Hi all,
Two very interesting ascents from 11Z today are shown below with a few
noteworthy features.

The Herstmonceux ascent shows the surface inversion starting at 975hPa
(MS0.1degC) and ending at 955hPa (8.6degC). The Watnall ascent shows the
boundary layer to be deeper with the inversion starting at 933hPa
(MS3.3degC) and ending at 889hPa (7.0degC).

http://weather.uwyo.edu/cgi-bin/soun...312&STNM=03354
(11Z Watnall)
http://weather.uwyo.edu/cgi-bin/soun...312&STNM=03882
(11Z Herstmonceux)

In addition, the surface wind at Herst. is de-coupled with the flow above
the inversion, a veer of approximately 90deg. This is not so at Watnall.

With the Watnall ascent you would expect more convective
overturning/turbulence to take place and hence more breaks in the StSc
sheet, but observations from the area show nothing different from those to
the SE. I'm lost, please help !

Thanks, Joe

"Joe Hunt" wrote in message




With the Watnall ascent you would expect more convective
overturning/turbulence to take place and hence more breaks in the StSc
sheet, but observations from the area show nothing different from those to
the SE. I'm lost, please help !

Thanks, Joe

Joe, there was some breaks over northern England and north Wales,
probably helped by lee effects. E.g. Hawarden :-
METAR EGNR 131350Z 14006KT 5000 SKC 05/03 Q1025=
METAR EGNR 131250Z 15006KT 6000 BKN018 05/02 Q1026=

Jon.


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"Jon O Rourke" wrote in message
news:d16e577a6d7d4b7e4801b2a1d066c449.62236@mygate .mailgate.org...

Joe, there was some breaks over northern England and north Wales,
probably helped by lee effects. E.g. Hawarden :-
METAR EGNR 131350Z 14006KT 5000 SKC 05/03 Q1025=
METAR EGNR 131250Z 15006KT 6000 BKN018 05/02 Q1026=

Jon.

Hi Jon,

Thanks for those METARs, which show that 5-7/8ths of cloud at 1800ft
observed at 1250Z had cleared by 1350Z, for those that don't understand
these things.

Rob McElwee mentioned the cloud breaking up over N. Wales and Wirral area
due to lee effects on NW Tonight, yesterday evening.

Joe

"Joe Hunt" wrote in message
...
Hi all,
Two very interesting ascents from 11Z today are shown below with a few
noteworthy features.

The Herstmonceux ascent shows the surface inversion starting at 975hPa
(MS0.1degC) and ending at 955hPa (8.6degC). The Watnall ascent shows the
boundary layer to be deeper with the inversion starting at 933hPa
(MS3.3degC) and ending at 889hPa (7.0degC).


http://weather.uwyo.edu/cgi-bin/soun...312&STNM=03354
(11Z Watnall)

http://weather.uwyo.edu/cgi-bin/soun...312&STNM=03882
(11Z Herstmonceux)

In addition, the surface wind at Herst. is de-coupled with the flow above
the inversion, a veer of approximately 90deg. This is not so at Watnall.

With the Watnall ascent you would expect more convective
overturning/turbulence to take place and hence more breaks in the StSc
sheet, but observations from the area show nothing different from those to
the SE. I'm lost, please help !

Thanks, Joe

I don;t think there is enough mixing to create the desired effect. It needs
something like the Welsh mountains to break the sheet up. High Res Vis
Afternoon pictures indicated a slightly different texture the to SCu sheet
the further north you went, but it would go largely un noticed below i
suspect.
The Inversion is almost low enough in the SE for the tops of the Downs to
stick through, however as you say further NE the moist boundary layer is
deeper still, and with the lakc of wind, this will make breaking the sheet
over Eastern England virtually impossible until gradient picks up.

ATB
Paul

"PJB" wrote in message
...
I don;t think there is enough mixing to create the desired effect. It
needs
something like the Welsh mountains to break the sheet up. High Res Vis
Afternoon pictures indicated a slightly different texture the to SCu
sheet
the further north you went, but it would go largely un noticed below i
suspect.
The Inversion is almost low enough in the SE for the tops of the Downs
to
stick through, however as you say further NE the moist boundary layer is
deeper still, and with the lakc of wind, this will make breaking the
sheet
over Eastern England virtually impossible until gradient picks up.

ATB
Paul

Hi Paul,

Thanks for that. Indeed, the inversion is very low and should all the StSc
clear by morning, with the increase in gradient, SE'ners may see a very
white view of the Downs. Rime deposition from FZFG is possible but only if
the inversion lowers a little more. It was sampled by the 03882 ascent as
being around 430m (1400ft).

Joe

"Joe Hunt" wrote in message
...

"PJB" wrote in message
...
I don;t think there is enough mixing to create the desired effect. It
needs
something like the Welsh mountains to break the sheet up. High Res Vis
Afternoon pictures indicated a slightly different texture the to SCu
sheet
the further north you went, but it would go largely un noticed below i
suspect.
The Inversion is almost low enough in the SE for the tops of the Downs
to
stick through, however as you say further NE the moist boundary layer is
deeper still, and with the lakc of wind, this will make breaking the
sheet
over Eastern England virtually impossible until gradient picks up.

ATB
Paul

Hi Paul,

Thanks for that. Indeed, the inversion is very low and should all the StSc
clear by morning, with the increase in gradient, SE'ners may see a very
white view of the Downs. Rime deposition from FZFG is possible but only if
the inversion lowers a little more. It was sampled by the 03882 ascent as
being around 430m (1400ft).

Joe

Indeed, it looks increasingly likely that there will be insfuccient mixing
in the Boundarly layer until later tomorrow to properly start to clear
things, with another gloomy and cold day on the cards in the SE tomorrow.
There may be enough to lift the bases somewhat and to generate a little more
overturning of the StSc Sheet.

Paul