Martin Rowley wrote:

Thursday, 02 November 2006
BRACKNELL (TAWFIELD)
0900 WSW F1 15km - 1/AC 4/AC T009D-006
RMK: [CAVOK] - tr Ac floccus~070, 4Ac (very thin/broken)~080. The Ac
flo may in fact be at the same level - not easy to tell - two distinct
(but small) areas of same, with ice streamers falling some way below the
cloud before evaporating. Slight hoar frost present.
[ OVERNIGHT DATA (18Z - 09Z):
screen min: -00.6 grass min: -02.8 precipitation: NIL [24hr total: 00.0
mm]
other data: not yet cold enough to freeze top soil - too much warmth in
the ground. ]=


I watched the movement of the cloud and the floccus was slightly below the
Ac. One example consisted of a broken straight line, rather like remains of
a con-trail.

I thought the cloud was a lot higher but one thing I learnt after more than
forty years in the Met Office is that estimating cloud height is next to
impossible at times. Many experienced observers have reported cloud bases
of 20-25,000 feet when they were actually at 4,000 feet and vice versa.

One other thing that struck me about this morning's cloud was that its
thinness and element size was similar to the 1000' Sc earlier this week.
Makes the recommendation I remember from my early days about using size of
the elements to estimate cloud height a bit unreliable at times.


--
Graham Davis
Bracknell