Weather Chart Question

[Kolibear]

This link :-
Weather Chart

takes you to today's forecast weather.

The chart shows cold, warm and occluded fronts, but what is the black line extending from the Orkneys north towards Iceland and also in the Davis Strait between Labrador & Greenland?

[2Donkeys]

It's a trough.

2D

[Send Clowns]

Looks like a damned weak trough to me.

b.t.w. a trough is a line where pressure is low compared to that either side, with generally poor weather, cloud, rain, poor vis and perhaps high winds, rather similar to a depression.

[Pie Man]

There is more info on the Met Office web-site, info about troughs is shown at:
Weather Chart Info
Regards
Pie

[2Donkeys]

... I reckon it's a trough.

[Whipping Boy's SATCO]

looks like a trough to me.

Sorry, did somebody already say that?

PS. Bets on it developing into a depression?

[High Wing Drifter]

Yes, the symbology is a trough, but I have to agree with Send Clowns, the one N of Scotland does look very weak sitting there on parallel isobars?? Can anybody explain that placement?

[2Donkeys]

Troughs can be thought of as either failed or future fronts. The one that you are highlighting is not particularly noteworthy, a rather weak affair, probably associated with a little more than a bit of cloud.

When troughs deepen it becomes very subjective at what point they are designated a front, with different weather sources often coming up with contradictory opinions.

2D

[High Wing Drifter]

Thanks for your helpful explanation 2Ds.

[B Fraser]

or in other words, a band of precipitation with no change of airmass.

Forecasters usually paint them on the chart to match an area of cloud on the satellite image. A good eraser sometimes comes in handy when the cloud is no longer there 3 hours later

[Kolibear]

Thanks for all your replies, which do beg the question - if troughs are marked, why aren't ridges indicated?

[average bloke]

a trough is different from a front in that the weather is being derived from one airmass only, with the weather being driven by converging air along the trough line.

ridges are not shown as they are not associated with bad weather, but with sinking air and clear skies.

[boomerangben]

I always thought that troughs were relatively benign, but some of the ones we have had on the West Coast of Scotland recently have been pretty ferocious. More like narrow cold fronts.