Cold Spell Late Feb/ Early March Technical Discussion only MOD NOTE POST #1

kod87

A much milder centre to the low pressure at 96hrs on the ECM.

munsterlegend

kod87 wrote: »

A much milder centre to the low pressure at 96hrs on the ECM.

More in line with the GFS then? This low seems to be blasting the block away very quickly.

JanuarySnowstor

munsterlegend wrote: »

More in line with the GFS then? This low seems to be blasting the block away very quickly.

The ecm is kind of the middle ground between gfs and UKmo
Still time for upgrades.
In the meantime ppn has been upgraded for the south Tuesday and Wednesday!! Looks disruptive

munsterlegend

JanuarySnowstor wrote: »

The ecm is kind of the middle ground between gfs and UKmo
Still time for upgrades.
In the meantime ppn has been upgraded for the south Tuesday and Wednesday!! Looks disruptive

By the coast or inland as well?

M.T. Cranium

That ECM depiction for days 5 and 6 would only need to be slightly further south for the snow to continue, heavy in most regions, and even on its maps as shown there is potential for snow to continue inland. Given some of the other output, I don't feel like we have anything very reliable for nailing down any sort of forecast beyond Friday morning.

The UK and ICON models appear to be holding the cold in place and weakening the low near Brittany where it either stalls or loops and drifts east. GEM has less mild air incursion and keeps trying to reset the cold blocking as far south as possible.

The Franz Josef Land high has spread out east-west (not the one you see on land) over the Kara Sea at 1052 mbs. I don't think the models had a very good handle on its interplay with the Scandinavian high and there may be a resulting bias towards Greenland taking over. The implication for western Europe would perhaps be that the cold would reload several times in the next two weeks. Extremely low temperatures in February have usually lasted 3-5 days with at least one return to near record cold in the past cases.

stephenjmcd

M.T. Cranium wrote: »

That ECM depiction for days 5 and 6 would only need to be slightly further south for the snow to continue, heavy in most regions, and even on its maps as shown there is potential for snow to continue inland. Given some of the other output, I don't feel like we have anything very reliable for nailing down any sort of forecast beyond Friday morning.

The UK and ICON models appear to be holding the cold in place and weakening the low near Brittany where it either stalls or loops and drifts east. GEM has less mild air incursion and keeps trying to reset the cold blocking as far south as possible.

The Franz Josef Land high has spread out east-west (not the one you see on land) over the Kara Sea at 1052 mbs. I don't think the models had a very good handle on its interplay with the Scandinavian high and there may be a resulting bias towards Greenland taking over. The implication for western Europe would perhaps be that the cold would reload several times in the next two weeks. Extremely low temperatures in February have usually lasted 3-5 days with at least one return to near record cold in the past cases.

Quick question MT and it might seem a silly one. Latest met forecast has rain and sleet tomorrow afternoon. Any idea where they're getting this from? Anything I've seen myself shows nothing but snow from tomorrow evening although I'm still in the early days of model reading. Thanks in advance

ninebeanrows

no agreement between the EC and UKM this morning

kod87

Weathercheck wrote: »

no agreement between the EC and UKM this morning

So what happens friday is all still up in the air (literally and figuratively)

Gaoth Laidir

Gaoth Laidir wrote: »

Snow radar for Germany. Note the dying out of showers over land.

Just look at the variation in this morning's snow depths in northern Germany. We have 20 and 25 cm right next to only 1 cm. Huge variation in the space of just a few km and all due to the geography of the area.

https://weather.us/observations/mecklenburg-western-pomerania/snow-depth/20180226-0600z.html

ninebeanrows

A brief look at the models this morning before the EPS comes out shows there is still significant uncertainty for Friday onwards with the passage of the low and whether it will be snow to rain, pure snow or snow not getting north of Dublin (still cannot be ruled out).

I certainly would not make the call but believe the UKM outcome more plausible.

M.T. Cranium

This rain thing, let's put this in perspective, back in 2010 also when we had some really good set-ups for snow streamers, you would sometimes get a few reports of rain, sleet, graupel, just right along the coast and for a few minutes at a time usually in the early stages of streamer formation. Don't forget, the water temp is 8 C, this air gets out over that and small parcels get warmed up faster than others in the early stages before larger and more powerful streamers get going. So nobody should be too surprised or alarmed to see the odd report of rain on Tuesday. I don't think it will be much of a factor compared to the heavy snow potential.

The other big point of discussion is likely to be alert level -- basically there is no reason outside of operational policy to be anywhere lower than orange right now, and I think the chances of a red alert by Wednesday are 80-20. So this current yellow alert is really an alert for an orange alert.

Oneiric 3

Snow accumulation chart (Arpege 00z) up to Wed 18z. Once again, take this more as a guide to where the probability of the heaviest snow showers are likely to occur, rather than taking the values stated in the chart at face value.



This model always had the showers starting off as rain/sleet in the east initially but readily turning to more snow as the colder air becomes entrenched by Wednesday.

Probably stand alone amongst my fellow westerners, but am looking foward reading the snow reports from the east this week without having to experience it to any great degree, because the current spell of weather is the nicest we have seen here in the west since God knows how long, and makes me realise how much I detest the painfully mediocre and mundane maritime climate that this country experiences 99% of the time. That is not say that I don't love my country, but its climate is pulp.

ninebeanrows

Latest Harmonie has those snow showers getting well inland tomorrow night...Looking at the 6z output Greater Dublin will be at a complete standstill Wednesday morning

Places like Kildare could do very well as snow showers slow a little inland and dump their goods.

