Flame spread characteristics are studied for water-in-oil emulsion layers floating on top of a water body - similar to a scenario in which an accidental oil spill occurs in open, rough sea. A comprehensive mathematical model is developed and numerical solution is obtained for the ignition and flame spread process which takes into account the emulsion break up into oil and water due to heating, oil vaporization, combustion of oil vapor mixed with air in open atmosphere, radiative and convective heat feed back from flames to the condensed phase (consisting of emulsion, oil, and water), and continuation of the emulsion breaking resulting in flame spread till the oil is consumed. Numerical results are compared with experiments conducted on Arabian Medium Crude oil emulsions made with up to 20% weathered oil (light fraction evaporated, by volume), having up to 50% water content in the emulsions. The flame spread rate decreased as the water content and the weathering level increased, with a reasonable agreement between experiments and model. The long term objective of this work is to assist the application of in situ burning as a measure for the cleanup of weathered and emulsified oils.