Page:1947SydneyHailstorm.djvu/16

37 (5) The possible mechanical lift due to the sea-breeze. There is no doubt that this has often been the cause of thunderstorms. There was a case some years ago of a heavy hailstorm over the Mount Lofty ranges when a light northerly wind and apparently humid drift was lifted by a sea breeze.

(6) A comparison of surface temperature and humidity data from inland suburbs with the radio-sonde station and the possibility of constructions a composite pusdeo-diagram. This construction may be open to question. However we might say that at least a thunderstorm was likely over somewhere in the area. Even if this where not at the spot where it was thermodynamically predicted, such a forecast might be considered sufficiently useful. Such a procedure would be an advance on forecasting a local thunderstorm empirically without such analysis.

Addendum : Note on estimation of vertical currents in a thunderstorm

"The size of the hailstones suggest very strong ascending currents. Some measure of these may be obtained from formulae developed by Jospeh Levine and C.E Buell as follows:

$$\overline{\delta G}=\frac{r}{u}.\frac{T_m}{h}.\frac{\delta_{ps}}{p_{s}} $$(Levine)

or approximately $$V^{2}=2\frac{R}{u}.T_{s}.\frac{\delta_ps}{p_s}$$ (Buell)

where $$\overline{\delta G}$$ is the mean acceleration.

R and u gas constants equal to 8.3 x 10 and 28.9 respectively

$$T_m$$ = Mean temperature $$T_s$$ = Surface temperature $$\delta_ps$$= Pressure oscillation $$p_s$$ = Surface Pressure h  = height

$$\delta_ps$$ is the pressure "bump" or sudden pressure rise as the thunderstorm passes the locality. ..../The Values of