639 replies to this topic

[reef]

A new thread for the new week. It would be very much appreciated if people could discuss what the models show and not what they think might happen in a few weeks. It makes it much easier for everyone.

Please continue here.

[DiagonalRedLine]

Generally, the models are in agreement of the weather becoming milder for all - this most particularly evident during Wednesday and Thursday with a rapidly decreasing snow risk. The beginning of this week looks to be fairly cool, however. A spell of rain will move in from the West during this morning (Monday), possibly falling as sleet and snow on hilly areas over Scotland.

GFS 18Z Precipitation and H500's Pressure Chart for 3pm, today. Some very wet weather moving in.


This should clear all areas by Monday night, and then a ridge of High-Pressure is forced to track Eastwards, with colder upper air spilling down on its Eastern part, with the far North of Scotland seeing uppers as low as -6 briefly. Most places should see a rain-free day on Tuesday. It will feel rather cool as well, especially in the far North with perhaps a few odd showers occuring their during the day - some maybe wintry in nature, too. Another batch of rain/showery weather is then expected to spill in from the West during Tuesday night and into the beginning part of Wednesday. It should become less colder as well, with warmer air being brought up from the South-West.

For the rest of the week and into the weekend, the South looks like it will stay fairly settled with the pressure higher their, while the North will continue to see more spells of rain and showers from Low Pressure systems to the North and North West. But even in the North, some drier, sunnier interludes look possible.

Their does appear to be some doubtfullness, from the weekend onwards, about how far North the High-Pressure system from the South can get. With all that energy to the North-West it may struggle to get far enough North to allow numerous places to see a cool/cold Easterly. But on the 18Z GFS run, the JetStream does briefly travel North over the UK. Be interesting to see how this gets further modelled.

Edited by Rainbow Snow, 19 December 2011 - 02:38 .

[vizzy2004]

Some more interest towards the latter stages of ECM. Am i right in thinking the 240hr chart shows a much stronger build of pressure towards Greenland and the troughs below possibly digging south?

[Tellow]

Isn't cold air supposed to push back Friday? The models do show a minor cool down from the mild on that day but could it be underestimated?

[Alex]

vizzy2004, on 19 December 2011 - 07:47 , said:

Some more interest towards the latter stages of ECM. Am i right in thinking the 240hr chart shows a much stronger build of pressure towards Greenland and the troughs below possibly digging south?

I wouldn't say this is a very strong ridge, you have probably noticed the deep low just to the south of greenland on this map, this would indicate that although the jet could be nw-se based, it wouldn't produce the extreme cold you are probably wanting coupled with the fact it is deep FI I wouldn't be too confident anyway.

[wolvesfan]

Morning all,
ECM this morning showing azores high being flattened around t192 and a return to a zonal flow,polar air back over the uk just after christmas.

All the three main models continue to show dissruption to the polar vortex on the northern hemisphere charts,wether we can can see dissplacement from it's current position around Greenland remains to be seen,but this would be a step forward for cold longevity next month.

[vizzy2004]

Alex, on 19 December 2011 - 08:06 , said:

I wouldn't say this is a very strong ridge, you have probably noticed the deep low just to the south of greenland on this map, this would indicate that although the jet could be nw-se based, it wouldn't produce the extreme cold you are probably wanting coupled with the fact it is deep FI I wouldn't be too confident anyway.

Yes i agree regarding the heights are not very strong but it could be a step in the right direction!

[happy days]

Nothing for coldies this morning.
Flat zonal all the way to the New year,stratosphere thread is the new samaritans.

Edited by happy days, 19 December 2011 - 08:29 .

[mikeocarroll]

happy days, on 19 December 2011 - 08:28 , said:

Nothing for coldies this morning.
Flat zonal all the way to the New year,stratosphere thread is the new samaritans.

Well if you're looking for a straw to clutch at, then at least the GFS ensembles have the mean declining steadily in FI, with a few proper cold members, which the ensembles haven't often shown so far this winter even in FI.

[Nick F]

Pretty hard to see any cold and wintry snap develop this side of the New Year from what the models are indicating this morning, with the polar vortex looking difficult to budge from the polar regions to the N and NW of the UK.

