Upper-tropospheric well-marked feature 28JUN2018

[Martin Rowley [West Moors/East Dorset]]

... interesting little beastie running smartly (east to west) across southern Britain just now: appears to be 'driven' by upper tropospheric activity (see 15Z and 18Z output from GFS below/ex wetter3.de).

Casting sharp shadows in final frames of the VIS sequence - all clearing here now after a couple of hours of fairly 'threatening' sky-scape.

Martin.

[Smartie]

In London the cirrus/As was preceded by well-scattered Cu humilis so perhaps the feature was producing some marginal instability in the lower atmosphere as well.

Attached WV& IR blend and GFS analysis pressure of PV 2 surface 18 UTC.

[Martin Rowley [West Moors/East Dorset]]

... indeed: here we had a short period (circa 90 minutes) of 'shot-gun' high-base Cumulus (or lowish-base Ac cas). Interesting few hours for a dedicated weather watcher!

Martin.

[Smartie]

I see there are reports of a brief thundershowers over night from the SW. I wonder if radiative cooling (destabilising the column profile) combined with the PVA?

Attached sflocs

[Smartie]

Camborne 00Z ascent showing steep lapse rate above a warm nose of dry, subsided air at 800 hPa.

[Colin Youngs]

<I see there are reports of a brief thundershowers over night from the SW.>

They can be seen on Blitzortung.

http://en.blitzortung.org/historical_maps.php?map=10

Review - 24 h Loop

Colin Youngs

Brussels

[Tudor Hughes]

     Yes, it did look just a little "threatening" for an hour or so.  "Now what's going on?" I thought to myself but remained a bit baffled so thanks for the explanation.

Tudor Hughes, Warlingham, Surrey.