"Joe Hunt" wrote in message
...

wrote in message
oups.com...
Further to the question about the CB cloud over Kent which could be
seen from near Heathrow, what's the furthest that CBs at our latitudes
can be seen?

In 2001 I saw two CBs that were apparently hundreds of miles away. Over
the August bank holiday I saw a CB from the South Downs (South Harting
near Petersfield) on the northern horizon which didn't look too distant
(I guessed London) but apparently it was over Norfolk, 200-odd miles
away. IIRC the date was 25th August (Saturday).

Further still I saw a very distant CB on the southern horizon from the
New Forest, the same summer. I remember looking at a lightning chart
for that day and the nearest was apparently in the Rennes/Nantes area
of western France, even further, 200 to 300 miles south? The date was,
IIRC, 26th July (Thursday).

Both occasions were very hot, humid, and sunny with no clouds apart
from these very isolated CBs.

Nick

Summer is the time when you see CBs at a greater distance due to their
larger height. Some CBs can touch 40,000ft in the height of summer in air
masses with high tropopauses. Conversely, in winter, CB tops in a
northerly can be as low as 8000ft. Think of Pythagoras' Theorem.

I remember this subject coming up before, I'd try Google Groups.

Joe
The distance to the horizon from an observer increases roughly with the
square root of the observer's height above sea level. For an observer at an
altitude of 1,000 ft, I think the horizon is about 40 miles away, and for an
observer at 4,000 ft, the horizon is 80 miles away, and so on. The same
formula applies to the height at which distant objects can be visible above
the horizon. Therefore (given sufficiently clear air of course) the top of
a cloud over 16,000 ft in height could be visible to an observer at sea
level at a distance of 160 miles.

A couple of years ago I was on holiday in El Hierro and Mt Tiede on Tenerife
was continually and very clearly visible at a distance of about 100 miles.

Regards, Roger