FI CHARTS AUTUMN/WINTER 2014/15 **Mod Note Post #1**

FWVT

Forget the models for a second and look at the bigger picture. This makes things a lot easier to digest when it comes to weeding out the details in the models later.

It is fairly certain that some sort of low will form along the waving polar front off to our west. The models all say this, though they differ greatly in the fine detail, so forget them for now.

What sort of airmass have we in place now and in the next day or two, because it is this airmass that will play a roll in what sort of air and hence precipitation will circulate around the low come the weekend. Having a northeasterly wind is one thing, but if that's just recirculating stale modified air then that's no good for snow. Here is where the track and depth of the low centre will be important, but it looks unlikely that there will be any proper feed of cold air from Scandinavia to cool things down enough for snow.

We must look to our north and what could get dragged down as the systems progress eastwards and southeastwards. Iceland and Greenland have cold in abundance, and some of that could make its way this way, but again, the path and depth of the low centre is key here.

NOW look at the models. The GFS is - no surprise - the coldest solution for snow. Looking at several layers, it shows a pool of deep cold (up to around 400 hPa) advecting down from Iceland through Saturday. This deep cold, shown on 700 and 500 hPa charts, would sustain heavy hail, graupel and snow showers for a time, but low-level modification on the way here will have to be factored in when it comes to deciding melting layer depth. Will the GFS win out? The ensembles are showing increased uncertainty in this key region between us and Iceland, so it's still all up in the air. I would side with the ECM as I think it has been performing better over the past few days.

One further note: don't blindly look at just 850 hPa temp charts without looking at the 850 heights too. Meteociel euro charts don't have the heights but their UK charts do. We may see -7 °C temperatures at 850, but if that is in an area of high pressure then the actual height of that level could be 200 m heigher (i.e. further from the ground) than in low pressure, and that could mean 200 m extra warm layer for any snow to have to survive through. As a reference, that's the height of Knock Airport, which can receive plenty of snow while the rest of us get rain. Models are hinting at 850 hPa heights somewhere between 1400-1500 m during Saturday, and increasing all the while as the high moves in from the west.

JanuarySnowstor

The long term trend isn't good this morning with the high getting stuck over us
Result being at 168h rs we are the mildest country in the Northern hemisphere. (Going by ecm)

It's a bore that might reap rewards going into 2015 just about sums it

Oneiric 3

One of the more interesting features of the upcoming spell of weather is the wild swing in surface pressure values that are being forecast in the 3 day period between Friday 00z and Monday 00z.

Just going by the ECM this morning, at Malin Hd, we have a pressure value of approx 1033 hPa by Friday 00z. This then falls to approx 998 hPa by 18z the same day. :eek: On the following day, it hovers between 1000 hPa & 1010 hPa before rapidly rising again on Sunday - to as high as 1037 hPa by midnight. I can honestly say that I have not seen such a wide variation in predicted pressure values over such a short space in time. From anticylonic to cyclonic back to anticyclonic - and yet, nothing much of interest weather wise in the offing at all :rolleyes::o

Kermit.de.frog

JanuarySnowstor wrote: »

The long term trend isn't good this morning with the high getting stuck over us
Result being at 168h rs we are the mildest country in the Northern hemisphere. (Going by ecm)

It's a bore that might reap rewards going into 2015 just about sums it

Disappointing alright - the med is the place to be on this morning's projections.

Strangegravy

Kermit.de.frog wrote: »

Disappointing alright - the med is the place to be on this morning's projections.

Nabber

Not a bad setup for 90hrs

Surface pressure

Dew point for same period


I think the North should see some snow if this was to come of as is.

Gonzo

looks like Scandinavia, Holland, Switzerland, Austria, Germany, Poland, Italy, Greece and maybe even Cyprus & parts of north Africa could see some heavy falls of snow over the christmas period and into new years.

Harps

Kermit.de.frog wrote: »

Disappointing alright - the med is the place to be on this morning's projections.

A bit of an odd post considering your optimism yesterday, if anything things are looking far more promising today for an easterly..

It was never going to happen within a few days but quite a few runs today move the HP towards Scandanavia, it wouldn't take too much tweaking for this to lead to an easterly around New Years, this mornings runs keep SE England in the freezer all week which is a big swing compared to this time yesterday.

