Ladyofthestorm

More experienced model watchers will be pretty happy with the way these models are churning out colder weather prospects. Remember the mantra the trend is your friend. All roads lead to cold and very cold. Enjoy this week. The colder weather is coming in from the North end of week , late January looks interesting. Who remembers the doom and gloom from last week when the SSW wasnt quite what they expected. Look what's happened , it's even better! .

How does the ECM compare to it's ensembles?

Matt best post of the whole winter!

Sending out a warning shot from the GFS model 18z had that potent NLy with snow arriving on Saturday 13th The ECM then confirmed. Fantastic BUT! 0z has the potent NLy arriving 2days later than this. Much drier, higher pressure less obliging to move westwards.

You are quite correct to call it cold.

It's onto something

Agreed!

I've seen a few confident tweets mentioned in Amy Butler's feed about colder weather in Northern Hemisphere not requiring a SSW. I think 2006 was the last time , cold dry Jan and Feb, after a really wet and stormy first half, March and April then was really snowy. It can and does happen.

My suggestion is look towards the teleconnections for clues. That negative NAO is critical for where our best chances of colder weather is coming from. That Greenie High is the source of colder weather, not a technical SSW, ( that might happen later), It's been forecast to happen all winter! First on the longer ranges and now quite dramatically onto the GFS, ECM etc, as always the devils in the details for snow casting and it's pointless and fruitless exercise. The settling down of the weather in January in my mind is a blessing in disguise, the trend is cooling which is also needed. The magic bullet snowy easterly , unlikely to bring snow. The major drivers are the high pressures which are mobile and dynamic this winter , big and high but moving around alot so not blocking anywhere for long. This situation won't last for much longer. Last night that was a huge Greenie high forecast , even moderated over time and model run, still high and big.

Trend is the friend. Temps on way down.

Hi Matt I'm just catching up , a huge thankyou for posting this up, I very much agree with all that you say. When I read Tamara, Eagle Eyes and Catacols posts, to name but a few.I dont sometimes understand it , but catch glimpses of what I do understand. The big atmospheric drivers in our part of the world will definitely play significant roles... We live at the end of a conveyor belt of a rather large ( thinking energy) duck pond. Tamaras post from a few days ago struck a cord when she mentioned the colder air could be as a result of pressure building to west and north rather than an SSW zonal wind reversal. I suppose we should be looking at negative NAOs for this. I have had my hunch on this for a while too, but I am no expert.

I have my rising suspicions now that colder weather for UK will come from a negative NAO with Greene high, blocking the Atlantic machine rather than an SSW reversing the zonal winds. The warming about to take place looks like it will stretch the PV , rather than displace it .it's a pretty fragmented /messy PV anyway. All change for January I think. A later SSW will be a technical SSW and this will reverse the winds. I would actually look at the GFS for these clues long term as it's resolution 6 days and less isn't brilliant. But it can

Ok A reversal of the zonal winds looks unlikely , this time around, but the experts are bullish about a negative NAO in Jan.

I was under the impression from the models that a SSW is going to happen , it's just unlikely to have any significant impact on the troposphere therefore zonal winds.... yet.

I think it's too easy to get wrapped up in individual runs of models when it comes to SSWs , patience it's coming and when it does it will be a cracker

Agreed, Trends are always friends and the ensemble models are actually in very strong agreement, pressure rising to the North, and decreasing to the south This ties in with this temp chart above and with what is beginning to unfold on the stratosphere front. Indeed on the longer range models you can see the effects of zonal wind reversal happening. I am very hopeful of something colder and more seasonal in January. Though I am sure it will come come from the North and NE this time not continental/ Siberia, true beast from the east. The west of Scotland is definitely having a true el Nino winter so far, still waiting on the NLy blast , it is not far away.

To be honest , Scotland and North England is already there. Ragged and already fragmented PV . It really isnt going to take too much.

Given the incredible amount of Nacreous cloud I saw a few days ago, It's has to be at least -85C in the stratosphere ( non polar regions) the now. And yes 1984, 1995, 2009, 2010, 2013 , and now this year are pretty good markers . Some say we will see them more die to climate change, not surprising as the polar stratosphere becomes unstable, and ragged and more likely to leak it's colder "air" to sub polar and mid latitude regions .

As always the trend is your friend . Its on the way down , temps and Zonal reversal, I note the increase first before it reverses, significant aspect of this SSW coming up and note that it doesn't fully recover and is significantly weakened . The GFS nearly always sniffs the trend out first . It feels like its got better longer term resolution than the ECM. That shouldn't be surprising as it's runs are longer. I noticed last night the 18z dropped colder weather signal into the new year and flattened the heights in the Atlantic, this morning it's back again ( to stay)

We live, allegedly, right on the middle of the the mid Atlantic drift. Subject to the brunt of the Atlantic wrath... Isle of Lewis Right now a WARM front is straddling our island and it's 1C with sleety precipitation. This is not normal or typical conditions. 10C yes not 1C Big Shouty Letters It not NOT MILD

I keep ending up back here and how similar this December setup is to December 1983 set up. The euro slug with empowered Jetstream , and then bang , the high pressure are over Iberia shifts westwards . Letting a flood of NLy break out in January Something to bear in mind , I really don't think synoptically we are far away from this set up.

ECM and the GFS both operationals running warm the mean.

Agreed! We have a very fragmented almost Split PV. The wintry weather will come in from the North or NW. To be honest I s the the direction that is significant but it's origin.

18z GFS a huge mild outlier. I would say the ECM is moving towards the 12Z GFS solution. Hang fire . Models all over the place

Personally, I think now is the time to actually stop model watching for the Christmas period as there are still huge number uncertainties to be ironed out. The ensembles for the major models are basically showing up as mild outliers on the operational. We should wait about 48 hrs for better agreement ( though the models agree to be all mild outliers around Christmas. ). Look at those green lines , as all models assume the high pressure over Atlantic flattens bringing in a warm front. The NLy all but a brief cold snap just before Christmas. Not confident on that one either. Nearly every run of the model colder than the operational. ( Especially true for the ECM) Is this the classic GFS picked up a wintry signal , drops it days 8 to 10 then picks it up again? Source : Wetterzendrale