Storm Ciara - Strong Winds & Potential Snow **TECHNICAL DISCUSSION**

leahyl wrote: »

What does that mean exactly?

528 dam (decametres, 5280 metres) between 1000 hPa and 500 hPa atmospheric pressure. Cold air is more dense so there is less distance (thickness) between those two atmospheric pressures as the air in between gets colder. It's a good indicator of snow potential but not a guarantee by any means.

Deleted User wrote: »

Can we possibly have a separate thread for the 'WHOITE GOOLLLLD' folk?

Three days of sustained wind and rain is a weather event worthy of itself.

I have it ready earlier just in case anyone wants a separate thread for the wind and the snow :pac:

MT's thread on Storm Ciara is here

https://www.boards.ie/vbulletin/showthread.php?t=2058051890&page=18

It is due to affect the country for a number of days. There are two very distinct and parallel affects - one is wind which is a big issue, the other is snow particularly in the west.

This thread is for the latter. If you are more interested in the wind or potential flooding please consult MTs official storm thread.

We have had a fairly mild winter so far but early next week the cold embrace of the Arctic will be pointing this way like a big vindictive finger and it's packing high cloud tops and snow showers in abundance.






Sunday night

On Sunday night much colder air will be moving in across the country from the northwest being driven through on very strong northwest winds.

Increasingly heavy showers in Connaught and Ulster quickly turning to sleet and then to snow overnight with accumulations here by Monday morning. Perhaps 2 - 5 cm should be anticipated by morning in many locations here.

Less and much lighter showers further east.

Over Munster and south Leinster showers will probably be more sleety rather than snow overnight.

Monday from sunrise

Early Monday sunrise more significant pulses of rain will move in to the southwest. As this advances through Munster and Leinster it should pretty much immediately turn to snow as it engages the colder air with between 2 and 8 cms likely in many areas across Munster and Leinster. This is potentially disruptive in some places.

After this clears later Monday evening snow showers will continue packing in to the west and north giving appreciable totals which could be in excess of 8 - 10 cms in some place overnight Monday.

Showers lighter and more scattered further east but could contribute more to snow already lying here.

Widespread snow showers through Tuesday. The snow showers die back to western coastal counties on Tuesday night.

To recap Sunday night to Wednesday morning:

Main risk of disruption: Snow showers (longer period of snow through Munster/Leinster on Monday)
Areas most at risk in order: Connaught/Ulster, South Leinster, Munster
Low Temperature: Temperatures will be near or just below freezing during snowfall and over snow cover particularly in the northwest

Some disruption is possible anywhere really.

Just seen ventusky has some snow for the capital.
And it looks like someone has finally given the city an appropriate name 😀

Snow will be the bigger disruptive influence rather than wind over the next few days.

Pangea wrote: »

To my surprise there is a light dusting of snow on the hills here in Donegal

Tops of some of the Mayo mountains got a dusting overnight also.

Deagol wrote: »

In fairness, the lad who got the yellow card had it absolutely right.

Regular normal bad couple of wintery days in Ireland. A bit windy, a bit wet and a few wintry showers.

I have no idea why this forum seems to be full of people wishing for natural disasters that will cause misery for 'other' people rather than thanking whatever deity you chose for a quiet life.

I ,for one, am glad that as in 80% of the time your doom and gloom predictions of 180km/h gusts and 10cm+ of snow is comprehensively being shown to be complete and utter tosh based on GFS model nonsense. Why anyone who knows anything about weather even looks at the GFS I have no idea as it is 100% time wrong on anything over 24 hours.

I have to say, I'm pretty much in agreement. I said similar myself in the past few days that I was not expecting this storm to be anything particularly noteworthy - a pretty much regular winter storm albeit with longer longevity than usual. That in itself, combined with a fair drop of rain, may well cause a bit more damage especially when it comes to uprooting some trees. Regarding the GFS model, it started off forecasting this as a "mega" storm and it has gradually tapered off in it's prediction of mass destruction as T-0 has drawn ever nearer and is now looking like an ever so slightly stronger than normal winter storm with longevity being the unusual part.

Across all the main models I'm not seeing anything excessive. What I would agree with is that many inland and eastern parts (where strong winds are not regularly experienced) are likely to have gusts around the 100 km/h mark or a little above for parts of tomorrow, particularly the first half of daytime hours. This in itself does lend itself an element of caution as Sundays are a time when a lot of people are out and about......Sunday walks, mass goers, local football matches, etc.

Snow wise, I'm just not seeing the levels of snow being predicted here, for the vast majority of the populations. High ground is pretty much a dead cert. I'd imagine areas above 200/300m will likely do quite well, especially in northern and western areas and also in the southern half/third of the country later on during Monday (still subject to change). It will be cold, yes, but meaningful/disruptive depths of snow look to be mainly in the areas just mentioned. Even if that more prolonged and heavier area of precipitation passes across (the southern half of) the country during Monday, I can envisage most populated (ie: low-lying) parts to experience a wintry mix of rain, sleet and wet snow with a fairly strong breeze. I can also expect reports coming in from many low-lying parts away from the north and west saying that the snow is not sticking or it's only sticking on cars and grass and roads are just wet.....that kind of thing.

Having said this, I love a good fall of snow and if I'm wrong on the above, I'll be delighted but my gut feeling an analysis of the charts sways me on the side of no meaningful snow for most people. Fingers crossed I'm wrong.

Finally, as is the usually the case with GFS and as touched on earlier in this post, Ciara was initially going to be a disastrous storm and as is often the case, it has backed down to near normal levels of intensity so in true form it is currently showing a fairly powerful storm for next Friday and for Tuesday 18th it is showing an extremely powerful storm with winds gusting in or around 150 km/h in inland parts including the south and east, Dublin etc, during daytime hours. Maybe it will happen and some day it will but I could bet a fair wad of cash that it will be tamed down a huge amount, at the very least. The 06z run is rolling out now and I would be surprised if that is not completely different.

If this morning's ECM is to go by, rainfall amounts could be just a big an issue as the wind over the next 24 to 36 hours.

Gusts up to 65 knots forecast at Shannon tomorrow morning. 60 knots at Knock. Wild enough!

A squall line developing West to East later today so 60 knots within that not out of the question. Around 1pm to 3pm I'd say

Barely any rain fell in Sligo since thunder last night