Very little opportunity to develop any amplification in the PFJ and once the Euro trough moves on out the way, the Azores ridge is allowed to move in across Europe giving what looks like a fairly mild and green Xmas Day - particularly in the north where we have the stronger southwesterly flow. GFS does indicate a chilly night Xmas Eve and again overnight into Boxing day across southern Britain where we have more of an influence under the high pressure.

[karyo]

vizzy2004, on 19 December 2011 - 08:23 , said:

Yes i agree regarding the heights are not very strong but it could be a step in the right direction!

The ECM chart you posted shows the return of cold zonality which I'd welcome with open arms!

Karyo

[nick sussex]

happy days, on 19 December 2011 - 08:28 , said:

Nothing for coldies this morning.
Flat zonal all the way to the New year,stratosphere thread is the new samaritans.

It looks like I'll have to get in extra staff to man the prozac hotline! In an attempt to derail the gloom train this morning the output is nowhere near as bad from a cold perspective but there will definitely be some milder conditions for a time, theres no way of avoiding this given the upstream pattern.

What happens post 192hrs is yet to be decided especially when we look at both the pressure and 850's ensemble spreads from the ECM.

http://www.meteociel...=1&map=1&type=2

And finally it wouldn't be the same without some reference to the stratosphere!

http://wekuw.met.fu-...cmwf1/temps.gif

A minor warming forecast at the 1HPa level, these are the most promising outputs for the stratosphere from a cold perspective so far this winter, whether this translates into some big changes in the output only time will tell.

Edited by nick sussex, 19 December 2011 - 08:55 .

[Great Plum]

Before I saw the ECM 240hrs, I was quite heartened by:

http://www.wetterzen...cs/Recm2161.gif

That high to the east looks promising or am I wrong?

[BLAST FROM THE PAST]

Great Plum, on 19 December 2011 - 08:56 , said:

Before I saw the ECM 240hrs, I was quite heartened by:

http://www.wetterzen...cs/Recm2161.gif

That high to the east looks promising or am I wrong?

Still be heartened, the 240 shows a -ve tilt occurring, which suggests a NW/SE axis an undercutting of HP to our E / NE.

Now looking at overnight models GFS makes more of the shift of the AZH and its influence over the UK and Europe. ECM less so. Crucial period is around 144+ mark, around Boxing Day/ 27th. I'm looking at a fairly windy/stormy day for most and ECM certainly seems to suggest this where as the GFS sends it way north. ECM then sends a ridge down from Arctic which would lend itself to a parttern change to much colder conditions. [A general pattern I think looks like developing in early Jan]. GFS has none of it and same old deep FI remains.

This week it looks like it doesn't turn mild until Wed and then cooler conditions move back in on Friday so a mixed bag ahead with a general west flow to dominate upto and on the big day so 'overall' average conditions. However, like I've been saying keep watch for developments around Boxing Day/27th

BFTP

[wolvesfan]

Morning all,
Models not looking good for short term cold prospects at the moment,but we are seeing signs from the main three models of a dissruption of the polar vortex that has been in sittu around Greenland.A dissplacement of this which IMHO is possible in the near future will give a greater possibility of northern lattitude ridging from the azores high,or even a mid atlantic block to our west.

A lot of talk has gone into a pressure rise to our north east but could this area be a location for the vortex to setup?.The GFS stratospheric 30hpa chart,which is forecasting a warming moving into northen Canada and reaching western Greenland shortly will surely help to dissplace the vortex from its current location?.The stratosphere is anomolously cold so a dissplacement of the polar vortex probably the best we can hope for.

I'm no expert though and what i'm seeing are my thoughts and oppinions so are more likely to be wrong as my model watching is still in it's infancy.

[12-barbluesmikey]

Just a question for the more knowledgable.Looking at the northen hemisphere charts the main polor vortex arouned n canada seems to be moving away and the polar regions look more displaced.I know it is in the later stages but may tie in with some of the strat reports.Just somthing to look forward to maybe.

thanks
mike

[Nick F]

wolvesfan, on 19 December 2011 - 09:35 , said:

Morning all,
Models not looking good for short term cold prospects at the moment,but we are seeing signs from the main three models of a dissruption of the polar vortex that has been in sittu around Greenland.A dissplacement of this which IMHO is possible in the near future will give a greater possibility of northern lattitude ridging from the azores high,or even a mid atlantic block to our west.

