Identifying precursor of Sumatra squall line

Abstract

Sumatra Squall Line (SSL) is a detectable mesoscale meteorological phenomenon at least prior to 3 hour using Doppler radar imagery interpretation. By identifying precursors, SSL can be detected 6-12 hours earlier before the occurences. Infrared data from MTSAT satellite were used to identify clusters of SSL clouds which then produce two types of SSL with different orientations, namely Northwest SSL (oriented northwest - southeast) and Northeast SSL (oriented northeast - southwest). Wind, helicity, and moisture transport were selected as precursor variables due to their importance information of squall line. The results of the precursor variable pattern comparison in the case of SSL with non-SSL showed clear differences. Bottom layer convergence and the westerlies wind patterns were proven to be formed in SSL cases. Helicity concentration was related to orientation of SSL cloud cluster. The convergence of moisture transport was detected 6 hours before the SSL occurences.