Model Outooks: Winter 2008/2009

shamwari

Danno wrote: »

Almost every year, it snows on December 29th, my birthday. This year I am going to be 29, I live at house number 29. The signs are in the numbers!

Im 10 years married on the 30th and am praying for a blizzard.....:D

Snowaddict

A much better GFS 18Z when compared with previous runs IMO.
Tonight, there is a clear trend in the hi-res part of the run towards what the latest ECM runs have been showing. There are clear hints of both possible retrogression and the building of strong heights over Greenland in the first half of this run. Now if this were to continue to trend towards the ECM, then the odds of a wintry spell would increase, however this is but one run and nothing is certain.

However the signs and trends are positive.

FI on the 18Z is all over the place, literally, with various synoptics wandering and meandering around. As I said earlier, the outputs over the next 48 hours or so will be crucial IMO in order to ascertain a clear path as to way things are trending.

SA.

Snowaddict

Many cold possibilities on the 18Z GFS set of ensembles.
Very interesting to note that the operational was once again a mild outlier at various points of this run. Thats probably the most encouraging set of ensembles out of the last 4 or 5 GFS runs.

There are some very interesting members in there, with some very cold solutions on offer.

All encouraging IMO, as is the mean pressure chart at various points, which points to hints of pressure rises over Greenland and Scandi. The key point which I take from these ensembles is that a clear majority of them keep the pattern blocked to very blocked right out until the end.

All to play for at this point.

Snowbie

Some head scratching going on with GFS outputs atm. I know that the GFS being a US based model is not handling blocks too well and is all in favour for the Atlantic to break through in FI while ECM is consistently showing the block throughout the runs and further blocking in FI.

I am all for ECM to come out trumps here and GFS to come back inline in next few runs. I still don't see any precip atm even on the windward coasts yet but a potential sustained cold dry block to our NE, N and NW could be in the making and holding for the majority of pre and post New Year. I can't see the ECM colapsing with it's blocking pattern now but 12z on Tuesday output should confirm this.

Snowbie

Snowaddict wrote: »

Many cold possibilities on the 18Z GFS set of ensembles.
Very interesting to note that the operational was once again a mild outlier at various points of this run. Thats probably the most encouraging set of ensembles out of the last 4 or 5 GFS runs.

There are some very interesting members in there, with some very cold solutions on offer.

All encouraging IMO, as is the mean pressure chart at various points, which points to hints of pressure rises over Greenland and Scandi. The key point which I take from these ensembles is that a clear majority of them keep the pattern blocked to very blocked right out until the end.

All to play for at this point.

A lot more members are now hinting at below -5C 850mb temps also there SA

Snowbie

Can't post up charts atm, due to tryin to earn a living but quick glance at the GFS and ECM 00z and it looks very good. GFS is coming back on track. Still looks very cold and dry but an outside chance of some trough appearing over Scandi when this HP retro's. Too far away atm to be certain.

I'd say by tomorrow if the ECM keeps going the way it is, a new thread be warranted for the cold spell

Snowaddict

Snowbie wrote: »

Can't post up charts atm, due to tryin to earn a living but quick glance at the GFS and ECM 00z and it looks very good. GFS is coming back on track. Still looks very cold and dry but an outside chance of some trough appearing over Scandi when this HP retro's. Too far away atm to be certain.

I'd say by tomorrow if the ECM keeps going the way it is, a new thread be warranted for the cold spell

Indeed Snowbie. GFS has certainly trended towards the ECM on the 00Z run... Once again, a clear blocking pattern on the ECM outputs. The big question still relates to whether this cold spell will deliver something big... I'm still very unsure...

ECM looking very good on its latest run. One concern for me would be that it is constantly delaying ever so slightly the retrogression towards Greenland. However, I do think the outlook is now very promising for this cold spell.

JanuarySnowstor

I must be looking at different charts.
All is see is a cold breeze. Upper 850's and thickness's are way too high. The whole thing has downgraded massively since last Friday. For once i agree with the Irish Met, as Gerry said last night turn cooler for the wkd!

Supercell

JanuarySnowstor wrote: »

I must be looking at different charts.
All is see is a cold breeze. Upper 850's and thickness's are way too high. The whole thing has downgraded massively since last Friday. For once i agree with the Irish Met, as Gerry said last night turn cooler for the wkd!

That is all that is showing currently, however the potential for something pretty rare is there which is why everyone is getting excited. All we can do is watch and see how it turns out I suppose

Kippure

JanuarySnowstor wrote: »

I must be looking at different charts.
All is see is a cold breeze. Upper 850's and thickness's are way too high. The whole thing has downgraded massively since last Friday. For once i agree with the Irish Met, as Gerry said last night turn cooler for the wkd!

