| Cumulus
base (above sea level) |
This
parameter has a theoretical difficulty and quite possibly that the actual
cloudbase will be higher than given here - so perhaps this should be considered
a minimum possible cloudbase.
Bradbury
(400 x dewpoint depression) is another method. |
| Thermal
strength of air (subtract glider) |
Airmass
strength of thermals ignoring what Dr.Jack calls "cloud suck".
With
cumulus development, thermals could be stronger especially under developing
showers. |
| Cloud
cover within boundary layer |
It
assumes a very simple relationship between cloud cover percentage and the
maximum relative humidity within the Boundary Layer. Dr.Jack does
not have a lot of faith in this prediction, since the formula used is so
simple, and expects its predictions to be very approximate |
| If
BLUE, best operating height |
This
indicates when the thermal might weaken to around 1 knot achieved rate
of climb |
| Average
wind within boundary layer |
Caution
if significant changes with height |
| Wave
/ vertical motion at 700 mbs |
Vertical
velocity at a constant pressure level, plus wind speed/direction barbs.
Such
upward motions can result from mountain wave or Boundary Layer convergence. |
| Shower
/ T'storm potential (CAPE) |
Convective
Available Potential Energy. The lower the number, the less the chance
of showers.
UK
values of 500 joules/kg (whatever that means) or more suggest thunderstorms |
| Heating
at surface |
This
should take into account any upper cloud.
Under
clear skies, midsummer is around 300 watts/sq metre, midwinter around 80
w/sq.m |
| Spreadout
level (if spreadout expected) |
Not
all that useful in that it gives the base of the spreadout (if any) strato-cu
but not where |
| Tdry
(temp surface) |
Might
help identify the hottest areas but bear in mind, this could be due to
lower inversion there |
| Tdew
(dewpoint) |
Blue
or not blue? If not blue, then Tdew can be used in conjunction with
Tdry to estimate cloudbase.
Tdew
is a very important parameter in planning where to fly cross country |
| Wind
at surface |
Self
evident |
| Wind
convergence |
Positive
convergence might indicate potential for shear lines, et
Negative
convergence indicates generally descending air |
