OldMetMan
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Posts posted by OldMetMan
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The surface analysis for 00h seems to be a bit deranged as it has a small HP cell of 1032 over E Anglia where the plotted pressures are nowhere near that. Anyway, the lowest pressure readings are just SE of the Bristol Channel near the Gloucestershire/Somerset border, There is also another set of lower pressure readings of the Northumberland coast so we seem to have an elongated circulation.
Think I'd better turn in now. Nite nite!
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Correct!! I only spent about £120 on my set up, as an experiment. It's a subject that fascinates me, but having 3 kids i don't get the time i would like to spend researching it and along with the majority of viewers on here - only around in the winter - end up disappointed after reading all the hype on the forecasting model thread!! Need to find the time to read though the educational threads me thinks ! Although I've noitced, in summer nobody complains too much when the precipitation misses them after being forecast :winky:
True, nobody really wants rain in the summer - unless it's a terrific thunderstorm of course!
These weather stations such as you describe are great for weather fans. It's when they substitute automation for official weather reporting done by trained observers that it bothers me! I spent 3 years observing and loved it - except the shift work which finally drove me to leave!
We're so lucky to have so much weather info these days. How I would have loved the Internet back in my young days when I first became interested in the subject!
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Looking at the 23Z surface chart there is a low centre analysed in the Bristol Channel but if you look at the actual plotted pressure readings, it looks more like either we have an elongated LP stretching down from Lancashire right down to where it's been plotted on the analysis or there is more than one centre. With that configuration, offshore winds seem less likely. However, the occlusion in the North Sea off thye east coast of Scotland is already fragmenting so we could still pick up a light easterly tomorrow - might pull a bit of that continental air back.
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Thanks OMM - It would seem years of experience are far superior to the more modern oregan weather station I have which is still indicating snow with a temp 1.9C and dew point of 2C even though it is absolutely 100% pure rain outside !!
Yes, that's true, that's what bothers me about there being so many automatic weather stations, you can't beat an experienced weather observer! And if the input data is dodgy, then we all know how that will affect the model output! Rubbish in, rubbish out!
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Thanks again OMM. We can all learn from your analysis and the PROS seem to have got this one spot on, wouldn't you say?
You're welcome, GTLTW. Yes, it did take the UKMet a while to latch onto this particular development (the GEM model was the first to show it as I recall) but these are such devilish tricky situations to call regarding where it will rain/snow and they did indeed do pretty well.
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Judeging by the latest surface chart at 22Z, the eastward movement of the milder air appears to have stopped near the Dorset/Hampshire border. In the next couple of hours, perhaps a bit more, the winds should begin to back to more of an easterly direction, so there is still a slim chance then of coastal snow, although the bulk of the precipitation will be heading into the Channel.
Rain persisting here with no change in temp - 1.6 but the wind has already backed slightly, more to the SE now.
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Sorry to ask, newbie here whats closed circulation. Many thanks
Katie
Ps - -0.1 and still snowing in high wycombe.
Hi Katie, a closed circulation is an actual low pressure centre, a closed isobar where there is easterly winds to its north. This is as opposed to a trough, which is just a kink in the isobars, like a "U" shape, whereas a closed centre is "O" shaped. Not sure I am explaining it very well! Be easier to draw it but can't do that here!
Take a look at the surface pressure charts and you will see what I mean by a trough! If an actual closed isobar appears in the middle of the trough, then that's closed circulation. It does of course depend on what intervals the isobars are drawn at too.
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Hello OMM I have lived down here since 1965 and never yet had more than I wished for and very rarely what I did wish for. I am a total snow nut living in a snow desert though so i think that says it all!
Hi coldfingers, yes snow is always very fickle here on the coast but sometimes it works to our advantage. On 8th December 1967, there was up to 11in of snow in Brighton as a polar low crossed the region and the warmth of the sea triggered strong convection which dumped a huge amount of snow along just the coastal strip.
But all too rare an event unfortunately.
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The latest radar is showing a distinct hook to the precipitation over mid/N Wales, so maybe we now do have a proper closed circulation.
There is a very sharply defined cloud clearance heading down across the Midlands so for those of us particularly who have had rain, it's likely to be VERY icy out there tomorrow morning! It won;t take much to freeze if the cloud breaks up.
