Models, teleconnections and nowcasting

[johnholmes]

2 hours ago, knocker said:

The ecm differs greatly from the above by amplifying the Bermuda high and interrupting the east bound energy and creating a weak trough in mid Atlantic. Which facilitates stronger ridging in the east and advection of warmer air in the south and then much of England and Wales, with the complication of the aforementioned trough in the north/ Quite obviously there are still issues to be resolved

 

Yes for those wanting more 'heat' then the EC is to be preferred to the GFS version.

Interesting how the two anomaly charts differ. Not looked at NOAA but will go and have a check on its positioning of the troughs-ridges

 

see below

Well not the same but perhaps nearer EC than GFS, remember they are mean charts

Edited May 21, 2020 by johnholmes
various additions

[mb018538]

Still a very impressive belt of high pressure stretching across the mid latitudes there!

[knocker]

The current position of the low

[johnholmes]

30 minutes ago, mb018538 said:

Still a very impressive belt of high pressure stretching across the mid latitudes there!

Don't be taken in by the red lines. They are the +ve anomaly heights but are pretty small. The only actual ridges in the contour lines themselves are down the N American west coast and off N Noway/Russia

[mushymanrob]

12 minutes ago, johnholmes said:

Don't be taken in by the red lines. They are the +ve anomaly heights but are pretty small. The only actual ridges in the contour lines themselves are down the N American west coast and off N Noway/Russia

........ but portend a drier then average outlook? if we accept that higher pressure = less precipitation? not totally dry, but no "monsoon" that often seems to arrive in early june..

[knocker]

Cs with some high Ac progressively invading sky here now

 

Edited May 21, 2020 by knocker

[knocker]

Rain and wind update with the 0600 ecm

[johnholmes]

4 hours ago, mushymanrob said:

........ but portend a drier then average outlook? if we accept that higher pressure = less precipitation? not totally dry, but no "monsoon" that often seems to arrive in early june..

Likely a NW-SE divide judging from the contour flow

[Kirkcaldy Weather]

Wasn't sure where to put this so mods feel free to move to relevant thread if needed. 

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[knocker]

Reasonable agreement between the ext mean anomalies this evening 

A ridge over NW North America adjacent to the tpv northern Canada which has tough extensions south and in particular across Greenland/Iceland towards the UK. A strong westerly upper flow exiting NE North America between the aforementioned trough and the Bermuda high but this diverges in mid Atlantic courtesy of low pressure to the south west of the UK that has been established during the evolution. Thus it has abated a god deal by the time it crosses the UK (aided and abetted by the strong west Russian ridge) and the indications are a relatively quiet period of weather and a continuation of the N/S split with temps a tad above average

Edited May 21, 2020 by knocker

[knocker]

The North Atlantic 500mb and surface analysis for midnight and sat image

The large area of heavy rain should clear northern Scotland by midday with heavy squally showers in it's wake across the north west and here it will also be very windy. Further south it should be mainly clear once the frontal system clears quickly to the east

By tonight the filling low is NW of Scotland so the strong winds will persist in the NW and there will be further continuous rain over northern Scotland courtesy of the complex frontal system

The low continues to move slowly NE through Saturday so remaining windy in the north with whilst the persistent rain continues over northern Scotland courtesy of the occlusion. Some showers across England and Wales, dying out in the afternoon. Cooler than of late

The low finally clears away by Sunday but another trough has tracked into the mid Atlantic and fronts associated with this bring more cloud and rain to the north whilst further south it becomes warmer as the subtropical high pushes north

Further amplification of the subtropical zones reconfigures the Atlantic trough into a positive tilt resulting in a mainly dry day on Monday but some patchy rain from the weakening front as it crosses the country

By Tuesday further trough movement suppresses the ridge in the western atlantic but the one over the UK stands firm so generally a fine day but some patchy rain on the weakening front

Edited May 22, 2020 by knocker

[knocker]

Over the next couple of days the elongated ridge ridge south of the main trough now over Iceland stands firm as energy tracks east south of the latter but there is a slight complication as a residual weak trough left in mid Atlantic from the earlier developments tracks east to bring some patchy rain to the country in Thursday

The GEFS 5-10 mean anomaly this morning illustrates this direction of travel quite well

Edited May 22, 2020 by knocker

[knocker]

The ecm has the residual trough tracking east over Weds/Thurs with an evolution that very much favours central and south east England

[knocker]

The ecm 5-10 mean anomaly

[knocker]

A clearance of sorts here but still allot of ci & Ac

 

[knocker]

A glance at the EC weeklies update for the middle two weeks of June

08 > 15

Still the ridge NW North America adjacent to the tpv northern Canada with extended trough south east next to the ever present (it seems) ridge into south east Greenland. Beneath this quite a benign westerly upper flow across a positively anomalous Atlantic which abates further in mid Atlantic courtesy of the weak trough to the south west of the UK This would indicate a fairly quiet period of weather but perhaps with a marked N/S divide, particularly with regard to temperature

16 > 23

So significant changes

 

[mb018538]

Looks mainly dry and warm-ish. Ppn will start to be a worry if that holds true - next to nothing showing right out to the middle of June.

