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phil nw.

Winter Model Discussion - Cold Hunting -12Z 30/12/12

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Here is a new thread where we can continue discussions from the earlier outputs and be ready for the 12z model runs.

Below is a reminder of the different places where you can post-please try and use this one only if you are referring to what the models are showing and your views related to them.

General views only icluding. moans and ramps should go into the Model mayhem thread.

Current Model Related Threads:

The winter / cold model output discussion thread (this one) - busy, fast moving, sometimes a bit of a rollercoaster, generally cold orientated, with views from a wide range of people with differing interests, biases and levels of knowledge.

In depth model discussion, analysis and summaries - slower moving, sometimes more technical, straight down the line type model analysis, info and discussion:

http://forum.netweat...-and-summaries/

Model mayhem - all the emotion from looking at the models, rants, ramps, hopes etc

http://forum.netweat...n-ramp-go-nuts/

Please refer to the relevant threads when posting to help keep model discussion on topic.

Thanks all.

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We cloud be looking at some very mild weather by the end of this week as high pressure begins to establish its self over the UK we could be looking at highs of 14c by Friday quite easily

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We cloud be looking at some very mild weather by the end of this week as high pressure begins to establish its self over the UK we could be looking at highs of 14c by Friday quite easily

Yes Gavin it looks like mild fans will be filling their boots soon, they better make the most of it though as the metoffice still think a marked change to cold is possible after mid month as the ssw shows itself, before then it looks very much like the ecm 00z run is showing with a north/south split, milder and wetter for the north, milder and drier for the south until mid month.

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The combined London Ensembles for the 2M temps.from the 00z outputs.

post-2026-0-66030800-1356876232_thumb.gi

as expected a few milder days in the first week of the new year as the high build from the south behind some higher 850hPa temperatures.

post-2026-0-17136400-1356876459_thumb.pn

It`s beyond this period into week 2 where the ens show surface temps. easing down as the low heights to our north show signs of easing away.

post-2026-0-99097200-1356877056_thumb.pnpost-2026-0-63758700-1356877071_thumb.pn

The propects for cold therefore is still a while away but we have a lot of interest now in the forthcoming runs as they try to work out the 500hPa pattern from week 2.

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Yes Gavin it looks like mild fans will be filling their boots soon, they better make the most of it though as the metoffice still think a marked change to cold is possible after mid month as the ssw shows itself, before then it looks very much like the ecm 00z run is showing with a north/south split, milder and wetter for the north, milder and drier for the south until mid month.

I suspect that the 12z will be a bit cooler, as the 0z op from ECM was on the mild side in the latter part of the run:

post-14819-0-53465900-1356877200_thumb.j

The GEFS mean, also for London do not really go above 8c from Wednesday:

post-14819-0-15160500-1356877770_thumb.j

I think that the fact it will be dry will be more significant than temps.

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I suspect that the 12z will be a bit cooler, as the 0z op from ECM was on the mild side in the latter part of the run:

post-14819-0-53465900-1356877200_thumb.j

The GEFS mean, also for London do not really go above 8c from Wednesday:

post-14819-0-15160500-1356877770_thumb.j

I think that the fact it will be dry will be more significant than temps.

It may be on the milder side of the ensembles but it's bang on the nail with the metoffice latest thoughts as far as a mild or very mild outlook through to at least mid january is concerned, so if the ecm 00z is indicating 15c for next saturday, if it's only 12 or 13c it will still be very mild, when you factor in the fohn effect, 15 or 16c is probable for areas to the east or northeast of high ground. Fingers crossed for beyond mid month though as I suspect things could become much more interesting by then from a cold perspective.

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Good afternoon. Currently we have low pressure of 968mb situated close to the Faroe Islands resulting in a fresh and also a showery westerly flow that we've seen during the past 12 hours or so. During this afternoon we lose the sub 528 dam air so the wintry precipitation in the showers across Scotland will be confined to higher elevations but routes such as the A9 at the Pass of Drumtocher could be a little tricky this afternoon. However it seems that during this afternoon the shower activity across Scotland will begin to decrease through this afternoon but for the next couple of hours atleast there should still be a theme of sunshine and showers. Through this afternoon the best of the sunny intervals are most likely down the eastern side of England and Scotland. In England and Wales there should be few showers but in the west cloud cover should increase this afternoon with some patches in light rain as we have a front moving into Ireland. And indeed, it should be an overcast afternoon in Ireland quite heavy and persistent rain spreading into Northern Ireland. Maximum temperatures this afternoon should be 4 to 10C.

