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Updates On Dorian: Figuring Out The Future

25 Jul 2013, 11:14 am

Watching tropical systems can be both entertaining, and challenging. In this case, we are so far removed from any actual landfall that we are still able to have some fun with it… while still dealing with some of the challenges surrounding the system.



That is one of my favorite graphics of the day.  When you first heard “Delorian” did you think of “DeLorean,” like I did?

Maybe I am unique, actually, that is probably the case… but it hasn’t stopped us (Todd Nelson and I) from using Back To The Future references throughout the past few days.

As of the writing of this blog post we were watching Dorian moving steadily west/northwest and strengthening slightly (about 60mph sustained winds as of the most recent update prior to 10AM CDT).  But where is it going to go?  Well, we can all look at the following image:


5am Dorian Track & Information
5am Dorian Track & Information


So you look at that image, and you know where Dorian is going, right?  Well, maybe you wonder this: WHY would Dorian take this route?

Well, there are many complications to forecasting tropical systems, so we are going to do a fairly simple analysis.

We’ll start with the pressure at the surface.  Right now, over the Atlantic Ocean’s central regions, there is a fairly robust high pressure center.  That, similarly to how it would behave on the continental U.S., is the blocking force that looks to keep Dorian south.  Here is what the picture looks like for today:



See all of those lines and numbers between the big “H” and the tropical-looking icon?  Those lines are isobars, or lines of constant pressure.  There is a very strong high pressure center over the central Atlantic, and it doesn’t look to erode much over the next week.

The other interesting thing?  Due to the earth rotating, you have what’s known as the Coriolis Force, which tries to turn things to the right in the Northern Hemisphere. (Click here to see more on the Coriolis Force)

Speaking of the Coriolis Force – how would you like to manipulate *this* equation?



That’s the type of stuff that your trusty meteorologists had to deal with while in college… thankfully things are a bit simpler once you’re using your meteorology skills in real life.

So what ends up happening with Dorian, is that it is constantly poking and prodding at the high pressure region that is blocking it from turning right, the direction it wants to go.  Should the high pressure ridge weaken, even for a very short amount of time, that is when Dorian would try to hook right, or in this case, northward.

While outside cold fronts and other forces can change the trajectory, this is where Dorian starts to show up on our models come early next week:


Dorian Extended
Dorian Extended


Notice how the high retreats a little bit, to the Northeast, and that is when Dorian slips northward.  Let’s hope this model comes true – and Dorian is allowed to just be a “fish storm” and move northward – away from large populated areas.

Stay tuned!

WeatherNation Meteorologist Aaron Shaffer @ashafferWNTV

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