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Jive Buddy
Friday, November 22, 2013 9:53:25 PM

I seem to remember last year (maybe the previous year), that there was some talk about pressure being to high for ppn to occur?


Anyhow, I'm currently seeing rain showers with pressure at 1016.7mb, seemingly being produced by a streamer getting going. Current temp is 8.3C, DP 5.1C, Wind NE 16mph.


I'm curious to know if anyone records PPN with higher prerssure in the coming season, and if so, what are your stats?


Genuine thread, genuine interest

It's not over, until the fat Scandy sinks.....

Location: St. Mary Cray, S.E. London border with Kent.
Quantum
Friday, November 22, 2013 9:59:10 PM


I seem to remember last year (maybe the previous year), that there was some talk about pressure being to high for ppn to occur?


Anyhow, I'm currently seeing rain showers with pressure at 1016.7mb, seemingly being produced by a streamer getting going. Current temp is 8.3C, DP 5.1C, Wind NE 16mph.


I'm curious to know if anyone records PPN with higher prerssure in the coming season, and if so, what are your stats?


Genuine thread, genuine interest


Originally Posted by: Jive Buddy 


High pressure doesn't help, because it decreases convective potential. But then if you get an extreme lake effect event then the pressure would matter less. Also convergence zones, would probably be capable of producing precipatation even in very high pressure. And if you think about it, solar heating is capable of producing thunderstorms even when pressure is in excess of 1020mb. I suspect the lake effect would do the same thing if the gradient was extreme, perhaps it happens in canada. 

Twitter: @QuantumOverlord (general), @MedicaneWatch (medicane/TC stuff)
2023/2024 Snow days (approx 850hpa temp):
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)

Total: 8 days with snow/sleet falling.

2022/2023 Snow days (approx 850hpa temp):

18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)

Total: 7 days with snow/sleet falling.

2021/2022 Snow days (approx 850hpa temp):

26/11 (-5), 27/11 (-7), 28/11 (-6), 02/12 (-6), 06/01 (-5), 07/01 (-6), 06/02 (-5), 19/02 (-5), 24/02 (-7), 30/03 (-7), 31/03 (-8), 01/04 (-8)
Total: 12 days with snow/sleet falling.
idj20
Friday, November 22, 2013 10:12:06 PM

I remember a couple of years ago on one winter's day when I got to see snowfall even though air pressure was at 1027 mb or something. I recall Retron saying about it as well where it all occurred in a very shallow layer of convective air.

Folkestone Harbour. 
lanky
Friday, November 22, 2013 10:15:45 PM

You sometimes see an "old" weather front trapped inside a high pressure cell on the weather maps


These can give cloud and drizzle and I seem to remember some time ago ( a few years ago probably) the BBC forecaster remarking on rain when the SLP was around 1036mb

Martin
Richmond, Surrey
Jive Buddy
Friday, November 22, 2013 11:29:23 PM

Thanks for the replies so far.


Now 1017.3, rain rate 7.2mm/hr, temp 7.6C, DP 5.6C, Wind N 12mph

It's not over, until the fat Scandy sinks.....

Location: St. Mary Cray, S.E. London border with Kent.
KevBrads1
Saturday, November 23, 2013 12:08:58 AM
This was remarkable from 8th May 1993, pressure above 1030mb and yet parts of Scotland had heavy thundery rain

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Gusty
Saturday, November 23, 2013 8:36:06 AM

I've had weak streamer type of showers caused by shallow convection on cold upper NE'lies at 1035mb in the past 

Steve - Folkestone, Kent
Current conditions from my Davis Vantage Vue
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Jive Buddy
Saturday, November 23, 2013 12:54:09 PM

New high (since this thread began )...


1020.6, showeretter of rain from a wet fart of a mini-streamer.

It's not over, until the fat Scandy sinks.....

Location: St. Mary Cray, S.E. London border with Kent.
doctormog
Saturday, November 23, 2013 1:05:06 PM

New high (since this thread began )...


