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Winter 2009 / 2010 in Western Europe?

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Author Topic: Winter 2009 / 2010 in Western Europe?  (Read 18768 times)
Roman White
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« Reply #390 on: February 10, 2010, 06:02:15 pm »

Hey guys,

I hadn't visited the forum for a while, as well as I didn't thoroughly monitor the weather conditions. But the weather doesn't let me to forget about itself. I spend a few hours each day cleaning snow in my yard - the depth is already 35cm (14 inch)! It is the biggest amount here since 2004. More good news: it is snowing this evening, and the forecast for 4 next days is (guess what?)  Grin blizzards and wet snow! Phew, we can easily get 40cm tomorrow!
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« Reply #391 on: February 10, 2010, 07:53:48 pm »

Very nice Roman can u send some over here now please, although as Martin says our chances of some snow next week are looking promising and thats all im saying...... Lips sealed
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« Reply #392 on: February 12, 2010, 04:41:49 pm »

That's nuts Roman - share some of that with us  Smiley

08Z Update 12th Feb

Subtle changes today, the European vortex which has dominated the headlines over the past day or so has sunk south into the Med (bringing snow to much of France incl the Riviera) and is now producing convection over the Med.  The cold pool of air (sub 516dam) has now warmed out somewhat and also slid away towards the SE, although the Upper low and inverted omega block persists over much of Europe.

The upper blocking high has re-orientated overnight and over the next 48hrs will slip slowly NW'wards as developments push it towards Greenland (both warm advection to the west and cold advection west of Svalbard)

A weak thermal zone containing a more maritime airmass has sunk around the high over the last 24hrs and is now covering the UK except the far SE, Outbreaks of rain,sleet still affecting the SE, bits of Snow above 200m, but WBFLs behind climb to around 500-600m meaning that Snow is unlikely from the showers coming into Eastern England exceppt over the Pennines and perhaps the higher parts of the N Yorks Moors.

Sunny this morning in the SW, parts of Wales and N England, but a lot of cloud elsewhere.  Clear areas likely to go into Fog tonight - esp towards the north where gradients fall out.

This evening and tonight another shortwave comes SSW from Denmark and the flow across the South veers somewhat and becomes less maritime.  850mb temps and WBFLs fall away again, with negative WBPTs coming back into the SE by 00Z and spreading west across other Southern parts overnight so that a cold end to the night is likely.   Into the Weekend and we alsmost have a repeat with less cold trying to come down from the north (more Atlantic Maritime influence and the colder air across the south.  Eventually the less cold air wins, but again light rain, sleet and patchy snow comes south across parts leading to a cold and grey weekend for some whilst others see more in the way of sunshine.  The NAE is considerably faster with the higher WBPT coming south, the GFS is slower along with the UKMO GM ans the High Res ECM delays until sunday the less cold air moving south and actually re-introduces snow showers to eastern Kent for a time tomorrow. We will see.

Into next week and there is considerable differences in the detail in an increasingly cyclonic pattern across the UK.  A Major trough extends SW from the Norwegian Sea as the high withdraws NW towards Greenland and the Davis Straight.  The extent and position of the trough and assoc surface depression is however not in agreement between modells.  There is more agreement for Monday into Tues as an occluding from comes southeast perhaps turning to snow ahead of it and behind it as warmer air is squeezed out, though this remains highly uncertain. The 00Z Models today having less of a snow signal than some of their predessors.  Speed and orientation of the band as it comes SE questionable even at this stage - and needs to be firmed up over the weekend.

Beyond that the models are not in agreement with the postiioning of the trough and low, and there is inter model and intra model disagreement. The GFS has however somewhat consistently preferred the Cog of the low to end up in a more easterly location that the UKMO GM or ECMWF, therefore maintaining a somewhat colder theme across the UK.  The ECMWF and UKMO prefer to keep the Cog of the low towards the west with higher WBPT and less in the way of cold air except across the more northern areas over highground.  A number of GFS ensembles  also keep the low centre further west, hence the weight of evidence suggests the ECM/UKM solution gains most support with the GFS colder scenario maintained as a lower prob solution at this stage - but its all subject to change.  The ECM for example had more cold air around on its 12Z Run last night than its 00Z sol today.

The far south and SW look relatively less cold anyway in all solutions.

