This Week's Storms - FORECAST, MODEL DISCUSSION ONLY

Deep Easterly · 13-12-2011 3:32pm

nacho libre wrote: »

ah yeah a horrible mix most likely. unless we get a proper northerly, i think it'll continue this way. i'd much prefer cold dry and crisp weather to this in between situation. still if it does snow tomorrow or later this week, forget this post ever existed;)

M.T put it perfectly yesterday "A mixed horror show".

Not the biggest fan of this slop either.

rhonin · 13-12-2011 3:39pm

nacho libre wrote: »

ah yeah a horrible mix most likely. unless we get a proper northerly, i think it'll continue this way. i'd much prefer cold dry and crisp weather to this in between situation. still if it does snow tomorrow or later this week, forget this post ever existed;)

Cold and crisp weather would be great. A good old storm would be great too. However, what we have now is slightly better than mild & wet.

The weather after the one o'clock news mentioned that the south could still get strong winds on Thursday. I guess the next run of charts will give us a better idea.

nacho libre · 13-12-2011 3:41pm

munsterlegend wrote: »

it may go north and turn to the left like other atlantic storms? is that the met office in the uk's thinking?

It could possibly, but none of the models seems to show it going north now. It seems to have disappeared completely on the ecmwf.

munsterlegend · 13-12-2011 3:46pm

nacho libre wrote: »

It could possibly, but none of the models seems to show it going north now. It seems to have disappeared completely on the ecmwf.

well was reading over on netweather and they believe the uk met office have identied something the models are not catching onto. also that colder air is plunging further south than anticipated..i won't go into the science of it as i haven't the foggiest!

nacho libre · 13-12-2011 4:07pm

munsterlegend wrote: »

well was reading over on netweather and they believe the uk met office have identied something the models are not catching onto. also that colder air is plunging further south than anticipated..i won't go into the science of it as i haven't the foggiest!

it's plausible. Last year they cottoned on to the cold outbreak in late November before the other models had. Perhaps they consulted with M.T.Cranium. The colder air being further south than anticipated might help invigorate the system as it tracks in? Although it does look like it still tracks to the south of us? The further south it goes the better for our cold prospects. Others would know more about all this than me, though.

Spindle · 13-12-2011 4:14pm

nacho libre wrote: »

it's plausible. Last year they cottoned on to the cold outbreak in late November before the other models had. Perhaps they consulted with M.T.Cranium. The colder air being further south than anticipated might help invigorate the system as it tracks in? Others would know more about this than me.

I think they still suffer from the Fish effect, if there is a possibility at all, that this storm comes off they are going to stick to it rather than be caught out.

Although their warnings seem very confident.

WolfeIRE · 13-12-2011 4:22pm

http://www.dmi.dk/dmi/index/danmark/vejrkort.htm

Click on Nedbor (today's word brought to you by ML

)to see the HIRLAM output on where that low pressure system will cross the midwest/west tomorrow evening. Some snow potential for a wide area if this comes to pass

munsterlegend · 13-12-2011 4:24pm

WolfeIRE wrote: »

http://www.dmi.dk/dmi/index/danmark/vejrkort.htm

Click on Bedbor to see the HIRLAM output on where that low pressure system will cross the midwest/west tomorrow evening. Some snow potential for a wide area if this comes to pass

Nedbor Wolfe Nedbor! i'm not pedantic or anything..if that did turn to snow it could be a major fall..

munsterlegend · 13-12-2011 4:26pm

munsterlegend wrote: »

Nedbor Wolfe Nedbor! i'm not pedantic or anything..if that did turn to snow it could be a major fall..

would it not be modified by the Atlantic though?

WolfeIRE · 13-12-2011 4:30pm

Yes, it is likely to bring a rise in temps (not considerable but enough to turn snow to sleet) My guess is that it would fall as snow above 200m and maybe lower down when precip is at its most intense. Snow for low lying areas more likely on the back edge as colder air whips in behind the system.

