A brief summary of the impact of targeted observations taken during NORPEX 98 and NORPEX 99 will be given. The remainder of the paper will present results from tests of the ability of a variant of the Ensemble Transform Kalman Filter (ET KF) to anticipate the impact of targeted observations on forecast accuracy. Like any other Kalman Filter, the ET KF allows the isolation of a covariance matrix which describes the reduction of analysis and prediction error covariance due to the assimilation of the targeted observations. We call this matrix the impact error covariance matrix. The corresponding part of the analysis increment is called the impact analysis increment. The results from two basic tests will be presented. First, the impact analysis increment produced by the ET KF with isotropic pre- conditioning is compared against the impact analysis increment produced by NCEP's 3-D Var operational data assimilation scheme. Our second test is a check of the extent to which the vector subspace of the orthonormal singular vectors of the impact error covariance matrix contains the impact analysis and forecast increments produced by NCEP's operational data assimilation scheme.
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12th Conference on Atmospheric and Oceanic Fluid Dynamics