Chief Meteorologist Eric Snitil explains the Fujiwhara Effect on the latest tropical systems.
If this doesn’t sate your appetite for unusual tropical talk, I don’t know what will.
August 20th marked the start of the climatological peak of our Atlantic Hurricane season, and it’s no surprise we’re beginning to see the tropics light up with what seems like a train of systems. Check out the previous discussion about the anticipated active season HERE.
The latest talk of the tropics is an interesting one for sure. The reason? We have the potential for not 1, but 2 tropical systems to threaten the U.S. simultaneously in the upcoming week.
We’re now looking at Tropical Storm Laura, and Tropical Storm Marco that are anticipated to have some sort of impact on the U.S. in the coming days. Here are the two systems below:
Now let’s take a look at the latest forecasts of the two systems from the National Hurricane Center (NHC):
No, your eyes aren’t fooling you. These forecasts are in fact portraying the potential for these storms to become Hurricane status around the same time, and just about in the same place.
But, how likely is this?
Realistically, it doesn’t seem likely that this exact situation will play out. Why? We’re still several days out from potential U.S. landfall and there are a lot of factors that go into this including their interactions with land, interactions with each other, and whether or not the incredibly warm ocean waters are enough to restrengthen them if they do weaken. Let’s discuss:
The Fujiwhara Effect
When two tropical systems get close enough to each other an interesting phenomenon occurs. It’s called the Fujiwhara effect.
This effect occurs when two spinning systems, often tropical, heading in the same direction get close enough to each other to interact, and they’ll often spin around each other like a satellite orbiting the earth. When this happens, the smaller and already weaker system will usually get absorbed into the stronger system, which ultimately ends up weakening both systems in the long run until the whole system fizzles out. Only on exceptionally rare occasions, if the absorbing storm is strong enough will it remain intact and/or strengthen after the interaction.
NOTE: The tracks shown above merely represent what could happen without taking into account this effect and are likely to change. The reality is, when these storms interact it could drastically alter their strength, size, and their line of direction.
The fact is that they are NOT going to combine to form one, large super Hurricane. What often happens when the Fujiwhara effect kicks in, is one of the systems takes away energy from the other and you end up with the two merging together, but ultimately weakens both systems along the way.
With the potential for two cyclones in the gulf at the same time it raises the question, has this ever happened before in history?
As shown in the tweet above, having two named tropical systems in the Gulf at the same time has only happened a few times ever in history; in 1933 where the systems both made landfall on the same day, and twice in 1959.
However, never in history has there ever been two Hurricanes occurring in the same vicinity at the same time like the current forecast portrays. So, how likely is it to see this situation play out?
First, it’s unlikely that these two systems merge and strengthen, but whether or not they interact and how they interact is still sort of up in the air.
What’s NOT being mentioned enough is the reality of the Fujiwhara effect on the two systems and how this will ultimately end up changing the current outcome of the forecast. As I hinted at above, the current forecast cones in place showing the strength and direction of their paths are most likely NOT taking into consideration what could happen when these two systems interact.
Given the current situation, we very well could have more than one tropical system threatening the U.S. coast, and it is best to prepare sooner rather than later, but let’s take this current information with a grain of salt as changes to the forecast are likely to occur.
All in all, I have a feeling that the talk of the Tropics is going to highlight our conversations going into next week, so we’ll keep up to date with the latest trends and forecasts on this unique forecast.
You can track the latest on these tropical systems at the NHC website HERE.
~Meteorologist Christine Gregory