Rare event simulation refers to the use of computational tools specifically designed to analyze events that occur very infrequently but are of acute interest. In many cases these events occur so infrequently relative to the simulation timescale that they cannot be accessed by direct simulation. Rare event tools allow direct interrogation of the event of interest without introducing additional model error and without wasted computational time simulating typical states of the system. With collaborators, I have begun exploring the use of these tools to study rare events in geophysical processes. An example of a rare event in the context of geophysics is the meander transition of the Kuroshio or Black Current that runs along the eastern coast of Japan is an example of just such a system. It undergoes infrequent but dramatic changes of state between a small meander during which the current remains close to the coast of Japan, and a large meander during which the current bulges away from the coast. In this talk I will survey one particular rare event simulation technique and its application in the context of on-line data assimilation of the Kuroshio. If time permits I will also comment on a recent data analysis of the Kuroshio’s meanders.