Fax chart question.

[Dave C]

Can somebody remind me what the Christmas tree lines are near the S.E corner in a couple of days time. Are they decaying fronts in situ, I've forgotten and are they of any significance?

[Julian Mayes]

That would be a convergence line, Dave.     When the flow is parallel to the coast of Suffolk / Essex, the greater friction of the airflow in relation to the land results in a backing of the wind direction very slightly (NE to NNE) which leads to the convergence.  Flow over the sea remains NE'ly (or thereabouts).   The result is convergence and enhanced convection / showers that some of us like to call the Thames Tickler - cause of hvy snow in times gone-by in Southend - as Keith would confirm - and around Maidstone / Medway towns.   It is also enhancing the pptn on teh front today, hence the modelled rainfall accumulations just mentioned on the BBC lunchtime forecast for NW Kent area.  

Julian     

[George in Edinburgh]

Convergence lines

George

[George in Edinburgh]

I should have added that they are not unusual  here in a NE'y wind as the air flows down the Scottish coast (the bit south of Stonehaven). Combined with the rising ground as they move inland off the Firth of Forth they are the cause of the heavier snowfalls experienced here. Rather than continous precipitation it's more a case of frequent and heavy snow showers.

George in Swanston  Edinburgh

[Dave C]

Ah, yes, thank you. I remember now but had forgotten the exact explanation. Only led to some very light rain. A Thames streamer would be good today in a near ice day and low DP. Did get three snow flakes on the car overnight so can't complain !

[jack.h...@gmail.com]

x/c weather has a wind arrow option:  https://www.xcweather.co.uk/GB/

I have used that in summer - arrows converging, albeit at an angle - to get an idea where showers might develop on a convective day.  The idea has shown promise.

Loch Glacarnoch (obs on x/c weather) is going to be very cold tonight.  At 1600 it was minus 11C.  Here in tropical Nairnshire, minus 4.5C at 1645 hrs.

Jack