RESULTS AND DISCUSSION
4.1 Nor'wester of 07 April 2012
4.1.9 Vertical Totals index (VT)
The model simulated time variation of VT for six different MPs coupling with KF and BMJ schemes at Chittagong are presented in Figs. 4. 0(a-b). The VT has- increased continuously (Fig. 4.1.1 0a) and reached > 30°C at around 0850 UTC for all MPs coupling with KF
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schemes and after that it has decreased sharply by Lin-KF, WSM6-KF and WDM6-KF combinations. The VT > 28°C indicates strong potential for the occurrence of severe thunderstorms. After that it has started to increase in an oscillatory nature.
In the morning, VT has decreased sharply and then increased from 0150 to 0700 UTC (Fig.
4.1.1ob) for all MPs coupling with BMJ scheme. From 0240 to 0810 UTC the VT> 28°C indicates strong potential for the occurrence of severe thunderstorms. Figs. 4.1.1 0(c-d) depict the model simulated VT at Dhaka. Up to 0350 UTC (Fig. 4.1.10c), the VT is> 31°C for all MPs coupling with KF scheme and then it has decreased slowly and fluctuates for all MPs coupling with KF scheme at around 0630 UTC. From 0100 to 0500 UTC, VT is > 28°C for all MPs coupling with KF scheme indicates strong potential of VT for the occurrence of severe thunderstorms at Dhaka. Up to 0310 UTC (Fig. 4.1.1od) the VT > 28°C for all MPs coupling with BMJ scheme indicates strong, potential for the occurrence of severe thunderstorms and then significantly decreased for all MPs coupling with BMJ scheme at 0320 UTC. After 0410 UTC it has again increased for all MPs coupling with BMJ scheme and the value is found > 26°C, which is favorable for the occurrence of thunderstorm.
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Fig. 4.1.10: Time variation of VT at(a-b) Chittagong and (c-d) Dhaka on 7 April 2012 using six different MP schemes coupling with KF and BMJ schemes.
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P
4.1.10 Total Totals Index (TT)The model simulated time variations of TT Index for six different MPs coupling with KF and BMJ schemes at Chittagong are shown in Figs. 4.1.I1(a-b). Up to 0410 UTC (Fig. 4.1 ha), the TT > 51°C is found for all MPs coupling with KF schemes. In the morning, the TT simulated greater than 51°C indicates the occurrence of isolated severe storms. After that it has decreased for all MPs up to 0710 UTC and then increased in an oscillatory pattern. From 0430 to 0740 UTC, the TT > 49°C or equal for all MPs coupling with KF scheme indicates the occurrence of likely thunderstonns. The maximum TT is found to be 58.09°C at 1130 UTC fr SBU-KF con.binaton, which indicates the occurrence of scattered severe storms. In the morning, the maximum TT is found > 51°C (Fig. 4.1.11 b) for all MPs coupling with BMJ schemes and is decreased up to 0630 UTC and then increased reaching maximum after 0900 UTC to 52CC. After that it shows oscillatory pattern for all MPs coupling with BMJ scheme.
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Fig. 4.1 .11: Time variation of TT at (a-b) Chittagong and (c-d) Dhaka on 7 April 2012 using six different MP schemes coupling with KF and BMJ schemes.
Figs. 4.1.11 (c-d) depict model simulated TT at Dhaka. The TT is found >56°C for all MPs coupling with KF scheme from 0120 to 0340 UTC (Fig. 4.1 .11 c). In the morning, the TT
>56°C indicates the occurrence of scattered severe storms. After that it has decreased slowly and fluctuates continuously for all MPs coupling with KF scheme up to 1000 UTC. From 0400 to 0600 UTC, the value of TT lies between 53 to 56°C which indicates the occurrence of widely scattered severe storms The maximum value of TT is 5998 and 5,9. 1 9°C has. been
) simulated by 'l'H-KF and SB1J-KF combinations at 0600 and 0630 UTC respectively. The TT simulated is> 56°C for all MPs coupling with BMJ scheme up to 0210 UTC (Fig. 4.1.11d), which indicates the occurrence of scattered severe storms. After that the TT is found >55°C
for all MPs coupling with BMJ scheme up to 0310 UTC which is favorable for the occurrence of widely scattered severe storms. After 0310 UTC, the TT has decreased significantly and aflcr 0410 UTC, the TI has increased again for all MPs coupling with BMJ scheme. From 0320 to 0420 UTC, the TT lies between 45 to 52°C for all MPs coupling with BMJ scheme and indicates the occurrence of likely thunderstorms and from 0430 to 0600 UTC, the TI> 51°C for KS-BMJ and TH-BMJ combinations, indicating the occurrence of isolated severe storms and then it has been changmg in an oscillatory pattern for all MPs coupling with BMJ scheme.
4.1.11 K ladex (K!)
The model simulated time variation of KI for six different MPs coupling with KF and BMJ schemes at Chittagong has been presented in Figs. 4. 1.1 2(a-h). Up to 0420 UTC (Fig.
749 4.1.12a) the K! > 41°C, which indicates extremely unstable atmosphere for all MPs coupling with KF schemes. In the morning, the K! greater than 40°C, indicates maximum possibility for the occurrence of thunderstorm. After that it has decreased gradually up to 0750 UTC and then again increased up to 1140 UTC for all MPs coupling with KF scheme.
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Fig. 4.1 .12: Time variation of K Index at (a-b) Chittagong and (c-d) Dhaka on 7 April 2012 using six different MP schemes coupling with KF and BMJ schemes.
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to K index has decreased sharply to 35.83°C for WSM6-KF combination at 0900 UTC, which has the probability of numerous thunderstorms. From 0430 to 0910 UTC, the KI> 39°C or equal, which is very unstable case for all MPs coupling with KF scheme and indicates the occurrence of very likely thunderstorms. Up to 0140 UTC (Fig. 4.1.12b), the KI is> 40°C, which extremely unstable case for all MPs coupling with BMJ schemes. In the morning, the K! greater than 40°C, indicates maximum possibility for the occurrence of thunderstorm.
After that it has decreased gradually up to 0740 UTC and then again increased up to 0940 UTC for all MPs coupling with BMJ scheme. From 0150 to 0940 UTC the KI is >39°C or equal, which is very unstable atmosphere, simulated for all MPs coupling with KF scheme, and indicates the occurrence of very likely thunderstorms.
Figs. 4.1.12(c-d) depict model simulated K! at Dhaka. The simulated KI is> 40°C up to 0420 UTC (Fig. 4.1.12c), which indicates extremely unstable atmosphere for all MPs coupling with KF scheme and the possibility of maximum for the occurrence of thunderstorm. Then it has decreased and subsequently fluctuates continuously for all MPs coupling with KF scheme. At 0640 UTC, the KI is> 40°C for KS-KF combination. The KI is > 40°C from starting up to 0310 UTC (Fig. 4.1.12d), indicates extremely unstable situation for all MPs coupling with BMJ scheme. In the morning, the KI greater than 40°C, indicates the maximum possibility of the occurrence of thunderstorm at Dhaka. After that it has significantly decreased and fluctuates continuously. The KI > 36°C during 0320 to 0340 UTC indicates very unstable atmosphere for the occurrence of very likely thunderstorms for all MPs coupling with BMJ scheme. The KI> 32°C during 0340 to 1500 UTC for all MPs coupling with BMJ scheme indicates for the occurrence of numerous thunderstorms.