Paul Blight
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« Reply #393 on: February 12, 2010, 11:40:03 pm »

Looks like the first true inland convection of the year could happen next week, much earlier than expected. Models are going for up to 400 CAPE for ROI, SW Britain and Wales mid to late next week so there's a real chance of thunderstorms!. NI missed out on the great CAPE but still enough inland instability to get convective showers (poss Wintry) going, however with so much change going on between high and low pressure anything is possible!
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« Reply #394 on: February 14, 2010, 09:50:22 pm »

Some more fun weather here. After another moderate snowfall on Fri-Sat night, the average depth is 35cm, but in the places where the snow is dumped the height is up to 0.7...1.5, even 2 meters (yes!). On Saturday evening we had several hours of rain ...while he the temperature was -4C  Shocked , you can imagine, everything was covered with a layer of ice. Later the same night it had turned into snowfall, adding a few fresh centimeters of wet snow. Today the temperature rose to +3C at noon, all that amount of snow started to melt, and there was dense fog in the afternoon.
Forecast for Mon-Tue looks different again: temperature drop to -3...-10C (more ice on the roads!) and more snow.
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« Reply #395 on: February 14, 2010, 10:14:32 pm »

Update - 14th FEB 10.15Z

A forecaster's nightmare this week - with temps at the crucial level where 1 degree either way will make the difference between Rain/ Snow.

Synoptically - The slow moving high which has been anchored nr NW Scotland for most of the week, is now slipping away NW as a result of warm advection off the east coast of N America and strong cold advection and cyclogenesis occuring over the Norwegian Sea.  OVer the coming days this low will slip SE, and then rather against normal protocal will extend SW (comes up against raising contour heights in SE Europe, will be steered SSW over the British Isles, with a deep layer cold pool extending SW just to the west of the UK, whilst at the same time the old cold pool over Europe is steered NNW.  Overtime both pools are modified by convective latent heat release, but over the UK there will remain an awkward temp level which will mean that either rain/sleet or snow is possible - largely dependent on time of day, wind, altitude and precip intensity. The worse mix of all for forecasting.

Initially we have cold air hanging on in the SE, and another weak baroclinic zone is trying to bring more modified Atlantic air SE, and warmer air is trying to push the cold air SE. Snow being reported this morning from Biggin Hill, Odiham, Stansted, Gatwick.  Snow largely above 200M elsewhere an awkward mix of rain & sleet.

A very sunny morning over Wales, Midlands, this tending to give way to a more cloudy regime as the day progresses, with lght rain breaking out over the Irish Sea later today.

As the new low comes SSW, it extends a front SE across the UK, initially rain falling into 400-600 WBFLs so largely rain, except over the Grampians where more snow will fall esp as some of the cold air gets dragged in from the European cold pool as it moves NW.  The front moves SE into Tuesday and becomes slow moving from the IOW to the Wash (within 100 miles or so). The ECMWF has the rainband a tad further NW than the GFS, UKMO in between the two.

Its overnight into Weds that it becomes very difficult to forecast.  The front will not only be sat nearly stationary overnight, but will entrain slowly a more continental airmass.  So a mixture of overnight temp falls, latent heat release through precip and colder air and lightwinds will make the band increasingly transition to Snow. Areas N and NE of London see most likely - The ECMWF has lower dewpoints at the time than the GFS and is more keen on turning the front to Snow (though 06Z GFS has more snow by 06Z than its predecessor (better))

4-6cm possible and up to 10cm in places cannot be ruled out - though considered low prob at this time as front will be weakening. (20%)

The front slowly dying out on Weds before more rain spreads from the SW later in the day as a low comes ENE across England at the end of the week.  This low will have cold air to the NW again the ECMWF has colder 850mb temps and dewpoints than the GFS, meaning a high prob of snow to the N and W of the low as it moves across to the N Sea.  Areas around N Wales, NW England the most likely areas to see some heavier snow falling as we go into the end of the week.  GFS 00Z had a strong snow signal also - though 06Z less so (all very marginal and as stated above 0.5 degrees both in terms of low pressure positioning and temp levels makes a lot of difference this week) However There is reasonable agreement on some heavier snow around the Merseyside, Manchester areas of the Populated NW - 5-10cm possible (maybe more) needs careful watching - esp intp Thursday night and first thing on Friday.

Another front comes east into Saturday with again cold air firmly in places across the north, rain in west wales, and the SW will turn to snow across the N Midlands, N England. ECMWF has a strong snow signal into Sat night with rain turning to heavy snow in places esp over 100m, but in heavier areas down to sea level.   

