FI Charts (T120+ onwards) Autumn/Winter 2016/2017 **READ MOD NOTE IN FIRST POST**

Rebelbrowser

Just worked out how to...

ninebeanrows

GFS latter reaches not too shabby either. As ever the EC will be watched closely. Certainly odds are now shortening for February to be a colder than average month.

nacho libre

Rebelbrowser wrote: »

Just worked out how to...

Just about cold enough for snow showers, then:pac:
That's 1987 territory with those kind of uppers. Of course we all know uppers that cold are unlikely to verify.

martinsvi

nacho libre wrote: »

Just about cold enough for snow showers, then:pac:
That's 1987 territory with those kind of uppers. Of course we all know uppers that cold are unlikely to verify.

Cold uppers mean nothing if they come together with high pressure.. it looks like a nice crisp weekend with blue skies and maybe some form of fog/haze here and there..

nacho libre

martinsvi wrote: »

Cold uppers mean nothing if they come together with high pressure.. it looks like a nice crisp weekend with blue skies and maybe some form of fog/haze here and there..

It depends on the proximity of the high to our shores and the orientation/tilt of the high. That GEM chart would bring very heavy snow showers to the south east of England, and moderate to heavy snow showers to the east of Ireland if it verified.

martinsvi

nacho libre wrote: »

It depends on the proximity of the high to our shores and the orientation/tilt of the high. That GEM chart would bring very heavy snow showers to the south east of England, and moderate to heavy snow showers to the east of Ireland if it verified.

the very same GEM is showing 1020 to 1025, CFM seems to agree to it. GFS paints isobars much closer together, but all seem to agree on a southerly flow

nacho libre

martinsvi wrote: »

the very same GEM is showing 1020 to 1025, CFM seems to agree to it. GFS paints isobars much closer together, but all seem to agree on a southerly flow

If those 850hpa temps verified, the flow won't matter too much, as long as the high stays far enough north, and you get a trigger low over the med to advect the cold air our way from the continent we would eventually get snow showers. The good news is all models seem to agree on an easterly of sorts, but it's whether it will be a dry cold one or snowy one is the issue, and how long any cold will last. The output will chop and change, but at the very least the Atlantic look certain to be kept at bay for a few days around then

martinsvi

nacho libre wrote: »

you get a trigger low over the med to advect the cold air our way from the continent

wouldn't air coming from the continent be kind of dry? And since we can agree that it would be cold air at this time of year, what do you get when a cold, dry air passes over cold-ish sea? Fog - yes, low stratus - possibly.. but snow showers? :rolleyes:

nacho libre

martinsvi wrote: »

wouldn't air coming from the continent be kind of dry? And since we can agree that it would be cold air at this time of year, what do you get when a cold, dry air passes over cold-ish sea? Fog - yes, low stratus - possibly.. but snow showers? :rolleyes:

Should a proper easterly(think the easterlies of the 80s), come to pass, you will have very cold upper air, in an unstable flow travelling over relatively warmer water, that will bring snow showers/streamers to the east coast, not fog. Fog might be the main issue, further west.

If it is a tepid continental feed we end up with, which is more likely, then fog and frost will be the main issue.

Gonzo

if that chart verifys on the day we would be looking at very beefy snow showers, merging snow streams while areas under the IOM shadow will have unbroken sunshine with dark skies all day long to the very south and very north.

JCX BXC

And if that happens, any chance one of those showers will be beefy enough to make it the whole way across to West Clare?

martinsvi

Gonzo wrote: »

if that chart verifys on the day we would be looking at very beefy snow showers, merging snow streams while areas under the IOM shadow will have unbroken sunshine with dark skies all day long to the very south and very north.

are we looking at the same chart? Is this the chart that promises beefy snow showers?

BLIZZARD7

martinsvi wrote: »

Cold uppers mean nothing if they come together with high pressure.. it looks like a nice crisp weekend with blue skies and maybe some form of fog/haze here and there..

Just to put this argument to bed-

January 2010 delivered heavy snow showers coming off the Irish sea to much of the East coast with air pressure as high as 1030 hpa at times.

ninebeanrows

Latest EC is on top end of the ensembles. Lots of significant cold options still available.

martinsvi

BLIZZARD7 wrote: »

Just to put this argument to bed-

January 2010 delivered heavy snow showers coming off the Irish sea to much of the East coast with air pressure as high as 1030 hpa at times.

when I raised my concern about the high pressure, the isobars were far away from each other, the center of the HP to our east, producing relatively low winds coming from south -east direction. This pattern is somewhat typical for early spring and from most of my memory produces some coastal fog but clear skies for the rest of the country. I didn't mean to imply that you can't get precipitation in high pressure, but rather that we must consider where the air mass is coming from.

