FI Charts ( T120+ onwards) Winter 2020 **READ MOD NOTE IN FIRST POST**

Billcarson

sryanbruen wrote: »

God lads, it's FI for a reason. I understand the disappointment but there is no need to get your knickers in a twist. In blocking situations, there will always be many changes to the exact scenarios. Remember how long it took before models latched on this coming week's easterly? People have rose tinted glasses now on the 2018 Beast from the East event being smooth sailing. Let me tell you, it certainly was not. It too had its changes every now and then with many comments on models backdating instead of things being brought forward. I remember this vividly because there was so much pessimism leading up to it. There were 3 peaks of uncertainty as well and each one coincided with 3 peaks in stratospheric warming before it started to calm down and the certainty built after 17 February with the odd run showing the anticyclone too far south.

Those 18z runs discussed previously were highly unlikely. They just were, those were best case scenarios. Same with some other runs. Perfect amplification to allow the flooding of cold air south. Whilst it is looking now that the GFS FI suggesting height rises over Europe may verify for mid-January, it was quite ridiculous to think of such with amplified blocking to our north. That is not looking the case now as the trend of late since my last post has been more of a mid-Atlantic ridge than a full on Greenland blocking feature. This will mean a flatter pattern overall and not enough to descend the country into the much plead for (on here) big freeze which was again unlikely, that some runs suggested.

As for sudden stratospheric warming, it is ongoing and set to become a major event (reversal at 60N) in a few days or so time. The stratospheric polar vortex is in the process of displacing from the North Pole at a similar time to that of the 2013 major SSW event and likely to reverse at a similar time too. The 2013 event took a week before it evolved into a split. If we do see a split this time, the similarities are likely to continue there.

What does the SSW event mean for us? Well it is all about where those vortices sit, displaced or split. Stratosphere and troposphere placements of ridges and troughs do not always correlate but with a major SSW event like this, more than likely they will. Historically, stratospheric warming events increase the risk of blocking in the higher latitudes which gives an increased risk of cold spells for Europe but it's not always as straightforward as that due to a few things:

1. Where the blocking sits.
2. If the warming downwells to the troposphere.

The 2018 SSW event was an extreme example of both a monster anticyclone to the north that retrogressed from Siberia to North America in the space of 2 weeks going completely against the zonal flow and the severe cold airmass associated that was brought in from Russia via a polar continental airflow. It was also an example of a quick tropospheric response with the major SSW event central date (day of reversal) being on 12 February 2018 and impacts were felt as soon as 9-10 days after as the Scandinavian High began to form. There is no comparison to that at the moment. 2013 is a better comparison but at the same time, all major SSW events are unique.

If we see downward propagation, which models like the Glosea5 do show occurring, the SSW event is likely to either prolong or reinforce the blocking unless we see something like a 2018 where the retrogression is strong enough to play against chances of a very cold spell in Europe. It is this that I am watching out for to result in a displacement (or retrogression) of the stubborn Russian high that has been chillaxing in its hammock for the past two months over there. We usually see a milder period before the effects of a major SSW event are felt down on the surface as happened in 2018 after a cold start to February. Again only using this as a reference point, not a comparison so do not start thinking a 2018 repeat on the way, definitely not.

Let the SSW do its thing and watch out for where the blocking sits in the second half of January if we do see a tropospheric response. If we don't and see a sudden collapse of all the blocking, it would possibly be the biggest flop there has been and bigger than December 2012. Fortunately (or unfortunately depending on your point of view with cold spells/snowfalls), that is highly unlikely.

Regards the 2013 ssw Ireland got nothing out of it. The uk got a fairly decent cold spell though nothing special during 2nd half of Jan. The cold didn't make it across the irish sea,so frustrating.

Roots 2020

Billcarson wrote: »

Regards the 2013 ssw Ireland got nothing out of it. The uk got a fairly decent cold spell though nothing special during 2nd half of Jan. The cold didn't make it across the irish sea,so frustrating.

Belfast was under snow for 10 days from 22/23 March! March was a record cold month. Plenty of snow. Waterford on 12th March. Where it was a rarity near the coast.

Roots 2020

March 11 2013.

sryanbruen

Billcarson wrote: »

Regards the 2013 ssw Ireland got nothing out of it. The uk got a fairly decent cold spell though nothing special during 2nd half of Jan. The cold didn't make it across the irish sea,so frustrating.

