Here’s what steers Tropical Storm Ian

Still uncertainty in short and long-term path

ORLANDO, Fla. – Florida is in the cone, but a lot can still happen over the next few days as the forecast is fine-tuned.

Ian is still a disorganized storm still under the influence of shear. While wind shear helps to keep the storm weak, it adds in the forecast uncertainty.

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Short-term uncertainty

As of Saturday morning, the thunderstorms are not located where the center of the storm is. It will be critical for the long-term path of Ian just where the low-level center becomes dominant.

In the short term, if Ian starts to track on the southern and western side of the cone, it will have ramifications that extend to the long-term future of the storm. This will suggest some of the models that take the storm toward the Big Bend or Panhandle of Florida may be correct. If the center forms closer to Jamaica, it would suggest the Central or Southern Florida track may be the favored path. These trends will be monitored closely through the weekend.

Subtle changes short-term could have big implications long-term.

Steering Pattern. European Solution. The American GFS is weaker with the upper trough and allows for a more west and northerly track.

Long-term steering

Ian will be lifted north out of the Caribbean and into the Gulf of Mexico or Florida Straits by a large dip in the jet stream. That dip, or trough, will be digging through the Northeast.

The European model solution, as of Saturday morning, has a stronger, or deeper, dip in the jet stream. This would help to pull Ian across the Peninsula. The American GFS model has a weaker dip that retreats into Canada which would allow the storm to go further west of the current forecast cone.

This is the main reason for the large differences in the model forecast long-term. The disturbance that will steer Ian is moving through the northern tier of the U.S. and will thus be sampled better by weather balloon launches.

To help sample the overall steering environment, the National Weather Service is sending up addition weather balloons. This data will then be put into computer forecasts which will help the accuracy and reduce the uncertainty.

If Ian does lift more north, that same trough would also introduce wind shear and dry air into the storm which would promote weakening. It’s too early to tell, however, if it would be significant weakening. The western/northern track would be better for Central Florida’s outcome, so to say, but potentially worse for the Big Bend and or Panhandle.

There is a lot to be ironed out in the long-term path of Ian, but it should become clearer over the next 48 hours.


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About the Author:

Jonathan Kegges joined the News 6 team in June 2019 as the Weekend Morning Meteorologist. Jonathan comes from Roanoke, Virginia where he covered three EF-3 tornadoes and deadly flooding brought on by Hurricanes Florence and Michael.