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..mmm..not sure i saw 15cm....annoying thing is i'm 38 now and still in search of a 1963 /47 scenario and don't think i'll be happy until i've seen one! I admit we've come close to a couple of channel lows in the last couple of years but it always seems to go wrong at T+24..Still like you say There's always next week!! :lol:
I'm old enough to remember 1963 when I lived on the Isle of Wight and we had snow on the ground until March!
If you want to see what a westward travelling cold pool can do, check out Boxing Day 1970. I was on the IOW then and it snowed heavily all day!
Be careful what you wish for!!
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I wish I was 50 miles more inland...always the same story being right on the south coast........there is snow in southern italy, southern france, turkey and north africa, but southampton come up trumps with a rain / sleety mix as usual
True, but we did manage 15cm+ on 3rd December 2010! Wait and see what next week brings, with a continental cold pool possibly heading W up the Channel. It would a very different ball game then!
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For those that missed it in the old thread I will repost Old Met Man's interesting analysis.
Well, it's moderate rain here right now, just one or two snowflakes I can see in the streetlight light outside. Temp 1.6, DP around zero.
I'm waiting to see the 19Z surface chart to see if there is a closed circulation yet. The satellite picture doesn't tell us much except the occluding front is already shearing away N between Iceland and Norway.
Just seen the 19Z chart, still no closed circulation but looking at the wind flow there could now be a centre just NW of Anglesea. From the surface obs it would appear the warm front is running SSE through the Welsh border down through Wiltshire/Dorset. So the low is probably tracking just S of SE, which, allowing for the fact that it may turn more towards the S as it goes, will mean it'll exit the coast somewhere around the Hampshire/Sussex border.
This evening's developments will be most interesting! Need to watch the cloud pattern associated with the occlusion as well as the rainfall/snowfall pattern as the system tracks towards us.
Kind Regards to Old Met Man, Cheers gottolovethisweather
Many thanks GTLTW, I appreciate it.
Looking at the IR satellite, the area of coldest cloud tops is slap bang over the region at the moment so the LP centre must be somewhere near mid-Wales, heading for Herefordshire/Gloucestershire. I mentioned in a reply to SnowMania that this low could be more complex, so we'll see what the hourly analyses come up with.
Still raining here with a temp of 1.6, but the wind has picked up from the S quite noticably.
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It seems we can never underestimate the power and warmth of the channel. This is the reason for the snow turning to rain along the Hampshire coasts, including the IOW. I really thought that the cold block would hold out, but like everything in weather, I missed the one crucial thing... a Southerly wind!
But now, another interesting development here, the wind has just switched around to the E and they temperature is on a nose dive! Was 1.8c now 1c... Interesting!
SM
The same thing happened in Dec 2010, with sub-zero temps shooting up as soon as the wind started to pick up from the sea. It's a very close call though, especially as we are approaching the time of year with the lowest sea temps. I think out in the Channel we're looking at temps of around 8C.
Interesting what you say about the wind shift and temp drop. Could be that the LP is more complex. Clearly, any change of wind direction which brings the air off the land will readily turn rain to snow as the cold air is still in plentiful supply ahead of the warm front/occlusion, over the N and NE of our area.
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someone in the snow risk forum has said heavy snow now it southampton??? anyone shed any light
Well I'm 2 miles from Southampton city centre and, apart from a few flakes now and then, it's moderate rain. However, temp is now 1.4 so if this rain keeps at this intensity for much longer it will cool the air down to close to the DP which is near zero and we will have snow. That could well be what's already happening in the higher parts of the city - I'm right down in the river valley.
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Well, it's moderate rain here right now, just one or two snowflakes I can see in the streetlight light outside. Temp 1.6, DP around zero.
I'm waiting to see the 19Z surface chart to see if there is a closed circulation yet. The satellite picture doesn't tell us much except the occluding front is already shearing away N between Iceland and Norway.
Just seen the 19Z chart, still no closed circulation but looking at the wind flow there could now be a centre just NW of Anglesea. From the surface obs it would appear the warm front is running SSE through the Welsh border down through Wiltshire/Dorset. So the low is probably tracking just S of SE, which, allowing for the fact that it may turn more towards the S as it goes, will mean it'll exit the coast somewhere around the Hampshire/Sussex border.
This evening's developments will be most interesting! Need to watch the cloud pattern associated with the occlusion as well as the rainfall/snowfall pattern as the system tracks towards us.
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Hi OMM.
Is this good or bad for our region?
