Perhaps cooling climate can give us an update on SWW

It suprisingly was. It wasn't cold here today at 5c, but in the sun you could actually feel it's warmth. Wasn't the same story when darkness fell though. Not quite evening patio weather just yet 

Yes indeed. Plus differences between Euro4 and Euro4 Parallel; plus now 18z UKMO-GM. However, Tues night reliably the period with greatest chance of some lower-level snow in parts of south (and Weds AM for SE: UKMO cite 40% probability e.g. Heathrow/Gatwick, but low (30%) likelihood troublesome... Chilterns perhaps at greater chance, especially with 18z GM widening the PPN envelope in SE through colder air). However, forecast remains under constant refinement and the broad theme (snow *mostly* Midlands northwards but some in south) is now where the nitty-gritty detail is being sought-out. Tricky one.          

From Ian  F on NW

With the bias corrected GEFS showing the MJO becoming amplified again during week 2 of the forecast period, I don't think it can yet be discounted as a potential driver for February, mainly because the Met Office and their models were beaten silly by the GEFS(BC) with regard to the MJO behaviour in the second week of January.

As for the stratosphere, the SSW hinted at by GFS yesterday remains in the far reaches of FI and is less intense now, so no clear signals for anything much to happen there that could influence trop. conditions until mid-Feb when many would consider it too little too late... those indications of marked changes sooner than that come from theoretical outlooks based on what 'typically' occurs, which seems to be less relevant than usual this winter - it could for example be something to do with the distribution of Arctic sea ice, or SSTs in the Atlantic... really can't say to be honest. It may come to light when the winter data is reviewed by various experts in the field.

Having said all that, there's little to indicate a standard zonal pattern as the likely situation as we close the month either... room for notable PM incursions with good frequency, reflected by recent GEFS suites for example.

Some models (NMM, GFS) develop two secondary lows, with one over Wales/The Midlands stronger, which races the front east across S. England while the stall and pivot happens across N. England.

Others (HIRLAM, EURO4) have only one secondary low, this being over The Channel, which brings the stall and pivot event across CS or SE England. This, drawing cold low-level air in from the east, is the only way that CS or SE England can see more than very transient snow, but in this scenario precipitation does look light away from the coasts where rain is favoured due to a slight onshore flow.

This is a troublesome forecast if you're briefing airports like Heathrow, otherwise it's just a matter of whether something attractive falls out of the sky or not, with roads easy to keep clear for the most part.

E4 delivers best snow chances C and N Midlands tonight into Weds before it fizzles and fades SE . Tricky to forecast but nothing significant showing and we move on to the next effort.

The Wnchester snow desert continues.So far this winter no lying snow ,no falling snow -not a single snow flake spotted.A very slight possibility of a snow falkliing  tonight but i don't think I will be staying up for it.

GFS FI has some interest with split pv and chance of pressure rises towards Greenland

I know it's abit guessworkish, but looking at the metoffice rainfall radar predictions somewhere just to the north of Birmingham could see quite abit of snow almost 12 hours of even light snow would leave a decent event for parts of Peak District, my favoured spot is somewhere like Ashbourne in Derbyshire. 

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY TUESDAY JANUARY 20TH 2015.

NEXT UPDATE WEDNESDAY JANUARY 21ST 2015 08:00

THE CURRENT GENERAL SITUATION A weakening occlusion will move erratically East across England and wales later today, tonight and tomorrow with slack winds following tomorrow.

MODELS-2 WEEK HEADLINE Changeable with rain at times and some snow on Northern hills. Occasional frosts at night with temperatures in general becoming close to average for late January.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Forecast shows the flow flattening over the coming days as the trough over Europe lifts out steadily. The Jet Stream then looks like steadily strengthening somewhat on West to East flow just to the South of the UK and Eastward through Europe.

GFS OPERATIONAL The GFS operational today shows the end of the cold and slightly wintry period by the weekend as more progressive Westerly winds cross the UK from the West. Temperatures will still fluctuate up and down somewhat as successive cold fronts cross over each bringing their own version of cloud and rain and in the clearer spells there will be some night frosts at times and snow on Northern hills will also occur at times. High pressure to the South of the UK may keep the heaviest rain away here especially next week.

THE GFS CONTROL The GFS control run is very similar in sequence of events over the whole period with less cold air filtering across the UK at the weekend but with some clearer intervals under ridges of High pressure still giving rise to frost at times by night especially over the South. In the second weel cold zonality takes much firmer command with some intervention of very cold Northerly winds with widespread wintry showers across all of the UK at tomes and sharp frosts at night.

