The
good day - how to see it coming
Wednesday 8 August 2007 provided
a fine example of a very good day that was anticipated well in advance;
predictions had been made with confidence.
Links are all available
from the main weather page
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Chart
from
Hirlam
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Sounding archive forecast noon from NOAA
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The
synoptic chart
shows high pressure nearby with the isobars curving
round the high - anticylonic curvature. The winds are very
gentle from a northerly point and that is usually the best, although
often there is cloud close to the North Sea in northerlies (and maybe
also N.Wales).
The
sounding forecast (in fact, this is an archive forecast) needs a preliminary check of blue or not blue.
(see soundings tutorial)
The brown moisture content
line traced upwards from surface dewpoint comfortably intercepts the red
line, so the day won't be blue.
Now by use of the sounding, look at the possible
cloud development
Surface maximum temperature
will be a little further to the right (of red line) so Tdry / Tdew split
could be as much as 14°C
That translates to cloud
base in excess of 5,500 feet. See the Bradbury
and soundings tutorials
The air around
cloud base has low humidity as shown by good split between the green
and the blue lines so little liklihood of spreadout or fill-in
The flying winds are confirmed as being the from north (usually a good direction) at 10 knots or less.
A
very important consideration was that the forecast charts and indeed
all the data for 8 August had been consistent over several days.
That gave great confidence. When each new chart issue for
a particular date is different from the previous one, low confidence is
indicated. The day did not disappoint with numerous flights in excess of 500 kms. Satpic below courtesy of MODIS
Rapid Response Project at NASA/GSFC 
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