Still potentially an interesting couple of days after Christmas as well so plenty to be optimistic about

Kermit.de.frog

Oh I agree. The timing is the disappointment. Plenty of potential there absolutely.

Be looking to see if we can get not only the cold surface and upper air on to the continent but if we can see that propagating toward us too eventually. The initial push though is on to the continent so it's better to have that in place in case we get Atlantic lows under cutting. Plenty to watch over the next couple of days.

icesnowfrost

fi at its best.

http://images.meteociel.fr/im/1342/gfs-0-336_ejk5.png

numilus cimbus

Kermit.de.frog wrote: »

Oh I agree. The timing is the disappointment. Plenty of potential there absolutely.

Be looking to see if we can get not only the cold surface and upper air on to the continent but if we can see that propagating toward us too eventually. The initial push though is on to the continent so it's better to have that in place in case we get Atlantic lows under cutting. Plenty to watch over the next couple of days.

Agree
If we can get Denmark eastwards at least covered in snow,then we have a reasonably close surface cold pool to draw on helping those snow flakes reach the ground
It's very hard to judge day to day what's going to happen in Europe either though,
I think this will happen eventually but from a fetch point of view if we do get an easterly in place by the new year or any stage late January/Feb,a NE component would be beefier showers

Kermit.de.frog

UKMO not too bad. A cold blocked situation - very cold at night incidentally, something to watch.


NAVGEM though - this is what we want to see to break the umbilical cord with the heights to the south - a negative tilt to the depressions in the Atlantic and undercutting of our block and ample amounts of very cold air to tap on the continent.

Oneiric 3

The ECMWF mean on day 10 showing a very flat pattern with any signal for any significant height rises to the east being scraped on this particular run.



The pattern itself is remarkably close to what you would expect the average north Atlantic pattern to be at this time of year, which could suggest that the trouble this model and others have been having lately with the short-term complications that are arising lately, that it may be doing nothing more reverting to this particular set up due to the to wide range of uncertainties within their respective ensemble suites. If not, then at least there may be an increased chance of some storminess down the line. Only time will tell I guess.

Kermit.de.frog

A lot of uncertainty between 96 and 120 hrs as to the orientation and location of the center of this high pressure. A lot of changes to come I think.

FWVT

The Euro4 has 850-1000 hPa partial thickness hovering just around 1295-1300 m through the north and midlands with that rain tomorrow, which for me is just 5-10 m too much for snow to low levels. GFS forecast soundings show this layer as saturated and almost isothermal, with around 700-800 m warm layer. This would lead to snow on hills, with sleet to wet snow lower down. Evaporative cooling will be minimal, apart from northeastern Ulster.

Saturday is much better, with steep lapse rates and a drier boundary layer helping to prevent any snow flurries from melting, especially in the evening.

Rebelbrowser

I know it's tomorrow, not FI, but anyone know why the gfs precipitation charts on meteociel and weatheronline look completely different (and it's nothing to do with the gfs parallel)? Anyway the gfs charts on the 12z on meteociel look snowy.... can't post charts I'm afraid.

Rougies

Rebelbrowser wrote: »

I know it's tomorrow, not FI, but anyone know why the gfs precipitation charts on meteociel and weatheronline look completely different (and it's nothing to do with the gfs parallel)? Anyway the gfs charts on the 12z on meteociel look snowy.... can't post charts I'm afraid.

Weatheronline precip charts show 3hr totals (by default, you can change them to 6hr) for the gfs, while meteociels are 6hr. Also meteociel's have a lower threshold for showing precip, so when some very light precip is showing on meteociel, it will be blank on weatheronline.

Oneiric 3

One to watch for next week maybe?



** yearns..

maquiladora

Oneiric 3 wrote: »

One to watch for next week maybe?



** yearns..

I think that's one of the strongest lows I've ever seen the ECM spin up in our neck of the woods. Would love to see the high res output at its peak. At 144 sustained winds are over 40 m/s, probably over 50 m/s at some point!

JanuarySnowstor

Charts are very poor the last couple of days with mild zonal setting up shop for at least ten days
What really annoys me is the way the likes of mushy on NW gets ridiculed for calling it as he sees.
For me this time of year is pivotal for how Winter shapes up
Rather than a bitter Winter we are now wondering will we get any proper cold spell

Sorry for sounding off but all this talk of strat warming, deeply negative NAO's, record SAI'S and OPI have been quite frankly a load of B'S.

