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phil nw.

Model output discussions pm 31/12/15

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Just now, bobafet said:

As someone who is still trying to learn I must say I am royally confused with the posts tonight, normally I get the jist of what  is going on! But there are so many conflicting posts Tonight I haven't got a clue what to expect!! I would appreciate a bit of clarity!!

Although I must say this is one of the best forums on the net and makes winter even more magical.

 

At the moment theres a strong signal for some colder weather with the flow from the nw/n. Currently the upper air temps look supportive of some snow and frosts however we're not sure of how long this will last.

The uncertainty is what happens next, this could be several options. The ECM T240hrs would likely lead to a sustained spell of colder weather with high pressure to the nw. The other avenue could be a shortwave running se'wards from Greenland going under the UK.

If low pressure hangs around central Europe with high pressure to the ne then its very difficult for milder conditions to effect the UK.

At this time if I had to choose I would go for a sustained spell of below average temps but how much below is more difficult to say.

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the 6-10 day mean EC / 500 & 850

 

IMG

fjnd3s.jpg

 

very encouraging, if its cold you're interested in! 

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Thank you sir!! That helps immensely and clarifies, much appreciated.

thanks to all who have replied, it has certainly helped, next to learn the charts myself.

 

keep up the good work!

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5 minutes ago, bobafet said:

As someone who is still trying to learn I must say I am royally confused with the posts tonight, normally I get the jist of what  is going on! But there are so many conflicting posts Tonight I haven't got a clue what to expect!! I would appreciate a bit of clarity!! 

Although I must say this is one of the best forums on the net and makes winter even more magical.

 

Ok, we are looking at Last with some Wintry weather for the Uk ....:closedeyes:

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And with this colder weather that hopefully will come,drier conditions for the flood victims thankfully.

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2 minutes ago, joggs said:

And with this colder weather that hopefully will come,drier conditions for the flood victims thankfully.

Hello! Cold and unsettled rather than  cold and dry looks the outlook,,,,,

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This is the anomaly at T240 with the northerly backing NW already discussed. According to the ext ecm the evolution from there to T360 is to move the trough south east and weaken the ridge which has the effect of backing the flow to WNW and increase the temp.

ecm_eps_z500a_natl_11.thumb.png.1b6963e4

 

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At about this time last year we had a  northerly cold spell similar to that being projected, that failed to meet expectations, at least for me in Norfolk. Charts below. While this potential cold spell could be upgraded, I feel a second bite of the cherry this time  will be needed to give us something exceptional. Here's hoping.

image.jpg

image.jpg

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Heres the NCEP view for NY state.

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
THE H5 FLOW IS IN GOOD AGREEMENT THROUGH FRI...BUT THEN DIFFERENCES
BEGIN TO TAKE SHAPE FROM THE INTERACTION BETWEEN A LARGE CANADIAN
VORTEX OVER HUDSON BAY AND A CUTOFF LOW PRES SYSTEM MOVING ONSHORE
OUT WEST. THE 12Z MODELS SEEM TO BE IN SOMEWHAT BETTER AGREEMENT
THAN THE 00Z RUNS WITH THE OVERALL PATTERN...THAT BEING THE
ELONGATED E-W ORIENTED VORTEX BECOMING N-S ORIENTED WITH A COLDER
AIRMASS DIVING INTO THE NORTHERN PLAINS/UPPER MIDWEST/GREAT LAKES
FOR THE WEEKEND. THIS VORTEX WILL THEN MEANDER ABOUT ERN ONTARIO
THROUGH THE MIDDLE OF NEXT WEEK.
 

Some uncertainty as they mention but I'm happy they said meander around Ontario rather than exit east! The north/south PV orientation is what we want to see upstream.

As long as we can hold the vortex there then we have a shot at developing either high pressure to the nw or some energy splits from southern Greenland going under the UK.

Interesting control run for De Bilt with quick changes in wind direction, this looks like a series of shortwaves dropping se.

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

The wind then settles towards the ne. Hopefully someone with access to the control run can let us know whether it ends up with a block to the ne with an eastern based negative NAO.

 

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Yes nick that's what scuppered our waa'@greenland on 12z Ecm.

However as pointed via NCEP' its looking if nothing else somewhat stagnant. ..rather than making progression in an' untoward placement. ...ATM.....

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13 minutes ago, knocker said:

This is the anomaly at T240 with the northerly backing NW already discussed. According to the ext ecm the evolution from there to T360 is to move the trough south east and weaken the ridge which has the effect of backing the flow to WNW and increase the temp.

ecm_eps_z500a_natl_11.thumb.png.1b6963e4

 

i was wondering how you might put an 'uncold spin' onto the extended eps. Given their range and and the anomolys /mean uppers shown, I'm surprised you see it like that. I would say it impresses me by maintaining the anomoly to our nw well into the 10/15 day period and it's likely to lead to

a) a sustained Scandi trough delivering a mean North/ nor'easter flow

b) a cold high drifting slowly in from the wnw of the UK and delivering some potential ice days 

c) an undercut of the Atlantic to approach from the sw and then potentially disrupt se

did you notice that by the end of the run, the Arctic upper ridge has found its way to sit over Svalbard? 

certainly the best extended eps of the season thus far. 

