Characteristic Errors in 120-H Tropical Cyclone Track Forecasts in the Western North Pacific

摘要

All large (>400 n mi at 96 h, >500 n mi at 120 h) Navy Operational Global Atmospheric Prediction System (NOGAPS) and U.S. Navy version of the Geophysical Fluid Dynamics Laboratory Model (GFDN) tropical cyclone track forecast errors in the western North Pacific during the 2004 typhoon season are examined. Responsible error mechanisms are described by conceptual models that are related to known tropical cyclone motion processes being misrepresented in the dynamical models. Of the 162 (135) cases of large NOGAPS (GFDN) forecast errors, 39 were due to tropical influences with excessive direct cyclone - tropics (E-DCI) interaction occurring most frequently. For the 217 large-error cases due to midlatitude influences, the most frequent error mechanisms were E- DCI (midlatitude), excessive response to vertical wind shear, excessive midlatitude cyclogenesis (E-MCG), insufficient midlatitude cyclogenesis (I-MCG), excessive midlatitude cyclolysis (E-MCL) and excessive midlatitude anticyclogenesis (E-MAG), which accounted for 68% of all large errors occurring in both NOGAPS and GFDN. Characteristics and symptoms of the erroneous forecast tracks and model fields are documented and illustrative case studies are presented. Proper identification and removal of the track forecast displaying an error mechanism could form a selective consensus that will be more accurate than a non-selective consensus.