They frequently end up covering huge areas of ocean, much larger than their tropical antecedents, moving at speeds of as much as 1000 miles per day in the process. Two recent examples of this process on the Eastern Seaboard of the U.S are Danielle and Mitch. Because of their size and speed of movement , systems which have the potential to make this transition bear close watch by all passagemakers. Just because a tropical storm system is a thousand or more miles away does not necessarily mean it won t have an impact on your future. They key to analyzing the risk factors inherent when one of these systems is lurking is understanding the mechanics of the transition process, and then watching both surface and upper level wind charts for telltale signs.
Weather systems depend on differences in temperature and humidity for their energy.
The greater the differential, the more energy available for surface level winds. Within a tropical storm an area of low pressure develops and surface winds rush in to fill the partial vacuum. Warm, moist air rises and releases energy into the cooler, drier upper atmosphere. If there is no venting mechanism at the top of the system, the central area of low pressure fills and the winds drop off. A key ingredient necessary for this process to start, and then continue is a minimum of wind speed differential between the surface and the upper altitudes.