SMU

watch this canadian ridge migrate @114 ....

Suprised noone has picked this up today updated Berlin & GFS ensemble data for the strat shows the SSW peak negativity at lower levels than yesterday- GFS Sorry for the slight misallignment however the GFS trending is for a landing zone low -30M/S & The ECM Has trended off the scale - again homing in on the -30M/S line- It is for this reason that the ECM operational run has moved to the Greenland high scenario- noting that the amount of Scenarios modelled by ECM this winter have been about 2-3 all trop lead disconnects from the Strat- Now The strats forcing is essentially allowing for ridges to propergate vertically into the polar regions rather than being sheered eastwards ... The ECM is similar to 2010- (11th November run @day 9 ) S

The models are now coming online with the transitioning period from the SSW in 4 days - This period is still developing & subject to revisions however the limited consensus there is seems to be a diving trough & some ridging North from the azores to formulate a block... Lots more exciting charts to appear over the next few days, For the bulk of the UK we are looking for -10/-11c uppers to really deliver the goods.... S

just a quick one - Thats not a strong AO on the UKMO, yes a negative AO probably indexing -2.5, The polar height field is not positive enough to create a bigger differential to go below -3/-4 However the trending is good- Proper Strong AO events have very pronounced HLB profiles

no. If it lands record breaking then its a 4 wave pattern.

To be honest - I coukd have spent 8 hours looking through the list- you could argue that all SSWS that have occured have made it through the barriers & that all should be included as the immediate tropospheric response signal woukd overide the background nino signal- however or took 3 hrs to do that 1 post so I stuck with Nina... If you have a spare 3-4 hours then whack them all through the system to generate the temps then day 11 anomaly ! or you could do 1 chart- the super chart if you like of all SSWs at day 10 500MB anomaly would be an OK match...

cold here already -0.3c @ 19:25 going for -3 tonight if we can squeeze it !

hi it was nino neutral so not on the list.. only analogued la nina winters..

Evening All Ice Cold hope your still with us .... So the much touted SSW is coming into view & here’s my thoughts + timelines of when / where to expect it... We have seen lots of posts & comments on it - but whats the reality likely to be -??? The Omni present warming in the GFS charts is usually due to the model & its poorer vertical resolution V the ECM, as a result there is an over reaction / over estimation of how much a warming is going to impact the zonal wind @10MB - so because of this 'bias' when viewing the mid / long term outputs churned out by the GFS we have to be a little on the sceptical side as these are normally moderated & scaled down even wiped out ! However we have now seen the evidence in the Berlin site that a downwelling SSW event will make it to the 10MB level & indeed go on to challenge the date record for the time lf year- ( this is NOT the same as the usual deceleration of the zonal wind we see at this time of year as that is more of a gentle reduction all the way to mid april when the vortex breaks its annual westerly influence ) So as highlighted we have passed the point of no return in the stratospheric modelling where a SSW is now just 5 days away for the 12th Feb *** Take note of this date -- The plots below show steep downward curve of a signature warming Note the main black line being Climo - but the ensemble mean from the GFS running out at mid -20 to -30 M/S... The clustering is quite close - further backed up by the another illustration of the ensembles from the hannah attard site With the mean bottoming out at -32M/S *The date record for this time is ~ -17 M/S & the all time record low ( using Merra data ) is -35 M/S The ECM berlin forecast below is not as bullish as the GFS coming out around -17 M/S @10MB but none the less still classed as significant event... So what we have in modelling terms of a SSW due is * The first one in 9 years ( I dont think last year was classed without checking ) * Possible record breaking reversal of tge zonal wind... If your thinking whats best in terms of impacting the UK its simple- The lower the negative number the better... - record breaker ? yeah I will take that please... Why?... The bigger the negative number the stronger the easterly flow is across the mid lattitudes. !! ( think feb 63 / jan 85 & so on ) Whats the models churning out then? The SSWs are classed as 2 types - Wave 1 displaced vortex or - Wave 2 Split Vortex .. This is whats expected - A classic wave 2 Split vortex- with 2 clear areas of poleward flux - over the far East & canada- Now luckily for me the historic SSWs have already been classified -we are looking for la nina years / W2 / split vortex- 6 years appear as matches - 28 Jan 1963 - 7 Jan 1968 - 18 Jan 1971 - 1 Jan 1985 - 21 Feb 1989 - 24 Jan 2009 Below are the 10MB increase in temps at the time when the zonal wind hits 0M/S Obviously they all have 1 thing in common- The huge rise in temps across the pole - Now the Date of the zonal Mean hitting 0M/S isnt the day of peak blocking - Looking at the dates above peak blocking appeared 7 - 11 days post Reversal - see below day 11 charts from the above warmings ( 500 MB anomaly ) Whats apparent is HLB is quite prevelent & most are centered ( for us ) around greenland & Western Scandi - Also all 6 Splits have varying levels of troughing to the south - but all have an anomaly- So that really leaves with a level of expectation that should at least give us some confidence for Feb over the following dates- 12 Febuary : is 'R' Day- as in the reversal of the 10MB zonal wind where the eastward progessional component is replaced by a westward one 13/14 Febuary : is peak 'R' days where we will know the magnitude of the warming & just how much westward ( reversal ) component there is - Sub -20 M/S is the date records & anything below is the jackpot - 16-18 Febuary - Mid to high lattitude transitioning - This is where depending on how lucky we are for our area we will see MLBs start migrating North to the pole as zonal wind lag filters through the lower layers of the atmosphere & support builds for HLB - look for the 3 key wave patterns ( atlantic / Scandi & pacific (-EPO) The UK can get very cold in this period if the migrating highs are favourably positioned from the outset.... 20-24 Feb - Peak HLB blocking across the NH - peak -AO signature & peak cold overall for the mid lattitudes ... *** IF the GFS lands with the depth of negativity then Late Feb early march will be on a par with 2013 for AO negativity & possible / probable UK cold / snow.... if the negativity is watered down then the cold signature will be watered down & less dominent in western Europe... Best S

