Winter Model Discussion 18Z 5/2/13 onwards.

[Tamara]

No spike (for 11th) shown here - in fact these are the best London ECM ensembles in a while.

No, interestingly it doesn't reflect here further west. Maybe the warmer outlier spike for The Netherlands reflects that the low is adjusted slighly further west in the ensembles and so consequently colder continental uppers are kept in place throughout.

[stratty]

you will have noted I mentioned the potential for large snowfalls, the models are still firming up on sun/mon. We shall soon find out but i'm rather looking forward to what could be a big event, at least the gfs has finally come to the party.

I just hope it's better than the 'severe' northerly you quoted! I like your ramping Frosty - hope you are right

[Frosty.]

Latest metoffice update is an upgrade, suggests a prolonged spell of cold and unsettled weather with an ongoing risk of sleet and snow, especially on hills and any less cold weather being brief, no sign of anything mild whatsoever in that update, cold and unsettled which is much better than the gfs 00z showed for next week, and also better than the ecm 00z in the later timeframes, it seems we are in for more lows sliding southeast through the outlook with continued undercuts and snow, really good news. I can only assume that mogreps has improved cold prospects in the medium and longer range, among other factors.

[mulzy]

No probs.

Yes, I do agree that the anomaly charts do look as if we should have been locked in the freezer all winter. The AO has been negative all winter though and matches well with these anomalies.

http://www.cpc.ncep....ent.ascii.table

But the problem this winter has been the positive NAO. The winter killer (Azores High) has been wandering around its home and popping into Iberia at times.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table

[Glacier Point]

An interesting morning's model runs.

The trend from both 00z and 06z GEFS, and perhaps more nuanced signal from ECM EPS days 6-10 continues with low pressure signal across UK and much of Europe with resident +ve heights over Scandinavia. GEFS in particular keen to pull the centre of the ridge away from the Azores in a NW direction allowing continued risk of low pressure systems dropping NW-SE across the UK into the upper trough, persisting a cyclonic and below average temp. signal.

Beyond that, the GEFS continues to simultaneously withdraw the PV away from Canada and develops mid Atlantic ridge signal, with this becoming the dominant force in upper circulation in our quadrant as the ridge over Scandinavia weakens in response.

Given the persistence of the +ve anomaly between Greenland and Svalbard, that makes for an interesting pattern to see out the latter half of the month.

Edited February 7, 2013 by Glacier Point

[Tamara]

Latest metoffice update is an upgrade, suggests a prolonged spell of cold and unsettled weather with an ongoing risk of sleet and snow, especially on hills and any less cold weather being brief, no sign of anything mild whatsoever in that update, cold and unsettled which is much better than the gfs 00z showed for next week, and also better than the ecm 00z in the later timeframes, it seems we are in for more lows sliding southeast through the outlook with continued undercuts and snow, really good news. I can only assume that mogreps has improved cold prospects in the medium and longer range, among other factors.

Yes, the ensembles have been an awkward mix and therefore open to daily tweeking and consequent tweeting amemdments That more amplified jet stream pattern forecast suggestion is clearly finding its way into all model ensemble data, and hence the more southerly tracking solution from the METO accordingly

[Summer Sun]

Following on from my earlier post in the MOD thread the 06z has downgraded the snow for many there is huge uncertainty but its looking quite marginal for many in England and Wales if you don't have decent elevation at this stage

The main reason for the uncertainty is the day time temperatures could be too high for some

Edited February 7, 2013 by Gavin.

[Severe Siberian icy blast]

I think we are now seeing the evidence in the models , showing what the anomaly charts have been showing recently ,( and by that I mean what they have actually been reading ) yes the anomaly charts are showing heights over Greenland to increase over the next 14 days , and I think the models are beginning to get a grip and feel we will see this now move forward and approach a more reliable time frame, but big hints from gfs now of heights building toward Greenland , with a trough south/southeast of uk , a southerly tracking jet , (more or less non existent )

Also notice the vortex removing itself from Greenland and pushing over the pole , with more energy keeping north of Greenland toward the pole and then down into Siberia also

Also I strongly advise ones to take A look at the 500 anomaly chart provided by John h earlier with his excellent summary of what we can expect the upper air flow to look like during this period , notice the areas east of Iceland , John eluded to in his post and the potential for disturbances (short waves ) to develop in these areas .

So all in all I think we can agree that we can expect to see height rises toward Greenland of some sorts .

Edited February 7, 2013 by Severe Siberian icy blast

[Ian Brown]

We will see Shaun but on both times I have progressed the anomaly charts this winter they have been behind the NWP and the result ended in zonality.

[MR EXTREMES]

its also worth noting that in march the greenland heights or alantic heights have been fairly dominant over the 3 or 4 years in later winter months.

[johnholmes]

We will see Shaun but on both times I have progressed the anomaly charts this winter they have been behind the NWP and the result ended in zonality.

two views hardly warrants a measured view of them Ian, how about you spend 12 months checking them every day as I did then give your views?

Mine are available on Net Wx, I say 70% of the time they give good guidance and that includes changes of type where they are a first class indicator, be that zonal to blocked or blocked to zonal.

anyway below is the link to the pdf I promised part 1

http://forum.netweat...11#entry2590411

Edited February 7, 2013 by johnholmes

[Coast]

How about a new thread shortly to catch up on the 12z output?