Developments to the southwest

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xmetman

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Dec 10, 2017, 10:21:35 AM12/10/17
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Smartie

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Dec 10, 2017, 11:22:55 AM12/10/17
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Cloud top striations indicative of explosive deepening, there was a cluster of sferics ~ 15 UTC as the nose of the dry intrusion started to dig in.



xmetman

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Dec 10, 2017, 12:10:17 PM12/10/17
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Dave, are developments going to plan with this feature?

Smartie

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Dec 10, 2017, 2:28:29 PM12/10/17
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Looks like the GFS is too shallow by at least 4 hPa but that's not unusual. The GFS T+3 did not quite match the WV imagery at 15 UTC. Haven't looked at the ECMWF. The GFS handled the Zeus storm, coming out of the same area, earlier this year quite well at short  range, but not a similar one in 2015(?). One area where small errors (ie at the mesoscale) might impact is on any snow forecast for the SE tomorrow.
19 UTC- cloud hook formed, likely sting jet in the next few hours but only over the sea. Cold conveyor belt  will produce the strongest winds over land.,

Smartie

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Dec 10, 2017, 2:44:24 PM12/10/17
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GFS T+6 pressure of 2 PVU surface overall is a good fit to the WV field at 18Z  (better than 15Z. 18Z UKMO analysis has a 976 hPa closed contour.


Richard Dixon

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Dec 10, 2017, 4:24:59 PM12/10/17
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Fascinated with some of the structure in the Arome model - esp the high-velocity "streaks" over Biscay ahead of the main wind "hook".

Richard


Smartie

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Dec 10, 2017, 4:37:20 PM12/10/17
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Should be a METOP pass about now, hopefully we'll be lucky and get some scatterometer winds.
D

Smartie

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Dec 10, 2017, 5:13:38 PM12/10/17
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GFS has too shallow a centre and thus this is  displaced to the SE in the model. SLP centre should be in the dry slot  near the bent back warm front and tear drop shaped.
WV IR blend 21 UTC GFST+9 MSLP and surface ob.


Smartie

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Dec 11, 2017, 3:38:32 AM12/11/17
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METOP B scatterometer pass timed at 2040 shows a strong CCB jet developed early, the patch of less strong winds (red barbs) between the hook and the cold front is likely the SJ.


Trevor Harley

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Dec 11, 2017, 3:46:28 AM12/11/17
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I apologise for posting a lot but I've decided the only way I'm going to learn is by asking about things I don't know - and that's a lot!
 
Cloud top striations indicative of explosive deepening, there was a cluster of sferics ~ 15 UTC as the nose of the dry intrusion started to dig in

Cloud striations I think I get - just the visible appearance
explosive deepening - a low forms very rapidly
What though is a cluster of sferics - lightning?
A dry intrusion - a body of low-humidity air?


Trevor 

Freddie

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Dec 11, 2017, 3:48:34 AM12/11/17
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Correct on all counts!

--
Freddie
Fishpool Farm
Hyssington
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296m AMSL
http://www.fishpoolfarmweather.co.uk/
https://twitter.com/FishpoolFarmWx for hourly reports

Smartie

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Dec 11, 2017, 4:00:13 AM12/11/17
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Trevor Harley

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Dec 11, 2017, 10:40:11 AM12/11/17
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Thanks, I'll look.

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