h850t850eu.png

ukprec.png

ukmaxtemp.png

hgt500-1000.png

During this evening we should see the band of rain located over Northern Ireland and spreading into southwestern Scotland and northwestern England and the precipitation could be quite heavy aswell. It should stay cold and partly clear in northern Scotland with some showers for the northern isles. There could also be a few clear spells in the very south of England with the threat of the odd shower in the channel. But across large swathes of the British Isles skies should generally be on the cloudy side. With low pressure of 984mb located west of Ireland, we should see winds turn to a southwesterly bringing in milder air.

h850t850eu.png

ukprec.png

ukmaxtemp.png

During the night the wet conditions should continue across much of Ireland whilst heavy rain pushes further north east across Scotland aswell as further rainfall for north west England and some precipitation for the west of Wales. There could also be some drizzle ahead of the rainfall in central and southern parts of England. With southwesterly winds sweeping over the British Isles it should be a mostly overcast night and overnight lows should also be milder at 4 to 11C.

h850t850eu.png

ukprec.png

ukmaxtemp.png

For the morning of New Year's Eve and much of the rain should have left Ireland with only some light rain lingering in Northern Ireland. The wet conditions should persist across western and central parts of Scotland with a risk of some local flooding with the melting hill snow and persistent and quite heavy rainfall and potentially a small landslide risk for the western highlands. The rain across northern England and Wales should be reduced to some patches of light rain but this all depends on the timing of events - possibly some further heavy rainfall in southeastern Wales - whilst heavy and persistent rain falls across southern parts of England. There could be some local clear spells in north west England for example and possibly one or two showers coming off the Irish Sea in quite a brisk southwesterly.

h850t850eu.png

ukprec.png

Into the afternoon and the main band of rain should be over the south east corner of England whilst possibly some other strips of rain push southeastwards across central England. As the front clears we develop a cool NWly flow which should bring some sunny intervals behind the front and also some showers feeding into western areas and these could be a mix of rain, hail and maybe sleet and possibly the odd rumble of thunder. Maximum temperatures should be 4 to 11C.

h850t850eu.png

ukprec.png

ukmaxtemp.png

hgt500-1000.png

For the evening of New Year's Eve and the band of rain should just be clearing the very south east but some other minor bands of light should be moving further south east and the skies should stay overcast. Along the coast of west Wales, the south west and the channel there could be a few showers and there may also be a few showers heading into the north west. Most of the showery activity should be in western and northern Ireland and southwestern Scotland and these showers should push further inland and there could be a wintry mix in these showers and not just to high levels as sub 528 dam air returns to western Scotland. But away from south eastern England, there should be some clear intervals in the sky - particulary in north eastern areas.

h850t850eu.png

ukprec.png

ukmaxtemp.png

hgt500-1000.png

And as we draw what has been the wettest year on record in England to a close the band of rain should be ready to leave the very southeast corner of England so there should be dry conditions for fireworks display at London. It should be a dry night away from the showers in western areas and in Scotland. There could be clear skies for parts of Wales, central and eastern England with clear intervals in many places. A cool night should be on the cards with lows 1 to 5C in the colder north westerly flow on the eastern edge of the area of high pressure to the south west that attempts to ridge northwards towards southern Greenland. With low pressure centred just to the north of Scotland there could be frequent showers feeding into western areas of Scotland and northern Ireland. With the sub -5C uppers in some areas and sub 528 dam air across much of Scotland and Northern Ireland then there could be some wintry precipitation during the first few hours of 2013 and possibly a fresh covering of snow on the high ground.

h850t850eu.png

ukprec.png

ukmaxtemp.png

prectypeuktopo.png

hgt500-1000.png

The risk of wintry precipitation should decrease throughout New Year's Day. Also as air pressure increases from the south west there should be fewer showers but we maintain the cool northwesterly flow and it could be quite a cold day with highs of 4 to 7C. There should also be plenty of sunshine - particulary in eastern areas - so it is looking like a pleasant start to 2013.

h850t850eu.png

ukprec.png

ukmaxtemp.png

Tuesday night should be settled with high pressure - particulary in the south - and it could be quite a cool night with lows of 1 to 4C and some clear intervals aswell. However north western areas are more vulnerable to milder, wetter atlantic conditions rolling ontop of the high so cloud cover should increase in north western areas and a warm front could bring some rain to parts of northern Ireland and western Scotland.

h850t850eu.png

ukprec.png

ukmaxtemp.png

There should be a spell of wet weather for northern areas and Scotland in particular during Wednesday and quite heavy precipitation for northern Scotland but this front could clear for the afternoon. Behind the warm front and the mild southwesterly flow should make for quite dull and murky conditions in north western areas in particular. Much milder with highs of 8 to 12C.