It could end up being a fairly wintry week in parts - esp the north, but not only on high ground.  The coastal west and SW the most definate areas to stay on the milder side of the rain/snow boundary.

Paul Blight
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« Reply #396 on: February 15, 2010, 02:48:14 pm »

Some very ominous convective showers about to hit lisburn! Let there be lightning! Smiley
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« Reply #397 on: February 15, 2010, 04:33:24 pm »

Plenty of big showers here today too, rain, sleet, and hail, one had a very long gust front. These could turn to snow later, and again over the next few days. Could be a chance of thundery showers on Wed, although it's low risk. Met Eirean have mentioned thunder on their forecast for Wed.
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« Reply #398 on: February 15, 2010, 07:20:07 pm »

Had sleet here today in one of the heavier showers, feeling very cold out but good to see lots of showers racing by and lots of potential for the rest of the week Smiley
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« Reply #399 on: February 16, 2010, 07:17:27 pm »

Again, again... a snowfall last night caused the depth of snow covering to increase from 35 to 41cm (the highest since 2004). Cleaning all this snow becomes a boring job... although I spend most of my free time doing this, I still can't clean the roads & roofs in my yard.
Now we expect to have a short break (along with temperature drop down to -18C next night), but next weekend will bring more rain/sleet/snow, so 41cm is possibly not the highest of this year. By the way, northeastern regions of Ukraine have almost twice as more - 50...80cm.
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Martin Mc Kenna
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« Reply #400 on: February 16, 2010, 07:52:48 pm »

The rest of this week into Sunday looks interesting - weak to moderate low end CAPE over NW, W, and central Ireland/ NI, especially on Sun when there could be 400-500 CAPE in W areas. There's certainly potential there for the first convection of the year and thunder!.

There was thunder over London today.
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« Reply #401 on: February 17, 2010, 08:22:12 am »

Well I thought I was seeing things when I looked out the window this morning-everything is white again, just measured it there at 5cm! Was this snow forecast cause if it was I missed it?  Nice surprise though Smiley Smiley
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« Reply #402 on: February 17, 2010, 05:40:57 pm »

I think that snowfall caught the forecasters off guard for sure, definitely wasn't mentioned on the TV. I was actually watching that cell over your area during the early morning hours via radar and it had a strong signature, thought there was going to be lightning from it at one stage. Could be more snow surprises in store over the next 10 days.

Look at ATD sferics...TONS of lightning over the Atlantic, W of Ireland.

Seen convection today, some ok updraught towers and a fairly big cell over Lough Neagh. All inflow, no anvils, but good to see again.
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« Reply #403 on: February 17, 2010, 06:17:05 pm »

Lightning!

http://andvari.vedur.is/athuganir/eldingar/
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« Reply #404 on: February 17, 2010, 07:51:55 pm »

19Z Update - 17th Feb

Headline - The Forecaster's headache continues with an awkward mix of Rain, Sleet and Snow for many over the coming few days.  The very low latitude Jet and inherently cold polar maritime air across the UK leading to areas of Heavy Rain, Sleet and Snow.... The hardest thing will be where, how much and when.

Situation

ON the 12Z 500mb Chart, a deep longwave trough is anchored just to the west of the British Isles with a high ridging north to Greenland and the Davis Straight.  At the surface, the old surface circulation which sank SSW to be off the SW coast of Ireland has now reached as far south as its going to get.  it will drift ENE over the next 48hrs as the longwave moves east. The main polar front jet remains well south of the UK, and is continuing to bring Atlantic Frontal Systems into the Iberian Pensinusla and another storm system is moving through the Canary Islands. (70mm in the last 72 hrs at Malaga and reports of quite bad flooding along the South Coast, and 26mm at Arrecife in Lanzarote)

The front which ground to a halt over the SE yesterday has been pushed NNW today and is now weakening under collapsing thermal and upper forcing and will continue to degenerate overnight (has brought a spell of Snow to parts of East Wales, West Midlands today esp over the High Ground)  The heavy snow across NE Scotland from yesterday has largely died out and a quieter spell of weather is expected here as activity switches to areas further S

