Cold Spell - General Discussion

[kold weather]

As has been mentioned before, its looking quite likely that we will see some snowfall over Wales, especially in western/central areas where Evap.cooling may play a role. Height will make a difference in this set-up.

Anyway tonight is cooling down nicely, spine of the country down to -1/2C, though the south is holding up more with temps around 2-3C in general. I'd imagine that will be of the mildest nights we'll get in the next 7 days here...

[damianslaw]

The main feature of the coming few days will be freezing fog - so some places will see a number of ice days. Had we a snow cover then some very cold mins in the coming days would occur, but alas we won't so until the cold uppers arrive I doubt we will see any particularly notably cold nights, perhaps a -8 or -9 degrees in frost hollows, nothing special.

Later in the week we may see some very cold nights if the cold uppers arrive as projected by GFS and ECM, maxima would struggle above freezing as well.

[Aaron]

we already came close to an ice day (max 0.5c) during that cool period earlier.. so hey, who knows

[toggerob]

January 1987 cold-snap for anyone wanting to get a gauge of snow depths, or rekindle memories. The worst of this ocurred in the South & SouthEast, I would expect however higher pennine/yorkshire routes would have looked more or less the same.

http://www.econet.org.uk/weather/graphics/drift2.JPG

http://www.econet.org.uk/weather/graphics/drift.JPG

http://www.flickr.com/photos/ajvajv/5513841483/

http://farm3.staticflickr.com/2464/4221978192_b1970947dd_z.jpg

The South comes grinding to a halt when a few cms falls to ground, can you imagine the logistical nightmare of dealing with 1ft of snow covering London again.

[greybing]

-10C in frost hollow isn't a story as such, that happens nearly every winter in England (usually further north). I'm pretty sure most year for example, Benson gets around, or near -10C. It's not that unusual. That said -10C, at say the East Midlands airport would be highly unusual. Like you suggest though, -10C should be reached somewhere.. I'd be very surprised if it wasn't.

My thoughts exactly ,more like double that figure. Edited January 29, 2012 by greybing

[Thundery wintry showers]

Pressure will have a significant effect in limiting convection even with cold uppers. I think that the south east may see a few showers when the flow becomes favorable however this will mostly be a dry and cold affair.

I don't entirely agree with that- I think the cold uppers and wind direction are the most important factors. If we get a direct easterly flow with 850hPa temps of -10 to -15C I think eastern areas will see plenty of snow showers even with air pressure of 1040mb, due to the deep instability provided by the airmass track over the anomalously warm North Sea. After all, parts of NE England saw 10-15cm of snow overnight 8th/9th January 2010 with air pressure in excess of 1030mb and 850hPa temps just short of -10C.

During tomorrow and Monday convection will be relatively limited due to the high pressure and lack of excessively cold air, though the 850s of -5 to -8C will probably give enough instability for shallow convection and some light showers- indeed there are a few surprisingly sharp showers out in the North Sea right now. The GFS has been very consistent in progging little or no convection off the North Sea during Tuesday/Wednesday regardless of the wind direction, due to a very dry and slightly less cold pool of air moving over (especially at upper levels). But if we get an easterly flow from Thursday onwards I'm pretty sure it will be a snowy one for eastern areas, as it will suck in that upper cold pool- the main question is whether we will get one. A southerly flow under a ridge of high pressure as per tonight's UKMO would not promote much convection due to the very short track over the English Channel and the cold pool at upper levels being held out to the east.

[summer blizzard]

It does indeed appear you may be correct, precipitation already getting going in the North Sea.

[Weather-history]

I think the high pressure (or rex block) is too far east, close enough to have some influence but too far for the really cold uppers and a more consistent easterly flow for the UK, IMO. If the high was over Scandinavia, it would be no debate. Also makes the UK more vulnerable to any Atlantic influence but that in itself could mean the threat of substantial snowfalls.

[A Winter's Tale]

Its been a while since I done a snow map but here is one for Sunday 29th January.

Expecting some snow around Wales and some of it possibly edging into the Midlands. South Western parts of England are also looking in for snow as well. Around the area's mentioned sleet showers may also occur.

Also Eastern parts of Scotland can expect snow as well.

I'll be looking forward to seeing more of your snow maps. I think it's just about certain that we are now in a cold spell, it's just a case of how cold and snowy it gets and for how long it lasts. Day by day, we'll get a clearer picture of this.

So if next week is a good if not better than what the models are showing, and the cold snap lasts a bit longer, well with cold air already here you can say that we may have just started the big freeze!

[A Winter's Tale]

http://forum.netweather.tv/blog/269/entry-4328-cold-spell-blog/ My Cold Spell Blog:

[Aaron]

Overcast.. hm.. I hope this isn't the theme for this 'cold spell' as the met office forecast suggests cloudy cloudy cloudy which won't allow for very cold night temps..

[Thundery wintry showers]

The showers ocurring currently out over the North Sea are aided by a 500hPa cold pool and not-so-dry air aloft. There's a lot of attention given to the 850hPa level temperatures, or "uppers", but, as the GFS and ECM indicate, the generation of relatively deep convection doesn't "get going" until the upper trough and associated 500hPa cold pool arrives (if it arrives) from the east late next week, despite 850hPa temperatures being very low and the general flow aloft coming from a E/NE direction prior to this period.

Just had a quick look at the 500mb synoptic setup for the 8th-9th January and it does look like the air aloft was cold during that period, with upper ridging and subsidence absent.

