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Model Output Discussion - Stormy Period Inbound...


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well there is no swing back on the extended eps this morning. If anything, it's support for the glosea/MOGREPS return of WSW zonality towards day 14 has slipped a bit.

of course, the output post day 10 is always subject to some tweaks but if we don't see a snow event over a fairly large part of the country in that 11/14 day period, I will be surprised..

Hints of the ridge following the sinking trough allowed to become a decent n Atlantic feature. no idea what the clusters show but the combination of slow sinking mean trough, lowish SLP and thickness in the 525/530 area is something we haven't seen for a long time.

I think we will have to rely on secondary features running into or around the troughing to deliver an event but at this time of year, even innocuous looking output can deliver under a slackish cold anomoly.

the gefs make a bit more of the Azores ridging which means we see the alternating cold with mild blips as warm sectors come through. I suppose the biggest illustration of this being around day 12/13 where gefs brings a mean ridge through with 552 dam touching the south coast.at that point, ECM has the south coast firmly under the trough with 534 dam on the coast. Actual thickness conrast from 530 on ECM to 536 on gefs. plenty to firm up on but seems likely that we will see a decent wintry period beginning with the storm midweek.

Thanks BA, well, just goes to show how things can change greatly from D8-10 to D11-14, wasn't expecting anything wintry to follow the D10 mean which is all I can see. It will be interesting to revisit the mean charts in say 5 days time to see if they are showing what you say.

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Righty-Ho. This can't pass without comment. Below follow just a random snapshot of detailed medium range briefings from Ops Centre made in first days of Jan, looking towards what was then the 10-15d

Je suis charlie

A bit of clarity re EC Monthly prognosis and expectations further ahead. The broad scheme of things sees a shift in balance re lows to NW becoming more aligned further away to the north from the UK, u

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Rjbw, depends on the Azores ridging. If ECM is right it will stay suppressed and the trough will sink se across nw Europe. if gefs are right, the nw/se axis of the jet will be there but the mean troughing will be just to our east allowing warm sectors to be evident across the uk.

Well illustrated by the Naefs/ecm anomolys at day 10

.

Given how much of a pain the Azores has been thus far, you wouldn't bet on the ECM being wrong but I would say that the extended ECM eps have had a very good season (to this point!)

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post-6981-0-37066400-1420970412_thumb.jp

Edited by bluearmy
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Friday and next weekend still looking stormy and cold....upgraded from the 00Zs. Looking at those charts anywhere in the country could be brown to some squally winters showers, even us in the South.

Edited by Ali1977
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Picking up on this part of the ba post

Rob, that mean upper ridging has been showing for a while in the svaalbard area. it very shallow though and is splitting the Siberian/Canadian vortices. I say splitting, but it's quite a weak split with the Alaskan ridging the other side far more evident. It does help to sink the troughing in our vicinity though. 

That is very true and it is not developed any in the last set of charts.

Just a brief one from me this morning with the usual links at the end

Nothing of any major change from what I suggested yesterday seems likely over how the anomaly charts have presented in the past 24 hours. The overall 500mb flow into, over the UK and east into Europe looks like remaining north of west with relatively cold air at this height. Negative anomalies are predicted on all 3, in varying degrees, to the NE of the UK and the flow remains quite strong Atlantic into UK/Europe but a bit less than currently with the 8-14 NOAA also decreasing. So fairly cold for most areas much of the time but no major deep northern cold seems likely. Further deep lows may still develop into mid January if the anomaly charts are correct. Snow seems unlikely to be a major hazard for southern low ground but could be for hills from the Midlands north at times(and low ground but chiefly central and northern Scotland) along with further wind issues. Looking beyond 10-12 days and there is not much indication, at least not solid enough, to suggest that any bitter northern outbreak is likely. The MJO although trending towards phase 7 looks increasingly likely to have insufficient amplitude to have any major impact on the weather patterns affecting the UK.

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/foroper.shtml

http://www.americanwx.com/raleighwx/MJO/MJO.html

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Hope this is not too off topic but wonder if anybody could assist. Presumably organisations like the Met have more tools to look at than the general public however presumably in the main they are looking at a lot of the same models.