h850t850eu.png

ukprec.png

ukmaxtemp.png

Overnight on Wednesday and skies could be largely cloudy with perhaps a few clear intervals in some eastern areas whilst drizzle and patches of light rain affects northwestern areas. High pressure continues to be situated to the south of the British Isles but the mild westerly winds should result in a mild night with lows of 5 to 10C.

h850t850eu.png

ukprec.png

ukmaxtemp.png

With high pressure strongly infuential, Thursday could see 'dry' conditions but with skies mostly overcast - possibly some clear skies in north eastern areas - with mild air coming off the atlantic then there could be some drizzle and patches of rain in some places. A particulary mild day in the south - typical highs of 8 to 12C.

h850t850eu.png

ukprec.png

ukmaxtemp.png

High pressure continues to control things through Thursday night with north western Scotland exposed to some areas of rainfall. For the majority it could be another cloudy night with some drizzle in places and another mild night with lows of 4 to 10C.

h850t850eu.png

ukprec.png

During Friday, Saturday and Sunday high pressure continues to be centred close to southeastern England with mostly dry and settled conditions for much of the British Isles.

h850t850eu.png

ukprec.png

Temperatures by night could be quite low

ukmaxtemp.png

High pressure on the GFS 06z is situated to the east of the British Isles beyond Sunday resulting in southerly winds and generally increased rainfall for the British Isles but with many more runs to come I'd say that details regarding the positioning of the high is likely vary - particulary beyond next weekend.

GFS 00z also had a theme of high pressure to the east but at the end of FI interestingly we end up with an impressive area of high pressure over Greenland.

h850t850eu.png

There's is a lot of things to be dealt with and to look out for in the longer term when viewing the models in the many days to come but it's worth keeping an eye on developments regarding the stratosphere as it seems that we are heading for a SSW at some stage during the first part of the January as the stratospheric vortex is now at a critical point. There is also interesting signs of a possible second warming. It will be most fascinating to follow further developments and if things go along nicely then possibly we could be in a decent position for height rises over Greenland and this would set up a very interesting second half of January.

When looking at the Aberdeenshire GFS ensemble there is a distinct trend of a drop in upper air temperature

t850Aberdeenshire.png

The ensembles for air pressure over Reykjavic will also be worth following during the coming days and weeks

prmslReyjavic.png

Interesting times......

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From now I on will aim to give a daily/bi-daily 'make of it what you will' forecast based on my interpretation of the current model output, hopefully it'll be of some use.

Forecast based on latest model output:

Showers initially today for many, especially in the W, before rain moves in from the W this evening and overnight, heavy especially across the NW initially before spreading S to most with 25-50mm over W hills by the end of tomorrow. Next week things look to dry and warm up as high pressure ridges in from the south. Increasing amounts of cloud and occasional rain and drizzle the further N and W you go. Driest and brightest in the SE. Mild or very mild for all with double figure temperatures widely.

As we head into the second week of January things look to turn somewhat more unsettled, windier and cooler for all as high pressure slips away SE with an increasing risk of systems moving in from the Atlantic. It is possible this increasingly unsettled trend will continue through to the middle of January although there is uncertainty with colder and drier weather also a possibility.

Severe weather watch:

Heavy rain and strong winds tonight and tomorrow, especially in the N and W with 25-50mm possible over W hills with local flooding possible given already saturated ground. Heavy snow on Scottish mountains.

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are we looking at a tentative bartlett setting up shop at the backend of next week? I hope not!

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are we looking at a tentative bartlett setting up shop at the backend of next week? I hope not!

I know a Bartlett when i see one and even if it tries to plot up as a Euro High it certainly wont last looking at dynamics from Mid Jan......well fingers crossed it wont anyhow.....fully expecting some lovely cold runs starting to appear now.........In keeping with teleconnections......Not saying we will hit jackpot but cannot see a Bartlett at all....

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are we looking at a tentative bartlett setting up shop at the backend of next week? I hope not!

Where have you been the last few days? :p

High Pressure is looking likely to dominate our weather over the opening week of 2013.

post-12721-0-63515800-1356883247_thumb.j

Which will halt the never ending rainfall and although mild, will provide some dry days. It's what happens with this HP cell in week 2 that is making for interesting model viewing currently.

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gfsnh-0-216.png?12

Not that great in isolation, but the huge siberian block (that has never really gone away) looks west to northern Greenland, while the Atlantic stalls and heights shoot up from Europe. Anything could happen from here.

Edit:

Indeed, this is where we end up a few frames later

gfsnh-0-276.png?12

A slider low (we should all take that with a pinch of something), a Svalbard high developing and heights rising from the Atlantic.