A good point, the 500mb outputs are also important, and it's probably no accident that the greater persistence of convection off the North Sea shown during Monday-Wednesday on tonight's runs is associated with a toning down of that warmer drier pool at upper levels. Nonetheless it looks like convection will still ease off around Tuesday- and depending on whether the ridge of HP sinks south, that could be our lot, though if it holds up to our north we could get a second bout of convection as the upper cold moves over on Thursday in those "easterly" scenarios.

I think the high pressure (or rex block) is too far east, close enough to have some influence but too far for the really cold uppers and a more consistent easterly flow for the UK, IMO. If the high was over Scandinavia, it would be no debate. Also makes the UK more vulnerable to any Atlantic influence but that in itself could mean the threat of substantial snowfalls.

I agree- everything just seems to be too far east, even the runs that have shown the very cold airmasses making it across from the east have had Britain very much at the "end of the line". Ideally for a full-on easterly spell the Scandinavian high should throw up a ridge to our north, but the recurring issue with recent outputs is the ridge often being too far south and east giving us more of a southerly flow.

[Zenarcher]

Snow map for Monday 30th January

Some snow can be expected in Southern Wales and South Western parts of England and anywhere near these areas could see some sleet as well. On Monday Night Northeastern parts of England and Southeastern parts of Scotland could see some sleet.

[Zerouali lives]

What's everyone's guess for the lowest temperature of the cold spell?

I think -20 around Shawbury could be possible towards next weekend...

[jean91]

What's everyone's guess for the lowest temperature of the cold spell?

I think -20 around Shawbury could be possible towards next weekend...

Concerning France

i think really depends , locally with snow on the ground some night temps here in France could really plunge well below -15c

forecast tonight on tv , they put Paris close suburbs ( mine included!!!!) at -11c for Friday and Saturday morning.Yesterday it was -11c for very far suburbs or country

[La Bise]

Well, what a pleasure to be back up in the hills covered in snow. Decent dump on Bleaklow, surprised by the amount actually and made the walking quite difficult at times whilst today on Ingleborough, less snow but frozen solid down to lower levels.

At last...

[summer blizzard]

Maxima struggling (1C near Leeds), showers coming inland and there were even a few snow flakes in the air when i was waiting for bus last night and the sun is out.

Oh how i love easterlies.

[Milhouse]

It would be nice if the sun was to come out here but in true easterly fashion its dull with a few spots of rain. Current temp is 4.4c

[summer blizzard]

Sunny and cold here although sadly the showers going passed Hull (in line for me) are breaking up, dew point has dropped to -1C.

Looking at the radar Aberdeen should be interesting in a few hours time.

Most of England seems to be in the 3/4C range with negative dew points so one would think that we could see a fairly rapid temperature drop tonight.

[Zenarcher]

Snow map for Tuesday 31st January

It shows snow could fall in Southwestern parts of England although only a very small part of it and anywhere around that area seeing sleet. Eastern parts of Scotland look to see the best snowfall on Tuesday a rather wide area is at risk of snow and sleet.

[Aaron]

Cloudy cloudy cloudy.. boring boring boring

[damianslaw]

The current cold spell looks like one of those classic dry easterly affairs - whilst uppers are certainly conducive for snow, we just don't have a strong enough flow and hence no convection - the air source is a very dry one indeed.

The weekend offers promise of a frontal snow event - these are very difficult to predict and snowfalls can be exceptionally, but we have no idea on how heavy precipitation would be, how quickly the front will make inroads, whether it will pivot, align itself on a NW-SE axis, N-S axis or SW-NE axis and whether it will stall or fizzle in situ or indeed retreat westwards.. I hope we don't get a dec 27th 2010 situation - a few hours of heavy wet snow quickly thawing with all signs of any of the white stuff gone the next day and a rapid thaw.. would be cruel blow indeed.

Longer term - heights likely to build to our NW are far better and more robust position in my book for guaranteed sustained cold and much more likely to produce snow.

[Thundery wintry showers]

A significant stand-off between the UKMO/ECM and GFS regarding Thursday and Friday. UKMO/ECM show the ridge of high pressure sinking south on Thursday as the cold airmass arrives, restricting eastern areas to just a few isolated coastal flurries on Thursday, but GFS persists in keeping a sluggish east to north-easterly flow across central and southern areas on Thursday and Friday, which would be likely to produce more in the way of snow showers, albeit mostly light to moderate ones due to the strength of the high pressure. Under the GFS scenario parts of eastern England would probably get about 2-5cm of snow.

It is looking strongly odds-on to be dry and cloudy in central and eastern areas tomorrow and on Wednesday as the sluggish easterly flow is also accompanied by dry and relatively mild air aloft- just isolated flurries here and there and stratocumulus trapped under an inversion. The colder airmass on Thursday should be associated with brighter conditions regardless of the number of showers.

[Aaron]

I want severe frosts.. but there is just too much darn cloud... what kind of cold spell is this? One of those easterlies that everyone in eastern England dreads.. cloudy, cloudy and no cold night temperatures.. is it thunderstorm season yet!?

Edited January 30, 2012 by Aaron

[Thundery wintry showers]

Current model outputs suggest that snow showers will struggle to make it onshore on Thursday as the GFS indeed overdid the duration of the easterly- there is now cross-model agreement on the ridge sinking for Friday.

Before, my thoughts were, "I'm happy to put up with 3-4 days of dry cloudy easterlies if Thursday and Friday end up with sunshine and snow showers", but now that the snow showers are in doubt I'm not sure if it's worth it...