That was likely due to the fact it was only a "wedge" rather than proper blocking. We had to wait until mid-March before the blocking really took hold and went to town, we have not seen such intensity and longevity of blocking since March/April 2013. At first, it was quite variable with regards to the wind direction and not very snowy whilst the final week of March 2013 was predominantly easterly. Many days of snow falling but little in the way of significant coverings (not helped by the solar radiation at that time of year) away from the north where Northern Ireland got a severe snowstorm on 22 March.

Can see that quick tropospheric response you mention which brought the cold spell on this cross section as the reds (above average heights) descended to the trop by mid to late January before a return to zonality into early February. Also spot the March blocking.



2013 was a case of much slower retrogression to what happened in 2018. We saw heights beginning to rise over Scandinavia in the second half of February 2013 but it wasn't until nearly mid-March that this evolved into a Greenland high.

Every SSW is unique, must remember that.

Billcarson

Roots 2020 wrote: »

Belfast was under snow for 10 days from 22/23 March! March was a record cold month. Plenty of snow. Waterford on 12th March. Where it was a rarity near the coast.

Wasnt forgetting march 2013. But was a bit late for my location.

Billcarson

sryanbruen wrote: »

That was likely due to the fact it was only a "wedge" rather than proper blocking. We had to wait until mid-March before the blocking really took hold and went to town, we have not seen such intensity and longevity of blocking since March/April 2013. At first, it was quite variable with regards to the wind direction and not very snowy whilst the final week of March 2013 was predominantly easterly. Many days of snow falling but little in the way of significant coverings (not helped by the solar radiation at that time of year) away from the north where Northern Ireland got a severe snowstorm on 22 March.

Can see that quick tropospheric response you mention which brought the cold spell on this cross section as the reds (above average pressure) descended to the trop by mid to late January before a return to zonality into early February. Also spot the March blocking.



2013 was a case of much slower retrogression to what happened in 2018. We saw heights beginning to rise over Scandinavia in the second half of February 2013 but it wasn't until nearly mid-March that this evolved into a Greenland high.

Every SSW is unique, must remember that.

Thanks. Wasnt sure if march 2013 was related to the jan 2013 ssw. Such a pity it was such a slow burner. If only we had got what happened in march 2013 many weeks before.

Kermit.de.frog

Snow showers would be piling on to the east coast with this next Friday. There is a good few opportunities in the next week or so for some snow in various parts of the country.

Artane2002

the models seem to want to drop a low pressure system over us from the north yet again, third time this winter! the GFS parallel also drops the low over us. also excellent post Sryan as always!

Kermit.de.frog

Some are definitely letting the perfect be the enemy of the good. These are good charts for Ireland in any winter (depending on perspective of course). Just roll with it and if the SSW event comes in to play later then all the better.

Gaoth Laidir

Oneiric 3 wrote: »

I don't put much stock in SSW events. They often seem overhyped and oversold by those talking about them. That is not to say that there is not something to them, but... I really just don't care enough to care.

One thing that annoys me about Meteorologists when they talk about SSW events, is that they never explain how that warming occurs. Is it a warmth that created by conditions on the ground, or some other source? It's never made quite clear, but there seems to be a trend that they start somewhere over Iberia and end up in NE Russia.

Yes, SSW has become a bit of a clickbait term that gets bandied about, with the world and its mother giving "expert" opinions on Twitter and the likes to get their tweets picked up by the Daily Mail et al. Personally I don't go in for this day-to-day tracking of it as it would only drive you around the bend.

The actual warming of the stratosphere is caused by compressional heating of air subsiding down into the polar vortex after it's been disrupted. It's like heating of a bicycle pump or Föhn warming of air down the lee side of a mountain.

Think of it like a bucket of water. Mix it quickly anticlockwise with a paddle and it will form a vortex in the centre. Think of this as the polar vortex, with the Pole at the centre. The higher level of the water out towards the wall of the bucket is the same as the rising geopotential heights moving south towards the equator (wall).

Now stick the paddle down into the moving water around half way in from the wall to simulate a mid-latitude tropospheric Rossby wave breaking into the stratosphere. The paddle will slow down the water and divert it in towards the centre, moving or splitting up the vortex. The water that first diverts in towards the centre simulates the air that sinks and warms in towards the Pole, hence the warming.

If you quickly start the water back rotating anticlockwise again then the effects may not fully reach the bottom of the bucket. It's the same with the atmosphere, where downwelling needs to be allowed to happen. Whether it does or not depends on a lot of factors.

What starts the whole process going in the first place is a sustained zonal flow below a certain critical speed (which depends on the wavelength or wavenumber). Depending on where this occurs, land or sea-land temperature contrasts can cause it to break up into the stratosphere.

