1) The document proposes using weight interpolation for the Local Ensemble Transform Kalman Filter (LETKF) data assimilation method to improve computational efficiency. 2) In LETKF, weights are computed on coarse grids and then interpolated to high-resolution grids, rather than computing the analysis directly on the high-resolution grids. 3) Experiments with a quasi-geostrophic model show that interpolating the weights produces analysis accuracy comparable to computing the analysis on full grids, while greatly reducing computational cost. Weight interpolation allows analysis to be performed in regions without local observations.