Models, teleconnections and nowcasting

[knocker]

So for the minute looking at the 6-11 anomaly unsettled will suffice

[knocker]

The ecm agrees with Exeter and tracks the developing low NNE across the country on Friday and has it over Scotland by midday Saturday

Remaining unsettled through the beginning of next week but further amplification of the subtropical zones does cause some trough disruption by midnight Wednesday. The detail is of course subject to change

 

Edited December 16, 2019 by knocker

[knocker]

The ext EPS pretty much as expected but perhaps with a tad more development of the two vortex lobes So still retrogression of the Atlantic trough with heights rising in the east portending a drier and warmer spell. Hallelujah praise the lord

 

[mb018538]

 

33 minutes ago, knocker said:

The ext EPS pretty much as expected but perhaps with a tad more development of the two vortex lobes So still retrogression of the Atlantic trough with heights rising in the east portending a drier and warmer spell. Hallelujah praise the lord

 

Nice to see the Atlantic trough backing west a bit to allow (hopefully) a drier spell. We could do with it really, been sopping wet for weeks now.

[knocker]

The Camborne midday sounding potentially very unstable in the lower regions but further up indications of the thickening Ac and Ci that have been progressing all day, courtesy of the warm front to the south. Very good depiction of the deep low in the western Atlantic on the sat image.

 

[knocker]

The ext GEFS still moving in the direction previously indicated

Salient points

Upstream two vortex lobes Siberia, northern Canada split by a strong Alaskan ridge which is adjacent to the trough down western North America

Strong westerly upper flow exiting the eastern seaboard south of the vortex extension and backing in the eastern Atlantic courtesy of the subtropical high amplifying over the UK before ducking south east thanks to the trough over Europe that has now replaced the long lasting European high, Thus a more settled period for the UK with temps aroundaverager but no longer toasty over Europe

 

 

Edited December 16, 2019 by knocker

[knocker]

After a quiet day tomorrow and start on Wednesday rain and strong winds will sweep in late Weds into Thursday courtesy of fronts associated with the deep low out in the Atlantic

And over the next 36 hours the upper trough re-orientates as the strong jet hits the buffers of the ridge in the east and a low develops in the south east quadrant and swings north over the country on Friday bringing more rain and strong winds

And this complex battle continues over the weekend so continuing unsettled

Edited December 16, 2019 by knocker

[knocker]

There are some major differences between the ext GEFs and EPS, particularly regarding amplification in the eastern Pacific and Europe, so for now just a watching brief

[knocker]

Continuing the run up to Xmas

The North Atlantic 500mb and surface analysis for midnight

The rain currently still effecting the south east will gradually move away this morning leaving most areas with a reasonably bright and dry day once the early morning fog has cleared but showers will persist in coastal regions and in particular in Scotland

Tonight showers may persist for a while but the generally a clear night with frost in many areas and fog mainly in central and southern England

The fog may linger a while in some areas on Weds but once cleared another quite reasonable and dry day but to the west the Atlantic is getting into gear and a deep low is now west of Ireland and the associated fronts will bring rain to N. Ireland and the south west by mid afternoon which will spread east accompanied by gales in the western regions

The rain will clear all areas though Thursday morning followed by showers but some heavy and persistent rain will effect southern England and then all other areas as it moves north courtesy of a wave on the trailing front and a trough running around in the circulation

Once all of this is out of the way not a bad day on Friday with just some heavy showers in the NW.N but things are getting quite complex to the west under the trough that is dominating the Atlantic

And part of this complexity is some quite intense cyclonenisis near the left exit of the jet with a deep surface low 956mb evolving south west of Ireland by midday Saturday.and this will bring heavy rain and strong winds to the south west late on

 

 

Edited December 17, 2019 by knocker

[knocker]

This sort of rapid development inevitably results in disagreements vis the detail and this is again the case this morning with the gfs having the deep low further north and then on to this quite messy solution by 0600 Sunday so some caution id required from this point

From here until midweek the eastbound energy is attacked on two fronts by the amplification of the subtropical high zones so continuing changeable albeit with no great intensity until inertia sets in. This is of course just the gfs take on this

 

Edited December 17, 2019 by knocker

[knocker]

I mentioned last evening the uncertainty vis the ext anomalies and in 12 hours the GEFS has shifted somewhat

[knocker]

The ecm predictable has a different tale on Saturdays low which merely emphasizes that at least three models are staring next week from a different position

with this in mind it's wise not to venture too far afield so suffice it to say the ecm rushes another low up from the south west to impact the country on Tuesday

 

Edited December 17, 2019 by knocker

[knocker]

The ext EPS continues to be a thing of beauty I wont waffle on as it is very much along the lines already discussed

And no disagreement from last night's NOAA

[Jordan S]

A Frosty night for most tonight except perhaps the far south with light winds for all allowing a risk of some quite dense fog patches to develop in places especially for England and Wales this would be slow to clear tomorrow morning. 

Arome picks it up well but always shows it as persistent drizzle.. Any fog lifting into low cloud then clearing later in the morning in places where they do form as a southerly wind begins to freshen from the west. 

