Cold Spell - Snow & Ice Possible Thursday 8th / Friday 9th

George Sunsnow

pistolpetes11 wrote: »

What models are the TAFs comprised from ?

They seem to change every model run , Im guessing there is also forecaster intuition involved also ?

In Heathrow in December ,which I posted about here,there was uproar and a lot of flight delays due to snow that was not forecast in the previous evenings Taf
Deicers were not ready
They are fallible in winter because forecasting where a snow shower will form and go is difficult enough to do besides trying to pin the trajectory down to a square mile or two
Dublin airport Xmas eve 2010 is a very good example
Prob 40 therefore is a good compromise ie be prepared

Gaoth Laidir

pistolpetes11 wrote: »

What models are the TAFs comprised from ?

They seem to change every model run , Im guessing there is also forecaster intuition involved also ?

The models will depend on the forecasting agency. Met Éireann in Shannon most likely use Harmonie meteogram and general Hirlam charts. The UKMO probably the Euro4. Of course the models are only a tool and it really comes down to forecaster experience and knowledge.

Gaoth Laidir

Snow warnings for paltry amounts of snow accumulation at Dublin, Casement and Cork airports from 11pm to 6/7 am.

EIDW AD WRNG 01 VALID 082300/090600 SNOW FBL < 1CM FCST =
EIME AD WRNG 01 VALID 082300/090600 SNOW FBL < 1CM FCST =
EICK AD WRNG 01 VALID 082300/090700 SNOW FBL < 1CM FCST =

1-3 cm at Knock from 10pm to 7 am.

EIKN AD WRNG 01 VALID 082200/090700 SNOW FBL 1 TO 3CM FCST =

Rebelbrowser

Gaoth Laidir wrote: »

Snow warnings for paltry amounts of snow accumulation at Dublin, Casement and Cork airports from 11pm to 6/7 am.

QUOTE]

Once it snows then in this set up you could get lucky locally. Mind you the RTE weather after the 1pm news suggested very little if any snow around this evening.

redsteveireland

In complete contrast to MTs forecast, the details discussed in this thread and even Met eireanns weather warning, the forecast on the national radio station just basically said it's a lovely day, nothing to see here.

Some drizzle in Leinster, milder with highs of 8-9 degrees and dry everywhere else.

If this was the only forecast I heard today I would be extremely confused getting caught out in wintry showers later on.

patneve2

Expecting some wintry showers here after 11pm, but not amounting to much obviously. Sunday looks very good for northern and western areas, -40s at 500 hpa creeping in, and differently from the mid Jan greenland train, winds will be a good deal lighter meaning longer and cleaner showers. Reckon parts of the North and North West could do very well on Sunday.

Rebelbrowser

redsteveireland wrote: »

In complete contrast to MTs forecast, the details discussed in this thread and even Met eireanns weather warning, the forecast on the national radio station just basically said it's a lovely day, nothing to see here.

Some drizzle in Leinster, milder with highs of 8-9 degrees and dry everywhere else.

If this was the only forecast I heard today I would be extremely confused getting caught out in wintry showers later on.

Yeah up to 1pm the forecasts on RTE sounded pretty wintery but a marked change since. They must have seen some further guidance suggesting very little if any precipitation tonight.

Gonzo

patneve2 wrote: »

Expecting some wintry showers here after 11pm, but not amounting to much obviously. Sunday looks very good for northern and western areas, -40s at 500 hpa creeping in, and differently from the mid Jan greenland train, winds will be a good deal lighter meaning longer and cleaner showers. Reckon parts of the North and North West could do very well on Sunday.

unfortunately those lighter winds usually mean the showers will also die out quicker as they cross from north-west to south-east unless something like a polar low gets involved. So far this winter the Atlantic cold spells have worked out better than most other years. Showers staying confined to the west and north hasn't really been an issue this winter.

BLIZZARD7

Gonzo wrote: »

unfortunately those lighter winds usually mean the showers will also die out quicker as they cross from north-west to south-east unless something like a polar low gets involved. So far this winter the Atlantic cold spells have worked out better than most other years. Showers staying confined to the west and north hasn't really been an issue this winter.

