 11.5C. The linear trend for the whole record is +0.14C per century. Following this trend gives an May CET of 11.5C. The linear trend since 1850 is +0.62C per century. Following this trend gives an May CET of 11.7C. The linear trend since 1950 is +1.09C per century. Following this trend gives an May CET of 11.8C. The linear trend over the last 50 years is +2.40C per century. Following this trend gives an May CET of 12.1C. The linear trend over the last 30 years is +1.57C per century. Following this trend gives an May CET of 12.0C. Last year, the 30 year average for May hit 11.8C (11.78C) for the first time on record. To take the 30 year average to 11.9C for the first time, a CET of 13.0C or higher is needed, while taking it back to 11.7C requires 9.9C or less.

Summers over jersey back on temperature has fallen from 5c 6.00am this morning to a current reading of 2c. The hills surrounding the Firth have fresh snow down to about 1000 feet. No dawn chorus from the birds this morning all taking shelter from the cold rain we had up to about 7.00am