Thankyou kindly.
gottolovethisweather
Hi GTL, it's very tricky indeed, if the LP tracks SSE across S Wales and Somerset/Dorset, we'll still remain on the cold side of the occlusion, with most of the precipitation on its forward edge where the LP is. At 16Z it was snowing as far west as the Welsh border, and the surface analysis for that time is suggesting the occuding process is happening fast, so the warm sector is going quickly too. The surface circulation seems to be forming near the Eire/Northern Ireland border.
As I see it at the moment, coastal areas will see more rain than snow (say up to 10-15 miles inland) or , God forbid, freezing rain, but mostly snow inland. However, as the low heads into the Channel and winds start to back round gradually to the E and then NE, even the coastal strip could get the rain turn back to snow. Bear in mind of course that the area of heaviest precipitation will be out into the Channel by then so the rain/snow will be fizzling out. The occlusion meanwhile will probably start to break up and slow down to the N of the LP, maybe start to bend westward behind the LP as it does so. Once the LP is well south of the UK, what's left of the occlusion will, I think, most likely be off the E Coast.
All this is assuming the LP tracks as predicted, it could be further E in which case the whole occlusion will push through and we'll be in less cold air with drizzly rain, still some sleet/snow on the higher ground.
I think the surface circulation could become quite complex so we could have more than one LP centre, in which case there could be areas of heavier precipitation. It's a shame it's getting dark now because the visible satellite would tell us much more than the IR. But the rainfall radar will start to show the surface circulation soon I would think.
In a sentence, this is a forecaster's nightmare!!
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Getting very close to starting here. Temp now 2.9, DP - 0.4. More low turbulence cloud appearing now so something must be falling, but not to the ground yet!
The last visible satellite pics show a much more definite SE-S drection to the high cloud over the Irish Sea and south of Eire, but no sign of any surface circulation. The occluding front is slowing off the NE coast of Scotland so it might finally grind to a halt somewhere near the E Coast.
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Temp now 3.2 and DP 0.4, with a thick layer of altostratus and a few patches of stratus forming so precipitation must be imminent. Unless it's heavy, it'll be rain with some snow mixed in, just hope it doesn't freeze on the ground.
Looking at the visible satellite, the triple-point is somewhere near Cumbria but it's hard to tell. There is still more SE motion to the cloud pattern than S, but it is clear from the radar that the occlusion process is happening quite rapidly.
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Hi OMM,
It is wonderful to see you posting but I have a question.
In relation to my post earlier shown here - http://forum.netweat...ost__p__2246559 can you confirm that this cold is likely to arrive in two waves?
That is, the first warming will eventually get replaced by a second cooling of airmasses?
Please advise as it might help lessen some confusion on here.
Kind Regards
gottolovethisweather
Thanks GTLTW. Sorry for the delay in replying, got a bit sidetracked!
I'd say there is a very good chance of the cold returning. I shall say more on the model forum later but the continental block is going nowhere fast, and the just isn't enough jet energy to displace it for the moment.
Anyway, more later!
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Temp -1.2, DP -3.5 here in Southampton. Cloud is spreading in rapidly, high cirrus/cirrostratus is streaming down from the NE, plus there is a light SW wind picking up.
Latest visible satellite suggests the triple-point low is forming, north of N. Ireland.
Surface warm front is just off the Welsh coast. Based on the satellite presentation, it looks as if the LP will track slightly further E, perhaps exiting the coast as far E as W Sussex. Very hard to tell until we can see the actual LP centre forming on satellite.
I shall be glued to the satlellite and radar today!
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Just been looking at the first high resolution visible satellite pics for this morning.
First thing that strikes me is that I don't see much southward or south-eastward motion to the cloud pattern - well at least not yet. It just seems to be marching steadily eastward.
If we are going to get a triple-point low forming, it's going to have to be soon and this should show up in the cloud motion.
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The one thing that isn't being spoken about but is arguably more dangerous than snow is rain hitting frozen surfaces. Although this will be a relatively short period of time, it could be a real problem. Snow you can see, Ice is more difficult. So if it starts as rain in your area then be mindful of this until the cold is out the ground.
Hi Snowdrift, I was going to say the same myself! We've had exceptional temperatures here in the middle of Southampton - -6.4 Friday morning, -7.4 last night. In 30 years that I have lived here, I don't recall such a cold night as last night. Goodness knows what the ground temps must be, could have been -10 to -12. Yes, I think there is a real danger of freezing rain as you say, once we start to get a fetch off the sea, might be enough to turn precipitation to rain on the coastal strip.