1020.6, showeretter of rain from a wet fart of a mini-streamer.

Originally Posted by: Jive Buddy 



OK, Jiries own up what have you done with the real JB.[sn_clown]

In all seriousness though I guess cold flows off relatively warm seas and old or decaying weather fronts can result in precipitation under conditions with relatively high pressure.
Aberdeen
Current conditions (personal WS) 
Jive Buddy
Saturday, November 23, 2013 2:02:43 PM


New high (since this thread began )...


1020.6, showeretter of rain from a wet fart of a mini-streamer.


Originally Posted by: doctormog 



OK, Jiries own up what have you done with the real JB.Clown

Originally Posted by: Jive Buddy 


No, Jiries means rain falling from a dirty high!

It's not over, until the fat Scandy sinks.....

Location: St. Mary Cray, S.E. London border with Kent.
doctormog
Saturday, November 23, 2013 2:04:38 PM


New high (since this thread began )...


1020.6, showeretter of rain from a wet fart of a mini-streamer.


Originally Posted by: Jive Buddy 



OK, Jiries own up what have you done with the real JB.Clown

Originally Posted by: doctormog 


No, Jiries means rain falling from a dirty high!

Originally Posted by: Jive Buddy 



😂
Aberdeen
Current conditions (personal WS) 
WMB
  • WMB
  • Advanced Member
Sunday, November 24, 2013 6:16:26 PM

This was remarkable from 8th May 1993, pressure above 1030mb and yet parts of Scotland had heavy thundery rain

Originally Posted by: KevBrads1 


Beaten to it, I was thinking of this, I was in Sothern Scotland at the time. It rained.

Jive Buddy
Sunday, November 24, 2013 6:39:23 PM

Well, we're creeping higher towards the figures quoted in the above posts.....1026.5mb, and light rain around 12:45 today!

It's not over, until the fat Scandy sinks.....

Location: St. Mary Cray, S.E. London border with Kent.
Arcus
Sunday, November 24, 2013 6:47:39 PM
1035 hPa and rain showers here.
Ben,
Nr. Easingwold, North Yorkshire
30m asl
Jive Buddy
Sunday, November 24, 2013 6:54:41 PM

1035 hPa and rain showers here.

Originally Posted by: Arcus 


That's it, p*ss on my parade why don't you?!


Right then, 1035 is the new high high to beat....

It's not over, until the fat Scandy sinks.....

Location: St. Mary Cray, S.E. London border with Kent.
Jive Buddy
Monday, November 25, 2013 12:01:29 AM

Right on the stroke of midnight, 1031.3 and a shower.

It's not over, until the fat Scandy sinks.....

Location: St. Mary Cray, S.E. London border with Kent.
JOHN NI
Monday, November 25, 2013 10:13:05 AM
Everything depends on the depth of the near surface boundary layer. Surface pressure can be quite high (on rare occasions very high) but if there is a steep lapse rate in the lowest 3000ft or so and enough moisture, some quite vigourous showers can be generated from coalesence of water droplets - effectively clashing and becoming heavy enough to fall. Only if descent / subsidence within high pressure extends right down to the surface will the likelihood of precipitation be reduced to near (but maybe not quite) zero.
John.
The orange County of Armagh.
Jive Buddy
Monday, November 25, 2013 10:48:32 PM

Everything depends on the depth of the near surface boundary layer. Surface pressure can be quite high (on rare occasions very high) but if there is a steep lapse rate in the lowest 3000ft or so and enough moisture, some quite vigourous showers can be generated from coalesence of water droplets - effectively clashing and becoming heavy enough to fall. Only if descent / subsidence within high pressure extends right down to the surface will the likelihood of precipitation be reduced to near (but maybe not quite) zero.

Originally Posted by: JOHN NI 



Nice info John, cheers!

It's not over, until the fat Scandy sinks.....

Location: St. Mary Cray, S.E. London border with Kent.
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