In spite of many experimental and theoretical studies the relationships between storm dynamics, severe weather,and lightning activity have been least understood.Measurements of electric ﬁeld made under a severe thunderstorm at a northeastern Indian station,Guwahati,India are reported. Lightning ﬂash rate increases drastically to about 84 ﬂashes per minute (fpm)during the active stage which lasted for about 7 minutes,from about 15 ﬂashes per minute during the initial phase of thunderstorm.Sudden increase in lightning ﬂash rate (‘lightning jump ’)of about 65 fpm/min is also observed in the beginning of the active stage.The dissipating stage is marked by slow and steady decrease in lightning frequency.Despite very high ﬂash rate during the active stage, no severe weather conditions are observed at the ground.It is proposed that the short duration of the active stage might be the reason for the non-observance of severe weather conditions at the ground.Analysis of Skew-t graph at Guwahati suggests that vertical distribution of Convective Available Potential Energy (CAPE)also may play some role in non-occurrence of severe weather at ground in spite of large lightning ﬂash rate and lightning jump observed in this thunderstorm.Further,all electric ﬁeld changes after a lightning discharge indicates the presence of strong Lower Positive Charge Centers (LPCC)in the active and dissipation stages. This suggests that LPCC plays an important role in initiation of lightning discharges in these stages.
Volume 128 | Issue 8
Click here for Editorial Note on CAP Mode