Hi all,

One of my clients reported rather unusual wind speeds during a flight from
Bedford last night. Thought I'd throw this open to ideas.

Balloonist let off a Met balloon at 1700 GMT. Straight up at about 1-2kt, as
per the light and variable forecast.

Balloon took off at 1745 GMT in a surface wind of 8kts. He then immediately
went into a 30kt southerly, this persisting to 2000ft, with a narrow band of
2-5kt winds around 1000ft.

Obviously sea breezes and thermals were playing a part in conditions last
night, but the 30kt wind is still high, even in those conditions.

Be interested to read any ideas you may have (baked bean theorists need not
apply ).

Best wishes,
Simon

Simon Keeling


--
Weather Consultancy Services Ltd / Flying High Weather Ltd
The Weather Centre, 188 Common Road, Wombourne, Staffordshire, England. WV5
0LT.
Tel: 08700 738 100 Fax: 01902 895242 email:
http://www.weatherweb.net
http://www.atlanticweather.co.uk

One of my clients reported rather unusual wind speeds during a flight from
Bedford last night. Thought I'd throw this open to ideas....
Hi Chris,
sounds like a 'nocturnal low level jet'
but I toiught these were strongest in the early morning hours,

--
regards,
david
(add 17 to waghorne to reply)

"Waghorn" wrote in message
...
One of my clients reported rather unusual wind speeds during a flight
from
Bedford last night. Thought I'd throw this open to ideas....
Hi Chris,
sounds like a 'nocturnal low level jet'
but I toiught these were strongest in the early morning hours,

--
regards,
david
(add 17 to waghorne to reply)

Hi David,

I was thinking along similar lines but there are some conditions lacking to
confirm it is. With a nocturnal LLJ, unlike one induced by a mid-latitude
cyclone, the cooling aloft (900-850hPa) can only occur through land at a
higher elevation. For example, the Great Plains is often used in examples
from papers I have read. However, is it possible that the urban heat from
London could have triggered an effect, such that there was a thermal
gradient between Bedford and London even to that height ? The nocturnal LLJ
is strongest in the early hours, rather than early evening.

There's a paper here, well it is used as a lecture presentation I think,
which is useful - Xuw, Ming "Chapter 2. Planetary Boundary Layer and Related
Phenomena, 2.3 Low-level Jet"
http://twister.caps.ou.edu/MM2004/Chapter2.3.pdf

And another, Blackardar (1957), Boundary Layer Wind Maxima and Their
Significance for the Growth of Nocturnal Inversions,
http://twister.caps.ou.edu/MM2004/Bl...ar1957BAMS.pdf (14.3MB)

Have you read the latter ?

Joe

I was thinking along similar lines but there are some conditions lacking to
confirm it is. With a nocturnal LLJ, unlike one induced by a mid-latitude
cyclone, the cooling aloft (900-850hPa) can only occur through land at a
higher elevation. For example, the Great Plains is often used in examples
from papers I have read. However, is it possible that the urban heat from
London could have triggered an effect, such that there was a thermal
gradient between Bedford and London even to that height ?

But 30 Kt ?
http://weather.ou.edu/~oscarvdv/maps...hetae_eur6.png
shws a surface convergence zone fed by Slies/SElies, presumably a heat low which wld make a
gradient.
Sdgs for Watnall and Herstmonceux 0Z have strong inversions but no low level jet.

And another, Blackardar (1957), Boundary Layer Wind Maxima and Their
Significance for the Growth of Nocturnal Inversions,
http://twister.caps.ou.edu/MM2004/Bl...ar1957BAMS.pdf (14.3MB)

Have you read the latter ?Joe
Now,I like 'obscure' papers ,but that one has evaded me!
;-)

--
regards,
david
(add 17 to waghorne to reply)

Thanks for the responses so far.

I have got reports from several balloonists and microlight pilots who were
flying around the same time last night.

It seems there was an area of strong winds to around 5000ft in the area
northeast of and bounded by bdefordshire, running north to Yorkshire.

The odd think is that the wind was reported as being steady throughout the
flight, no real shear to it, apart from initially at the surface.

Simon

--
Weather Consultancy Services Ltd / Flying High Weather Ltd
The Weather Centre, 188 Common Road, Wombourne, Staffordshire, England. WV5
0LT.
Tel: 08700 738 100 Fax: 01902 895242 email:
http://www.weatherweb.net
http://www.atlanticweather.co.uk
"Waghorn" wrote in message
...
I was thinking along similar lines but there are some conditions lacking
to
confirm it is. With a nocturnal LLJ, unlike one induced by a mid-latitude
cyclone, the cooling aloft (900-850hPa) can only occur through land at a
higher elevation. For example, the Great Plains is often used in examples
from papers I have read. However, is it possible that the urban heat from
London could have triggered an effect, such that there was a thermal
gradient between Bedford and London even to that height ?

But 30 Kt ?
http://weather.ou.edu/~oscarvdv/maps...hetae_eur6.png
shws a surface convergence zone fed by Slies/SElies, presumably a heat low
which wld make a
gradient.
Sdgs for Watnall and Herstmonceux 0Z have strong inversions but no low
level jet.

And another, Blackardar (1957), Boundary Layer Wind Maxima and Their
Significance for the Growth of Nocturnal Inversions,
http://twister.caps.ou.edu/MM2004/Bl...ar1957BAMS.pdf (14.3MB)

Have you read the latter ?Joe
Now,I like 'obscure' papers ,but that one has evaded me!
;-)

--
regards,
david
(add 17 to waghorne to reply)

In message , Weather
Consultancy Services writes
Thanks for the responses so far.

I have got reports from several balloonists and microlight pilots who were
flying around the same time last night.

It seems there was an area of strong winds to around 5000ft in the area
northeast of and bounded by bdefordshire, running north to Yorkshire.

The odd think is that the wind was reported as being steady throughout the
flight, no real shear to it, apart from initially at the surface.

Simon

I saw 4 balloons flying from Great Missenden at about 7.15 p.m. last
night. They didn't appear to be moving fast although it's a bit
difficult to be sure from a moving car.

Norman.
(delete "thisbit" twice to e-mail)
--
Norman Lynagh Weather Consultancy
Chalfont St Giles
England

Thanks for the responses so far.
I spose apart from addressing you as 'Chris' for some reason!.Sorry Simon,

--
regards,
david
(add 17 to waghorne to reply)

I was gliding on Tuesday, and I guess we experienced a version of the same
phenomenon. We flew Dunstable to Retford and back. Thermals were being
broken up very badly by wind shear. At the surface and very low level,
there was scarcely any wind at all. But above 3,000, wind was broadly
westerly 15 knots (more further north)

Jack