Interpreting tropical forecast projections

Breaking down the basics of a forecast fan
Hurricane Fan
Posted at 9:24 AM, Jul 30, 2020
and last updated 2020-07-30 09:24:35-04

We got our ninth named tropical system in the Atlantic Ocean this week.

The storm's name is Isaias, and it is currently tracking toward the United States.

When you watch a broadcast meteorologist, or do a quick internet search, you'll often see a projected track for any tropical system. This is what's called a 'fan.'These forecast fans can be a little deceiving though.

First off, the forecast itself is based on a consensus from spaghetti plots. We talked about these before, but feel free to get a quick crash course.

The forecast fan shows the trend or unanimity of the spaghetti plots. The fan forecasts a few days out with labels for every 12 hours and an estimated strength level.

Now for the tricky part.

There is a center line throughout the fan. Many people think the center line is the path the tropical system will most likely take. This line is simply the middle of the fan though, and not a more likely scenario than any other route within the fan.

And now you'll be a little bit more weather wise.