The hunt for cold - Model discussion (late November)

[terrier]

I know this is the hunt for cold. But does seem on the gfs12z we could have some potentially damaging winds Friday into Saturday. Looks like Scotland and northern England could see some pretty damaging winds. Not great. 

[Iceaxecrampon]

4 minutes ago, terrier said:

I know this is the hunt for cold. But does seem on the gfs12z we could have some potentially damaging winds Friday into Saturday. Looks like Scotland and northern England could see some pretty damaging winds. Not great. 

Yes.

Thanks for the reminder - maybe METO on board with warnings soon.

Iain

[Met4Cast]

Slightly more amplified and slightly further West so far

Promising to see Westwards corrections this early in the run..

[P-M]

1 minute ago, Iceaxecrampon said:

Yes.

Thanks for the reminder - maybe METO on board with warnings soon.

Iain

The warnings are already out Iceaxe - perhaps some areas will get an upgraded warning though...

[Methuselah]

Only hope that noob of HP splits right:

[terrier]

1 minute ago, P-M said:

The warnings are already out Iceaxe - perhaps some areas will get an upgraded warning though...

Could definitely see upgrades to the warnings regarding this storm looking at latest output. Could see north of Scotland and much of northern England seeing gust of 70-80mph as the storm pushes across. 

[SMU]

The UKMO & GFS are all alligned now with a potent Northerly bringing ~-8 air in, which moderates to -4/-7 depending on your proximity to the source of air-

Then a slight subsidence of the cold which still needs to be finalised however the -5 line is unlikely to receed any further East than the central point of the country before being pushed back west as the NE / E flow builds-

Post that 1 undercutter seems very likely, then some more atlantic influence could well bring so more widespread rain & snow with tricky forecasting parameters ....

Optimal areas for snow- ENE & E Scotland transferring further south past day 6...

Looking very seasonal-

Stratospheric forecast in the 'means' now down to 2 M/S on the 00z GFS for 20th December indicating a high probability for a cold Christmas- to put this into context the climo means for christmas week ( ironically the least probable chance of snow in winter ) is 38 M/S .... very rare times - 1962 & 1965 Had December Warmings...

*** Update The MERRA data which runs back to 79 indicates that the weakest strat zonal for this current week is Dec 81 @ a negative 2 M/S - hence why Dec was cold that year ***

 

 

Edited December 5, 2018 by Steve Murr

[Iceaxecrampon]

3 minutes ago, P-M said:

The warnings are already out Iceaxe - perhaps some areas will get an upgraded warning though...

Cheers - just saw the Wales Yellow early on.

[P-M]

Just now, terrier said:

Could definitely see upgrades to the warnings regarding this storm looking at latest output. Could see north of Scotland and much of northern England seeing gust of 70-80mph as the storm pushes across. 

Would you say inland gusts of that though?  They always say this but when it comes to it it's never usually as bad come the day (thankfully).

[Methuselah]

I'm seeing (or rather hoping) that some wintry showers will affect eastern counties?

With a band of 'snow-killer' higher DPs?

Edited December 5, 2018 by Ed Stone

[Nick F]

37 minutes ago, Glacier Point said:

Tend to disagree with this statement Nick.

Mike Ventrice's plot shows increasing depth VP centred east Indian Ocean / Maritime Continent week 2:

These tend to under represent anomalies in the week 2 range, so an increase in depth of the -ve VP anomaly is significant (and this increased from yesterday's plot as well). So whilst the RMM values might be weak, the angular momentum tendency signal will be increasing once more. The eastward propagation of this will lead to an increase in total AAM as well weeks 3 -4 through the Pacific.

So whilst the +AAM signal through 30N will decay, new inertia off the tropics will hold up the global AAM budget to elevated Nino levels. The real fun and games start when that signal begins to decay, and should coincide with the MJO in phase 8.

I see, the VP200 does indeed suggest increasing -ve anomaly depth propagating east, perhaps a good reason not to rely on the RMM plots alone. So do you think this more coherent signal of MJO propagation through eastern hemisphere may lead to a temporary relaxation of the block to the NE and resurgence in the Atlantic zonal flow towards the UK? Or do think we can maintain blocking with energy going underneath?

[SMU]

4 minutes ago, Ed Stone said:

I'm seeing (or rather hoping) that some wintry showers will affect eastern counties?

Use the Theta E charts - Sub 12c for Wintryness away from coasts, sub 10c ideally...

[Met4Cast]

Well well well..

GFS has effectively put the Atlantic on hold and told it to naff off, blocking further West and the first signs of energy disrupting South-Eastwards.. look at the isobars to the W of Wales and SW England.

[frosty ground]

East west split, block holding firmer but the cold air is further east than the 06z 

[Spah1]

We wait for easterlies for ages then when we get one it only lasts for a few days before slipping East. 

Is it only me that’s a bit disappointed that it can’t stay in situ for a bit longer? 

[Met4Cast]

Just now, Spah1 said:

We wait for easterlies for ages then when we get one it only lasts for a few days before slipping East. 

 Is it only me that’s a bit disappointed that it can’t stay in situ for a bit longer? 

Yes. 

Cold 850hPa temperatures aside, the 12z GFS is a vast improvement on the overall picture..

[Met4Cast]

Predictably the second we get into low res the low explodes and blocking melts away like butter

Improvements in the short term. Great 12z GFS. Great UKMO 12z.. ECM, over to you.

[booferking]

Just now, Daniel Smith said:

Yes. 

Cold 850hPa temperatures aside, the 12z GFS is a vast improvement on the overall picture..

You thinking this could back west 250-350 miles before time??

[Met4Cast]

Just now, booferking said:

You thinking this could back west 250-350 miles before time??

Possibly.. 250-350 miles isn't that far, probably a good 50 mile correction West on the 12z run alone.. not to say it's right, of course. But baby steps

[SMU]

Guys stop panicking about the atlantic pushing through-

* ITS A MODEL BIAS *

 

Wait for another 48-72 hours & then see what it shows in terms of the block holding strong-

[Mapantz]

There is a slightly disappointing aspect to the GFS for me, that there is more colder air to our West, than there is to our East.

As an example;

However, something cooler and more seasonal is still very much welcome.

[Methuselah]

I reckon the GFS has an ongoing contract with WINMAU? Bloody dartboards!

[Eskimo]

I was going to say, I have noticed through the years that the GFS always blows up lows when faced with a block. 

 

[Mike Poole]

GFS no good at T222 the low's blown up and this is well before the drop in resolution, 

GEM also pushes the Atlantic low through by T240,

I think anything beyond T144 is totally up for grabs and will only be resolved in future runs

Edited December 5, 2018 by Mike Poole

[mountain shadow]

6 minutes ago, booferking said:

You thinking this could back west 250-350 miles before time??

Boofer, you've been on here long enough to know about the GFS bias to over playing the strength of Atlantic lows.

My own gut feeling is that the lows will disrupt more and slide under the ridge. The upper air may be marginal for any associated snowfall but the best falls can come from such situations.

Another crucial ECM coming up!