Short range model discussion - into 2018

[knocker]

Just to note out of interest that over the weekend although clear skies and some CAA in the lower levels promotes quite a hard frost tomorrow morning the Atlantic airmass is having a last hurrah with warm air still there aloft. Thus the real cold has not yet arrived

48 hours later with only a slightly more severe frost the much colder air has very definitely arrived.

Edited February 23, 2018 by knocker

[Snowyowl9]

Inversion cold weekened,havn`t had that lately from the east either,surface cold easterly/SEly.

[knocker]

The ecm this evening brings the wave seen near south west Norway on the T72 fax south west to Wales by T96 bringing with it some concentrated snow showers along the track. This clears to the south west by T120 veering the winds across southern England and Wales a tad and snow showers running up the Channel

[sawan]

57 minutes ago, knocker said:

The ecm this evening brings the wave seen near south west Norway on the T72 fax south west to Wales by T96 bringing with it some concentrated snow showers along the track. This clears to the south west by T120 veering the winds across southern England and Wales a tad and snow showers running up the Channel

Hi Knocks, what track this precipitation, originating from Norway will follow?

Edited February 23, 2018 by sawan

[knocker]

2 minutes ago, sawan said:

Hi Knocks, what track this precipitation will follow?

According to the ecm, and I would want this confirmed by the METO, the NE coast through the north midlands to south Wales.

[knocker]

A quick recap tonight as to where we are at vis the NH 500mb anomaly pattern.

Aleutian ridge with a trough down the western N. America upstream whilst downstream the intense high cell is over the tip of Greenland phased with the trough dominated Atlantic to the south that culminates with the subsidiary vortex lobe over the UK. The main lobe is over northern Russia. This would portend very unsettled weather over the UK with possibly significant snowfalls in some areas which the det runs will need to sort and the temps will be significantly below average.

[knocker]

Some complications Tuesday with the wave and cold front. The fax has them over Ireland and the Hebrides at 1200 and the gfs has a fair bit of snow for the north east and then a complicated snowy pattern with shallow waves littered about by Weds 00

Edited February 23, 2018 by knocker

[knocker]

Despite a widespread hard frost this morning the UK is still in the warmer air as can readily be seen by glancing at the 00 sounding for Nottingham where the 850mb temp is a mere 2C less than the surface. From here a sunny day for most with temps rising to the 5-6C region but there may well be some cloud in the south west, N. Ireland and western Scotland. Feeling cold in the easterly wind.

A clear night leading to another widespread frost tomorrow morning and another dry and mainly sunny day but temps struggling in the east to get to 3C as the colder air now starts to encroach (the forecast sounding in East Anglia shows the much colder air aloft) and feeling very cold as the easterly wind picks up a tad with some snow flurries in the east.

From this point the UK is well and truly into the cold easterly regime and starting to feel bitterly cold with a significant wind chill factor but also with some complications over Monday and Tuesday involving the little wave tracking south west from southern Norway into Ireland that has been discussed previously.This could well bring a more concentrated area of snow showers mainly affecting the North East whilst at the same time with the easterly wind pepping up snow showers becoming heavier and more frequent in the east and spreading further inland. Snow showers may also run up the channel.

Wednesday a bitterly cold day in the strong easterly wind with temps in many places not getting above freezing with heavy snow showers in the east common place but the interface between the warmer and cold air is still apparent over southern Norway.

And just look at the temp profile now with the tropopause down around 450mb

 

Edited February 24, 2018 by knocker

[knocker]

The ecm has the little wave feature over the Humber at 0600 Tuesday and south Wales by 1200 and then NW of Cornwall by 1800. This could be accompanied by more concentrated snow showers from the Humber through the Midlands to south Wales and a also a line of showers across the south east and up the Channel.

And prior to that over Monday according to the fax update a weakening cold front traverses the country east-west which probably accounts for the increased snow shower activity.

Edited February 24, 2018 by knocker

[knocker]

The ecm 850mb temp contour and anomaly

[BA Baracus]

GFS hd from the 00z run picks up snow showers for eastern Scotland as early as 3am Sunday morning. I'm ignoring the rate of precipitation as this is rarely accurate but the fact the hd charts are picking up signals this early is encouraging. 

[BA Baracus]

Cold front now approaching UK east coast at around 9pm Sunday to midnight Monday.  Will be interesting to see if these change this morning.

[knocker]

17 minutes ago, FiftyShadesofSnow said:

Be interesting to see your first take on the forecasted Azores Low track late next week.....