True, maybe we will get lucky and a polar low will form in one of these cold North westerly bursts.

patneve2

Gonzo wrote: »

unfortunately those lighter winds usually mean the showers will also die out quicker as they cross from north-west to south-east unless something like a polar low gets involved. So far this winter the Atlantic cold spells have worked out better than most other years. Showers staying confined to the west and north hasn't really been an issue this winter.

Agreed. It was the sheer strength and unstable nature of the flow in Jan that managed to drive those showers all the way to the E coast and we won't have that in the next few days. The stronger feb sun may give us a small hand but you really can't expect much away from the North and West/Midlands. From an imby perspective, there are two avenues to a significant snowfall in my location in the next 3/4 weeks (I would classify 5cm+ of dry snow as significant in these parts)

a. A trough or front with with PM air wrapping around it giving me a rain to snow event. Models have been showing signs of this for some days, but its always so marginal here..

b. A complete pattern change with a Greenland or Scandi block and cold north/north easterlies. Hard to come by, but chances are increasing somewhat..

JCX BXC

Gaoth Laidir wrote: »

Only Cork and Knock have it as likely. Dublin and Belfast just PROB40

Still in the forecast though, just didn't mention whether it was BECMG, TEMPO or PROB30/40

I'd agree with your stance on it, was the way I learned, however there was ridiculous tension on the Aviation and Aircraft forum as a result of this before so I generally refrain from discussing it.

ninebeanrows

Rebelbrowser wrote: »

Yeah up to 1pm the forecasts on RTE sounded pretty wintery but a marked change since. They must have seen some further guidance suggesting very little if any precipitation tonight.

I really would not read much into it, trust me. Nothing has changed. Widespread wintry showers tonight, increasingly to snow from around midnight. Once trough moves through to full hail / snow but then more scattered. Intensity needed in trough for snow to sea level.

pauldry

just looking at sat24 there looks to be heavy rain coming towards ireland in next few hours followed by wintry showers

West and Southwest look damp this evening but no mention in forecast

Kermit.de.frog

Weathercheck wrote: »

I really would not read much into it, trust me. Nothing has changed. Widespread wintry showers tonight, increasingly to snow from around midnight. Once trough moves through to full hail / snow but then more scattered. Intensity needed in trough for snow to sea level.

Precisely what I was going to say. Midnight on.;)


I expect some accumulations in many areas, particularly the north west but in other places too. Even the east coast has a shot here.

My focus in more Saturday night onward though. Some good stuff for snow fans!

giveitholly

patneve2 wrote: »

Agreed. It was the sheer strength and unstable nature of the flow in Jan that managed to drive those showers all the way to the E coast and we won't have that in the next few days. The stronger feb sun may give us a small hand but you really can't expect much away from the North and West/Midlands. From an imby perspective, there are two avenues to a significant snowfall in my location in the next 3/4 weeks (I would classify 5cm+ of dry snow as significant in these parts)

a. A trough or front with with PM air wrapping around it giving me a rain to snow event. Models have been showing signs of this for some days, but its always so marginal here..

b. A complete pattern change with a Greenland or Scandi block and cold north/north easterlies. Hard to come by, but chances are increasing somewhat..

Would cold from the east/northeast not mean dry weather for the majority of the country

Nettle Soup

Very heavy snow here in Galway. Big beautiful fluffy flakes of white gold. At least 2cm already on the ground. People throwing soft snowballs at each other with glee. Snowmen appearing out of nowhere. Young fellas jumping off the diving board with joy. Galway girls on the prom covered in the white stuff and loving it.

Oh wait...I am hallucinating again. Sorry. I picked a bad day to stop taking amphetamines!

BLIZZARD7

giveitholly wrote: »

Would cold from the east/northeast not mean dry weather for the majority of the country

Generally yes, it is the setup that delivers the most snow to the east though. Also if it gets cold enough and things line up correctly the rest of the country can get snow either through embedded troughs or from the Atlantic systems attempting but failing to break back in.

munsterlegend

Kermit.de.frog wrote: »

Precisely what I was going to say. Midnight on.;)


I expect some accumulations in many areas, particularly the north west but in other places too. Even the east coast has a shot here.