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^^ sorry was referring to the large vortex lobe @canada..^^^before I get shot down for non mention of what I was referring to.;-)

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Not sure anyone has posted the NOAA 8-14 dayer, but I'm pretty sure John Holmes would confirm this would score 8/10 on the "it's going to get cold" scale

814day.03.gif

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BA do you have access to the control run? can you spill the beans? Thanks.

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3 minutes ago, bluearmy said:

i was wondering how you might put an 'uncold spin' onto the extended eps. Given their range and and the anomolys /mean uppers shown, I'm surprised you see it like that. I would say it impresses me by maintaining the anomoly to our nw well into the 10/15 day period and it's likely to lead to

a) a sustained Scandi trough delivering a mean North/ nor'easter flow

b) a cold high drifting slowly in from the wnw of the UK and delivering some potential ice days 

c) an undercut of the Atlantic to approach from the sw and then potentially disrupt se

did you notice that by the end of the run, the Arctic upper ridge has found its way to sit over Svalbard? 

certainly the best extended eps of the season thus far. 

Actually Nick...gensnh-21-5-384.thumb.png.7ebcb222c18544

Now that's what we call a -ve AO/NAO!

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10 minutes ago, bluearmy said:

i was wondering how you might put an 'uncold spin' onto the extended eps. Given their range and and the anomolys /mean uppers shown, I'm surprised you see it like that. I would say it impresses me by maintaining the anomoly to our nw well into the 10/15 day period and it's likely to lead to

a) a sustained Scandi trough delivering a mean North/ nor'easter flow

b) a cold high drifting slowly in from the wnw of the UK and delivering some potential ice days 

c) an undercut of the Atlantic to approach from the sw and then potentially disrupt se

did you notice that by the end of the run, the Arctic upper ridge has found its way to sit over Svalbard? 

certainly the best extended eps of the season thus far. 

Agree entirely Nick. At first it looks like we may be in toppler city, but when one looks in a little more detail, the positive anomalies don't fade away - hence the second bite at the cherry on the deterministic. The EPS ensembles are the best of the season by a long way and days 10-15 tend to reinforce the anomaly rather than letting it fade away......

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11 minutes ago, Man With Beard said:

Not sure anyone has posted the NOAA 8-14 dayer, but I'm pretty sure John Holmes would confirm this would score 8/10 on the "it's going to get cold" scale

814day.03.gif

Can I ask why and what this is telling you? I have got a very limited understanding of the ECM/GFS charts but can't get my head around these. Thanks!

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8 minutes ago, nick sussex said:

BA do you have access to the control run? can you spill the beans? Thanks.

Similar evolution to the op and the second post day 10 amplification brings a system se across the UK a with a cold ne to follow. the high stays out west in general and nw Europe stays cold. 

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While the UK is seeing very little in the way of winter, on the other side of the pond the winter is very close – unexpectedly close! In a very small country like the Netherlands, this small ‘winter outbreak’ is creating a huge divide in temperature. In a distance of merely 300 kilometres, temperatures differ by an impressive 13*C! Also, people have been able to skate on roads due to glazed frost outbreaks. That truly is winter, though a very dangerous one!

Just as impressive is that electricity has been going on and off at many places in the north due to frozen rain getting stuck on power lines. That must be quite eerie to witness. Also, some schools are being closed due to risks on glazed frost. Time to explore this unusual wintry setup!

Winter has reached the Netherlands.

Sneeuw.thumb.jpg.f3bf3b8d162f9758f78e629

From winter to spring temperatures – just in one country! Courtesy to weerwoord

A winter outbreak has rarely caused such large temperature differences over such a small distance in the Netherlands. Whereas temperatures are a mild 9*C in the southwest, in the northeast freezing temperatures are observed down to about -4.6*C, almost moderate frost!

T_current.thumb.png.628c93632793cd871ca3

Current temperatures in the Netherlands. Courtesy to Weerplaza.

Separated by a very narrow line

The vast difference in temperature is represented by a very small line (a surface trough), where the wind jumps from south to east.

Wind_current.thumb.png.3fe315ebcf69e2cc0

HIRLAM (HIRES model of the KNMI) wind forecast for today 21Z. Courtesy: Weeronline.

Above the black line, winds are blowing from the east. These winds are transporting very cold continental air bringing winter weather. On the other hand, to the south of this line southerly winds are advecting mild air into the Netherlands as well. And this interplay is creating a fierce battle – a very dangerous one as well.

Warm air above cold air – extremely slippery and glazed frost!

The fierce battle is played mainly to the north of the aforementioned surface trough. The warm air brought in from the south is unable to ‘remove’ the surface cold layer to its north. Therefore, the only way it can go is up. In this way the warm air slides over the cold air. The result is a dreaded ‘ice triangle’ as it is called in Dutch.

