Jan 2025 - Snow & Freezing Conditions - Discussion PART II

It's back…

Are we neighbours 😮😮

🤣

. If you remember back in 2000 and 2010 the cloud cover wasn't an issue because the upper air temperatures were low enough. Also the lack of a severe frost last night would indicate the airmass isn't as cold as projected. If it was the mild sector that WolfeEire spoke of yesterday evening wouldn't have inhibited a severe frost forming last night. Anyway I am coming across as ungrateful, the scene outside certainly beats the usual blow torch south westerlies we have to contend with in January. Although I appreciate some posters might like blow torch south westerlies right now

It seems despite advances in weather modelling the Greenland area cannot be modelled accurately at all because heights there in recent years have been consistently over egged only to be far weaker come time.

Perhaps it's something to do with the topography there?

Expected/hoped for more of a thaw here near Mallow today. Still roofs covered in snow and cars. The footpaths are lethal in patches and roads a slushy mess where not treated.

Sunny now with a thaw setting in. Surprised by the snow we got this morning. Will we have much snow later tonight?

Just south of knock airport

Elevation 159m

Snow just kicked off again here big time! Started as rain so I said I'd take the dog out and check the roads, maybe chance shops in the 4WD, but it escalated fast! Not risking it even with 4WD, visibility is terrible.

Heavy snow now and wind picked up too, it's a whiteout 🙂

Nth tipp/laois/Offaly borders, 140m

Question for you:

Can anyone explain why there were no streamers like in 2018 and 2010 coming on to the East coast during this episode?

Not one!!

I mean the wind was from the east/northeast like during the other major snowfalls??

And we're off again... snowing North Kilkenny 180m asl. Surprised the showers have made it down this far

The upper temps were not cold enough so there wasn't enough of a differential between sea and air. You need minus 8 or lower uppers, preferably lower than minus 10 uppers for convection to kick off

Storm Emma local farmers had a stand off with council as they were clearing local road and they shouldnt have been.

I do agree with alot of what you are saying though. Drove through local town. Footpaths are leathal as no one wants to clear them and its someone elses job.

Long time lurker on this thread. Thanks for the pictures and updates! Ne'er a flake to be seen in Dublin 9 but it looks like a lot of the country got a good pasting. It seemed sleety for a while here yesterday afternoon but we had nice blue skies this morning. Stay warm everyone!

Lol 😂 It has stopped here now , but the skies are still full of it. If you get what I mean.

I love in SW Kerry (castle cove) and I have no pictures, but We've not had a shower today that's not been hail, sleet or snow. Very rare for us, the oceans next door! Surprisingly, I have a few weather apps, and not a single ones shown this for us, just rain.

The bigger issue with Greenland heights is shortwaves around Iceland that aren't initially modelled very well or at all, and they generally spoil the party. You are just going to struggle big time to get strong WAA and a clean rise of heights to the NW once that bulge around Iceland forms, it's a bad omen. You'll just end up with a weak wedge, unless your blocking development is coming from something else (dropping Arctic high or Scandi block retrogression west for two examples).

Shortwaves are never going to be reliably modelled at the Day 7-10 range, they're really quiet the short term development. It's why so many Greenland blocks look so good until we start to get into the reliable and suddenly the shortwaves develop into something far more troublesome. They're an absolute nightmare for developing to the point that they start interacting and phasing with LP systems out to our SW, and they then end up blowing up lows to the point the weaker block can't hold the LP back from barreling through.

We got just enough on the right side this time that the Azores LP was able to slide to our south. On some of the runs in the buildup, that phasing went all wrong and the low went far too north and would have been game over.

I've attached x2 GIFS below. In the first, one of the 'good' runs before the New Year. Look around Iceland, shortwave develops but it stays out of the way sliding well into the north sea as a separate entity to the Azores low. WAA occurs and a nice high is developing, and the Azores low is pushed well south and is going to slide into south France/Portugal. So no frontal event but you have a stronger block and colder air progressing south.

Now one of the runs from the 1st of January. Far more becomes of the Icelandic short wave and it starts interacting with the LP to our SW, and the Azores LP now is pulled much further north. You lose out on the WAA and the block is much weaker. So we got our frontal snow event out of it in the end but with no block now to maintain any sort of locked in pattern. The wedge of high pressure that has formed still has managed to do just enough to keep wintry weather about in the wake of the sliding LP.

That's my take on it anyway. I imagine as more recent data starts feeding into these AI models, that those models will dangle a lot less carrots in terms of strong blocking developments. I think shortwaves have caused every Netweather meltdown in the last 10 years. We should probably expect them more in fairness. I did say early on in the FI thread that the Greenland blocking on the GFS in particular was not going to come off as strong as those runs were says, based on recent years.