How do meteorologists predict a tropical system's path?

I went to a wedding last weekend and among the weather questions I was asked was how forecasters make the cone of uncertainty to determine where a tropical system will go. Well, a lot of it, at least in the beginning of an Atlantic-based tropical systems life is determined by the high-pressure system that typically sits around the 30-degree latitude line and the general flow of winds. Based on the heating of the earth’s surface as well as the way the earth spins, we typically see a ring of low-pressure systems around the equator and a right of high-pressure systems around 30 degrees. Wind goes from high to low pressures and we get standard flows, westerlies and easterlies. Since most tropical systems form in this region between the equator and 30 degrees, they have a typical flow toward the east.

Directional flow is caused by the rotation of the earth and the typical pressure forces at different latitudes. Usually there is a strong high-pressure system over the Atlantic called the Bermuda High that pushes systems. Depending on where it is, the tropical system will sort of orbit it. If it's weak and in the middle of the Atlantic, systems will go into the middle of the Atlantic. If it's stronger, they could hit the east coast, and if it's stronger still they move into the Gulf of Mexico. But it isn’t just the Bermuda high that can influence, other pressure systems can as well. A low-pressure system that was over Texas made Helene turn further inland, which is why we saw some rain from it. A blocking high over Greenland made Sandy turn towards New York. All pressure systems move hurricanes, and forecasters use that knowledge to predict the path of the hurricane.