Forecasting tropical cyclone turning motion from surrounding wind and temperature fields ( West Indies).

An analysis of tropical cyclone forecast track errors shows that the largest errors are typically associated with storms undergoing turning motion. This paper presents results obtained from a composite study of tropical cyclones occurring in the West Indies during 1961-77. These results suggest or verify previous ideas that 1) by measuring certain parameters around a storm (sense of surrounding wind rotation, vertical wind shear between 200 and 900mb, or gradient of tropospheric mean temperature) one may be able to make a better 24-36h forecast of cyclone turing motion; 2) the turning motion of tropical cyclones is controlled by large-scale flow fields surrounding them; and 3) there seems to be a time lage between the changes in the environment and the response of the storm center to such changes. -from Authors