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How Exactly Are Hurricanes Tracked?

Why Hurricane Matthew Is Difficult to Forecast 1:37

Just where is Matthew going?

As hundreds of thousands of people in South Carolina and Florida prepare to evacuate while the deadly hurricane barrels closer to the U.S., meteorologists continue to watch the mega storm in an effort to predict what’s going to happen — and how to keep everyone out of harm's way.

But hurricanes are particularly tricky to track.

“We’re always waiting for the next curve ball,” said Frank Giannasca, a senior forecaster for The Weather Company.

Hurricanes are tracked in several ways: Via satellite, reconnaissance aircraft and balloons that collect data including temperature, humidity and wind speed.

Those various data streams are then compiled to create computer-forecast models that attempt to predict the path and intensity of the storm.

Related: Thousands of Americans Head Inland to Escape Hurricane Matthew

But lots of the data — especially ridges (areas of high atmospheric pressure) and troughs (areas of low atmospheric pressure) — are constantly changing.

“Even the forecast of Matthew has evolved so much because new information develops as the storm moves along ... Just three days ago, there was a question on whether or not it would even reach the United States. And now we’re talking about it coming very, very close to Florida and Georgia,” Giannasca said.

There are plenty of other confounding variables, too. For example, a storm system on the West Coast could affect a storm on the East Coast, but you can’t sample a lot of that data until the storm actually moves on shore, explained NBC News meteorologist Bill Karins.

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In the case of Hurricane Matthew, the area of high pressure was stronger in the Atlantic than initially thought, which is why it’s is coming closer to the United States than once anticipated, he said.

“The reason that hurricane forecasting isn’t more of an exact science is because we are limited by the data that we get. We’re limited by the data that’s given to us by these satellites, by these drones that fly through these storms, or the hurricane hunters who fly right through the eye. There’s only so many of them and the storm is so huge. All that data goes into a computer model. The computer models would be a lot better if it had a lot better data,” said Karins.

Related: Hurricane Matthew: Here's What You Need in Your Survival Kit

Depending on which angle the hurricane is coming in on, its path can also be more difficult to predict. When the hurricane is perpendicular to the coast line, it’s an easier forecast compared to when it’s running parallel — as is the case with Matthew — because the route can change more easily.

Although it’s an inexact science, Karins said hurricane predictions have come a long way since the first satellites were launched decades ago

“The science has gotten 100 times better over the last 50 years. So although we’re still going to have little minute differences of opinion of what’s going to happen right until landfall, [it's] fortunate that we have the data we have now. It’s much better than your parents and grandparents had,” he said.

IMAGE: Hurricane Matthew projection
A forecast map issued late Tuesday night projects Hurricane Matthew's possible course through the end of the week. National Hurricane Center