Model Output Discussion. 3/12/2022. How cold will it get?

[Derecho]

3 minutes ago, Skullzrulerz said:

Disappointing start, noteworthy cold is gone even before the weekend.

850s not representative of the surface.

Friday afternoon, temps widely at or below freezing:

Saturday afternoon, same again:

Sunday afternoon, same again:

[Eagle Eye]

Just now, Kasim Awan said:

the short term models are 3d so they would factor in any layer interactions meaning that this mechanism wouldnt really be much of a limiting factor imo

 

True but something just seems off in the models.

This amount of shearing would surely have quite a lot of effect.

To quote the RMet..

"Genesis is intimately tied to the magnitude of the tilt and is found to occur once the mid-level vortex has precessed into the up-shear flank. For smaller values of maximum tilt, vortex precession is comparatively rapid, aided by “showerhead” moistening provided by the up-shear advection of frozen condensate aloft. With the up-shear flank pre-moistened, rapid precession of the mid-level vortex, at smaller radii, leads to near saturation on the mesoscale and the onset of rapid intensification. When the magnitude of the tilt is quite large, precession is much slower and the showerhead effect is significantly reduced until just prior to the emergence of the mid-level vortex in the up-shear flank."

 

 

[Vikos]

16 minutes ago, Kasim Awan said:

man if we can deliver that low to italy then the potential to our NE is crazy....

It is somehow a possible outcome… in Germany we call it south westerly stream development…

Edited December 4, 2022 by Vikos

[LRD]

Moot point because it won't look exactly like that but I reckon if iICON ran another 48 hours that low would be going under. Danger with ICON is if it stalls, which would probably inflate Iberian heights

TSNWK's jet stream map would indicate there is enough energy to make sure the low gets a move on but there is energy near/over us too. If it could go under and get to Italy, as other have said, that would advect some very cold air westwards to the UK. A cold pattern could then prove resilient

[MATTWOLVES 3]

10 minutes ago, MattStoke said:

ICON is hopeless, in my experience. No matter what some might claim.

Well I make a claim that it is the model that nailed that failed cold snap 2 or 3 years back! Then all the others followed suite. Let's see where the other 12s go before rubbishing it's credentials.

Edited December 4, 2022 by MATTWOLVES

[Tim Bland]

Dusting in many areas & perhaps more for some on icon by Friday 

[MattStoke]

2 minutes ago, MATTWOLVES said:

Well I make a claim that it is the model that nailed that failed cold snap 2 or 3 years back! Then all the others followed suite. Let's see where the other 12s go before rubbishing it's credentials.

And has lagged behind every other model 99% of the time I’ve looked at it.

Even a broken clock….

2 minutes ago, Tim Bland said:

Dusting in many areas & perhaps more for some on icon by Friday 

But given the dumping it has got me, I could be persuaded to believe in its credentials

Edited December 4, 2022 by MattStoke

[Kasim Awan]

2 minutes ago, Eagle Eye said:

True but something just seems off in the models.

This amount of shearing would surely have quite a lot of effect.

To quote the RMet..

"Genesis is intimately tied to the magnitude of the tilt and is found to occur once the mid-level vortex has precessed into the up-shear flank. For smaller values of maximum tilt, vortex precession is comparatively rapid, aided by “showerhead” moistening provided by the up-shear advection of frozen condensate aloft. With the up-shear flank pre-moistened, rapid precession of the mid-level vortex, at smaller radii, leads to near saturation on the mesoscale and the onset of rapid intensification. When the magnitude of the tilt is quite large, precession is much slower and the showerhead effect is significantly reduced until just prior to the emergence of the mid-level vortex in the up-shear flank."

 

 

Shear based weakening is a function in tropical storms theres too much extratropical influence for shear to cause much weakening

4 minutes ago, Vikos said:

It is somehow a possible outcome… in Germany we call it south westerly stream development…

you wouldnt want to know what we call a southwesterly stream development in britain, probably be banned from the forum

[Notty]

Wish I hadn’t mentioned that storm now. Shall we just wait and see what happens?

[Johnp]

26 minutes ago, Kasim Awan said:

The, as stated by some, "impossible" low is funnily enough back with a vegence - and further north on Icon 12z (the globe's most powerful short range model). Not too encouraging.

 Most powerful short range model? Do you have a link for that claim?

[Eagle Eye]

2 minutes ago, Kasim Awan said:

Shear based weakening is a function in tropical storms theres too much extratropical influence for shear to cause much weakening

 

I know it's a bit out of date but the system forms from a tropical wave sourced roughly off just the West coast of Africa and quoting @Ben Sainsbury yesterday

"That blow-up low on the ICON 12z & GFS 6z is definitely a tropical system. Obvious warm core on the models, but I just cannot see it strengthening/deepening like it does."

[Allseasons-Si]

I'd say the ICON is a vast improvement to this mornings 00z suit with better height's to our north suppressing/elongating the trough over the UK,this too far away anyway to call yet for days to come and i will be pretty sure it won't end up like that

on to the 12z we go then.

 

[Metwatch]

18 minutes ago, Skullzrulerz said:

Disappointing start, noteworthy cold is gone even before the weekend.

Not to say that low will deepen because it's near impossible but gets strong enough it will wreak the entire thing!

The 850s aren't representative of what happens at the surface as quick silver pointed out.

Slack winds, very low sun / short daylength, low heights, that would make surface temperatures cold or very cold, not much above freezing during the day and well below by night.

[Skullzrulerz]

Just now, Metwatch said:

The 850s aren't representative of what happens at the surface as quick silver pointed out.

Slack winds, very low sun / short daylength, low heights, that would make surface temperatures cold or very cold, not much above freezing during the day and well below by night.

For most of England yes that is true, however for costal areas, parts of Wales and the south west they do recover temperatures back to around average.