1cm

Heavy snow 1cm xxx

Looking at the 22:45 radar things still moving along ok ?

Just got home ! I remember this like yesterday I had a race @ buck more park that day & was tracking the front but saw many reports of rain so didn’t expect to much - The temp @ home when I left at 5 was about 4c in Bexleyheath- Driving down the A2 & looking out towards the Thames the sky was going black- I walked up to the clubhouse at buckmore by then it was dark & it started lashing it with rain, but after 2 mins & a crack of thunder a wall of snow came over the hill- It snowed for 2 hours & there was 3 inches on the ground- everyone got stuck in the car park waiting for the farmer to grit the hill- fantastic memory !!! Anyway just got home temp on the garden gauge now -2.1c !! Cmon snow don’t break up even if we get a cm !! S

Right off out with the fam - taking a break till 9-915 current temp here 0.0c Snow band - intensified significantly on the eastern flank in the last 30 mins just off the wash up to the Humber- moving SSW.....

Early March are when the North Sea temps are at their lowest lol- I will try & dunk a post in about 930 tonight S

Guys the trajectory of the blob means that unless it does a major swerve or falls to pieces on the western edge then more places will see snow tonight- 1.2c here already

nice little flurry here -

Light snow new ash green- outdoor thermos saying 1.5c Pulled one of the cars out - 0c

Temps dropping off nicely now 2.3c & low dewpoints

Light flurry barnehurst kent

I believe the NE part of the front that over the Humber will swing south then slightly SW as well hitting Kent / Essex Norfolk etc s

Yep the warnings are good however it really is a now cast- im just wanting the PPN to hold out till later on in the eve-

This current winter I have found the HIRLAM to be the most accurate high res output casting my mind back to the slider event it was the only model to have snow in South Essex & North Kent which turned out to be correct anyway PPN echoes for later

Well the ‘blob’ has broken up leaving a somewhat crystal clear day here current temp 1.5c- Expecting the maxima at 3.5 ish- Tonight is really a now cast- but with the PPN coming in late / overnight then ahead of this we should have widespread sub zero temps so good preperation ! Im aiming for zero ~7-8pm tonight ... S

It’s tracking south - / SSW