22nd Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction


Analysis and prediction of Sumatra squall lines

Lan Yi, Nanyang Technological University, Singapore, Singapore; and T. Y. Koh

Strait of Malacca is one of the world's most important shipping lanes. It is a narrow waterway between Malay Peninsula and Sumatra island. The most significant weather around the area is the Sumatra squall line (SSL). SSL is a fairly impactive convective storm that frequently forms along the Strait and sweeps across Singapore during nocturnal, pre-dawn and morning hours, most notably from April to November.

Radar data and upper air sounding data were analyzed to understand the origin, structure, propagation and convective development of SSLs. Idealized and semi-idealized COAMPSŪ* model simulations were carried out to identify what environmental parameters affect SSLs. Ensemble Kalman Filtering technique was applied to assimilate the radar data in order to improve the initial mesoscale trigger of SSLs in these simulations. Additionally, a real-time forecast system built from COAMPS (which uses the Multivariate Optimal Interpolation technique for data assimilation) has been implemented. Twice daily weather forecasts in Southeast Asia were made routinely at 81 km, 27 km and 9 km horizontal resolutions. The strength and limitation of the forecast system in predicting SSLs was evaluated in the real-time context.

*COAMPS stands for Coupled Ocean/Atmosphere Mesoscale Prediction System. COAMPS is a registered trademark of the US Naval Research Lab.


Session 7A, Convective Systems
Wednesday, 27 June 2007, 2:00 PM-4:15 PM, Summit A

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