Look at it this way, Cold frosty weather first so the snow will stick when it falls!

Snowaddict

Yet again, there is a clear trend on the GFS 06Z towards the ECMWF evolution that has been shown over recent days.

There are considerable signs to substantial pressure rises to our north on this run. One chart that I am posting from this run is the frame at T+264.

This is a clear trend towards the ECM output, and most encouraging IMO.



There is certainly substantial potential for something big in terms of cold if this continues. As I said last night, the runs for the next day or so will be crucial to see if things keep trending towards ECM.

Something very important to note is that the UK Met Office have now updated their Winter Forecast, stating that January mean temps will now be below average. There is a clear trend to colder conditions on this forecast:

__________________________________________

Updated 22 December 2008

Forecast for the remainder of Winter 2008/9


Temperature
UK mean temperatures are likely to be below average in January and nearer average in February.

Mean temperatures for other parts of Europe during the rest of winter are more likely to be near average, but near or above average in south-east Europe.

Rainfall
Precipitation for the remainder of winter is more likely to be average, or below average over much of Europe, including the UK. However, above-average precipitation is favoured over parts of south-eastern Europe.

Forecasts are expressed as variations from 1971-2000 averages.

Snowbie

JanuarySnowstor wrote: »

I must be looking at different charts.
All is see is a cold breeze. Upper 850's and thickness's are way too high. The whole thing has downgraded massively since last Friday. For once i agree with the Irish Met, as Gerry said last night turn cooler for the wkd!

It's a warm inversion Hp that will deliver a cold wind in fact for now. 850mb temps are not too significant when wind is due off the continent in this setup atm, the air is dryer and so dewpoints lower. We look for the 850mb to see where the significant cold pools are but surface levels will be much cooler and could be similar to 1500m temps as cold air hugs the ground.

An 850mb temp of 0C could be 2C at the surface from this east setup. But if we get the retro of the Hp, the 850mb come into play as a northern source airmass is colder now than the continent atm and should have lower heights with much colder mid to upper levels.

Not expecting any snow just yet as there is little indication and too far out in FI but with these setups, trough, low level circulations do pop up but really only if the wind goes N'ly. Nowcast for those.

Snowaddict

A clear cooling trend on the 06Z ensembles.

Snowaddict

After running through all of the GFS ensembles for the 06Z run, I have noticed the following:

01. That we are on course for a cold spell beginning around the 26th/27th.

02. The cold spell will have an easterly flow to it, and from what I can see, it will not be conductive to snowfall for the first while at least.

03. Many of the ensemble members go for a significant drop in both 2m and 850hPA temps from approximately the 3rd to the 5th of January onwards.

04. This marked drop is due to one principal component... Several of the ensemble members are in agreement with the ECM's recent evolution of events, and clearly suggest retrgoression of the high / height rises over Greenland. This then paves the way for a northeasterly flow, one which would be conductive to snowfall IMO, as the airflow would be unstable. A considerable number of ensemble members go for this evolution, hence the mean drops to near -5 from about the 5th, as shown above.

This is all deep FI at the moment, but it does show a clear trend towards the ECM modelled evolution. Therefore, I think that we are indeed heading into a cold spell. It may be somewhat lackluster at the start as the building blocks shore up, but there is the potential for something more significant as we head into the new year.

Whether this will materialse is very much uncertain at this point, but there are clear signs there towards a possible wintry outbreak in the first week of the new year. Of course, these are only possibilities at the moment. The fact that UK Met have now revised their forecast to below average temps for January, this would add to my optimism regarding the colder outbreak.

So a lot of positives in terms of cold to very cold possibilities IMO.

Regards,
SA.

Deep Easterly

GFS ensembles for the North West look okish too!



Roll on the omnipotent easterly. Hopefully a lot of haze in the flow too giving some spectacular sky and land scapes. I can't wait.

An easterly is divine; anything else is second.

arctictree

Just had a look at the charts. So it looks like easterly gloom here in the east with temps around 5c for a week or more? Very little precip around for at least the next 7 days.

Edit: The only possible snow event I can see is on the GFS at +180. Precip for the south east with buoy temps at 4 or 5c. Borderline event if temps inland are low enough.

Supercell

arctictree wrote: »

Just had a look at the charts. So it looks like easterly gloom here in the east with temps around 5c for a week or more? Very little precip around for at least the next 7 days.