Given the intensity of the cold we've been getting it'll take quite a while for the ground to warm up.
Think I'll stay indoors and watch from a safe distance!
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It’s amazing how much model output can change in but a few days!
There is fairly broad agreement on maintaining the current block but for the 12Z ECM that is trying to bring in a NW flow late in the period. There are some variations in the location and intensity but HP is maintained over or near the UK, with a light flow off the near Continent or a high cell right over us.
The main area of interest at the moment is the LP forecast to move S over the country during the weekend. Again, there are slight variations but the general predicted path is down the middle of the country with snow on its E side. Once it is past, then pressure is expected to rebuild to the N.
It is going to be extremely difficult to assess snowfall in this situation. The projected path would certainly provide several hours of snow over the E Midlands, NE England and central and S/SE England, but with a slight fetch off the Channel coastal areas may escape. It is worth bearing in mind that the forecast is for a shallow LP that is unlikely to develop much so snowfall amounts could vary enormously from place to place.
That apart, the GFS shows another similar development next Wednesday, with the LP in this case heading S over the W of the country. It is hard to say at this stage how well surface temps will support snowfall with this event, if it happens, although with a mostly slack pressure field over the country and a pool of stagnant, cold air, there could certainly be some.
In the longer term, the models show a general trend of retrogressing the HP W, eventually leading to HP in mid-Atlantic. Upper air developments are showing some significant changes upstream with increasing meridional flow. Over the US/Canada, there is now a developing upper low over the W, moving E and amplifying, with a fairly strong ridge over the E Pacific. The upper low to our NW is moving little with the upper high holding firm over us, with an upper low covering much of Europe. This pattern has the look of a more stable wave pattern so the longer-term model depiction of a mid-Atlantic HP is a distinct possibility.
The jet is also showing some interesting changes. The is a complex split flow over US/ Canada with one arm heading NW towards us, and a more southerly branch which looks as if it will start to propagate on a much lower latitude. This raises the possibility of the UK being attacked on 2 fronts, with the development of an arctic front with LP heading down from the NW, together with the polar front displaced well south bringing systems in from the SW. If the cold air largely persists over the UK in the coming days with a light E or SE flow, this could provide some entertaining situations, especially if the HP over mid Atlantic extends W towards Canada – that’s the sort of pattern associated with prolonged cold spells.
I suspect the GFS may be first to indicate whether the above looks likely to happen. Meanwhile, the weekend will be very interesting!
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Despite the odd GFS run suggesting HP to the east over recent days, it looks to me as if there is a better consensus between the main 3 models for keeping things moving across the Atlantic. Even the ECM looks a little less deranged than it did a couple of days ago and is broadly similar to the UKMet and GFS.
There just seems to be no end to the constant succession of LPs coming out of Canada/the US. There were signs the other day of a slowing down of the US jet but, in spite of there being more meridionality over the E Pacific in the last few days, the NW jet into the Pacific Northwest seems to be pepping up again and the sub-tropical jet is still racing NE across the southern US states, so the 2 combined seem to be generating these endless LPs.
The only point in all the runs where there may be some chance for a slow down is between about 96Z and 120Z where the Atlantic flow slackens off, whilst a rapidly developing LP south of Greenland gets its act together, but the main models at present are pushing its frontal zone well ahead of its centre towards us and keeping the mobility going. If this LP, should it verify,deepen enough to slow right down and turn N, then it might allow some room for HP to build westwards across the Norwegian Sea towards Iceland as the end of train LP near the UK heads away to the E, letting some cold NE winds come at us. But I think that is a big "if".
All in all, there seems little prospect of any cold E flow just yet, although the 528dm thickness moving N and S across us in the next few days will most likely allow for some wintry activity, mostly in the N I would think.
We'll see how the models handle the 4-5 day timeframe in the next couple of days - the output could conceivably change quite a lot.
South Central England Regional Discussion Thread Part 4
in Regional
Posted · Edited by OldMetMan
Hello folks.
Yes finally we've got some snow. Moderate snow right now, started around 2030, temp 0.6, DP -2.1, all thanks to a light easterly drift, not like Saturday!
Seems the warnings didn't expect snow along the coast. Most of the heavier precipitation seems further to the E than the official forecast predicted. The west and the Midlands are feeling the effects of a weakish warm frontal wave whereas the snow we're getting is associated with a more active occlusion/cold front sliding SE, so unless the wind turns to off the sea again, I think we're in for several hours of light to mod snow.