Harmonie has streamer action lined up on Dublin from 10pm tomorrow through until 10am Wednesday, 2-3cm an hour, some sweet spots could total 20cm by Wednesday lunchtime but more generally 5-10cm

YanSno

I suspect 6z gfs will be very different regarding the low on Friday as more data is collected and complied for this run

munsterlegend

YanSno wrote: »

I suspect 6z gfs will be very different regarding the low on Friday as more data is collected and complied for this run

The trend seems to be going further west and north. I am hoping further south and east but this will go down to the wire I'd say.

dacogawa

Flurries arriving on the north east coast now, near Downpatrick

ninebeanrows

ICON is what we want to see for keeping the cold in and getting an all snow event.

Similar to UKM

stephenjmcd

Weathercheck wrote: »

Latest Harmonie has those snow showers getting well inland tomorrow night...Looking at the 6z output Greater Dublin will be at a complete standstill Wednesday morning

Places like Kildare could do very well as snow showers slow a little inland and dump their goods.

Harmonie has streamer action lined up on Dublin from 10pm tomorrow through until 10am Wednesday, 2-3cm an hour, some sweet spots could total 20cm by Wednesday lunchtime but more generally 5-10cm

Thanks for this. Far too many people relying on the snowfall accumulation graphics and saying that places along the coast in Dublin etc won't see snow at all. Some are in for a rude awakening

cherryghost

GFS rolling out, so far we are getting a deeper low and the cold pool is extending slightly further west... so far.

LP is further east and north before a westwards swing, we are still battlegrounds scenario but all areas could get 6-12hrs of heavy snow from Thursday evening/night, before changing to sleet/rain Friday afternoon into evening. DP should still be negative for the most part despite the milder air moving northwards.

- The GEM wants the cold to hold out for another 24hrs, absolutely pasting the country as the LP stalls south of the country.
- UKMO more or less the same boat as GEM
- FIM was modelling similar to GFS last night but in current rollout it wants to agree with GEM and UKMO
- ICON agrees with GEM, UKMO and FIM except it wants the low sliding eastwards, south of the country.
- NAVGEM has an identity crisis, as its between GFS and the rest.

JCX BXC

Looks like Fridays low is slightly east in this run.

Edit: nevermind makes a swift procession west.

TECH85

Weathercheck wrote: »

ICON is what we want to see for keeping the cold in and getting an all snow event.

Similar to UKM

So where exactly would be the ideal position for the low to end up for an all snow event.
Obviously its in a better position there than some of the other charts where it pulls up north and west .!
Off the south coast of england somewhere would be best ?
If it does end up there would it stall or be pushed back south again ?
Whats your thinking on that secondary low ?
Thanks

Longing

120h the GFS 06 is is heading towards the UKMO outcome. A little further east with the Friday low and its a snow to snow scenario.

snowstorm445

Incremental changes in the GFS, good to see I suppose. We still have the ECM to contend with as well don’t forget. Apart from the UKMO and the ICON I wouldn’t rate the others that highly.

ninebeanrows

GFS 6z is a big step in the complete snow direction with development of second low towards southern England and keeping the cold in for much of Ireland.

ThaitaniumM

The GFS has slightly better uppers and the low a bit more east then the last run. A snowy affair for thursday night and friday looking at some freezing rain with lying snow fields lowering the air temps.
If the next GFS rollout has the low further east or south, ww could be looking at all snow.

JCX BXC

giveitholly wrote: »

Is that good or bad for us

As posted in this thread, we want this to move South East, not west or north.

cherryghost

ThaitaniumM wrote: »

The GFS has slightly better uppers and the low a bit more east then the last run. A snowy affair for thursday night and friday looking at some freezing rain with lying snow fields lowering the air temps.
If the next GFS rollout has the low further east or south, ww could be looking at all snow.

Yes, most of the charts are going with the latter so will be interesting to see if the 90% are wrong or right.

mirrorwall14

leahyl wrote: »

What time can we expect this Calibos? I love this thread - everytime I see an update to this thread by yourself or any of the other resident experts, I just know it's usually "good" news

I put this list together based on replies here. These are the roll out times, not the start of the runs


300am ICON
330am GFS
350am UKMO
530am Euro 4
6am ECM
930am GFS
1130AM Euro 4
1500 ICON
1530 GFS
1550 UKMO
1740 Euro 4
1800 ECM
2130 GFS
2330 Euro 4

downwiththatsor

mirrorwall14 wrote: »

I put this list together based on replies here

300am ICON
330am GFS
350am UKMO
6am ECM
930am GFS
1500 ICON
1530 GFS
1550 UKMO
1800 ECM
2130 GFS

Euro 4 11.30am 5.30pm 11.30pm etc

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=euro4&MODELLTYP=1&BASE=-&VAR=weas&HH=9&ARCHIV=0&ZOOM=0&PERIOD=&WMO=&MOUSE=1

Speak Now

bennyob wrote: »

What's the pub run that I've seen mentioned a few times.

2130 GFS