Abstract
Heavy rainfall (HRF) forecasting in hilly region is always a challenge to the operational forecasters. Synoptic Analogue Model (SAM) is considered as one of the useful tools for HRF forecasting in topographically influenced hilly regions. In every monsoon season, the Teesta river catchment and its adjoining areas in Sub-Himalayan West Bengal and Sikkim (SHWB-S) generally receive several events of HRF. With the primary objective to find the method to issue HRF warning over Teesta river catchment and adjoining areas in SHWB-S, a SAM has been developed by analyzing 18 years (1998-2015) data comprising prevailing synoptic situations affecting the area and daily rainfall data of subsequent day of HRF. In addition, impact of different synoptic systems on the distribution of HRF has also been studied. The results revealed that there exists a good agreement between daily HRF warnings issued with the corresponding HRF event observed over this region on the next day.
Highlights
IntroductionSub-Himalayan West Bengal and Sikkim (SHWB-S) is one such area where Heavy rainfall (HRF) is a very common phenomenon during south-west monsoon season (JJAS)
Teesta River Catchment and its adjoining areas inSub-Himalayan West Bengal and Sikkim (SHWB-S) is one such area where Heavy rainfall (HRF) is a very common phenomenon during south-west monsoon season (JJAS)
(a) The impact of various important synoptic systems on the HRF activities over Teesta basin & adjoining areas in SHWB-S for the period 1998 to 2015 are summarized in the Table 4. From this table, following points may be inferred: (i) Upper air cyclonic circulation over Bihar along with trough passing through SHWB-S responsible for Various synoptic systems identified over SHWB & Sikkim during 1998 to 2015
Summary
Sub-Himalayan West Bengal and Sikkim (SHWB-S) is one such area where Heavy rainfall (HRF) is a very common phenomenon during south-west monsoon season (JJAS). These HRF activities often results water induced hazards like flash floods and landslides causing significant loss of lives and damage to the properties. Rao et al (1997) have shown that statistical analog procedure gives a good idea for predicting average areal precipitation semiquantitatively for Teesta basin. In this present study, daily rainfall data and synoptic situations prevailed on the previous day over. Impact of different synoptic systems in the distribution of HRF (65 mm and above) during this season over Teesta basin & adjoining areas in SHWB-S has been studied
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