Evolution

The low to the SW is the key.  The GFS has now finally come onboard with the evolution forecasted some days ago by the ECMWF and the UKMET in forecasting the low to the SW to move NE and develop an active occlusion as a shortwave trough rounds the base of the longwave trough and engages it, In addition a strengthening SW Jet stream over N France tomorrow aids both the Shear Vorticity on the low's NW Flank and also increase the baroclinicity across the Occlusion.   The ECM was originally too far north 72hrs ago but the signal for a potential snow scenario has been present and highlighted in my posts above.   There is now reasonable agreement on the low coming ENE over the next 48hrs to be in the N Sea by Friday.  As the low moves NE it organises and the front becomes more consolidated, as this engages some cold air over the N of the UK it sucks it into the Circulation and we see the potential for a heavy spell of Snow to develop across the area from SE Wales to Eastern England - incl the populous areas of the Midlands later tomorrow.

The low initially comes into the SW tonight as a largely convective affair (some heavy rain, hail and thunder possible with deep layer cold air assoc with the upper low moving NE.  During the omorrow an occlusion type feature tends to form lying NE to SW across S England with a wrap around feature eventually curling around the Low.  The precip a mix of convective but increasingly dynamic (thermal based) with time.  The precip coming into the SW and South Coast tonight and then slowly extending NE tomorrow.  As the precip sets in any rain is increasingly likely to turn to snow across SE Wales (possibly N Devon and Exmoor - though this is uncertain) and then extend NE so that by 18Z tomorrow , showers or rain/snow cover most of England and the Se'ern half of WAles.  The main Snow on the NW flank of the low as cold air is engaged.  This combined with darkness, light winds will mean that latent heat is released and drags the WBFL down from its 200-300m to nr the surface.   The GFS is somewhat quicker with the process than either the UKMO NAE, GM or the High Res ECMWF .

COmparison of the Low at 18Z tomorrow, we have the GFS at West London 986mbs, UKMO NAE 985mbs over Weymouth, UKMO GM 988mbs West Sussex and ECMWF 987mbs Bournemouth.  Therefore the available evidence suggests the GFS is a little quick both with the low.  However this seems to make little difference to the precip field which is similar in all models.  The ECM, NAE and GFS all have 10-15mm widely across the region with peak amounts of 20-25mm across the Midlands.  Snow depths are greatest from SE Wales across GLoucs, Herfordshire, Shropshire, all of the Midlands into Lincs and Eastern England. ROughly NW of a line from Norfolk to Swindon to EXmoor.  Rainfall equivs are not expressively converted to snow equiv as precip may start as rain and leave the ground wet. However both the GFS and UKMO NAE generate between 8-15cm of Snow across these areas with a few isol grid poiints above 15cm by FRiday morning over the higher ground of the Midlands. Given the heavy wet nature of the snow - disruption is highly likely if the snow does set in.  the snow could be quite persistant across the Midlands in particular as the developing wrap around devleops.

There is considerable uncertainty with regards the speed the low moves away. The NAE still having the low over Essex at the same time the GFS has it over the Western North Sea. As a result the precip lingers for longer across Eastern England.  The ECM is a compromise between the two as is the UKMO GM. Expect most of the precip to be gone by 09Z on Friday Morning, though the lingering wrap around adds another few cms across Lincs, the far east Mids and into Cambridgeshire and Rutland

Friday is quieter for most - but colder air (sub 522 TT) has spread to even southern England by then. The GFS and UKMO GM run a wave along the English Channel on Saturday, bringing another area of Rain/Sleet and Snow NE, the ECM is not keen on this - so uncertainty remains here.

Into next week - there is considerable uncertainty =still= w.r.t the low moving NE from La Coruna.  The GFS is oscillating between bringing a developed low NE and degenerating the system to a flat wave.  It seems the model cannot decide whether to develop the foreward or rearward centre- and in the case of the 12Z GFS it doesnt decide and degenerates into a flabby pressure system.   The GFS Ensemble indicates a variety of solutions - but the postage stamps suggest the operational run is in the minority and that the majority favour a much more cyclonic scenario portrayed by the UKMO GM  which has consistently brought the low close to SE England.  The 12Z ECM is at the other end of the extreme and takes the low NE further NW and takes frontal precip towards the borders. 

In essence to the NW of the low cold air is engaged and wherever this ends up being another area of Snow is likely to develop with rain to the South and SE of the low.  It needs careful watching.

Paul Blight
UKww Manager - Education/Warnings
Associate Fellow Royal Meteorological
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