Low cloud forecast.. 

Edited December 17, 2019 by jordan smith

[johnholmes]

Not done any copying for over a week although have kept tabs on the 3 outputs, this morning Tuesday 17 December shows

Ec-gfs and as over most days in past 8 some differences ec-gfs. This morning ec again shows a push of contour heights from sw Europe towards the uk, almost combining with the ever present nw euro/Russian high and a weak link towards the heights over parts of n America towards Greenland. There have been days when this link was quite pronounced with a system of low heights to its south. The low heights are mainly off n America with a suggestion of them e of the uk (on gfs) and a cut off (on ec) over central/east med. For the uk both show a w’ly flow but created by differing ridges and troughs as the charts show

Noaa, not too different from what it has shown over the past 2-3 days, has the major trough from the PV off nw Greenland with its attendant trough, fairly rounded, south of Greenland with +ve heights still showing from n Russia/Norway across to central Canada, giving a general w’ly atlantic flow into the uk, stronger in the south than the north. (is this a possible clue to further out?) Heights into the uk range from 534 dm over Scotland to 552 dm just s of the uk. So the air for the uk, on this noaa chart, and for a few days past, originates from different sources, real Pm in the north less so in the south?

The 8-14 shows the upper trough from the PV sharpening thus backing the atlantic flow into the uk to arrive from s of west, heights ranging from 540 dm in n Scotland to 558 dm just south of the uk.

This possibly suggesting a rather milder air into much of the country, with just a slight signal for ridging well e of the uk.

 

Summing up, to me, there is little indeed no signal for any cold air into the uk once this current coldish airmass clears later this week,  at least for 2 weeks? I never attempt to use these charts to go beyond 15-18 days.

Sorry if this is not what most folk want to read, just my honest attempt to use these charts to try and predict the overall weather pattern for 2 weeks ahead.

Copying into both main threads.

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

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

[knocker]

The gfs 06 take on Saturdays low

[knocker]

A 'tongue of descending Stratospheric air at midday

[knocker]

The baroclinicity within the complex upper trough is still causing problems regarding detail next week until the subtropical high flexes it's muscles The question is how transient will it be?

[knocker]

The gfs 7-12 anomaly is along the lines of recent thinking from the mean ext ens anomalies

Edited December 17, 2019 by knocker

[knocker]

This evening's ext mean GEFS anomaly has the east Pacific ridge/ west N, America trough combination in conjunction with quite an intense vortex northern Canada with extension into the NW Atlantic A strong westerly upper flow south of this but backing and abating appreciably in the east thanks to strongly amplifying subtropical ridge extending over the UK into Iceland. This would indicate a much more settled period of weather. Of course there hasn't been good agreement with all the ext outputs so await the EPS and NOAA

 

Edited December 17, 2019 by knocker

[knocker]

The detail for this weekend is proving elusive, probably because there is a lot of energy in the mix

But through the beginning of the week the amplification of the subtropical high just to the east of the UK does interrupt this energy flow to some extent so becoming far less unsettled But the detail is far from a done deal

[knocker]

The differences between the ext GEFS and EPS are readily apparent without me going into waffle mode. Suffice it to say at this stage that the percentage play would certainly appear to be ridge/trough combination over Europe but the structure and orientation of which awaits pinning down

[knocker]

Tonight's NOAA suggests nothing to question the above conclusion

[frederiksen90]

Really strong blocking signal at Greenland and Iceland at 300+ hours in GFS ensemble

http://modeles7.meteociel.fr/modeles/gens/runs/2019121712/gensnh-21-5-300.png

http://modeles7.meteociel.fr/modeles/gens/runs/2019121712/gensnh-21-5-360.png

And at the same time, the east wind is now hitting 30 hPa:

https://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_UGRD_ANOM_ALL_EQ_2019.png

Maybe this can help amplify the blockages at solar minimum, which can expand the cold potential? Maybe the trends between Christmas and New Year can really be the start of something?

[knocker]

The North Atlantic 300mb wind field and surface analysis for midnight and the 0400 UK chart

Fog in eastern areas will be slow to lift this morning but once it does there will a fair bit of sunshine in many areas but cloud will quickly encroach from the west and rain will effect N. Ireland and the south west by 1000 and then spreading east though the rest of the day. All courtesy of the fronts associated with the complex low to the west

The rain will continue to spread east tonight, with some heavy bursts, accompanied by strong winds as one intense low centre tracks just west of Ireland. In the early hours further heavy rain will move north through southern/central England thanks to the cold front starting to develop a wave

Much of the rain will clear Thursday morning but a further band of heavy rain will track north through the afternoon courtesy of the now developed wave. Quite a marked temp spread

The initial wave will continue to move north overnight Thursday but another wave will bring further heavy rain to southern and eastern areas through Friday morning

The rain will have cleared by Saturday but cyclogenisis is still occurring in the complex trough to the west and rain from fronts associated with another deep low will effect the south west during the afternoon and spread east and ease over Saturday night

The country is still under the umbrella of the trough on Sunday so a day of sunshine and showers with some longer periods of rain in some areas

Edited December 18, 2019 by knocker