Exactly the sort of potentially 'interesting' scenario that could be expected out of a SSW event

EDIT 2:

In the end, it came to nothing (a fleeting -5upper cold spell), but it is more interesting than anything we have seen for a while and it could be a trend. could be a trend.

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Nice 12z, more blocked, setting up for something much colder down the line.

Rtavn2761.png

It will be fascinating watching the evolution of the Major warming in the strat and how the NH pattern is affected. Exciting times.

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What are the prospects of it being sunny as opposed to overcast next weekend? A sunny weekend could put thoughts of spring into a lot of people's heads!

Mind you, no doubt many people thought there were days in January 1947 that were springlike....

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Interesting GFS in the longer range, the key is the pulling back West of the intensely low heights towards Baffin, we then see pressure rising to the North and then anything could happen. What is being shown can only be a response to the Stratospheric situation, as the set-up looks pretty poor on the face of it by day 8.

We want to see the models firming up on the above over coming runs and there could be wild fluctuations in the NWP in the longer range over the coming days.

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What an odd chart

gfs-0-252_qvm5.png

A bit of promise there, the trend remains for the high to flatten and low pressure to return from Atlantic though.

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Following on from my post regarding the 12z GFS yesterday, I think we may be seeing the first signs of the pattern shift I hinted at

h500slp.png

This is at 216 hrs. Yes it's a way out but look how it begins to develop....

276 hours......

h500slp.png

312 hours...

h500slp.png

The best FI we've seen in a while.

Remember those heights I said would start to appear between 10th-14th Jan yesterday? Well here they are.

The reality may be that these heights get a real foothold slightly later than this, but it's promising to see.

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@JasonM

You posted this:

"Just as a point of interest for any newbies, the chart being shown is actually virtually snowless for the UK. The uppers under the low sitting over the top of us are actually well above zero. Assuming that the low moved to our south or south east we would pull in colder air afterwards. Of course the detail at that range isn't worth worrying about, but sometimes snowy looking charts are not all that they seem."

Yes as you say this chart is snow-less for most of the UK, however if you were able to move the frame by say 12hrs more, like I said the low would probably move east, allowing a strong northerly to develop, and because of the blocked Atlantic and Greenland high you would probably find a low coming down from the North, which will then give us a very snowy outlook..

Fi however......but the 12z is looking interesting with Greenland heights towards the end of the run, I wonder if this is a trend?...

post-17320-0-06934000-1356885332_thumb.p

post-17320-0-13547800-1356885706_thumb.p

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What are the prospects of it being sunny as opposed to overcast next weekend? A sunny weekend could put thoughts of spring into a lot of people's heads!

Mind you, no doubt many people thought there were days in January 1947 that were springlike....

I would think there could be some sunny spells especially in South coast counties, though further North largely cloudy.

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Ahum, vortex DESTROYED by t300 here, I'm beginning to feel that special tingle that something special is coming.. Greenland high trying to build also

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finally we see the destruction of the PV deep in FI but its a trend we are starting to see from mid month but first we will be stuke with a bartlett HP for a week or so

gfsnh-0-360.png?12?12

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Ian Brown's assessment seems fair. I think sunshine amounts in the south will largely depend on how cloudy it is over the near-continent, as the high pressure will pull in some continental air from central and southern parts of western Europe. Continental air is generally dry and clear in the summer half-year but in the winter half-year banks of cloud can get trapped underneath inversions and then drift in off the continent. Thus I cannot really commit regarding sunshine amounts in southern Britain at this range.

Tropical maritime air off the North Atlantic is usually cloudy at this time of year so the further north you are, particularly to the west of high ground, the more likely it is that a cloudy quiet spell is impending.

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What an odd chart

gfs-0-252_qvm5.png

A bit of promise there, the trend remains for the high to flatten and low pressure to return from Atlantic though.

It's high pressure from the north we are looking for, so personally I don't see any flattening of high pressure, more like a slight northward shift.

These kind of FI charts are an indication of a major pattern shift IMO. Not really to be taken literally but when GFS is playing with such a pattern shift FI charts will often be changeable but often cool/cold.

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Good support from the UKMO at 144 for the GFS

UKMO 12z

UW144-21.GIF?30-17

12z GFS

gfs-0-144.png?12

Differences

UKMO GFS

-1035mb high over UK - Probably warmer than UKMO

-Deeper troughing either side of the high over UK

-Cooler feed from europe rather than N Africa

Positive that there is good similarities between them and ooh eck i cant wait for some cold runs over the next few weeks search.gifacute.gif

Hope my post is correct in what i've stated, ignore it if its wrong, slate it, whatever, just giving my two pence :)

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Some posts that were argumentative have been deleted -let`s have no more.

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