Sondage.thumb.png.ff312fd06edab609c2fe1b
GFS sounding for the northeast of the Netherlands for 21Z. Courtesy: Meteociel

The black line indicates the zero degrees line. Note that whereas at the surface temperatures are below zero, between 300 and 1000 meters the temperature is significantly above zero. This is definitely not the most usual configuration you see in the atmosphere.

What happens is that snow melts in the aforementioned melting layer into rain. Just before reaching the surface, the rain freezes again, creating an ice floor on the roads, and thereby very dangerous and slippery conditions. Somewhat further to the northeast, this warm layer is not present, so there precipitation falls just as snow.

Warnings for very dangerous conditions

It is expected that about one centimetre of glazed frost will fall in the northeastern parts of the Netherlands over the next day or so. Such situation could cause life-threatening situations, and therefore the KNMI (Dutch version of the MetO) has issued warnings for these provinces.

More glazed frost to come?

It seems that even more parts of the Netherlands are becoming prone to glazed frost in the short run. On Wednesday, the frost near the surface is expected to expand all the way to the centre of the Netherlands. Along with some precipitation forecast, glazed frost is quite likely. I have seldom seen so many days with glazed frost in the Netherlands in a row.

Also very impressive is to see such large differences in an ensemble forecast over such a small distance. To show this, below are the ensembles for the southeast and the center of the Netherlands.

Ens_middle.thumb.png.19784b20ba05a333137ENS_Southeast.thumb.png.29da3084e012a181

ECMWF ensembles for the middle (left) and southeastern parts (right) of the Netherlands. Courtesy: Weerplaza.

Note how the spread for Wednesday for the middle of the Netherlands is about 7*C, only for 2 days out. But also the spatial differences are remarkable. In the southeast no member is showing any winter on Wednesday. And yet, almost all ensemble members in the center of the Netherlands do show winter weather for Wednesday. And that two locations located only about 150 km from each other!

Winter weather in the end?

To end with a long-term wintry outlook, what all ensembles do show as well is that temperatures will steadily drop in the long range after a mid-term peak. The majority of the members is indicating some kind of wintry weather as well, with night frosts and daily temperatures a few degrees above zero.

Concluding note

Much more can be said about the glazed frost, but I hope this gives a nice overview of this impressive event occurring in the Netherlands. This definitely was not envisaged by the models over the past few days, though the cold was always worryingly close. This all is nice evidence that you really need models with high spatial resolution to capture the temperature pattern over the Netherlands properly, and to make a good forecast. All in all, a very interesting meterological situation is unfolding!

 

 

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1 minute ago, bluearmy said:

Similar evolution to the op and the second post day 10 amplification brings a system se across the UK a with a cold ne to follow. the high stays out west in general and nw Europe stays cold.

Thanks BA, that's good news.

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From Ian F on Twitter...

 

W COUNTRY Signs continue for some colder, drier conditions into mid next-week...a 'snap' most likely, albeit exact longevity tricky to call

That is a bit more positive for coldies and those flooded areas.

 

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45 minutes ago, bobafet said:

Thank you sir!! That helps immensely and clarifies, much appreciated.

thanks to all who have replied, it has certainly helped, next to learn the charts myself.

You have nailed the answer above as one of the best ways to learn is using the huge range of charts on this forum.

The trick is, to switch through the timeframes, but at the same time change which chart you view. You can view the charts often posted in the model thread but by a quick switch can view temps, winds, 850a and snow risk if that's what floats your boat.

It is easy to get lost in some of the rhetoric but don't worry, stick with it as it becomes even more fun, stressful when you start to see the trends out in fi, which this thread is mostly about.

Here is a link to the charts, just in case you were unsure:

http://www.netweather.tv/index.cgi?action=nwdc;sess=

Enjoy:hi:

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4 minutes ago, Ali1977 said:

From Ian F on Twitter...

W COUNTRY Signs continue for some colder, drier conditions into mid next-week...a 'snap' most likely, albeit exact longevity tricky to call

That is a bit more positive for coldies and those flooded areas.

WIth an update shortly after...

Quote

Ian Fergusson @fergieweather 53s53 seconds ago

W COUNTRY CONT'D However, 'snap' may prove improper lexicon, as it's anticipated to be a marked change in weather type & hemispheric pattern

 

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1 minute ago, i luv snow said:

WIth an update:

 

 

Wow for me that is the best news of the winter  met office starting to see a pattern change

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4 minutes ago, Sperrin said:

Can I ask why and what this is telling you? I have got a very limited understanding of the ECM/GFS charts but can't get my head around these. Thanks!

With pleasure! These charts show anomalies and what upper level thicknesses are predicted to be. The red lines indicate a positive anomaly (higher than average upper level thickness, and hence more likely to be reflected by warmer upper level a), blue lines a negative ...

 

Do you know what, let's keep it simple. It shows fairly strong heights towards Greenland, troughing to the east, net result is the wind blows between the two from north to south, and the strength of the block shows pretty good confidence in the evolution, as much as you can be confident in a 8-14 day chart.

 

John H, help me out here, you'll put it much better than I can!!

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