1536 replies to this topic

[The PIT]

Interesting so we may have been looking at duff data. Would be interesting to know how long this has been going on. Pity we don't have the orginal from noaa. A quick google doesn't reveal anything.

[Paul]

I wouldn't read much into it at all - a few duff buoys is not likely to make a huge difference when you consider the amount of data they pull. They also do QC on data every run and remove anything that is iffy.

[Crocodile23]

Paul, on 19 January 2012 - 18:13 , said:

I wouldn't read much into it at all - a few duff buoys is not likely to make a huge difference when you consider the amount of data they pull. They also do QC on data every run and remove anything that is iffy.

QC?

[thunderman24]

Quality control

[lorenzo]

Hopefully GP can provide a summary at some point, am lacking in expertise for the GWO charts. Can see a tendency here though and it isn't for more of the zonal train.. If I am looking at this right the mountain torque figures are hammering into the global momentum.

[summer blizzard]

Decided to post this here since the normal model thread just swamps posts within minutes.

As the prospect of the easterly is now within the timeframe of a few days i believe it is the best idea to drop the models and focus on the FAX charts as these are based on all UKMO and ECWMF ensembles (top 2 global models) in addition to the forecasters knowledge and experience.

I first bring your attention to the actual chart for 12z and the forecast chart for 12:00 tommorow...


You can see from the forecast chart for tommorow that the Russian High is already present, strengthening and retrogressing westward with the low north of the UK split and weakening as it moves south..


That in itself is a crucial development as the processes leading to the potential cold are occurring as we speak.

Perhaps most importantly is the trend in the models though which some have described today as negative however in relation to the close range FAX chart this is not true. You can see from the 0z run forecast for 12:00 tommorow that the Russian High is 2-3mb stronger than previously forecast and the low over the UK is a little stronger which will ultimately prevent the Azores High coming in that bit earlier and enhance cold air advection from the east...


So certainly in the mesoscale timeframe what we see is if anything an upgrade.

I would also add that the Met Office do forecast a snow event on Monday and have the high win..

http://www.bbc.co.uk...xtra-uk-content
http://www.bbc.co.uk...xtra-uk-content

[Sonnia]

Summer Blizzard - At last someone had posted something that I can understand "plain English" simple and polite, without bad mouthing the other charts, or anyone else or being totally bias.

Keep up the good work - A very pleasant post

[lorenzo]

For a well written post on the GWO and AAM changes have a read here. Covers the pattern shift, the stratosphere, GWO and MJO.
One image used from the map room shows the scrubbing of the Westerlies GP mentioned some posts ago on this thread.

Edited by lorenzo, 26 January 2012 - 20:49 .

[Catacol_Highlander]

GP - for a man whose winter forecast is just about to become the stuff of legends you are very quiet.

From a technical angle, now that the cold is on our doorstep and it looks as though the high may retrogress ala GWO phase 8 as you stated - where are we sat for more specific details through February, or is it just a case of sitting back and watching weeks of cold? I read the article from Lorenzo's post above on WX the other night which, apart from having my head spinning, suggested and phase 8 -1 - 2- 3 shift perhaps mid month. In a more simplistic way than that post what are the signals going through later Feb and on towards March?

Apologies for asking you to do more work. :-)

Edited by Catacol_Highlander, 28 January 2012 - 23:24 .

[karyo]

I'd love to know as well :-)

Karyo

[jethro]

A query for all you clever people.....

When we get a winter Easterly like now, more often than not we get bitterly cold, but predominately dry weather. Further East where the cold winds originate, the continent gets lots and lots of snow too - why do we get cold but often no snow? I understand the concept that very cold air is usually also lacking in moisture but it's even colder in say Poland and it doesn't stop it snowing there.

[damianslaw]

jethro, on 01 February 2012 - 20:00 , said:

A query for all you clever people.....

When we get a winter Easterly like now, more often than not we get bitterly cold, but predominately dry weather. Further East where the cold winds originate, the continent gets lots and lots of snow too - why do we get cold but often no snow? I understand the concept that very cold air is usually also lacking in moisture but it's even colder in say Poland and it doesn't stop it snowing there.

I'll let others with more knowledge and experience explain, but I suspect it is down to how unstable the airstream is. Here we have very light winds and the air is very stable indeed hence no convection or trough formation over the N Sea. Had heights been closer to the northeast then we would have seen a much tighter squeeze in the winds and convection and trough formation would be occuring - as we saw in Jan 87 and Feb 91. We also don't have low heights to our south.

