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lkj & xtZ ds lkFk rwQku vkSj vkSykof"V vYi vof/k izpaM ekSle dh ifj?kVuk ds uke ls tkuh tkrh gS tks dHkhd {ks= esa izkdfrd vkink dk :i ys ysrh gSA bl {ks= esa ekulwuiq ds vkidMksa dk mi;ksx djrs gq, dksydkrk ds vkl ikl ¼22-5 m-) 88-5 iw-½ vk, 70 xtZ okys rwQkuksa dk v/;;u fd;k x;kA blds fy, ekud laoguh lwpukvksa tSlh lh- ,- ih- bZ-) lh- vkbZ- ,u- bZ-) ,y- vkbZ-) ch- vkj- ,u- vkSj oh- th- ih- dk vkdyu fd;k x;k vkSj budk lkaf(;dh; :i ls fo'ys"k.k fd;k x;kA pwifd bl {ks= esa xtZ okys rwQkuksa dk iwokZuqeku yxkus ds fy, laoguh lwpukvksa dh dksbZ fuf'pr izHkko lhek miyC/k ugh Fkh vr% o"kZ 2005 ds nkSjku xtZ okys rwQkuksa dk fo'kys"k.k djus ds i'pkr~ if'peh caxky ds xkaxs; {ks= esa xtZ okys rwQkuksa dh laHkkfor ?kVukvksa ds fy, bu lwpukvksa dh izHkko lhek dk irk yxkus dk iz;kl fd;k x;k gSA bu laoguh lwpukvksa dh os/krk dk irk yxkus dh fy, dksydkrk ds MkWIyj ekSle jsMkj }kjk vfHkysf(kr o"kZ 2006&2007 ds xtZ okys rwQkuksa dh 34 ?kVukvksa dh tkip dh xbZA bl v/;;u ls ;g irk pyk gS fd ek= MkIyj jsMkj mRiknksa dk mi;ksx djrs gq, lgh ifj'kq)rk ds lkFk de ls de 2&3 ?kaVs igys xtZ okys rwQkuksa dk rkRdkfyd iwokZuqeku yxk;k tk ldrk gSA rFkkfi Mh- MCY;w- vkj- vkidM+ksa ds vykok ;fn laoguh lwpukvksa dk Hkh fo'ys"k.k fd;k tk, vkSj budk mi;ksx fd;k tk, rks rkRdkfyd iwokZuqeku dh le; vof/k esa lq/kkj yk;k tk ldrk gSA bl 'kks/k i= esa de ls de 3&4 ?kaVs igys xtZ okys rwQkuksa ds csgrj iwokZuqeku ds 'kks/kdrkZvksa }kjk ,d ljy rduhd lq>kbZ xbZ gSA ABSTRACT . Thunderstorm and hailstorm are well known short term severe weather phenomena which sometimes turn in to natural hazard especially in Gangetic West Bengal region of India. Large vertical extent of the cumulonimbus cloud, very high reflectivity, squally wind speed sometimes exceeding 100 km/h and heavy rainfall are the main features of these thunderstorms during pre-monsoon period in this region. A study of 70 thunderstorms has been carried out during the pre-monsoon season (March-May) of the year 2005 around Kolkata (22.5° N, 88.5° E) using Doppler Weather Radar and Upper air data. Standard convective indices like CAPE, CINE, LI, BRN and VGP have been evaluated and analyzed statistically. As no definite thresholds of the convective indices are available for thunderstorm prediction in this region, an attempt has been made to find threshold of these indices for possible occurrences of thunderstorms in Gangetic West Bengal region after the analysis of the thunderstorms during year 2005. The validity of these convective indices has been checked with 34 occurrences of thunderstorms during 2006-2007 recorded by Doppler Weather Radar Kolkata. The study reveals that nowcasting of thunderstorms may be done at least 2-3 hrs in advance with a fair degree of accuracy using Doppler radar products only. However, the lead time of nowcasting may be further improved if the convective indices are also analyzed and used in addition to the DWR data. A simple technique has been suggested by the authors for better prediction of thunderstorms at least three to four hours in advance. |