Vizual Pics · 13-12-2011 4:34pm

Just looking at http://www.sat24.com/?culture=en&ir=true - anyone know if the large system west of Iceland is going to have any bearing on things in the next day or so, it just seems to be sitting out there drawing energy from the system affecting us now, waiting to pounce...

maquiladora · 13-12-2011 4:51pm

If you haven't already seen this, check it out.

http://www.bbc.co.uk/weather/features/16165125

WolfeIRE · 13-12-2011 4:54pm

Vizual Pics wrote: »

Just looking at http://www.sat24.com/?culture=en&ir=true - anyone know if the large system west of Iceland is going to have any bearing on things in the next day or so, it just seems to be sitting out there drawing energy from the system affecting us now, waiting to pounce...

I am fairly certian the remnants of that system will hit the west coast tomorrow and push sse inland. It could bring some falls of snow tomorrow eve and night especially on its back edge in west Munster and south Connacht

It is basically going to spin anticlockwise to its sw, then south and then southeast toward Ireland overnight and during the first half of tomorrow. Its' centre will intensify before becoming less organised by tomorrow eve. Having said that it will bring plenty of precipitation with it unless of course the subsequent GEFS runs downgrade the system or divert its path.

rhonin · 13-12-2011 4:56pm

maquiladora wrote: »

If you haven't already seen this, check it out.

http://www.bbc.co.uk/weather/features/16165125

Thanks for that.
It's really well explained and goes to show that it is still uncertain of where the strongest winds will be.

ninebeanrows · 13-12-2011 4:58pm

GFS increases the chance of the system hitting southern England.

WolfeIRE · 13-12-2011 5:00pm

maquiladora wrote: »

If you haven't already seen this, check it out.

http://www.bbc.co.uk/weather/features/16165125

Now that is how you present a weather forecast. Offering possible scenarios beat vague "we are still unsure" type forecasts hands down.

Deep Easterly · 13-12-2011 5:01pm

Both the latest HIRLAM and NAE showing a narrow band of showery precipitation on the north side of the trough feature tomorrow:

EMHI HIRLAM 12z for 12z:

NAE 12z for 18z tomorrow:

Some issues with actual timing between the two models but it is within these showery bands that any snow would most likely fall (esp on high ground as mentioned, though cannot be ruled out on lower terrain). Actual specifics may change again later.

snow ghost · 13-12-2011 5:05pm

maquiladora wrote: »

If you haven't already seen this, check it out.

http://www.bbc.co.uk/weather/features/16165125

Who is that Guy?

maquiladora · 13-12-2011 5:07pm

12Z has the low about 12mb more intense and about 100 miles further north than on the 06Z.

Stronger winds for south and southeast England along the coast on this run, along with France, on the 06Z there was no strong winds for England at all.
Shows how much things in the short term can change on the models after just 6 hours.

NIALL D · 13-12-2011 5:10pm

YAHOO NEWS ;

Amber weather warnings have been issued for snow and gales through the rest of this week with southern and west England expected to bear the brunt of a powerful winter storm on Thursday.

The Met Office has warned of a repeat of the windy and wet weather that crippled Scotland and the north of England last week, but this time there is a risk of heavy snow showers giving accumulations of up to 10cm.

Deep Easterly · 13-12-2011 5:10pm

snow ghost wrote: »

Who is that Guy?

Chris Fawkes, a UK Met Office weather presenter for the BBC. Well presented forecast I have to say.

ninebeanrows · 13-12-2011 5:11pm

maquiladora wrote: »

12Z has the low about 12mb more intense and about 100 miles further north than on the 06Z.

Stronger winds for south and southeast England along the coast on this run, along with France, on the 06Z there was no strong winds for England at all.
Shows how much things in the short term can change on the models after just 6 hours.

if we can 10mb in the next run, another 8mb in the next, 6mb in the next, 4mb in the next...

Crazy volatility.

maquiladora · 13-12-2011 5:15pm

Weathercheck wrote: »

if we can 10mb in the next run, another 8mb in the next, 6mb in the next, 4mb in the next...

Crazy volatility.

And how many times have we seen lows end up going further and further north as we get nearer?

I'm just sayin... :P

Deep Easterly · 13-12-2011 5:15pm

If we can get the entire nation to all breathe in deeply at the same time as the low draws nearer so as to create a pressure vacuum to draw in the low pressure closer to us.

