In the subtropics, the Hawaiian Island chain surrounded by the open ocean is an excellent place to test the impact of remotely sensed data in the analysis and numerical weather prediction. In this study, the ocean surface winds derived from the QuikSCAT satellite are assimilated in the initial conditions of the regional domains over the Hawaiian Islands using WRF (Weather Research and Forecast) three-dimensional variational data assimilation system (3D-Var) for a Kona low and a cold front cases during 5-7 April and 11-13 April, 2008 respectively.

Assimilation of QuikSCAT oceanic surface winds improves the analysis of the low-level cyclonic circulation associated with the Kona low as compared with the initial conditions provided by the NCEP Global Forecast System (GFS). In addition to improved low-level circulations, the pressure field associated with the storm is also better resolved with a well defined low-pressure center at the surface. The improvement in the wind field significantly extends from the surface to the 750-hPa level. The numerical experiments with assimilating oceanic surface winds result in a relatively stronger Kona low northeast of the Hawaiian Islands.

For a cold frontal system during 11-13 April, 2008, the propagation of the surface cold front with the wind shift or wind confluence over the ocean north of the Hawaiian Islands can be captured by the analyses of QuikSCAT ocean surface winds. With the assimilated ocean surface winds, the increase of low-level east-to-northeast winds over the nearby Hawaiian Islands during the passage of the cold frontal system can be better analyzed and simulated.