mountain shadow

Certainly some exciting and disturbed weather coming up for the island, particularly areas exposed to a sustained North Westerly wind. Low pressure systems passing to the North of Scotland will have just enough amplification behind to bring in some Polar air. Now, i wouldn't expect much snow to low levels as the coldest air would have mixed out, however, hilly areas could see some decent falls, and throw in the strength of the wind then blizzard conditions likely in some favoured areas, Glenshane or Pomeroy's House could be a choice spot!! Even for those not fortunate to see snow, it will be bitter with a marked wind chill where ever you are. If you haven't got your hat and scarves out yet, now is the time.

Hi festivalking A negative AO is good in that it means cold air will be spilling from the Pole into the mid latitudes, however, only the presence of a negative NAO will bring it the direction of these islands of mid latitude. So, whilst the AO is keen to go negative by mid month we need that NAO to go negative as well.

Not one member has the NAO going negative over the next 15 days and until it does there can be no sustained spell. At least there will be some lowland snow in the North West from the brief passing cold air as lows move North of Scotland... http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml

Echoes my thoughts. And with the PV segment unable to shift from Greenland it seems any decent cold spell is a long way off. The Start thread quietness isthe bbiggest worry.

Thanks Fergie, it is always the case that uncertainty decreasess in a zonal pattern. I think most have given up on any sustained proper cold until after the 20th at least and possibility into the new Year. The MJO is a little better than yesterday with a couple of runs showing a decent amplitude in Phase 8 which would encourage heights into Southern Greenland. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/foregfs.shtml

Good luck with the forecast. Here's hoping the December cold comes in over the festive period.

Well Steve, Whilst your forecast might be similar to this sites, many, including myself, would still like to read it. Indeed, yours is one of the few forecasts I look forward to each year. I hope you reconsider.

The MJO could be supportive of Greenland heights rises from around the 8th December onwards as it should progress towards Sectors 8 and 1 which aid blocking the Greenland local. Clearly the further away from the centre the better. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/foregfs.shtml

If we had a raging Polar Vortex then I would agree with this, however, the PV is fragmented and a displaced Azores High towards our shores is not necessarily a bad thing. Many a cold spell has began with a UK local mid latitude high. As the 6z GFS P shows, it can retrogress weswards and then Northwards in reaction to the East moving trough to give a Northerly. Again the 8th December showing a possible cold snap. One thing we always need to get rid off before a cold spell can kick in, is the Greenland vortex segment, hopefully this is the start of a trend to increase upper height in the Greeland area. https://max.nwstatic.co.uk/gfsimagesnew/gfs.20141127/06/264/h500slp.png

Fair doos Neige, but I was only going by the opening thread which indicates a greater chance of a strat warming with a measurement below 110.

I notice the solar flux index is moderate at 167 units, Ed indicated in his opening post that readings of 110units or less can increase the likliehood of warmings. Whatever happens in the Stratosphere this Winter, I don't think we'll get much help from the Sun. http://www.wm7d.net/hamradio/solar/index.shtml

Model output rather tedious at the moment whilst we wait and hope that wave activity on the Polar Vortex delivers. Seems likely now that we are at least a month away from any snow and ice.

Models are wet and windy this am, however for those coldies feeling downcast, check out the start thread. Been a while since I've seen May Hugo so animated. far FI might start to become interesting.

Ok, see you in Mid December.

Well the OPI will certainly be tested this Winter Sundog. Personally, I am happy with the way the models are looking at present, particularly in the upper atmosphere. The coldest and snowiest of winters are often preceded by very wet Novembers. This for me is due to low pressures systeme stalling in the Eastern Atlantic as they are impacted by the relatively higher pressure to the North. Eventually the wave lengths will change to give our cold.

I think the OPI only really works at the extremes of it scale. This years OPI was extreme so a high probability of at least two winter months with a -nao

The one South East of Greenland John.

It is said enough, but it is really is waiting game, but this year will deliver. As long as the jet remains meridonial we will get our chance. I liken the jet stream to a piece of rope, with a meridonial jet, its like giving it a flick and watching the ripple move along. In time, if you remain in the same place you will end up in a trough, which will hopefully be sometime in early December. Once again though, those pesky Southern Greenland shortwaves scupper any hope in the next 2-3 weeks.

Pouring down again. The general conscenus appears to be we will get a very wet 6 weeks or so with the cold and snow arriving around the end of December. Fingers crossed.

Then post a chart which shows what you mean, not what doesn't. Didn't mean to be patronising. I read your post, and saw a chart which didn't make sense to what you said.

?? Suggest you go to learning page and read up on the Polar Vortex. You certainly cannot get an idea of where it;s at from that view. The Northern Hemisphere view shows a different story.

Hopefully short term pain, for longer term gain. The warmer air pushing North feeds the WAA, hopefully when it comes down on the CAA, we will be on the cold side of the block. Need to see more heights into Greenland.

That tomorrow thing was there yesterday though indicating it should have been issued today.

On Friday night, the BBC Northern Ireland forecaster using information from the Met Office said the following " The weekend would be a good weekend for walking the dog, blues skies and temperatures around 10oC". The only rain on the NI chart was in the Irish sea, slightly hugging the County Down coast. The reality was it rained all day Saturday and most of Sunday in many parts of Northern Ireland. The reason I use this, it to remind people, that even 12/24 hour forecasts can be significantly wrong, never mind looking a month or a season ahead. The state of the vortex at the present time is clearly favourable towards a higher probability of colder weather hitting the UK, however, the Met Office, will always sit on the fence until they are sure. As said previously, forecasting a wet and windy Winter is easy and likely to be correct 8 times out of ten.

The GFS is slated because it is the worst performing model of those three. That is fact