Forecasting the motion of North Atlantic tropical cyclones by the objective MOHATT scheme

Abstract

An objective scheme for forecasting the motion of tropical cyclones (MOHATT) , under development since 1967 by the U.S. Navy Fleet Numerical Weather Central and the U.S. Naval Postgraduate School, Monterey, Calif., is described and applied to the 1967-71 North Atlantic tropical cyclones for forecast intervals up to 72 hr. The MOHATT scheme involves steering of the center of the cyclone by geostrophic winds derived from heavily smoothed isobaric height fields (both analyzed and prognostic) and a statistical correction determined by the behavior of the first 12 hr of the steering forecast. The developmental sample (1967-70) used to establish the potential accuracy of MOHATT indicates 700 mb as the optimum steering level, but the fully operational test in 1971 suggests that the 850-mb level may be an improvement for forecast intervals beyond 36 hr.