This is a typical streamline analysis weather chart of a double typhoon in the Pacific. Streamline analysis is the methodology used by the forecaster to analyse the wind direction/speed/RH and temperature for areas of the tropics where observed data is very sparse. The advent of satellite data has greatly improved our ability to track storms across vast areas of the ocean. Tracking the movement of the areas of cyclonic (C) and anti-cyclonic (A) circulations and refining the analysis with satellite data the forecaster can predict the movements of these storms across the oceans continuing to refine the forecast as the storms near land areas which allow for additional data from land stations to assist in analysis and forecasting.