The picture that we're seeing for the 10th of February looks nothing like we saw in 2010. You can't take one prerequisite that's required for snow (cold uppers), take it out of context and make a big announcement that heavy snow fall is on it's way.. You have to use pressure charts together with upper temps and it looks like none of you want to do that. I get it, you are all snow lovers here, I like my fair share of white stuff too, but does that mean that we can completely ignore the other prerequisites required for heavy snowfall, such as the nature of the air mass. Sometimes I feel there is so much wishful thinking, "alternative fact-ing" and evidence ignoring going on on this thread, it would nearly belong to Politics, Religion or Conspiracy theory sections instead rather than "Science, Health & Environment"

the chart I posted shows rather breezy flow coming from the continent, which typically is dry as a bone and stable as a rock, for this time of year (nothing to trigger convection as far as I can see). Can any of you snow advocates please show me a chart for the given time period, that indicates the air mass might indeed pick up considerate amount of moisture and become unstable to produce a heavy snow fall? I would be more than happy to put this argument to bed, go prepare my camera and winter hiking gear

D9Male

Well said, Martin.

nacho libre

martinsvi wrote: »

the chart I posted shows rather breezy flow coming from the continent, which typically is dry as a bone and stable as a rock, for this time of year (nothing to trigger convection as far as I can see). Can any of you snow advocates please show me a chart for the given time period, that indicates the air mass might indeed pick up considerate amount of moisture and become unstable to produce a heavy snow fall? I would be more than happy to put this argument to bed, go prepare my camera and winter hiking gear

Last nights GFS was promising for a convective easterly.
Today's outputs are mostly disappointing( we are too far west) although there are some promising ensembles, but you knew that when you asked the question. The form horse is cold and dry weather with perhaps some sleet or snow around for the east, then back to Atlantic mobility, while much of England remains cold.


There is no alternative facts and ignoring of evidence going on, just differences of opinion. I am well aware how difficult it is to get snow here and spoke only of potential. There are many parameters involved in us getting snow. A -10 isotherm doesn't guarantee snow but it increases the chances, especially if you get a battleground scenario.

Generally though if the 500mb heights are too high then PPN will be limited. surface pressure can be as high as 1025 and still deliver big, but you need cold 850's with steep lapse rates up to 500mb as well, significant falls from Easterlies have occurred with heights at least below 530dam.

Lets leave it there.

John.Icy

The output has generally got a little worse from the main models over the last day or so where Ireland is concerned anyway - the GEM is the best of the lot currently but at that it's bringing in a SE wind which isn't as good for snow potential and also it runs the risk of dragging up warmer air into the mix rather than tapping directly into the masses of cold out East.

There's still plenty of time for things to develop more favorably - it all depends on the sliding low at around +150 (seems like this has remained at +150 for what seems like forever!) and that decides whether we see a brief timid SE'ly before the block crumbles/azores ridges up etc or whether it can lock in a colder pattern with movement of the the high over Scandinavia westwards. Think of how extensive the blocking was in 2010 - we really need to see it edge towards Greenland to displace any low pressure there at the South tip of Greenland (these lows are a pain as unless they undercut they'll either keep the block far enough East so it doesn't influence our weather hugely or it can sink the block).

It's funny over on Netweather how a few days ago when the ECM and GFS were wild cold outliers it was OK as you trust the operationals BUT now that the operationals are backing off a more potent Easterly it's still OK as there's ensembles that still go cold . In saying that, they're is plenty of interest in the ensembles which show favoured outcomes if the undercut is more favorable. Take the below for example (ignoring the deep low as it's unlikely to look like this but for the sake of it) - we've more energy diving SE and we lose the low pressure hanging around Greenland which opens the door for the block to move West towards Greenland. Other runs divert some energy SE but we retain low pressure to the S and SE of Greenland so we don't see the below happening (the ridging of the high towards Greenland).



The 12z suite could bring better runs - it's still finely balanced so plenty of interest still.


Aside - If people want they're 2010 IOM streamers, you want high pressure over Iceland ideally dragging down ENE/NE winds - that's nothing like what's been on the models lately. You can get convection over the Irish sea with other wind feeds but in respect to the two lines of snow trains either side of the IOM moving SW from origin to land you wouldn't get them off a SE wind.

Nabber

ECMF 12z looking good at+168
Looking forward to the r st of the 12z. I bet the GFS follows suit

Rougies

Possible snowfest for south and east @192 hrs, then it goes tits up for the rest of the run.

Nabber

Bingo.... -8 Uppers for 90 hours

snowstorm445

Not going to happen but still... *drool*

Meteorite58

Indications of a cold February coming up perhaps with NW'ly, NE'ly and E'ly sourced weather from the week end .

snowstorm445

Only 4 days away lol. As if.



Models seem to be suggesting a cold spell next weekend anyway, with a Scandinavian high bringing easterlies. Is it for real this time or another receding mirage? Only time will tell!

pad199207

snowstorm445 wrote: »

Only 4 days away lol. As if.



Models seem to be suggesting a cold spell next weekend anyway, with a Scandinavian high bringing easterlies. Is it for real this time or another receding mirage? Only time will tell!

We might get to the stage where we will be able smell the cold from England over here and then the Atlantic will swallow us up....... again

nagdefy

I suppose having deep cold as far west as England is better than Poland! At least we've a better chance of tapping into it..

sryanbruen

nagdefy wrote: »

I suppose having deep cold as far west as England is better than Poland! At least we've a better chance of tapping into it..

We could have a MUCH better chance if the NAO would be negative. It's staying positive into mid-February whilst the AO is trending negative. So far this Winter, it has often been the other way round with the NAO rather negative but the AO positive. So what could this mean with the opposite?

icesnowfrost

So far it's looking nice for cold. But loads of dry weather. Need some precipitation to mix along the northeast and east coast, maybe a few light streamers coming in off the Irish Sea. It's lovely to look at and will get interesting as the week goes on.
I still don't trust the gfs though.

pedigree 6

Happy Valentines Day.:p

ninebeanrows

Interesting 12z coming out this evening..

Still chance we could get a bite of this easterly. 12z GFS looking very interesting so far...