Arbtalk.co.uk | Discussion Forum for Arborists

Happy to put a laymans slant on it J and although I may sway into technical terms at times I do strive to keep away from the high almighty academic "iv`e got a degree from reading books" type of forecasting and rely on good old knowledge from looking out the window and years of simply paying attention to patterns
Theirs an old guy in the states who predicted exactly when a certain river would thaw in spring as opposed to some 2 bit boffin who had every Phd you could think of yet she was way off the mark and the indigenous old timer proved her wrong so the university of "life" beats any other quali in my eyes!
Waffle over - back to basics:
Fatal signs in the overnight model runs this morning.
Remember how important Heights are in the Iceland, Greenland & Denmark straights region in maintaining and strengthening the block to keep any Eastern US seaboard & Atlantic influence from affecting us?
well the trends are nothing to show any blocking therefore the relenting Jet has an open door regardless how strong it is as the "fluid dynamics" of things always chooses the path of least resistance which in turn cuts short any prolonged cold forcing for the UK due to our proximity regardless how strong any Scandinavian, W Russian etc etc. Anticyclone is!
I would love for someone to detail why a truly massive shift of the Jet forecast for thousands of miles from no Northern arm with a southern Medflow to the exact opposite overnight?
Key Day moved back to Thursday but definately Colder up to then.
My Kudos go to the European Centre for Medium Weather Forcasting who were never that keen and must have noted the relentless Cyclogenesis in pushing Lows through Iceland etc areas.
lets hope theirs more chop n change to come but the swings soon back in the Milder court and cold snap looks just that & nothing more this morn.

Although some very heavy penetrating temps overnight are on the way the pattern looks settled with very little signs of accumulations and precipitation anywhere?
Western fringes of Sco and NIre will also be on the boundaries of the cold dry air and the running milder Atlantic westerlies so in all the downgrade is very probable now all due to a failure of any High pressure transgressing westwards from Scandinavia to the Icelandic region.
Temps returning back to average from early next week Mon/Tues is the highly probable outcome as things stand.
Ice scraping = Certain
Sledging = Unlikely

Current forcast pressure charts for 12:00 UTC on the 2nd do show a high forming over Greenland, with another high to the north of Norway. This appeared to me to following your scrip very nicely?

Initially it was very viable Ironb but now we have a Shortwave projected to form from the Southern Baltic/Ger/Danish region moving Southwards, Westwards and just about any-what-waywards that`s thrown the charts back into relative uncertainty?
But the milder breakdown is very much on the cards as the Shortwave will split the huge Russian High in two but with the new divergence hunckering down west offshore Spain/Biscay (azores ridging), as opposed to a more northerly point where we initially focussed on a latitude of 60° degrees or more - namely we offered over the Iceland, Greenland, Norwegian sea etc area.
So a South-westerly airflow across the whole of the UK by end of play Sunday is a fair assumption but the temps will depend how cold the uppers are and how entrenched the ground temps will be following the hard frosts in the coming nights? Sometimes the fronts bringing the change petre out and the ground temps remain low, particularly more South and East you are, until another push (front) is required?
Looking at next week then its likely, albeit eventually, back to a Zonal Atlantic feed with avg. temps and unsettled outbreaks between drier periods after a quiet start Monday but a fair few 500mb heights models have toyed with a mid-Atlantic ridge holding off the Jet stream oncemore introducing a more straight polar Northerly feed further down the line?
We`ll see,,,

Thanks for the explaination.

I think I can see shortwave you refer to, but it's beyond me to understand its significance.

These mid to upper level (300 -500hpa layers) disturbances can be a forecasters nightmare as they periodically appear to be more or less in-detectable other than on water vapor imagery but they can drastically change a projected pattern, the failure of a locked in easterly/continental flow in this case as it forces or opens the way for the ridging south-west of the UK thus the anticyclonic or clockwise milder airflow in simple terms.
The last FAX chart shows the shortwave as a trough just East off Sweden that quickly evolves into the associated baroclinic low which should be interesting for eastern areas Saturday?
The cold sector will take some shifting over the SE by the looks of things however, with the air mass over Europe Scan W Russia etc. never being to distant East from the UK.
Overall uncertainty in the charts in terms of timing the force of the block diminishing back eastwards and the ridging to our southwest along with low pressure intensity on the northern Jet arm through the GIN or Greenland/Iceland/Norwegian seas corridor.
Feeling bitter tomorrow that`s for sure but I`m still not in favor or swayed by any keys to show anything substantial this Winter wotsoever (omitting Saturdays potential)

Eastern europe is having some decent amounts of snow. News said -42C in Russia. Wind here is changing to the east so here's hoping on some snow.

On Saturday I was pumping sweat, , on Monday my fingers were frozen solid. , Keep the cold, give me sweat anytime. Hard to climb with numb fingers..

I'm trying very hard to follow this and although I can see the trough it just looks like it turns into a very weak area of low pressure (1036mb.. I gues in a high of 1060+ that is low), but remains weak and static

Then the current high/ridge extending down from scandanavia just sort of splits forming what looks to me like an Azores high with further embedded highs over Denmark and Northern Finland and the main high where it's always been over Russia.

But remeber I'm punching well above my weight here because when I was training to be a pilot climatology was explained to me by an old RAF guy. "High pressure over the oceans and high pressure over the continents during their winter", and that was it

First rule for weather forecasting - look out of the window.

BBC are forecasting loadsa snow north midlands for Thursday night, nothing on the Met office site as yet.