Humberto Salazar

Kermit.de.frog wrote: »

Snow showers would be piling on to the east coast with this next Friday. There is a good few opportunities in the next week or so for some snow in various parts of the country.

Love the optimism, and you could well be hopefully right. I'll always play the damp squid card, just for balance. And because I've been disappointed far more often than pleased with decent weather events. I'll get on the coaster then, just for one circuit mind....

Gonzo

latest GFS 12z is delaying the return to mild by a few days to Monday 18th at the very end of the run. Stays generally cold up to Sunday 17th of January but mostly dry.

Wine Goddess

sryanbruen wrote: »

God lads, it's FI for a reason. I understand the disappointment but there is no need to get your knickers in a twist. In blocking situations, there will always be many changes to the exact scenarios. Remember how long it took before models latched on this coming week's easterly? People have rose tinted glasses now on the 2018 Beast from the East event being smooth sailing. Let me tell you, it certainly was not. It too had its changes every now and then with many comments on models backdating instead of things being brought forward. I remember this vividly because there was so much pessimism leading up to it. There were 3 peaks of uncertainty as well and each one coincided with 3 peaks in stratospheric warming before it started to calm down and the certainty built after 17 February with the odd run showing the anticyclone too far south.

Those 18z runs discussed previously were highly unlikely. They just were, those were best case scenarios. Same with some other runs. Perfect amplification to allow the flooding of cold air south. Whilst it is looking now that the GFS FI suggesting height rises over Europe may verify for mid-January, it was quite ridiculous to think of such with amplified blocking to our north. That is not looking the case now as the trend of late since my last post has been more of a mid-Atlantic ridge than a full on Greenland blocking feature. This will mean a flatter pattern overall and not enough to descend the country into the much plead for (on here) big freeze which was again unlikely, that some runs suggested.

As for sudden stratospheric warming, it is ongoing and set to become a major event (reversal at 60N) in a few days or so time. The stratospheric polar vortex is in the process of displacing from the North Pole at a similar time to that of the 2013 major SSW event and likely to reverse at a similar time too. The 2013 event took a week before it evolved into a split. If we do see a split this time, the similarities are likely to continue there.

What does the SSW event mean for us? Well it is all about where those vortices sit, displaced or split. Stratosphere and troposphere placements of ridges and troughs do not always correlate but with a major SSW event like this, more than likely they will. Historically, stratospheric warming events increase the risk of blocking in the higher latitudes which gives an increased risk of cold spells for Europe but it's not always as straightforward as that due to a few things:

1. Where the blocking sits.
2. If the warming downwells to the troposphere.

The 2018 SSW event was an extreme example of both a monster anticyclone to the north that retrogressed from Siberia to North America in the space of 2 weeks going completely against the zonal flow and the severe cold airmass associated that was brought in from Russia via a polar continental airflow. It was also an example of a quick tropospheric response with the major SSW event central date (day of reversal) being on 12 February 2018 and impacts were felt as soon as 9-10 days after as the Scandinavian High began to form. There is no comparison to that at the moment. 2013 is a better comparison but at the same time, all major SSW events are unique.

If we see downward propagation, which models like the Glosea5 do show occurring, the SSW event is likely to either prolong or reinforce the blocking unless we see something like a 2018 where the retrogression is strong enough to play against chances of a very cold spell in Europe. It is this that I am watching out for to result in a displacement (or retrogression) of the stubborn Russian high that has been chillaxing in its hammock for the past two months over there. We usually see a milder period before the effects of a major SSW event are felt down on the surface as happened in 2018 after a cold start to February. Again only using this as a reference point, not a comparison so do not start thinking a 2018 repeat on the way, definitely not.

Let the SSW do its thing and watch out for where the blocking sits in the second half of January if we do see a tropospheric response. If we don't and see a sudden collapse of all the blocking, it would possibly be the biggest flop there has been and bigger than December 2012. Fortunately (or unfortunately depending on your point of view with cold spells/snowfalls), that is highly unlikely.

Excellent post as always, thanks for taking the time to post such a comprehensive analysis of the SSW.

Gonzo

Gonzo wrote: »

latest GFS 12z is delaying the return to mild by a few days to Monday 18th at the very end of the run. Stays generally cold up to Sunday 17th of January but mostly dry.

