TROPICAL AND SUMATERA SQUALL LINES

SQUALL LINE, TROPICAL SQUALL LINE

Meteorologist usually define a squall line as a line of thunderstorms. A tropical squall line is associated strong convective activity and consists of clusters of rain cells whose physical dimension can be several hundred kilometers. The individual rain cells tend to be aligned at the forefront of the squall line. Since the associated wind gust fronts of the individual rain cells usually merge to form a single gust line, it seems to be appropriate to call such rain event squall line.

SUMATRA SQUALLS

“Sumatra Squalls” are tropical squall lines or thunderstorms that affect the Malay Peninsula and Singapore. During the colonial period (before 1962), the British meteorologists at the forecast offices in this region called this special type of thunderstorms “Sumatra Squalls” because they believed that they have their origin at the island of Sumatra. Later weather satellite observations have shown that the Sumatra Squalls are often triggered
by the arrival of equatorial super clusters of thunderstorms (a component of the Madden–Julian oscillation) that propagate into the region from across the Indian Ocean (from the crest).

THE DEVELOPMENT OF SUMATRA SQUALLS 

Weather radar images have revealed that the development of a Sumatra Squall starts with strong convective activities in the Malacca Strait during the night. Individual rain cells begin bubbling up in the Strait of Malacca from about 2000 local time.As the convective cells grow more widespread and intense, they align themselves into a line, sometimes extending more than 300 km from south to north. During the night, the line of thunderstorms are held off the west coast of the Malay Peninsula, probably by land breeze. During sunrise, they sweep in over land, generating in the early morning hours strong gusts and heavy showers in Singapore and the southern region of Malaysia.


REF: http://smart.as.ntu.edu.tw/publication/journal_papers/03_An_ERS-1_Syntheric.pdf

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