I guess we can't complain tbh 

[Kasim Awan]

2 minutes ago, Eagle Eye said:

I know it's a bit out of date but the system forms from a tropical wave sourced roughly off just the West coast of Africa and quoting @Ben Sainsbury yesterday

"That blow-up low on the ICON 12z & GFS 6z is definitely a tropical system. Obvious warm core on the models, but I just cannot see it strengthening/deepening like it does."

its not deepening due to high ssts and 0 shear tho like a tropical system

tropical core yes but deepened via extratropical interaction

so not subject to same functions as a tropical system

[Ali1977]

This could be better

[Met4Cast]

Slowly slowly.. better core heights across Scandi on the 12z run. We’ll likely see slow changes re the low until we reach a tipping point and suddenly the entire ensemble suite will be in agreement, one way or another.. 

[Eagle Eye]

Just now, Kasim Awan said:

its not deepening due to high ssts and 0 shear tho like a tropical system

tropical core yes but deepened via extratropical interaction

so not subject to same functions as a tropical system

If it's a warm core then it acts like a tropical system.

The extratropical interaction you influence is very little in it's initial stage, moisture coming from it's south but as a warm core it still works as a convective centre influenced tropical system and the shearing will disassociate itself from it's low level circulation unless it happens to be very 'lucky'.

[ItNeverSnowsInWindsor]

19 minutes ago, Quicksilver1989 said:

850s not representative of the surface.

Friday afternoon, temps widely at or below freezing:

Saturday afternoon, same again:

Sunday afternoon, same again:

Is that rain coming in on Sunday in Southern counties possibly turning to snow ? 

[TSNWK]

Just now, Ali1977 said:

This could be better

Why.. I was just thinking slightly better thread of link to the Asia lobe for our trough., but just noise I thought? You seeing then?

[Liam Burge]

9 minutes ago, Kasim Awan said:

Can you provide the maths to prove that there is a limit to deepening potential on the conditions modelled?

personally i dont buy into the idea that modelled outputs can be labelled as impossible

its bringing up extremely warm uppers from africa & very cold air aloft, the high keeps it in situ in this highly volatile environment for a good 72 hours

Okay. Let's take this scale for example, which shows that a Cat3 hurricane (which is classified as a major hurricane) should have a pressure of 946-960mb (which is the same in hpa).

At 5pm on Tuesday the 6th, Icon has the low pressure system at around 995hpa.

Moving on to Wednesday the 7th at midnight (7 hours after the previous image, the storm has already dropped 23mb, which is around 3mb/hr. I don't think any storm has ever sustained this level of deepening for this long. This would already put the storm at a category 2 according to the chart I've posted. This would also suggest a case of extreme bombogenesis, Bombogenesis by definition is: 'occurs when a midlatitude cyclone rapidly intensifies, dropping at least 24 millibars over 24 hours. A millibar measures atmospheric pressure.'. This specific icon run is showing a 24mb drop in just 7 hours.

Let's take one of our well known storms, Storm Doris. This storm dropped 30mb in 24 hours. Are you seeing just how unrealistic and unfeasible this is now?

If this still isn't enough proof that Icon is completely off the rocker, this is the system exactly a day later,Thursday 8th at midnight. This is showing a further drop of 9mb in another 24 hours. Although this isn't rapid deepening at all, this would put it into the high-end cat2 territory, and approaching cat3 strength, which has a pressure of 960 or less. So, this particular run shows it strengthening from less than a tropical storm to a high-end cat2, low-end cat3 system in just 2 and a bit days. windy.com doesn't go past this timeframe, but Icon is still showing this system dropping in pressure even further, to around 950mb.

If we take the Icon 950mb as 100% real, this would mean the storm would be a high-end Category 3 in just 3 days. The numbers and pressure gradient is so tight I theoretically can't see if it strengthens any more than this, but it really does look like it strengths to even lower than this 950mb threshold, which would put it in a category 4 strength.

As you can see here, the system is showing 965 with multiple numbers behind this, which would suggest probably another 15-20mb drop behind this.

 

So yes, this is practically impossible. It's literally not possible for a system in this environment to rapidly strengthen from nothing to a category 4 hurricane in just 5 days.

 

 

[Ben Sainsbury]

10 minutes ago, Eagle Eye said:

I know it's a bit out of date but the system forms from a tropical wave sourced roughly off just the West coast of Africa and quoting @Ben Sainsbury yesterday

"That blow-up low on the ICON 12z & GFS 6z is definitely a tropical system. Obvious warm core on the models, but I just cannot see it strengthening/deepening like it does."

It definitely does form from a tropical wave, but judging by the runs today it doesn't look like it really deepens much until it approaches much closer to the UK, probably more akin to sub-tropical rather than tropical. That's my mistake.

Edited December 4, 2022 by Ben Sainsbury

[Paul]

Probably a plan to move on from the low deepening debate at this point, or perhaps start a thread dedicated to talking about it, if you want to continue. 

[winterof79]

24 minutes ago, nick sussex said:

No major drama from the ICON .

I don’t see a mild solution from its T180 hrs and the slack low heights over the UK are quite unusual .

Theres also a possibility we’ll see surface pressure building over Scandi which should help .

Not a bad start . No bells and whistles but equally the NW helpline shouldn’t be overloaded .

Onto the GFS and UKMO now ! 

The last slack low heights of note was 2009/10 our own home grown cold pool and streamers off the irish sea dumped heaps of the white stuff.Much to look forward to peeps

[Ali1977]

2 minutes ago, TSNWK said:

Why.. I was just thinking slightly better thread of link to the Asia lobe for our trough., but just noise I thought? You seeing then?

Was thinking it could cut off the area of heights around Svalbard, when may help it all head further south!! We shall see