Edit: The only possible snow event I can see is on the GFS at +180. Precip for the south east with buoy temps at 4 or 5c. Borderline event if temps inland are low enough.

If it plays out per the charts than that's it exactly. Though temperatures would be on a slow downward trend even here in the east. Gloomy it will be on the east coast for sure. That said this pattern will eventually bring clearer cold air and if retrogression happens towards Greenland a classic could be on the cards.

Cool and gloomy i'll take for a while given the massive potential for a classic (cold spell) that is on offer.

nacho libre

I'll take it too Supercell if it eventually leads to, as someone mentioned to me earlier;), a battle between the mild atlantic air and siberian air over Ireland with the cold air winning out.:D

Snowaddict

Supercell wrote: »

If it plays out per the charts than that's it exactly. Though temperatures would be on a slow downward trend even here in the east. Gloomy it will be on the east coast for sure. That said this pattern will eventually bring clearer cold air and if retrogression happens towards Greenland a classic could be on the cards.

Cool and gloomy i'll take for a while given the massive potential for a classic (cold spell) that is on offer.

Indeed, another very good ECMWF run again this evening. As I said earlier, the cold spell may be pretty much lackluster in terms of wintriness for a while, but all of the building blocks are coming together and at present time I would put 35% on the possiblity of a top classic cold spell. Although ECM has backed away somewhat this evening from retro of the high, there is a clear cold spell on the cards.

GFS 12Z operational showed another clear trending towards the ECM. If this continues, we will have the best potential in many years for a classic outbreak.

Snowaddict

The latest GFS 18Z operational run (in the more reliable timeframe and higher resolution part at least) once again pushes everthing slightly further west.

This is exactly the manner in which we need things to be trending, because we need that high to back westward, preferably northwestward to Greenland as much as possible. This, if it continues to take place, may eventually us a very good chance of a more potent easterly / northeasterly flow.

Very positive signs now from the GFS on the last few runs.

At T+144, there are significant height rises over Greenaland of 1040mb.

Snowbie

I think this might be the first hiccup in the ECM. The HP not only is weaker,(lesser block over Scandi), there is a sign it is slipping into Europe. Biscay LP has nothing but modified air well into the wrong side of marginal
The height rises are also less over GL and no retrogression.
The Atlantic will break through if there was one more chart past 240hrs.

I don't see this as a good run.

Edit: Have to add, that an easterly at this point is not good for a cold spell.(EU being milder) The retro of the high into GL would give a more potent cold spell. Although could still back track again.??? but only 2 more runs and this was nailed in.:(

Snowaddict

Snowbie wrote: »

I think this might be the first hiccup in the ECM. The HP not only is weaker,(lesser block over Scandi), there is a sign it is slipping into Europe. Biscay LP has nothing but modified air well into the wrong side of marginal
The height rises are also less over GL and no retrogression.
The Atlantic will break through if there was one more chart past 240hrs.

I don't see this as a good run.

Well it certainly backs down from the retrogression aspect, but I still think its fairly good, but certainly not near as good as previous runs and as you point out very correctly, the atlantic could well break in if there was another chart past T+240.

Another possiblity shown on the latest GFS run up to T+159, is that the initial high may be not exactly sink completely but fizzle out somewhat in situ, only to be replaced by substantial height rises over Greenland... Its also at this point that we would really need high pressure to the west to be sustained...

This chart is very interesting to me... I would have thought yesterday that a fairly definate call could be made on general trends by tomorrow, but that now seems uncertain. Probably will have to wait one or two more days, but with this chart on GFS, there is great potential about. My interest in the chart would be around Greenland at this point. However, I must say that this run is looking a bit suspicious, and even at T+144 is quite different to some of the other models.

Regards,
SA

Snowbie

It will seem we will have to wait a tad longer for sure before all is known.

Snowaddict

I posted above regarding the possible Greenland height rises on the earlier part of this run.

Now these are once again on the end part of this run, with the showing of a 1048mb Greenland high. The chart below demonstrates what could potentially (in some sort of manner) evolve from such high pressure over Greenland. Now if the high pressure on the chart below was slightly further west, or there was a larger area of high pressure over Greenland at this point, then it would be 'game on' in terms of a wintry outbreak.

But to be honest, its too difficult to call with any certainty at this point. Next 4 GFS and 2/3 ECMWF runs will be vitally important IMO. We should be able to get a clearer picture as to whether this possible retrogression shows up more or less consistently.

18Z ensembles will be interesting, to see how many go for Greenland height rises and possible retrogression.

