The 23rd Conference on Hurricanes and Tropical Meteorology

11C.8
THE BOGUSCANE- A SERIOUS PROBLEM WITH THE NCEP MEDIUM RANGE FORECAST MODEL IN THE TROPICS

John L. Beven II, TPC, Miami, Florida

This paper examines a persistent problem with the NCEP Medium Range Forecast (MRF) model in the tropics. During the mid­1990s, the model produced a series of spurious small­scale spin­ups in the tropics. Despite corrections, the model now develops very realistic looking, yet still fictitious, tropical cyclones (TCs). A series of model runs from June 1998 highlights the problem. Not only did the model develop a large number of imaginary TCs in the Eastern Pacific, but four of them actually appeared in the model initial analysis. One part of the problem may arise from a too­efficient convective parameterization, as these spurious TCs form mainly during episodes of enhanced convection. Another part is possible shortcomings in the model analysis, with insufficient low level data reaching the model to contradict its first guess field. This problem has serious implications for TC track forecasting since the Aviation run of the MRF serves as a background field for most of the TPC/NHC track prediction models

The 23rd Conference on Hurricanes and Tropical Meteorology