1926z: Rain just started. Still windy.

Hugh

--

Hugh Newbury

www.evershot-weather.org

On Sat, 17 Jan 2009 19:27:43 +0000, Hugh Newbury
wrote:

1926z: Rain just started. Still windy.

Ditto down here at Hilton: constant roar in the trees behind me and I
stopped the dog walk slightly short for safety reasons.
Occasional bursts of heavy rain but nothing extraordinary. 10.6mm
since midnight Friday so you seemed to catch it.
I was on the Mendips this afternoon (on the surface) and it was brisk
but dry. Tomorrow underground near Priddy and slightly curious if snow
showers appear by 1430 when I surface
R

Hugh Newbury wrote:
1926z: Rain just started. Still windy.

Having a look at what happened overnight, I find some surprising (to me)
movements of the pressure, temperature and humidity at about 2030 last
night. The barometer went from 995.9hPa to 998.2hPa, the temp from 8.5C
to 5.0C and the humidity from 95% to 89%, all in a matter of a few
minutes. The rain was coming down in torrents at the time too.

These figures are taken from my AWS.

Please could some kind person explain the physics/meteorology behind
these jumps.

Hugh

--

Hugh Newbury

www.evershot-weather.org

On Sun, 18 Jan 2009 08:29:23 +0000, Hugh Newbury wrote in


Having a look at what happened overnight, I find some surprising (to me)
movements of the pressure, temperature and humidity at about 2030 last
night. The barometer went from 995.9hPa to 998.2hPa, the temp from 8.5C
to 5.0C and the humidity from 95% to 89%, all in a matter of a few
minutes. The rain was coming down in torrents at the time too.

These figures are taken from my AWS.

Please could some kind person explain the physics/meteorology behind
these jumps.

Cold front passage?

--
Mike Tullett - Coleraine 55.13°N 6.69°W posted 1/18/2009 8:51:38 AM GMT

Mike Tullett wrote:
On Sun, 18 Jan 2009 08:29:23 +0000, Hugh Newbury wrote in


Having a look at what happened overnight, I find some surprising (to me)
movements of the pressure, temperature and humidity at about 2030 last
night. The barometer went from 995.9hPa to 998.2hPa, the temp from 8.5C
to 5.0C and the humidity from 95% to 89%, all in a matter of a few
minutes. The rain was coming down in torrents at the time too.

These figures are taken from my AWS.

Please could some kind person explain the physics/meteorology behind
these jumps.

Cold front passage?

Thanks for that. It explains the temp jump and perhaps the humidity. But
why such a sudden jump in pressure?

Sorry to be boring.

Hugh

--

Hugh Newbury

www.evershot-weather.org

On Sun, 18 Jan 2009 08:29:23 +0000, Hugh Newbury
wrote:

Having a look at what happened overnight, I find some surprising (to me)
movements of the pressure, temperature and humidity at about 2030 last
night. The barometer went from 995.9hPa to 998.2hPa, the temp from 8.5C
to 5.0C and the humidity from 95% to 89%, all in a matter of a few
minutes. The rain was coming down in torrents at the time too.

These figures are taken from my AWS.

Broadly speaking similar on my AWS down here at Hilton ( and at work I
will look at those figures_tomorrow morning.

The intense rain, that I noticed was flowing down the front of the
house like a stream, clocked up a rate of 200mm per hour for a very
very brief period. This some what suprises me - again the other
machine may have something similar though even a 1mile proximity can
produce different readings

R

On Jan 18, 9:20*am, Hugh Newbury wrote:
Mike Tullett wrote:
On Sun, 18 Jan 2009 08:29:23 +0000, Hugh Newbury wrote in


Having a look at what happened overnight, I find some surprising (to me)
movements of the pressure, temperature and humidity at about 2030 last
night. The barometer went from 995.9hPa to 998.2hPa, the temp from 8.5C
to 5.0C and the humidity from 95% to 89%, all in a matter of a few
minutes. The rain was coming down in torrents at the time too.

These figures are taken from my AWS.

Please could some kind person explain the physics/meteorology behind
these jumps.

Cold front passage?

Thanks for that. It explains the temp jump and perhaps the humidity. But
why such a sudden jump in pressure?

Sorry to be boring.

Hugh

--

Hugh Newbury

www.evershot-weather.org- Hide quoted text -

- Show quoted text -

I am doing the Open University "Understanding the Weather "course.
They say that it is difficult for forecasters to identify the position
of fronts from isobaric charts, but there is a kink in the isobars at
the fronts. They are straight lines in the warm sector, but are
curved in the rest of the cyclone/depression. If the pressure was
dropping as the cold front approached then that may explain the rapid
rise when it arrived.

HTH,

Cheers, Alastair.

Alastair wrote:


I am doing the Open University "Understanding the Weather "course.
They say that it is difficult for forecasters to identify the position
of fronts from isobaric charts, but there is a kink in the isobars at
the fronts. They are straight lines in the warm sector, but are
curved in the rest of the cyclone/depression. If the pressure was
dropping as the cold front approached then that may explain the rapid
rise when it arrived.

HTH,

Cheers, Alastair.

It certainly does help, Alastair! Thanks for that. I was thinking of
doing that course: maybe now I will.

Hugh

--

Hugh Newbury

www.evershot-weather.org

Robin Nicholson wrote:

Broadly speaking similar on my AWS down here at Hilton ( and at work I
will look at those figures_tomorrow morning.

The intense rain, that I noticed was flowing down the front of the
house like a stream, clocked up a rate of 200mm per hour for a very
very brief period. This some what suprises me - again the other
machine may have something similar though even a 1mile proximity can
produce different readings

R
Robin, just looked at the rain rate here. A bit less than yours, but
nevertheless a remarkable 2.6mm/min (156mm/hr) @ 20:36 on 17/01/09.

And probably more to come!

Hugh

--

Hugh Newbury

www.evershot-weather.org