On a site like this we can sometimes see that two people can look at a model and see totally different things therefore I wondered bow much human input there is to analysing the data as obviously they do not issue raw output - again sorry if off topic just curious.

Yes obviously the MO have a lot more forecasting tools than we can see on here for example MOGREPS and GLOSEA5 but they also use the ECM and GFS and other input data from around the world..

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Friday and next weekend still looking stormy and cold....upgraded from the 00Zs. Looking at those charts anywhere in the country could be brown to some squally winters showers, even us in the South.

Friday and Saturday offer nothing to pretty much all of the UK as the low hangs around and leaves us in a warm core

gfs-1-150.png?6

850s range from 0C to -4c  so just the higher levels receiving anything wintry on this run. Parallel similar so we might have to wait until Sunday to receive the colder air from the north.

In the next 5 or 6 days, Tuesday looks the best bet, if the cold 850s hold out and verify of course.

 

Better from the Parallel at the end of hi-resolution

gfs-0-168.png?6

the -8C isotherm gets across most of the UK by Sunday. Lets not talk about the operational to day 8, or beyond......   :nonono:

Edited by Captain shortwave
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Ba/john... Cheers, i hadnt noticed it before, my bad :)

Not really rob - that weak ridging on the ens affects the axis of the jet, in tandem with the pull back of the Azores ridge. It is important - it's just not likely to lead to a sustained surface pressure rise or a significant block in the next two weeks though I would be reticent about saying no chance after day 12.

Also, re a GH - a fully fledged block seems very unlikely but a decent wedge of heights in the s greeny area is certainly a possibility through week 2, especially later.

Edited by bluearmy
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The gfs 06z ops certainly at odds with the ECM ens in week 2. Given that they are also at odds with their own ens to a fair degree, perhaps best ignored (unless this becomes a trend).

 

...Or it may be worth looking a bit earlier. The GFS at D5 has the storm's eye in situ over NE Scotland warming out whilst ECM pushes the low into Norway:

 

post-14819-0-33030500-1420974804_thumb.p   post-14819-0-81814800-1420974804_thumb.p

 

If that is wrong then anything after must be very uncertain. If you look at the D5 clusters from ECM it is apparent the op is not in the main cluster. Cluster 1 in fact is closer to the GFS op take on the D5 storm status: http://old.ecmwf.int/samples/d/inspect/teasers/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa%21120%21pop%21od%21enfo%21enplot%212014011912%21%21

 

ECM also has a surface low at T144 running on the jet through a surface HP. This stalls the Azores as it sinks to Iberia propping up the low heights there:

 

post-14819-0-26026200-1420975806_thumb.p

 

GFS has this LP running over the high and disrupting the Atlantic ridge. I do not know whether that ECM short wave is just a figment of the algorithms but to me the GFS solution looks more viable. GFS therefore does not inhibit the easterly movement of the Azores and in the D10-15 period further pulses of HP coming from the US help to ease the Euro trough east and we get more TM influence. No idea if that is the correct solution.

 

So I would say uncertainty is high due to how the storm is managed and to what happens with the short wave in the Atlantic. You can see from the GEFS that there are multiple outcomes at T144: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=144

 

I am more inclined to believe that with further heights coming from the US corridor there will be a push east of the Azores and the slow movement of the Scandi/Euro trough eastwards. On the surface that would mean a flatter zonal flow over the UK. Small variations on the overall theme of Canadian PV driver as we wait for a blocking pattern to set up.

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I think this could be a classic case of gfs picking up a trend for height rises to our north west in the longer term, then the op runs seemingly back tracking but ensembles sticking with the trend and then the op runs going back to the original trend. I think we will be seeing much better output over the next couple of days and I think the extended ecm ensembles will be much colder when they update tonight.

Just going back to my post yesterday. After viewing the 06 gfs and ensembles, I am seeing the gfs going back to it's original trend of height rises towards Greenland circa 11 days from now. It first spotted this at 16 days out then dropped the trend and now the 06z has picked it up again.