How we miss GP and his valuable (non cold biased) forecasts!!

AnotherYear

JanuarySnowstor wrote: »

Charts are very poor the last couple of days with mild zonal setting up shop for at least ten days
What really annoys me is the way the likes of mushy on NW gets ridiculed for calling it as he sees.
For me this time of year is pivotal for how Winter shapes up
Rather than a bitter Winter we are now wondering will we get any proper cold spell

Sorry for sounding off but all this talk of strat warming, deeply negative NAO's, record SAI'S and OPI have been quite frankly a load of B'S.

How we miss GP and his valuable (non cold biased) forecasts!!

I'm not sure where you are seeing this mild zonal for at least 10 days. The charts are showing a continuation of earlier this month alternating between cool polar maritime and mild days. So certainly not mild zonal. Plus every model has been terrible lately in the short term never mind FI. We're not even 1/3 of the way through Winter yet so it's a bit early to be waving the white flag.

Elmer Blooker

AnotherYear wrote: »

I'm not sure where you are seeing this mild zonal for at least 10 days. The charts are showing a continuation of earlier this month alternating between cool polar maritime and mild days. So certainly not mild zonal. Plus every model has been terrible lately in the short term never mind FI. We're not even 1/3 of the way through Winter yet so it's a bit early to be waving the white flag.

sorry but when you see a winter chart like this with an Atlantic warm front heading into Russia its game over. Let me be the first to say a "sting in the tail" winter as March will probably be the coldest month.
http://www.meteociel.fr/ukmo/fax/fax120s.gif?2
The usually terms and conditions apply - I'd love to be 100% wrong .... blah blah blah .........

AnotherYear

ECM Has negative uppers(-850hPa) over Ireland for 6 of the next 10 days. Not mild zonal as I said. It's not even January yet so brave call with March being the coldest.

esposito

Elmer Blooker wrote: »

sorry but when you see a winter chart like this with an Atlantic warm front heading into Russia its game over. Let me be the first to say a "sting in the tail" winter as March will probably be the coldest month.
http://www.meteociel.fr/ukmo/fax/fax120s.gif?2
The usually terms and conditions apply - I'd love to be 100% wrong .... blah blah blah .........

Enough of that negativity! It most certainly is not game over. So what if the next 10 days/ two weeks are not great for cold lovers. Late January/ early February we could well get a significant cold spell. A lot can happen between now and March. Plus I don't have much faith in the models right now. This time two weeks it could be whole different story.

Nabber

You got to take the good with the bad. Every winter the charts turn and change to much for Ireland. There is still too many variables and not enough processing power, to top all of that off we still don't understand the intricacies of weather. The relationship between stratospheric and sea level.

But to jump in and call it until March. Based on a model out put we know is unreliable.

I'm on the phone so can't insert images. But we are looking at HP sitting over us for 2 days. We will have somw nice frosty weather. I'm not sure the charts know how this HP will break down.
When the charts are unsure they tend to output Atlantic Zonal. We see 910 lows forming 200-300miles of Irish coasts. Although we know it's not impossible, we tend to dismiss these as 'I'd love to see that roll in' I think everyones opinion deserves it's say. But each opinion deserves a rebuttal.

I tend to look at charts up to 76hrs. Try to have an educated guess on whow the next 24 hours will work out. Then 90+ is just FI. Be it good, bad or indifferent, it's still judt FI.

To sum it up, I'd say, we cant pedict past 3days, so why predict up to 3 months?

maquiladora

Not enough FI charts in the FI charts thread.

icesnowfrost

hows that for fi

Oneiric 3

maquiladora wrote: »

Not enough FI charts in the FI charts thread.

Bring it on! but I wager that 174hr chart will go from this:



to this



by the time it gets into the 24h territory**


** based on nothing more than bitter, splenetic experience.

Harps

:cool:



Slight chance of a storm overnight on the 1st, most runs keeping it well north but ECMWF and a few others have it further south but weaker

maquiladora

Harps wrote: »

:cool:



Slight chance of a storm overnight on the 1st, most runs keeping it well north but ECMWF and a few others have it further south but weaker

Can ya imagine that with the centre just north of Donegal Bay. A ~70mb gradient over Ireland.
Eventually something like that will happen, statistically it has to. But it might not be for another 100 or 200 years...