A rather interesting development, I’m unsure what it would deliver in terms of weather though...

I'm guessing 'windy' would be a safe bet.

Polar lows do occasionally hit scotland, they are usually pretty good snow and soft hail makers but since they are fuelled by tropical processes they die really quickly when they go inland, so don't expect anything out of it if you are away from N or W coasts.

And yes I am of the opinion that polar lows are more similar to TCs than depressions. Unlike (most) TCs they develop out of baroclinic disturbances but like TCs there intensification and maintance is determined by surface fluxes rather than horizontal temperature gradients. Although since they are extremely shallow and underneath cold core lows it may be more accurate to describe them as being like subtropical cyclones.

Although that thing yesterday was not a subtropical cyclone, it was a catogary 2 hurricane.

 

What a guess - flattened at +252 on 06z

http://www.wetterzentrale.de/maps/GFSOPEU06_252_1.png

 

run but 0z run brings that HP to Scandinavia:

http://www.wetterzentrale.de/maps/GFSOPEU00_252_1.png

 

 

Eventually it makes yet another attempt and finally gets there @ 336z

http://www.wetterzentrale.de/maps/GFSOPEU06_336_1.png

Nice to see an easterly could be still on the ca\rds even if it's in FI!

ICON.

 

This is not a baroclinic system. It has an eyewall and a warm core.

What the actual hell?

Q - where is that warm core originating from?  From the air drying?  IF its sourced from colder climates, how can it create a warmer (albeit still frigid) core?

 

Eventually it makes yet another attempt and finally gets there @ 336z

http://www.wetterzentrale.de/maps/GFSOPEU06_336_1.png

Nice to see an easterly could be still on the ca\rds even if it's in FI!

Yes, it's the second successive GFS operational run to produce something broadly similar in FI, so perhaps it's picked up on something. It would be consistent with the Met Office extended outlook. One lives in hope. :) 

 

 

Q - where is that warm core originating from?  From the air drying?  IF its sourced from colder climates, how can it create a warmer (albeit still frigid) core?

Look at the 500hpa temperature profile, the anomolies are ridiculously low. Tropical cyclones form under regions of low wind shear and high vertical temperature gradient. Usually that's the tropics but cooling the top of the atmosphere is just as effective as warming the surface of the atmosphere and that's what we have going on here. The SSTs over the north at altlantic are relatively warm at 10C or so but there is frigid air moving over the top. This creates convective instability, which is exasserbated by latent heat release as showers form and consensation occurs.

Usually, of course, you just get showers because the wind shear is too high but apparantely its going to be low enough to actually spin up some kind of tropical like cyclone.

It does happen semi regularly on the ice front near svalbard where you can get frigid arictic air moving over relatively warm seas. But polar lows occasionally get as far south as scotland.

You can think of a polar low as an extreme varient of the lake effect. Where, instead of shallow convection under high shear you have deep convection under no shear.

 

Yes, it's the second successive GFS operational run to produce something broadly similar in FI, so perhaps it's picked up on something. It would be consistent with the Met Office extended outlook. One lives in hope. :) 

Yes! We wait with anticipation! But it has been like this now for two consecutive runs albeit different timings post +252. I don't suppose there will be an upgrade in the ECM tonight as it only goes up until 240. At least this is a start! BUT will this trend continue?

Polar lows do occasionally hit scotland, they are usually pretty good snow and soft hail makers but since they are fuelled by tropical processes they die really quickly when they go inland, so don't expect anything out of it if you are away from N or W coasts.

 

And yes I am of the opinion that polar lows are more similar to TCs than depressions. Unlike (most) TCs they develop out of baroclinic disturbances but like TCs there intensification and maintance is determined by surface fluxes rather than horizontal temperature gradients. Although since they are extremely shallow and underneath cold core lows it may be more accurate to describe them as being like subtropical cyclones.

Although that thing yesterday was not a subtropical cyclone, it was a catogary 2 hurricane.

 

That's not correct Q - some can be quite long-lasting, even over land. I recall one from 2006 (I think) that tracked down on a northerly through Scotland and into N. England, and delivered several cm in a very short space of time.

 

That's not correct Q - some can be quite long-lasting, even over land. I recall one from 2006 (I think) that tracked down on a northerly through Scotland and into N. England, and delivered several cm in a very short space of time.

It may well have undergone something equivalent to an extratropical transition and become a cold front or something like that. But the tropical structure of the PL is very quickly degraded as soon as it hits land.

 

Yes! We wait with anticipation! But it has been like this now for two consecutive runs albeit different timings post +252. I don't suppose there will be an upgrade in the ECM tonight as it only goes up until 240. At least this is a start! BUT will this trend continue?

 

No need to worry about the ECM Op at day 10 - it has been completely consistent over the past few weeks - consistently wrong that is.

I have lost all faith in that particular model - prefer ICON and UKMO and then as we get close to an event (such as this week) - switch to the fax charts (although even they can change quite dramatically at t+96 as Matt demonstrated above).

 

It may well have undergone something equivalent to an extratropical transition and become a cold front or something like that. But the tropical structure of the PL is very quickly degraded as soon as it hits land.

 

Nope, it retained classical characteristics all the way. I remember discussing it with Paul Hudson at a book signing he did in York...

 

Nope, it retained classical characteristics all the way. I remember discussing it with Paul Hudson at a book signing he did in York...

Can you find out more details or get the date of the storm?

I'm very skeptical a PL can survive a while over land without transitioning.

 

Can you find out more details or get the date of the storm?

I'm very skeptical a PL can survive a while over land without transitioning.

 

I'll have a dig around on the archives.

 

Look at the 500hpa temperature profile, the anomolies are ridiculously low. Tropical cyclones form under regions of low wind shear and high vertical temperature gradient. Usually that's the tropics but cooling the top of the atmosphere is just as effective as warming the surface of the atmosphere and that's what we have going on here. The SSTs over the north at altlantic are relatively warm at 10C or so but there is frigid air moving over the top. This creates convective instability, which is exasserbated by latent heat release as showers form and consensation occurs.

Usually, of course, you just get showers because the wind shear is too high but apparantely its going to be low enough to actually spin up some kind of tropical like cyclone.

It does happen semi regularly on the ice front near svalbard where you can get frigid arictic air moving over relatively warm seas. But polar lows occasionally get as far south as scotland.

 

Thanks for the explanation 

Would it be possible to get a PL forming in a very cold easterly across a relatively warm North Sea?

 

Thanks for the explanation 

Would it be possible to get a PL forming in a very cold easterly across a relatively warm North Sea?

 

I think the north sea environment is too dry for it to happen. I've near heard of it happening over the north sea.

 

No need to worry about the ECM Op at day 10 - it has been completely consistent over the past few weeks - consistently wrong that is.

I have lost all faith in that particular model - prefer ICON and UKMO and then as we get close to an event (such as this week) - switch to the fax charts (although even they can change quite dramatically at t+96 as Matt demonstrated above).

Very true, Maunder. 

The ECM has been a poor performer of late, it has to be said. 

Possibly some hints of a reversal of the trend to mildness in the GEFS long term, although still lots of scatter.

Milder runs in GEFS can also be a pre-cursor signal to blocking.  Its not always a bad thing to see in the suite.