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?

Originally Posted by: Russwirral 

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. :) 

Originally Posted by: jhall 

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.

Originally Posted by: Quantum 

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.

Originally Posted by: Arcus 

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?

Originally Posted by: tallyho_83 

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.

Originally Posted by: Quantum 

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

Originally Posted by: Arcus 

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.

Originally Posted by: Quantum 

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.

Originally Posted by: Quantum 

Thanks for the explanation 

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

Originally Posted by: RobN 

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).

Originally Posted by: Maunder Minimum 

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

Originally Posted by: Rob K 

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

Originally Posted by: Russwirral 

GEFS 06z have trended colder in the longer term again.

Originally Posted by: Brian Gaze 

Snow Rows for Brighton not looking particularly inspiring 

Originally Posted by: kmoorman 

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.

Originally Posted by: Quantum 

2m temps never below zero from February. Tbh still can’t see where met office are scrawling their text from.

http://old.wetterzentrale.de/pics/MT2_London_ens.png

Originally Posted by: White Meadows 

Indeed. Not sure if you've seen, but the snow row league and historic graphs are now here:

https://www.theweatheroutlook.com/twodata/snowrow.aspx?location=Brighton#Brighton

Originally Posted by: Brian Gaze 

2m temps never below zero from February. Tbh still can’t see where met office are scrawling their text from.

http://old.wetterzentrale.de/pics/MT2_London_ens.png

Originally Posted by: White Meadows 

Well, either it is:

A.  Obviously they use GFS exclusively and therefore someone in Exeter is going to get the sack for gross incompetence.

or

B. They have their own forecast models and they are telling a different story.

I think B is just slightly more likely, don't you?

Originally Posted by: Gandalf The White