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Looking at the snow stamps large parts of the UK have a decent chance of seeing some snow on Tuesday (final chart 2nd row right at the bottom is the mean if your struggling to read the text)

 

snow_60_ps_slp.png

 

Beyond this the mean doesn't offer much away from the higher ground in northern Scotland

 

Charts TWO

Edited by Summer Sun
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having looked at the models this morning things becoming even more messy in the later runs the gem has dropped its last couple of days of eye candy charts but then its not a suprise due to the pattern set up were in now.

most models also project a split but this soon gets swept aside and tries to reset back to the pattern were in now.

 

i think that the fax charts say it all when coming to this weeks weather often wet windy snow for the north and at times midlands and perhaps futher south at times as the 528 dam pushes through but very marginal in the south as the 528 line might not get as far as projected on the fax.

 

the southwest of england could well have some excitement and the chilterns downs ect id of thought would be better locations if snowfall is what your looking for.

fax120s.gif?1

what is interesting about the fax is how far away the azores heights is held back,

to be fair id like to see this continue to be held back if a string of low pressures are going to bombard the uk id rather the azores is where it is now as when a gap is there it will try to build to the west at least giving a more arctic flow rather than polar flow....

 

if this does happen then the southeast might get to see at least a bit of wintry weather its all a little marginal but we seen suprise fall many times i remember april 2008 here on the south coast my kids had never seen snow it only lasted half the day but was amazing for us all as it been a fair amount of time since even i had seen anything wintry.

 

but my excitement for futher changes has dropped to 70% now but still enough to keep watching.

the problem is the jet is very strong and directed straight at us keeping us in this very mobile pattern but there most certainly will be change right now i still punt for colder end of jan but little more less confident although which such a rapid flowing pattern i would not rule anything out even blowtorch record breaking sw flow.

 

gfs-5-192.png?6

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http://www.meteociel...6&carte=&mode=0

 

it seems the storm now is much further  south so  the that  could make things interesting to say  the  least!!!

 

Track still uncertain according to UKMO but Yellow warning just been issued for strong winds and heavy rain for Wednesday and Thursday: here

 

60-80mm rain on high ground and gusts of 75mph on southern and western coastal regions. Not a good day for travelling.

Edited by i'm dreaming of...
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also worth noting that the ecm does have a ridge trying to build around the ne of the states which i suspect would influence the trop vortex to move towards the ne into scandi area.

 

ive done a little diy job hopefully we can get the azores to move as arrowed and the ne states to have a much more robust ridge continue to build north east.

 

and the scandi vortex drop a little more south even perhaps a little southwest to we can set up a better angles.

the ecm jet being a little futher south is ok but really need this to start coming to a closer timeframe.

 

but im still hopeful the the movement of the vortex might give a more grounds for height movement.

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The set up is ripe for secondary low developments springing up out of nowhere thanks to shortwave activity to our NW, the FAX charts are suggesting such a scenario come Thursday, such features can bring surprise snowfalls out of the blue at this time of year (memories of the infamous localised snowfall that hit much of Yorkshire in late Jan 1995) spring to mind, with marked demarcation of cold air to the north of frontal activity clashing with tropical maritime air to the south.

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Just going back to my post yesterday. After viewing the 06 gfs and ensembles, I am seeing the gfs going back to it's original trend of height rises towards Greenland circa 11 days from now. It first spotted this at 16 days out then dropped the trend and now the 06z has picked it up again.

I would agree with this, We have seen this so often in the past before. It could be that the model is at first to progressive on 

a pattern change. It could also be the possible effects of a MJO wave and its implications on the atmosphere. Again the 

amplification could be down to the strong  heatflux that we have seen in the stratosphere will have effects as it propagates 

downward towards the troposphere. 

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The GFS 06z shows a very disturbed week ahead with bouts of heavy rain and severe gales but early in the week it looks like becoming colder from the NW with a risk of some snow in places on tuesday, midweek is a bit milder but very wild and rainy and then colder air digs south to all areas to end the week with wintry showers and frosty nights. FI shows a risk of northerly reloads, especially if high pressure becomes centred further west. Met Office going with a brief lull next Sunday before further wet and windy / cold and showery spells return.

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