Su Campu

Ulster again looks favourite for snow. Further south the frontal gradient will dissipate, meaning precipitation will fizzle out later in the evening. With that little low pressure centre forming to the south, it will probably mean an easterly marine layer along the east coast, so a real battle of physics at play to decide what Dublin gets. Very little, I would say.

The ECM high res Theta E shows the warm seclusion from Wednesday's storm currently crossing us from the north, with cold following on behind in place for tomorrows precip. By Wednesday the standard run has that cold northwesterly advecting sub-522 dm thicknesses again. After that it has a zonal setup in a restrengthening polar vortex.

That blob over Ulster looks like it will intensify and form a concentrated band of snow for Leinster in the next hour or two. Should be snowing in Dublin around school time. A nice little bonus for us as here as we got a raw deal this week.

While I do think the 91 knots was a mistake (synop reports the gust as 41 m/s), to say that it should be the same as in the METAR gust is wrong. Synop gusts refer to the previous hour, while METAR gusts refer to the preceding 10 minutes. Therefore in this case (18Z report) it is possible that there was a massive strong gust (but not 91 kt) some time in the periods 1700Z-1720Z and 1730Z-1750Z. The METAR (1730Z and 1800Z) gusts were taken from the periods 1720Z-1730Z and 1750Z-1800Z, respectively. It is, of course, also possible that both METAR and synop reported gusts are the same if the gust occured during the METAR periods. [/pedantic]

2300 Belmullet 47 gust 65 kts Mace Head 47 gust 61 kts Mace Head live wind

ASCAT winds this tonight. The backbent occlusion has a sting in the tail for Connacht.

Knock still has 15 cm of lying snow at 10 am, Lough Fea 11 cm and Castlederg and Ballypatrick Forest 5 cm

Snow depths at 8 am: Knock Airport 15 cm Lough Fea 8 cm Castlederg, Ballypatrick Forest 6 cm

With the wind increasing the snow will not survive and dewpoints will rise all the time. It looks a memorable event in Derry, though it's a pity Magilligan No. 2 is not reporting live snow-depths this morning but both Castlederg and Lough Fea report 6 cm at 7 am.

Well that was one hell of an airmass from Baffin Bay to survive the Atlantic track across and still produce those snow streamers to low levels. Fair play to all those who scored, just no forcing available for more than a couple of flurries here in north Kildare. Just to highlight how much colder the airmass was than Saturday's, the 850 hPa temps were roughly the same, but this level was around 150 m lower down. Regarding the incoming storm. It is a classic Shapiro-Keyser setup, therefore I think many people will be surprised by the sting in the tail on THURSDAY. Some areas will see stronger winds then than they will tonight as the back-bent occlusion reaches us. We need to watch water vapour imagery for signs of a stingjet, which could make things interesting across the centre third of the country through the 2nd half of Thursday. Behind that then there looks to be another brief grapple with graupel and snow for some, maybe not quite down to sea level.

The northwest...as in Scotland. There's nothing of note more than what's there already for Ireland. Conditions were never there for a proper snow setup. Too much low level modification took place and it's too windy for any real cooling at the surface. 850 temperatures and 500-1000 thicknesses are not the most important factors to look at when it comes to marginal situations. Some more snow above 150-200 m but don't expect much any lower down.

Patrick wrote this nice piece about it on Irish Weather Online http://irishweatheronline.wordpress.com/climate-of-ireland/historic-weather-events/night-of-the-big-wind/

Depressions will initially track parallel to the isobars in the warm sector, changing to parallel to the isobars just ahead of the warm front as the occlusion process takes place. This means a curve to the left (north), away from us. The Rosenbloom Rule states that rapidly-developing lows generally track to the left (north) of the model forecast track. Well this used to be the case, but I'm not sure if the latest updates have tackled this.

Just something that's bugged me for quite a while now. We have a wonderful resource in the ECMWF, which is supported by tax revenue from 30 countries. Maybe THE best model in the world, however, apart from a few basic model fields, the vast bulk of the model data are not freely-available. I know some national agencies (notably Iceland) have at least better time intervals available, but still with only the basic fields (and CAPE, in the case of Iceland). Compare this to the US, from where we have an endless list of models fields available from the GFS, NAVGEM, etc., freely-available to the World and its mother. Tax dollars pay for these, so why can't our tax euros/pounds/krona/francs give us access to data that we pay for?

Kerry reached 15 °C (so somewhere between 14.5 - 15.4) for several hours on the METARs today. Could be a bit of Föhning from the Reeks going on..

14 °C at Kerry Airport now METAR EIKY 010930Z 21014KT 9999 OVC019 14/12 Q1014 RERA=

Mullingar has been reporting <50 m visibility in the last few hourly synops, and temp/dp most recently -4.9/-5.6 °C at midnight. It's reported Light Snow but that is most likely instrument error. AAXX 29001 03971 17190 /0000 11049 21056 30269 40401 53004 69901 77187 88/// 333 88/01

Some streamers going to affect the east coast now. Nice wind direction for maximum sea-fetch. Temperatures are already down below zero so if they don't fall as snow they could be freezing rain.

Not much, actually. Looking at that chart the low centre will follow the thickness contours (so more or less along the coloured contours) for a bit until it starts to occlude and curve to the left (north), away from us. What it would do would be help pump heights northeastwards and contribute towards any collections that are going around for a Scandi high...

The Euro4 and GFS (soundings) are showing marinal partial thicknesses (850-1000 hPa) of 1295-1300 m to the north of the low tomorrow, made up of a saturated and almost isothermal layer. I would prefer to see 1290 m, or a drier boundary layer, to allow for evaporative cooling. As it looks now only Ulster may have any appreciable cooling tomorrow, but even at that probably only giving sleet or wet snow to low levels. Saturday looks much better, especially in the afternoon and evening. Any showers should deliver hail and graupel.

Move along now, nothing to see here. Come back in January. I still fail to see where the evidence for optimism sprung from. Maybe people are beginning to subconsciously become brainwashed by the likes of Jimmy Maddman's ramblings, because of course he says doesn't use the models! ;-) ECM is king and has stuck to its guns. If I were a betting man I would go for a Rosenbloom northerly shift in the 27th's storm track. Too far north and too much modification for a proper snow event, apart from the north.

The only one the was ever showing anything to raise an eyebrow - and which is doing so now - is the GFS, which has a bias for overdoing cold outbreaks. It shows the 27th as the only window - and a narrow one at that - for snow, with the UK a bit better. The other models are not, and have never been, having any of it. Let's all now just turn to page January...

Highest sustained 10-minute wind was reported at Sherkin Island some time between 0000-0100 on Friday morning. 27 m/s (54 knots/62 mph/97 km/h).

Smithy, it was 70 mph full crosswind, which is no joke and is well beyond the limits of aircraft. Sustained winds touched 40 knots, which is also out of limits, especially for the Ryanairs (737-800s). Add to that a wet runway and these limits drop to even lower. It had been widely progged that winds would be least severe in the north. Just because you live there doesn't mean that what you get is what everyone else got. Try actually thinking next time before typing.

11.9 m significant wave height reported by the K2 buoy southwest of Kerry at 0600 this morning. This is the average of the biggest third of the waves, so some individual waves will have been bigger! Surf's up in Lahinch this morning, guys!