My focus in more Saturday night onward though. Some good stuff for snow fans!

Always a glass half full poster! Where in the country is good from Saturday on?

power pants

Think his glass has been overflowing for some time now

Gaoth Laidir

There's an area of enhanced cumuli/a comma system approaching the northwest in the next hour. Cloud tops associated with the comma are around 8000 m and cooling, so there is a (small) chance of thunderstorms, as mentioned in the latest TAFs for Donegal and Sligo (but mention of snow removed). Look at the loop here and the Rapidly-Developing Thunderstorms tool here.

TAF EIDL 081400Z 0815/0821 22018KT 9999 BKN040
TEMPO 0815/0816 22019G29KT
BECMG 0816/0818 22020G30KT
TEMPO 0816/0821 5000 SHRAGS BKN010 SCT018CB
PROB30 TEMPO 0818/0821 3000 TS
BECMG 0819/0821 28016KT=

TAF EISG 081400Z 0815/0824 22012KT 9999 FEW020 BKN040
TEMPO 0817/0819 23015G25KT
TEMPO 0817/0821 4000 SHRAGS BKN010 SCT018CB
PROB30 TEMPO 0818/0824 2000 TS
BECMG 0819/0821 27012KT
BECMG 0821/0823 29020G30KT
TEMPO 0821/0824 3000 SHRASNGS BKN005 SCT018CB=

downwiththatsor

Gaoth Laidir wrote: »

There's an area of enhanced cumuli/a comma system approaching the northwest in the next hour. Cloud tops associated with the comma are around 8000 m and cooling, so there is a (small) chance of thunderstorms, as mentioned in the latest TAFs for Donegal and Sligo (but mention of snow removed). Look at the loop here and the Rapidly-Developing Thunderstorms tool here.

TAF EIDL 081400Z 0815/0821 22018KT 9999 BKN040
TEMPO 0815/0816 22019G29KT
BECMG 0816/0818 22020G30KT
TEMPO 0816/0821 5000 SHRAGS BKN010 SCT018CB
PROB30 TEMPO 0818/0821 3000 TS
BECMG 0819/0821 28016KT=

TAF EISG 081400Z 0815/0824 22012KT 9999 FEW020 BKN040
TEMPO 0817/0819 23015G25KT
TEMPO 0817/0821 4000 SHRAGS BKN010 SCT018CB
PROB30 TEMPO 0818/0824 2000 TS
BECMG 0819/0821 27012KT
BECMG 0821/0823 29020G30KT
TEMPO 0821/0824 3000 SHRASNGS BKN005 SCT018CB=

Euro4 looks good

Rebelbrowser

Euro 04 still playing ball for many...



GFS likewise save some small parts of the country (sobs quietly...)



Hirlam still making this potentially interesting for the east coast



Whilst the Aperge model doesn't want to know.....

DellyBelly

Those charts look interesting. We got lucky in Dublin and avoided the snow the last day so hoping it will be the same again. We will wait and see

redsteveireland

Euro4 and GFS both look good for me, makes a nice change. Euro4 in particular with that dark pink section right over me, it has a worrying blue border on it though.

Kermit.de.frog

Trough coming in to the west that is bringing in the colder air behind...winds switch northwesterly afterward

http://www.raintoday.co.uk/

JanuarySnowstor

It seems to be all about tonight really as pon is gone by the morning.
We used to complain about 24 hour topplers the trend this year is 12 hour ones lol

Kermit.de.frog

JanuarySnowstor wrote: »

It seems to be all about tonight really as pon is gone by the morning.
We used to complain about 24 hour topplers the trend this year is 12 hour ones lol

Patience, the weekend is coming

Kermit.de.frog

munsterlegend wrote: »

Always a glass half full poster! Where in the country is good from Saturday on?

Primarily the west and north but everywhere is at risk of some snowfall from Saturday evening. Some frontal snow possible Monday night too especially in the western half of the country.

Oscar Bravo

Temperature dropping quickly at Knock .1800 was 4 degrees with a dew point of 3 degrees. 1830 2 degrees with a dew point of 2 degrees.

Kermit.de.frog

That cold front coming in to the west starting to look tasty. Some departing end snow on this I reckon.