Models, teleconnections and nowcasting

[knocker]

The hiatus next week when the high cell domination. is briefly interrupted starts, according to the ecm, when the cut off upprer low in mid atlantic merges with the ext of the vortex over Greenland at t108, Over the next 48 hours the whole shebang moves east and then deconstructs as the subtropical high once more surges in mid Atlantic/

Edited December 28, 2019 by knocker

[knocker]

[knocker]

1400

[knocker]

Dry area above the low level clag but obviously moist aloft with some thick medium level cloud. Not sure associated with what?

[knocker]

The gfs 5-10

Aleutian ridge into the Arctic; intense vortex moving east towards Greenland; strong westerly upper flow across the Atlantic.

No surprises

 

[knocker]

Not a lot to add to previous comments vis the ext GEFS mean anomaly

Reasonable upstream amplification with the east Pacific ridge/western N. America trough as the tpv drifts east to NW Greenland.

Strong westerly flow across the Atlantic around the subtropical high which retains some influence over the UK

 

[knocker]

A couple of interesting soundings at Camborne and Nottingham at midnight for the end of December

Both feature large radiation inversions below a warm subsiding airmass with a  high lapse rate tropopause

Camborne

Surface temp 8.8C and temp 973mb 18.0C; Trop. 149mb

Nottingham

Surface temp 5.6C; 965mbb 16.2C and Trop 146mb

Edited December 30, 2019 by knocker

[knocker]

The EPS this morning has a cessation of any Atlantic anticyclonic wave breaking around t168 and thus much of the subtropical high amplification over the UK is fast disappearing in the 5-10 period, albeit retaining some influence against the eastbound energy

In the ext period this influence has virtually disappeared as the vortex/trough to the north west becomes the dominate feature with a strong westerly upper flow across the Atlantic

Edited December 30, 2019 by knocker

[knocker]

And if you are wondering why the gfs and ecm have different temp profiles for the weekend check the surface analysis

[Blessed Weather]

A strongly negative Eastern Pacific Oscillation (EPO) has reappeared as a potentially important influence on the NH pattern as we move into the New Year. The 8-10 day mean 500mb heights anomalies ending 8th Jan showing the strong Alaskan ridging towards the Pole, coupled with a strong Atlantic ridge, resulting in the TPV being squeezed and splitting.

6-8th Jan mean hgt anom:

For comparison, today's (30th Dec) 500 hPa anomalies for 8th Jan:

ECM:  GFS:

And for interest, the GEFS heights anomalies for 6th Jan (8th Jan not available) at 100hPa:

Meanwhile, up at the SPV level of 10hPa the squeeze is currently being applied by the Alaskan/Siberian combo which fits with the Ventrice tweet of yesterday. GEFS 10hPa for 6th Jan:

Ventrice tweet:

Sources:
500mb heights anom: http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html
100 and 10hPa heights anom: http://www.atmos.albany.edu/student/hattard/realtime.php

[knocker]

Continues to be indicative of the pattern

[knocker]

Pity we can't get the warm air down to the deck. Still a massive low level inversion here from from 9.2C on the surface to 18.4C at 968mb with a spot wind of 215/23kts at 989mb advecting in cooler air along with banked Stratus that has given virtually total cloud cover all day with just the odd breaks

Edited December 30, 2019 by knocker

[knocker]

The gfs 5-10 pretty much as expected with the vortex lobes Labrador Straits, northern Russia with a very strong upper flow across the atlantic battling with the quite resident subtropical high centred to the south west of the UK. Thus a very fluid Atlantic but retaining high pressure influence over the southern part of the country but tending to be quite windy and wet to the north and north west as systems track east quickly

 

Edited December 30, 2019 by knocker

[Dorsetbred]

41 minutes ago, knocker said:

The gfs 5-10 pretty much as expected with the vortex lobes Labrador Straits, northern Russia with a very strong upper flow across the atlantic battling with the quite resident subtropical high centred to the south west of the UK. Thus a very fluid Atlantic but retaining high pressure influence over the southern part of the country but tending to be quite windy and wet to the north and north west as systems track east quickly

 

Thanks Knocker, a breather for a while down here on the South Coast then?

[knocker]

21 minutes ago, Dorsetbred said:

Thanks Knocker, a breather for a while down here on the South Coast then?

Certainty what it looks like Dorset

[knocker]

The ext GEFS mean anomaly pretty much as expected

The salient points

Aleutian ridge and trough NW North America

Main vortex lobe Labrador Straits

Strong westerly upper flow across the Atlantic and around the weakening subtropical high

Indicating a continuation of a N/S split

 

[knocker]

The ecm has a lobe of the vortex dropping down the west coast of Greenland around t162 resulting in a very strong jet and some rapid cyclogenisis which could bring some very strong winds and some wintry weather to the north. But of course the detail is subject to change

 

[knocker]

The ext EPS not a million miles from the GEFS; some differences vis the amount of influence of the subtropical high which of course is not unimportant regarding the detail for the UK

And a quick glance at the stv which remains quite a tight feature.

 

 

[damianslaw]

Eventual trend I suspect given the robustness of the PV and cold core temp profile will be for it to force down on the sub-tropical high, which as we approach middle part of the month could see some more lively conditions with some wintry precipitation for the north at times as we see cold polar air mixed in with the westerly airflow.

 

[damianslaw]

Just now, damianslaw said:

Eventual trend I suspect given the robustness of the PV and cold core temp profile will be for it to force down on the sub-tropical high, which as we approach middle part of the month could see some more lively conditions with some wintry precipitation for the north at times as we see cold polar air mixed in with the westerly airflow. There are signs this is the direction of travel forecast for the 3rd, as a brief incursion of colder uppers from the NW rotates in around the high, and with little sign of amplification thereafter, the pattern looks like shifting ever further south, heights migrating further south in time, lower heights dropping down from the north in time.. with that cold air over the Pole increasingly threatening to spill into the UK.

 

 

[knocker]

A glance at last night's EC weeklies update for the last week of January and the first week of February

24 Jan > 31 Jan

A strong Aleutian ridge (the strength of the east Pacific ridge has recently become apparent)  adjacent to the vortex covering the rest of the Arctic but centred over the Labrador Straits.

The vortex trough extension id aligned into the north west Atlantic which allows the subtropical high to ridge north east over western Europe and include the southern half of the UK within it's sphere of influence.

Thus the strong westerly upper flow exiting the eastern seaboard abates somewhat in the east and perhaps backing a tad suggesting a N/S split

01 Feb > 08 Feb

Not a huge change. Still a strong Aleutian ridge with perhaps a more concentrated vortex with the trough extension more aligned to mid Atlantic which tends to negate the influence of the subtropical high over the UK somewhat. Thus perhaps less emphasis on a N/S split

 

Edited December 31, 2019 by knocker

[knocker]

A quick look at this weekend

This is the position midday Friday according to Exeter but once all the cold front to the north has moved south and introduced colder air the ridge can then do the rest and the weekend becomes quite cold cold except on Sunday in the north where it becomes quite windy as the Atlantic ingresses around the top of the ridge according to the gfs

The gfs Sat/Sun

But the ecm is not keen on clearing the cold front south and introduce the colder air

So obviously then has a different take on the weekend

 

Edited December 31, 2019 by knocker

[knocker]

The EPS 5-10 anomaly pretty much as expected and we know that this type of pattern can throw up some varied temps and weather as per examples

The ext EPS emphasizes the strength of the east Pacific ridge allied to the vortex and associated troughs, Echoing last night's NOAA

Edited December 31, 2019 by knocker

[knocker]

[knocker]

The cold front at midnight Saturday 0600 gfs/ecm