On impacts of cloud-tracked wind observations on numerical tropical cyclone forecasts

The impacts of the cloud-tracked winds on tropical cyclone forecasts, which were reprocessed for the period of the tropical cyclone field experiments TCM-90 operated in the western North Pacific in August and September 1990, were investigated. To achieve this purpose, we made reanalysis and forecast experiments with the operational global analysis and forecast models of the JMA. Our results are as follows: (1) The predicted tracks of tropical cyclones successfully improved by the reprocessed cloud-tracked winds. (2) Forecasts of geopotential fields in the western North Pacific areas in which these observations were distributed, also improved by the reprocessed winds. These results suggest that the improvement of tropical cyclone track prediction depends on the improvement of forecasts of large scale fields. (3) With level reassignment of the cloud-tracked winds as in the operational model, their impacts were not so significant. Rash enhancement of observations does not introduce the improvement of tropical cyclone forecast. The appropriate level assignment is more important.