[mushymanrob]

18 hours ago, johnholmes said:

Likely a NW-SE divide judging from the contour flow

yep... i had figured that but thanks for the confirmation.

im ok with the skew t charts now, in principal, i understand what they show at a basic level. now its a question of honing the detail more, a lot more..

one question i do have though. the synoptic charts for 36-48 hours are usually near enough correct with a very high level of accuracy.

my question is.... are the forecast skew t charts (found in the free area on here) as accurate for the 36-48 timeframe? i ask because id like to be able to sharpen my understanding of the likely cloud conditions in that timeframe. the gfs charts on wetterzentrale give mean cloud cover, (and predicted cape values), but its not so easy trying to determine what cloud type they show.

[knocker]

As the intense low to the WNW of Ireland tracks north east through the rest of today and overnight it will bring very strong winds tp the north, in particular N. Ireland and western Scotland. The associated fronts will also bring a fair amount of rain to NW Scotland and a trough embedded in the circulation some heavy showers to NW England and west Wales

[knocker]

The midday analysis

[johnholmes]

2 hours ago, mushymanrob said:

yep... i had figured that but thanks for the confirmation.

im ok with the skew t charts now, in principal, i understand what they show at a basic level. now its a question of honing the detail more, a lot more..

one question i do have though. the synoptic charts for 36-48 hours are usually near enough correct with a very high level of accuracy.

my question is.... are the forecast skew t charts (found in the free area on here) as accurate for the 36-48 timeframe? i ask because id like to be able to sharpen my understanding of the likely cloud conditions in that timeframe. the gfs charts on wetterzentrale give mean cloud cover, (and predicted cape values), but its not so easy trying to determine what cloud type they show.

As the model outputs are always 3-dimensional they will be accurate at that time scale be it at 1000mb or 500 mb. You ask about cloud 'types'. This can be gleaned from both a surface chart, Td (dewpoints) and the skew-t chart which gives an idea of instability in a more precise form.

 

In fact I think we can see what I'm trying, not very well, to say, by using the post above from k showing the Fax actual and the satellite for about the same time.Well behind the cold front notice how the cloud pattern looks 'speckled', showing instability, check this out for say the Camborne skew-t SW England and compare with, say, one in Holland, in the warm sector, so likely not showing much if any instability and thick cloud layers as the cold front approaches or where the warm front is approaching.

 

It is a good idea to look at the actual Fax chart with a satellite picture, compare the visual with the Infra Red as well, to give you a good idea of what conditions are like at the Fax chart time. Then compare the Fax chart prediction 24, 48 72 hours ahead to see how the model (with an experienced human input, shows the possible positions. Of course when you use the 500 mb anomaly charts they will never, and are not there to predict cloud amounts but will give an idea of whether an airmass  is stable or unstable.

 

Not very well explained mushy but connecting all the things together is extremely complex. Anyway I hope it may help clear things a bit and please do ask questions.

To the team please drop me a note if you would prefer these comments to be via pm?

[mushymanrob]

9 minutes ago, johnholmes said:

As the model outputs are always 3-dimensional they will be accurate at that time scale be it at 1000mb or 500 mb. You ask about cloud 'types'. This can be gleaned from both a surface chart, Td (dewpoints) and the skew-t chart which gives an idea of instability in a more precise form.

 

In fact I think we can see what I'm trying, not very well, to say, by using the post above from k showing the Fax actual and the satellite for about the same time.Well behind the cold front notice how the cloud pattern looks 'speckled', showing instability, check this out for say the Camborne skew-t SW England and compare with, say, one in Holland, in the warm sector, so likely not showing much if any instability and thick cloud layers as the cold front approaches or where the warm front is approaching.

 

It is a good idea to look at the actual Fax chart with a satellite picture, compare the visual with the Infra Red as well, to give you a good idea of what conditions are like at the Fax chart time. Then compare the Fax chart prediction 24, 48 72 hours ahead to see how the model (with an experienced human input, shows the possible positions. Of course when you use the 500 mb anomaly charts they will never, and are not there to predict cloud amounts but will give an idea of whether an airmass  is stable or unstable.

 

Not very well explained mushy but connecting all the things together is extremely complex. Anyway I hope it may help clear things a bit and please do ask questions.

To the team please drop me a note if you would prefer these comments to be via pm?

thanks john, understood. ill ask any further qs by pm unless they pertain directly to the current synoptic charts so not to derail this thread further.

[knocker]

Just to add to John's excellent points above I was just about to post the Camborne sounding with the forecast sounding from the 0600 gfs ( I don;t have access to NW). I have no way of proving this but my gut feeling is the forecast soundings are too broad brush to pick up rapid changes of the moisture content in the atmosphere which would make cloud levels a no no. This is just my opinion of coarse

 

Edited May 22, 2020 by knocker

[johnholmes]

31 minutes ago, knocker said:

Just to add to John's excellent points above I was just about to post the Camborne sounding with the forecast sounding from the 0600 gfs ( I don;t have access to NW). I have no way of proving this but my gut feeling is the forecast soundings are too broad brush to pick up rapid changes of the moisture content in the atmosphere which would make cloud levels a no no. This is just my opinion of coarse

 

I tend to agree there k, I've never checked but as NW Extra gives predicted soundings every 6 hours for most locations perhaps possible to do this?

[knocker]

Between t120 > 168 the ecm has the residual trough in mid Atlantic swallowed up by further movement of the Icelandtrtough as a front skirts northern Scotland

 

 

Edited May 22, 2020 by knocker