Well I don't know about my first take but it's all apparently tied in with general pattern change of the intense high tracking west with energy tracking east south of the movement driving the troughs. I think the detail of this a long way from being set in stone

[johnholmes]

Would agree with your last sentence k, and thank you for your inputs in this thread.

I have just spent half an hour with the latest 500 mb anomaly charts, outside this period of 72 hours but there are changes being predicted on them, more so with ECMWF-GFS than NOAA but I'll drop that into the main thread.

In here then 72 hours from now the Fax charts will be the best indicator probably of what may happen. IF the GFS output seems to fit them then, if you have it, use Net Wx Extra for detail on 24-48 hours re temperatures, how unstable the air is for your locality etc to give an idea of if you will get snow. For once with the values being predicted on any model we do not have to be concerned about will the ppn fall as snow, other than perhaps right on the coast. Even here as the week progresses that may not need to be a concern. Obviously I am talking about the east. How far west any of the showers get will depend on wind strength and if there is any minor troughing, as indicated on the Fax charts.

Anyway enjoy a wintry spell over the coming week.

Edited February 24, 2018 by johnholmes

[knocker]

One thing if the gfs evolution turns out to be near the money it would shift the very cold air.

[knocker]

Guess where the cloud is? (Image courtesy of Dundee Satellite Receiving Station)

[knocker]

And overhead at 1300 would you Adam and Eve it. Temp 5C

[knocker]

gfs-wrf

Fax

Edited February 24, 2018 by knocker

[knocker]

Whilst awaiting the fax updates a quick glance at the gfs 500mb pattern for Thursday. You can see why it still indicating a more northerly track for the surface low as the upper trough seems to be being forced more NE by the orientation of the massive high over Greenland. I'm led to believe that the size of the positive anomaly of this is something not often seen. It can also be seen how just minor adjustments of this will impact the surface analysis

[knocker]

With this evening's fax updates we can follow the little wave feature until it ends up over Wales 1200 Tuesday. And the ecm has it very similar so more concentrated snow showers across the north, n. Midlands and Wales Tuesday morning.

Edited February 24, 2018 by knocker

[knocker]

The ecm 850mb temp contour and anomaly

[knocker]

Further movement of the upper pattern this evening vis the anomalies as it continues to evolve. Although not total agreement they are all very much in the same ball park. The intense high cell continues it's westward drift to be over the coast of north east Canada accompanied by an intensification of the vortex over northern Russia. And although the Atlantic is still dominated by the upper trough the subsiduary center that was over the UK has weakened considerably and moved west of the UK leaving a very slack gradient from the northern half of the UK west into the central Atlantic. Energy leaving the eastern seaboard runs east under this and south, or not, of the UK. How far north this will track is rather the key question because that will dictate the movement and intensity of surface lows so over to the det runs. And until that is decided temperature forecast are a bit of a lottery although remaining below average is a safe play.

[knocker]

The little wave feature on this evening's gfs

[EllyTech]

10 hours ago, knocker said:

Guess where the cloud is? (Image courtesy of Dundee Satellite Receiving Station)

Beautiful imagery. 

[knocker]

The witching hour is finally upon us and later today the very cold air will arrive from the east bearing gifts, wanted or unwanted depending on your inclination. Thus from tonight and through the next few days the ideal convection conditions will breed an increasing number of snow showers which will spread further afield than the eastern parts of the UK in the strong wind and at times be more concentrated as small disturbances run west in the flow. Plus it will be bitterly cold which the strong wind will exacerbate giving a very high wind chill. Snow accumulation will increase and spread during this period but will be impossible to accurately forecast so down mainly to observation. Anyway enough waffle

Today a clear cold day with maybe some patchy cloud and a cold night with a widespread hard frost by morning  The GFS-WRF on the snow showers and a forecast sounding for tomorrow illustrating the much colder air.

Another very cold night and a severe frost Tuesday morning but the much mentioned wave feature tracks south west overnight and through Tuesday morning and brings more concentrated snow showers along the route as indicated with the charts.

Another very clod night with a severe frost Wednesday morning heralding a bitterly cold day with extensive snow showers but changes are afoot,  The blocking high cell gears up and starts to move west which allows the Atlantic upper trough(s) to nudge in from the south west with the associated surface low west of Iberia by 1800.

Another bitterly cold day on Thursday but the surface low is now taking closer order with much warmer air entering the mix with the possibility of frontal snow and blizzard conditions for the south west. Have to leave it there

This is of course according to the gfs

 

Edited February 25, 2018 by knocker