Still, quite a positive 18Z run. The key once again being, that the atlantic is not left in, the pattern remains blocked to very blocked and thats a fairly big part of the puzzle when looking for a potential classic wintry outbreak. However, until these charts show up in the more reliable, or at least a clear and consistent trend towards these charts, there is not much certainty.

SA.



EDIT: After looking at the ensembles, I think its nice to show what the GFS control run went for in FI this time, because it shows clearly a very good synoptic setup for a classic cold spell.



EDIT: Some absolutely fantastic ensemble members on the 18Z GFS run. If retrogression of the high was to take place, perturbation number 6 from tonight's run demonstrates clearly the net gain for this island - if retro to Greenland of the high was to occur.

Finally, the scatter deomstrates that all options are still available. Quite a few members still going for retrogression, which is very positive. Note also how the operational run was yet again another mild outlier for the majority of the run, almost until the end, when it drops off sharply.

Deep Easterly

Snowbie wrote: »

I think this might be the first hiccup in the ECM. The HP not only is weaker,(lesser block over Scandi), there is a sign it is slipping into Europe. Biscay LP has nothing but modified air well into the wrong side of marginal
The height rises are also less over GL and no retrogression.
The Atlantic will break through if there was one more chart past 240hrs.

I don't see this as a good run.

Edit: Have to add, that an easterly at this point is not good for a cold spell.(EU being milder) The retro of the high into GL would give a more potent cold spell. Although could still back track again.??? but only 2 more runs and this was nailed in.:(

I thought the ECMWF run was fantastic....but thanks for blowing my bubble....:pac::D

Snowbie

The ECM retrogress's the HP in to GL

arctictree

Major upgrade on the 00z GFS

Snowaddict

Absolutely stunning charts again this morning. I was getting a tad worried about this cold spell last night, but it certainly seems very much on track again this morning. With an ECM chart like this and the GFS chart below, there is a great chance of prolonged cold and certainly possible wintriness.



I suppose this chart could be described as almost perfect in terms of wintriness, because of the strength of that Greenland high. Indeed, if these outputs once again continue, there is still great potential for a top classic wintry outbreak.

Snowaddict

The outlook from Met Eireann is now trending in favour of the cold spell. I think they base their forecasts mainly on the ECMWF model output? But I'm not sure. A very encouraging forecast either way.

''Mainly dry, settled weather during the Christmas period, from Thursday 25th until Sunday 28th, inclusive. Cloud cover will vary- some sunny intervals should occur by day, but fog may develop on Wednesday night and may be slow to clear some sheltered areas on Christmas Day. After that, fog is unlikely, due to a moderate or fresh easterly wind. Thursday, Christmas Day, will be quite chilly, but it will turn much colder in the following days. Nights will be frosty and frost is likely to be severe from Friday night onwards, with sub zero air temperatures at night. Early indications suggest that the cold, settled spell will continue from Monday next onwards and over the New Year, with moderate to fresh easterly winds persisting, but there is a small chance of a few scattered wintry showers.''

Snowaddict

The retrogression of the high to Greenland certainly occurs on this run, and its a chart like the one below that sets the heart racing...
To sum it up in one sentence = Almost at the point of a wintry outbreak.
Its absolutely stunning... Not because of that particular timeframe, but because of what will follow on from it.

Here's where the retogression begins to take place, this is the start of the final phase of the process which could potentially lead to the wintry outbreak. The key for me is that the retrogression is taking place at the back end of the much more reliable timeframe.





And just look what happens:



On this GFS run, the cold and increasingly severely cold spell, continues for at least 10 days.

In my honest opinion, we are possibly on the cusp of a severe wintry outbreak.

This will have to be an outlier IMO, otherwise I will be shocked. But it does show exactly what could possibly happen over the next 2 weeks.

Indeed, if this run verified, we would see significant snow accumulations, particularly in the eastern half of the country, several ice days and widespread transport disruption. In essence, its winter armageddon, probably a bit too extreme given its GFS, but still a classic set of charts that show what can happen if retrogression to Greenland takes place.

However, I still think that the 31 Dec may be a small bit early for the ounslaught of this potential wintry outbreak, it may take a little longer. But I will now put 40% on the chances of a top classic wintry outbreak occuring as we head into the new year.

Very very exciting times. The normal caveats apply of course and this is but one run, but the signs are clearly there for retrogression of the high and for enourmous height rises over Greenland. If this does take place, as suggested by several of the ensemble members on previous runs, things could get very very interesting.