In central and eastern europe - the air is much more unstable thanks to a squeeze in isobars caused by a low over Italy and the high over NW Russia - this is creating a very strong wind and stirring the upper atmosphere much more than here enabling heavy snowfall thanks to disturbances in the airflow caused by trough formation.

Easterly set ups such as Jan 87 and Feb 91 are rare, and we often see dry easterly airstreams at this time of year.

A much better place for heights to set up is to the NW of Norway enabling a much more unstable flow from the NE or even better still over Iceland and E Greenland enabling trough and frontal snow formation from the north/northeast as we saw in late Nov 2010 - superb synoptics!

Edited by damianslaw, 01 February 2012 - 21:59 .

[Robbie Garrett]

Interesting setup this Saturday/Sunday nights. Looks to me that this is going to be a huge headache for the MetOffice to get this right, cold front stalls from the west, and then warm front bumps into it, giving an occlusion.... small LP developed near Amsterdam, which dissapears.

[lorenzo]

An interesting projection on the MJO from NCEP, not looked at this for a bit.. Strongest movement on this chart have seen in what seems like months..
Ties in with your thoughts GP from the Model Thread.

[chionomaniac]

lorenzo, on 03 February 2012 - 11:51 , said:

An interesting projection on the MJO from NCEP, not looked at this for a bit.. Strongest movement on this chart have seen in what seems like months..
Ties in with your thoughts GP from the Model Thread.
NCPE_phase_21m_small.gif FebruaryPhase8500mb.gif

As Hannibal used to say - 'I love it when a plan comes together'!

[geoffw]

lorenzo, on 03 February 2012 - 11:51 , said:

An interesting projection on the MJO from NCEP, not looked at this for a bit.. Strongest movement on this chart have seen in what seems like months..
Ties in with your thoughts GP from the Model Thread.
NCPE_phase_21m_small.gif FebruaryPhase8500mb.gif

i take it thats a very cold and snowy chart? even for northern ireland?

[lorenzo]

Quote

i take it thats a very cold and snowy chart? even for northern ireland?

Yes Geoff that is correct, this chart keeps us in the Freezer and some of the charts on the NWP in FI land just now are depicting good Northerly / Northwesterly incursions, so I would be positive about your chances. Excitement around this relates to the playing out of the Winter forecasts, and how patience this winter has been thin on the ground at times, looks like it's well been worth it though..

[BLAST FROM THE PAST]

geoffw, on 03 February 2012 - 21:04 , said:

i take it thats a very cold and snowy chart? even for northern ireland?

Geoffw
Green is HP blue is LP. On that chart expect a flow from Northerly quadrant and I would say E of being prevalent....so freezer conditions

BFTP

[Terminal Moraine]

jethro, on 01 February 2012 - 20:00 , said:

A query for all you clever people.....

When we get a winter Easterly like now, more often than not we get bitterly cold, but predominately dry weather. Further East where the cold winds originate, the continent gets lots and lots of snow too - why do we get cold but often no snow? I understand the concept that very cold air is usually also lacking in moisture but it's even colder in say Poland and it doesn't stop it snowing there.

The easterly we've been experiencing has arisen due to a large block of high pressure over Scandinavia and western Russia .This synoptic situation forces the jet stream south through the Mediterranean and drives areas of low pressure eastward into the eastern Med, the Balkans and the Adriatic where they can linger for days with little filling.
The areas of eastern Europe which have received the most snow, such as Poland and adjacent areas, have been on the northern edge of the low to the south and squeezed between that and the high to the north with a constant feed of bitterly cold but moist and unstable air resulting in copious amounts of snow.
The source of our air flow has been from further north, northern Germany and southern Scandinavia, where the air is much drier and more stable as it flows out of the high.
The situation in the snowy areas of eastern Europe is akin to us having a large area of high pressure stretching between Scandinavia and Greenland and areas of low pressure moving into southern England from a south or south westerly direction, much as happened in February and March 1947.

[Backtrack]

A question for the more advanced users:

Today in Cheshire all I have had is freezing rain with the odd flake thrown in. It started at -3C with a DP of -5C, which I thought was shocking at best.
The uppers at the time were -3C ish.
Manchester had the exact same uppers, dewpoints & surface temperatures, yet they've had lots of snow (knew this would happen anyway)

Now I'm wondering if the warm front had brought in some kind of warm sector between the 850hPa boundary and the surface level that was not picked up on by the models flirting with coastal areas & the Cheshire area that missed Manchester and surrounding areas out?

Thanks.

Edited by Backtrack, 04 February 2012 - 17:42 .