Case Study: Sumatras over the Straits of Malacca during the Southwest Monsoon 2009

Publication Date :
Author : Fadila Jasmin FakaruddinLim Ze HuiKhairul Najib IbrahimMarcella James J.Mat Kamaruzaman Mat AdamYip Weng SangNursalleh K. ChangDr. Fariza YunusMuhammad Helmi Abdullah
Countries : Malaysia
Disaster Management Theme :
Disaster Type : Other
Document Type : Research Paper
Languange : en
Link :

Abstact :

Sumatras are defined as lines of thunderstorms which usually occur between April until November each year. These lines of thunderstorms which are develop at night over Sumatra or Straits of Malacca and move east towards Peninsular Malaysia usually during the pre-dawn and early morning. They are often characterised by sudden onset of strong gusty surface winds and heavy rain, lasting from one to two hours as they move across the island. This study is performed with the aim of investigating and identifying the conditions, which could lead to the occurrences of Sumatras in the Straits of Malacca. Based on the observational data obtained from the Malaysian Meteorological Department (MMD) and reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim, this study investigated several events of the Sumatras and non-Sumatras days along the Straits of Malacca between May to September 2009 to determine the favourable environmental conditions, which could lead to the occurrences of sumatras. In this study, the environmental conditions during the Sumatras days have been identified, namely; (i) strong westerly winds (15 to 20 knots) from the Indian Ocean at the low level bring along the moistures to Sumatra region; (ii) strong low level convergence (indicates with occurrences of a vortex at the low level and divergence at the upper level); (iii) high humidity (85% to 100%) over the Straits of Malacca at the low level, and high humidity also occurs at mid level to support the stronger convection; and (iv) warmer surface air temperature, approximately 26°C to 28°C above the surface.