A lot of talk has gone into a pressure rise to our north east but could this area be a location for the vortex to setup?.The GFS stratospheric 30hpa chart,which is forecasting a warming moving into northen Canada and reaching western Greenland shortly will surely help to dissplace the vortex from its current location?.The stratosphere is anomolously cold so a dissplacement of the polar vortex probably the best we can hope for.

I'm no expert though and what i'm seeing are my thoughts and oppinions so are more likely to be wrong as my model watching is still in it's infancy.

I can't see any major disruption of the Polar Vortex, and the 00z 8-10 day H500 comparison shows the continuation of low height anomalies in the high latitudes:

http://www.meteo.psu...0z/hgtcomp.html

Certainly no large displacement to more southerly latitudes. ECM does hint in the later stages of the 00z operational run that cold uppers may sink south from Greenland which would push the PFJ further south, but, not wanting to be a killjoy, what the charts show at the end of the medium range often change, though occasionally they latch on to an evolution and follow it through to a more realistic timeframe.

12-barbluesmikey, on 19 December 2011 - 09:38 , said:

Just a question for the more knowledgable.Looking at the northen hemisphere charts the main polor vortex arouned n canada seems to be moving away and the polar regions look more displaced.I know it is in the later stages but may tie in with some of the strat reports.Just somthing to look forward to maybe.

The Polar Vortex in the Northern Hemisphere is not static but tends to wobble around and elongate with troughs developing from it here and there, so it may appear that its moving away from parts of Canada, and indeed a ridge is shown to build in across NW Canada from the south. But as I mention above, the cold upper air / low heights continue to remain bottled up at higher latitudes towards the arctic circle and there are no strong signs of a major displacement of this cold upper air southwards this side of the New Year and this may last into early Jan.

[wolvesfan]

Nick F, on 19 December 2011 - 10:16 , said:

I can't see any major disruption of the Polar Vortex, and the 00z 8-10 day H500 comparison shows the continuation of low height anomalies in the high latitudes:

http://www.meteo.psu...0z/hgtcomp.html

Certainly no large displacement to more southerly latitudes. ECM does hint in the later stages of the 00z operational run that cold uppers may sink south from Greenland which would push the PFJ further south, but, not wanting to be a killjoy, what the charts show at the end of the medium range often change, though occasionally they latch on to an evolution and follow it through to a more realistic timeframe.



The Polar Vortex in the Northern Hemisphere is not static but tends to wobble around and elongate with troughs developing from it here and there, so it may appear that its moving away from parts of Canada, and indeed a ridge is shown to build in across NW Canada from the south. But as I mention above, the cold upper air / low heights continue to remain bottled up at higher latitudes towards the arctic circle and there are no strong signs of a major displacement of this cold upper air southwards this side of the New Year and this may last into early Jan.

Hi Nick,
I agree there's no major dissruption to the polar vortex at the moment,my guess is the models could start to show this in the next 7-10 days as the strat warms around northern Canada into west Greenland.As i've said before though i'm no expert.cheers.

[Nick F]

wolvesfan, on 19 December 2011 - 10:44 , said:

Hi Nick,
I agree there's no major dissruption to the polar vortex at the moment,my guess is the models could start to show this in the next 7-10 days as the strat warms around northern Canada into west Greenland.As i've said before though i'm no expert.cheers.

Yes, I agree there are signs of a strat warming taking place very high up, but it remains to be seen whether the warming will work down into the tropospere where our weather is. Even the milder winters we've had probably have had some warming high up at some point that hasn't worked down to the tropo. A straw to clutch I suppose.

06z continuing by default into FI with very low heights to the N and NW and high pressure over Europe ( strongly +ve NAO) with the Polar Front Jet way north than average, though with the scope for some pretty dry conditons and perhaps some chilly nights for southern Britain under the influence of the high.

[bluearmy]

nick sussex, on 19 December 2011 - 08:54 , said:

What happens post 192hrs is yet to be decided especially when we look at both the pressure and 850's ensemble spreads from the ECM.

http://www.meteociel...=1&map=1&type=2

still a significant clustering showing a block to our west day 10 (not dissimilar to the op GEM run).

(and i note more runs going cold in holland beyond - though not a trend as yet)

assuming that most of us are in agreement that the op runs are not the best tool for looking at the period days 8 through 10, why do we take too much notice of the meteopsu output which is a mean representation of both the ecm and gfs op runs, days 8 thru 10. ????