THE GFS CLUSTERS The GFS Clusters today look like siding with cold polar maritime air across the UK in the latter half of the output with a much as 60% of the clusters suporting synoptics delivering cold zonality conditions with rain or wintry showers at times in quite strong WNW winds.

UKMO UKMO this morning shows less cold Westerly winds well ensconced across the UK at the weekend with occasional weakening troughs crossing East in the flow bringing occasional outbreaks of rain, especially in the North with clearer spells in between with slight night frosts in places.

THE FAX CHARTS The Fax Charts continue to illustrate trough disruption over the coming days with stark complexities near to Southern England over the next 72 hours delivering a mix of rain and snow in places. The pattern then shows Westerly winds driving further troughs East and SE across the UK at the weekend bringing temporarily less cold air and rain for a time before a chilly NW flow returns at the latter end of the weekend.

GEM GEM today shows early trough disruption over the next 36-48 hours as cloud, rain, sleet and snow in places slides SE. Through the weekend milder conditions spread East over the UK as repeated cold fronts cross East and SE across the UK then and beyond. High pressure not far to the South and SW of the UK will limit rain amounts here but permit some night frosts in the wake of cooler air behind each front.

NAVGEM NAVGEM too shows milder westerly winds becoming established next week as the disrupting troughs pattern we have currently flattens. Some rain from occasional troughs spreading east over most areas will bring all areas occasional rain with brighter and fresher conditions perhaps with some frost at night in between.

ECM ECM this morning too shifts cld air out of the way on Friday as troughs spread across from the West with rain for all. A colder, brighter weekend with some frost at night seems possible before rinse and repeat patterns of troughs moving across from the West bring further outbreaks of rain followed by brighter and drier conditions. Things look like turning more deinitively unsettled under an active Westerly flow late in the period

ECM 10 DAY MEAN The ECM 10 Day Mean Chart is trending towards a more flat pattern as the trough over Europe lifts out somewhat. This allows a push of milder Westerly winds across the UK under Low pressure to the North and High to the SW with rain at times and nearer to average temperatures more likely though still with occasional interventions from the NW with more widespread wintry showers at times and frosts by night.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The main trend continues to illustrate milder Westerly winds displacing the cold pool across the UK currently.

MY THOUGHTS There seems irretrievable evidence to suggest anything other than the fact that the current cold spell will be dead in the water by the weekend as the trough over Europe lifts out and milder Atlantic Westerly winds push the cold pool of air across the UK at the moment away East over Europe. After the next 24 hours or so when a few could see some snowfall the next troughs on Friday looks a mostly all rain affair as Westerly winds begin to take command. With High pressure migrating close to the South and SW at times amounts of rain look far from huge across the South at least and with clearer, fresher conditions spilling down over the UK behind each trough some night time slight frost is still possible in places. With time the models suggest that the Jet Stream will fire up into a stronger tone later with deeper Low pressure areas to the North and NE and bringing more deeply unsettled conditions with gales and heavy rain at times as well as spells of wintry showers and cold zonal conditions again become likely. Once again it's the Azores High and Jet alignment in unison with this feature plus synoptics across the Greenland plateau and NW Atlantic in general that has not allowed the High to ridge sufficiently North over the Atlantic to cut off the supply of milder air constantly attempting to dislodge the UK cold from the West and it was inevitable that eventually the cold pool would become dislodged from this direction. Looking ahead and for those looking for future cold it once again looks like we are going to have to continue to look North or NW for polar incursions of air rather than anything from Europe as there remains too much strength in High pressure poorly aligned for sustained UK cold to the SW and a Jet Stream that refuses to weaken or lie down sufficiently across the Atlantic.

Really? Where? That very slight clustering around 2nd Feb? Otherwise broad scatter.

Looking at the low res-end of the ensemble charts during a zonal set up is a bit like staring at one of these . . .



You'll keep looking it until either something suddenly leaps out or you get a raging migraine. 

35 09 061
106 35 09

Now pass me a couple of asprin please

Excellent analogy Ian :-)

No thread for tonight's snowmageddon? ;)

I see a yellow warning is now out.

I personally see a repeat of winter 2012/13 whereby the southeasterly flow means it stays mainly dry in my back yard, whereas both West of Manchester (and just east of it) gets a decent covering.

The Met Office map sums things up quite well http://www.metoffice.gov.uk/public/weather/forecast/map/gcw2hzdew#?locId=310013&fcTime=1421722800&map=SignificantWeather&zoom=8 

True Gandalf!

There are marked differences between the high res models now. Euro4 for example has no precipitation north of Crewe now.

Going to the wire!

 Given the uncertain synoptics, any snow tonight is going to be more of a "nowcast" event than usual. Some people may get something when they were not expecting it and vice versa.

We will just have to see how it pans out over the next 24 hours.