FI Charts ( T120+ onwards) Winter 2024/2025 **READ MOD NOTE IN FIRST

So close but yet so far for the GFS and ECM this morning, moving in the right direction but not sure we'll get there!

Thanks for your time and efforts on this, Wolf.

It's a great read and very much appreciated.

GFS 06z goes for a major SSW and PV split. This would be in a position to opening the floodgates down the line for a polar continental easterly flow. Just one run though. See if it lasts to subsequent runs or a trend develops and I'm sure there's a lot of stratospheric fatigue after hearing it so much this decade.

isn’t Strat warming modeling meant to be a lot more accurate,including in FI than ordinary tropospheric modeling though?

@sryanbruen when was the ssw in 2018? Considering the impacts were seen in the final 3rd of February in Europe, we could do with this one coming asap.Our cold chances fall off quickly in March. Spring can be a great season, it can also be woeful…

I am writing this for the benefit of Boardsies who may nout understand the background to all of the above. Apologies to the absolute experts on the issue if any of my explanation is incorrect.

You may hear the terms Polar Vortex (PV), PV split and Sudden Stratospheric Warming (SSW) mentioned over the coming days in relation to goings on in the stratosphere above the North Pole. You will also come across online news articles and Twitter posts confidently suggesting stating that the 'B***t from the East' is imminent.

In short, the BFTE is not imminent, but weather models are hinting that the building blocks that produce such an outcome could materialise in around 2 weeks days from now with a potential cold spell impacting somewhere in the mid-latitudes, which includes Ireland, in early March.

It really is a case of ‘ifs, buts and maybes’ this far out.

To Beast or not to Beast? That is the question.

About those building blocks.

The PV is a band of strong westerly winds that forms in the stratosphere between about 10km and 50km miles above the North Pole every winter.

When the vortex weakens, shifts, or splits, the polar jet stream often becomes extremely wavy, allowing warm air to flood into the Arctic and polar air to flood south.

See below.

A SSW refers to a swift jump in polar stratospheric temperatures. The warming is preceded by a slowing then reversal of the westerly winds in PV.

Such disruptions of the PV can lead to extreme cold air outbreaks in the mid-latitudes, in place like Eurasia, Europe and the United States. It should be noted that despite there being an estimated 25 major SSW events during the past 40 years, a relatively small number have led to a BFTE outcome in Ireland.

For example, a major SSW around February 10th, 2018, produced the infamous Beast From The East of late February and early March that year. A SSW in January 2019 had little impact on Ireland's weather, which, in fact, remained relatively mild for the rest of the meteorological winter. Another SSW in January 2021 produced cold conditions in Ireland and Britain, but it was much less severe that the 2018 outcome.

Back to what is happening in winter 2024-25 and, more importantly, between 10km and 50km above the North Pole. Right now, the PV is rather stable but models like the ECMWF and GFS indicate that a warming of the stratosphere will commence later next week and just about pull off a PV split in approximately two weeks, sending two lobes of cold air south into the mid latitudes. There is limited support for a Major SSW but growing support for a minor SSW. See animation below.

The ECMWF is more resolute on producing a definitive PV split as the image posted by @sryanbruen shows.

This is one to watch and the outcome is far from certain. Models struggle with forecasts beyond 3-5 days out, never mind two weeks out. Furthermore, should the ECMWF output verify in two weeks, it will take another 2.5 to 3 weeks for the impact of PV split and any accompanying SSW to be felt in the mid-latitudes.

Stories about an imminent ‘Beast From The East just like 2018’ will be pushed at you over the coming days by your neighbours and friends who will parrot what they have read on social media or elsewhere online. The truth is that there is a small possibility of such an outcome in early March (there goes spring if it comes off). However, there is far more unknowns than knowns due to the uncertainties surrounding long range forecasting.

BFTE talk is akin to the Chinese whispers surrounding your local sports team who are supposedly “flying it in training”. We all need to wait and see for ourselves should Championship Day (SSW / PV split) eventually come around.

when exactly does spring start in Ireland anyway, certainly not at the beginning of March.

PV on last legs by the look of this but ……

More of a textbook/classic Polar Vortex split on the 06z run of the GFS model. Polar stratospheric warming over the North Pole squeezes the vortex and sends two lobes of cold air flooding south into the mid-latitudes. These charts are in the far echelons of the model run, but there is trend there for there to be 'all change at the top'.

On a separate note and the topic of spring as mentioned above, for farmers it has been a difficult winter with drying opportunities limited across the country. The past week alone has seen 140% to 320% of the average rainfall amounts recorded, according to Met Éireann in its latest farming commentary.

Valentia in Kerry has recorded 194.4mm in the month up to yesterday. The monthly average here is 173.8mm. The Midlands and some parts of the northwest have recorded lower than average rainfall totals for the month to date.  However, all moderately and well drained soils are saturated across the country, while poorly drained soils are close to waterlogged.

There will be moderate drying conditions during the rest of today and for much of Sunday, as well as late Tuesday morning through Thursday.

Winds will be largely variable between W and S, apart from Thursday next week when easterly to southeasterly winds will provide more favourable drying conditions. Rainfall is expected during Saturday, Monday and on a more regular basis beyond Thursday of next week.

The long term outlook remains uncertain, but a return to a more Atlantic dominated setup for the second week of February is favoured at present. 

I wouldnt be surprised if an SSW occurs greece will becolder than ourselves!

Interesting one here

Hints of a not so beasterly easterly on the horizon.

Tonight's ECM (European model) operational run shows an easterly wind becoming established over Ireland by the end of next weekend. However, the airmass does not tap into a deep cold source i.e. there is a distinct absence of entrenched cold over the continent.

In such a setup, we could expect slightly below daytime temperatures for the time of year and frost at night. It would be largely dry away from the east and south coasts where convective activity could develop as cold air passes over the warmer Irish and Celtic seas and produce mixed wintry showers.

The GFS (US model) shows something similar with a Scandinavian blocking high, but its' ensembles only show slight to moderate support for such an outcome. The GEM (Canadian model) and UKMO also show heights over Scandinavia, but easterly winds do not progress further west than Britain.

Plenty of interesting prospects for out likely weather at the end of next week into the following week, particularly in light of a forecast polar stratospheric warming. For more, see below.

While Gfs 18z did not really produce interest early in the run, a massive warming of the stratosphere and a split of the PV lobes is produced later on. A quick response by the NWP modelling and an interesting winter chart appears. Eyes are peeled

Some eye candy overnight from the ECM and JMA