Just might work.. Who's on?

Elmer Blooker · 13-12-2011 5:16pm

snow ghost wrote: »

Who is that Guy?

It looks like some serious fireworks for Southern England according to that guy Chris Fawkes !!

M.T. Cranium · 13-12-2011 5:22pm

Best chance for a storm tracking far enough north to bring strong winds to any part of Ireland would appear to be a slower evolution delivering more towards late Friday. The faster this comes out into the current set-up the further south it will be forced to track. That's because the Wednesday short wave is going to leave the jet way too far south to allow the mid-Atlantic low to get a grip on the energy in time to deepen and move north. If it happens to take longer to emerge from its comfortable den near Bermuda then it might find the jet starting to rebound a little.

Awaiting the 12z GEM with interest because the regional out to 48h shows the low considerably further west than the GFS, at 42N 48W on Thursday at 12z. That position is nowhere near far enough east to get the storm even if sheared into the Channel by Friday morning. So it could come out slower on that model and begin to push further north. Will let you know how that turns out at about 1645h as the global run is just starting to come out now.

On the subject of the Wednesday short wave feature, it looks fairly weak and the uppers are not as cold by then as they will be tonight. I think the rain-snow line might retreat up to about 300m but the more squally convection in the wake might bring in some accumulating snows lower down for a while at least.

WolfeIRE · 13-12-2011 5:38pm

Latest EUMETSAT image

Sponge Bob · 13-12-2011 5:44pm

Weathercheck wrote: »

if we can 10mb in the next run, another 8mb in the next, 6mb in the next, 4mb in the next...

Crazy volatility.

A "Bomb" cyclone is, variously 24 or else 30 millibars of deepening in 24 hours driven by a favourable jet stream overhead. These are the hardest to forecast with any accuracy.

There is plenty enough time for a "Bomb" to develop by thursday. In fact there may be enough time for one even if the system is benign enough as late as tomorrow midnight. If it grows an eye be very afraid.

I think one of the christmas storms in 1997/8 was a bomb cyclone.

M.T. Cranium · 13-12-2011 5:49pm

No go there, the GEM 12z has the same evolution as the GFS. Would say that the global 48h is somewhat less focused than the regional 48h was, so there might be a faint hope of something much different to come in later runs (a more powerful storm taking longer to eject).

Here's what is currently happening in the storm's formation zone south of Nova Scotia and just to the northeast of Bermuda. The system was an inverted trough at 06z and is slowly developing a 1010 mb centre which you can see in this animation:

http://www.weatheroffice.gc.ca/satellite/animateweb_e.html?imagetype=satellite&imagename=goes_ecan_1070_m_..................jpg&nbimages=1&clf=1

(the 48h GEM shows this plodding northeast and deepening to 984 mbs).

So far all of the models want to take the leading edge of this system and shear it off, producing a fast-moving wave into northern France Friday, then bring along the bulk of the system around Saturday or Sunday into France.

The only scenario that would now work to create a stronger storm affecting Ireland would be in two parts, first the short wave tomorrow needs to track a bit further north and get pulled northeast towards the remnants of today's deep centre, then the jet needs to start rebounding and give the western Atlantic low somewhere to go instead of limiting its eastward progress and shearing it in half. It would not be totally unprecedented for that sort of model miscalculation to verify, but chances are probably about 10-20 %.

Spindle · 13-12-2011 5:52pm

Sponge Bob wrote: »

A "Bomb" cyclone is, variously 24 or else 30 millibars of deepening in 24 hours driven by a favourable jet stream overhead. These are the hardest to forecast with any accuracy.

There is plenty enough time for a "Bomb" to develop by thursday. In fact there may be enough time for one even if the system is benign enough as late as tomorrow midnight. If it grows an eye be very afraid.

I think one of the christmas storms in 1997/8 was a bomb cyclone.

This is what I have been thinking all along, it just has bomb written all over it, can just pop up when you least expect it, all is in place for it anyways.

This Week's Storms - FORECAST, MODEL DISCUSSION ONLY

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