Whereas the ECM is speeding it up,you couldn't make it up could you
Regardless these 192 to 240 charts are unreliable anyway no matter what they're showing
The minus 7 and minus 8 uppers in the coming weeks northeadterlies will generate hefty showers in the Irish sea and many will fall as snow
All snow above 150 metres which would mean snow cover in a lot of populated ares of wicklow wexford and South Dublin and obviously points inland I'd expect too like carlow and kildare
NCD ,Louth and meath might have Isle of man issues

pad199207

Alas this evenings models continued to provide the interest going forward through January. So I won’t write it off just yet

Gonzo

AuntySnow wrote: »

Whereas the ECM is speeding it up,you couldn't make it up could you

NCD ,Louth and meath might have Isle of man issues

Meath always has IOM issues, we had it during the BFTE which resulted in very little snow until Storm Emma arrived, while Dublin and much of Kildare was getting dumpings of snow several days before. December 2010 we had issues then too, although the easterly wind was variable from day to day so we found outselves drifting in and out of the shadow several times.

As for this week I don't see Meath or Louth doing that well from showers, the Ulster shadow and the IOM shadow will kill the showers for quite a few areas in the northern half of Leinster. Hopefully the wind will be variable so the same areas aren't constantly under the shadow.

feckwunker

Humberto Salazar wrote: »

Love the optimism, and you could well be hopefully right. I'll always play the damp squid card, just for balance. And because I've been disappointed far more often than pleased with decent weather events. I'll get on the coaster then, just for one circuit mind....

Damp squib

Cork2021

I’m hedging my bets after reading this article

https://www.severe-weather.eu/global-weather/january-2021-winter-weekly-weather-forecast-united-states-europe-fa/?fbclid=IwAR3DvZHK-X-KtV5FcG6IiKcOJLE_3gGu13n9-gKh6KKYkHkg_RYP5ZUK2Kg

Roots 2020

Cork2021 wrote: »

I’m hedging my bets after reading this article

https://www.severe-weather.eu/global-weather/january-2021-winter-weekly-weather-forecast-united-states-europe-fa/?fbclid=IwAR3DvZHK-X-KtV5FcG6IiKcOJLE_3gGu13n9-gKh6KKYkHkg_RYP5ZUK2Kg

You should send it on to Little Snowy Old Fella:D

Billcarson

Cork2021 wrote: »

I’m hedging my bets after reading this article

https://www.severe-weather.eu/global-weather/january-2021-winter-weekly-weather-forecast-united-states-europe-fa/?fbclid=IwAR3DvZHK-X-KtV5FcG6IiKcOJLE_3gGu13n9-gKh6KKYkHkg_RYP5ZUK2Kg

Showing less cold weather for western Europe 2nd half of Jan, the charts on that article, wouldn't be surprised if that's turns out to be the case.

nacho libre

AuntySnow wrote: »

Whereas the ECM is speeding it up,you couldn't make it up could you
Regardless these 192 to 240 charts are unreliable anyway no matter what they're showing
s

I don't think so in this instance Blackbriar. There has been a consistent trend now to lift out the cold around mid-month. I think it will happen. 2 out of 3 SSW work in our favour, so hopefully, as the UK Met Office are suggesting, we see cold returning later in January.

Reckless Abandonment

Blackbriar.. haven't heard that name in a while. Welcome back

Scubadevils

Indeed, I wondered was it the very man! Earthman once upon a time too?

Where is Weathercheck? There can be no easterly till he arrives, doesn't matter how many SSW's split etc. :pac:

Kermit.de.frog

...

TheMilkyPirate

Great to see the old posters but do they wanted to be "outed"? I'm sure there was a reason for closing older accounts or name changes

mcburns07

Scubadevils wrote: »

Indeed, I wondered was it the very man! Earthman once upon a time too?

Where is Weathercheck? There can be no easterly till he arrives, doesn't matter how many SSW's split etc. :pac:

Read on here recently that Weathercheck is a meteorologist with Met Eireann now.

Scubadevils

mcburns07 wrote: »

Read on here recently that Weathercheck is a meteorologist with Met Eireann now.

Ah yes, I remember he was going to study meteorology a number of years ago. Great to hear his passion has become his career, not enough people can say that.

Kermit.de.frog

TheMilkyPirate wrote: »

Great to see the old posters but do they wanted to be "outed"? I'm sure there was a reason for closing older accounts or name changes

Aye yeah, I guess so.

YanSno

Is WolfeIRE still around?

Kermit.de.frog

Back on to the models. They've been on the brandy for the pub run tonight at least to 180 hrs. Bit of a cracker overall actually.





Interesting to see the focus again on continued height increases up around GL mid term on this run.