🌴 Tropical Storm Edouard: How Does A Thunderstorm Become A Tropical Storm?
It's Tuesday, and we've got another interesting tropical system to talk about.
As expected, Tropical Storm Edouard formed yesterday evening, and once again we're seeing one of these incredibly short-lived tropical storms. In fact, Edouard probably won't even make it to 24 hours as a named storm before moving inland along the Texas coast.
That's pretty remarkable.
We're talking about a cluster of thunderstorms that comes off the Louisiana coast, gets itself organized, and then somehow manages to wind itself up into a tropical storm in just a matter of hours.
So how does that happen?
That's the part I find fascinating.
How Does A Thunderstorm Become A Tropical Storm?
It starts with the thunderstorms.
Inside a cluster of very deep thunderstorms, tremendous amounts of warm, moist air are rising. As that moisture condenses into clouds and precipitation, it releases latent heat into the atmosphere.
That heat is incredibly important.
The release of latent heat warms the air in the storm's core, which can cause the surface pressure to fall. As the pressure drops, air begins to accelerate inward toward the developing low-pressure center.
And once you get that circulation started, you've created a feedback process.
More thunderstorms develop.
More latent heat is released.
Pressure falls further.
More air flows toward the center.
And the circulation becomes stronger.
This is where the concept known as CISK — Conditional Instability of the Second Kind — comes into the discussion.
Essentially, the convection and circulation begin working together.
The thunderstorms help strengthen the circulation, while the circulation helps concentrate the thunderstorms.
And because the system is sitting over the incredibly warm waters of the Gulf of Mexico, it has an almost unlimited supply of heat and moisture to work with.
The system can essentially start spinning itself up.
We've Seen This Happen Several Times
What's amazing to me is that we've now seen this type of rapid development happen several times this year.
These systems can go from:
Thunderstorm cluster → organized circulation → tropical depression → tropical storm
in an incredibly short amount of time.
And sometimes it happens so quickly that you're watching the satellite imagery and thinking:
Wait a minute... where did that tropical storm come from?
It was just a bunch of thunderstorms a few hours ago!
This is not necessarily an unusual physical process. Similar convective circulations can develop within large mesoscale convective systems, where the enormous amount of heat and moisture released by thunderstorms can help establish a broader circulation.
The difference is that when you're over warm tropical or subtropical water, the ocean continues supplying heat and moisture to the system.
That can allow the circulation to persist and, under the right conditions, become a tropical cyclone.
Edouard Is A Perfect Example
Edouard is another great example of how quickly this process can occur.
The system developed from thunderstorms that moved off the Louisiana coast and rapidly became organized.
It was eventually named Tropical Storm Edouard late yesterday evening, and now it's already heading toward the Texas coast.
Edouard is expected to move inland north of Houston and Galveston, but that doesn't mean those areas are going to escape the storm's effects.
The primary concern is going to be heavy rainfall.
Several inches of rain could fall across portions of southeastern Texas, and some locations could experience flash flooding, especially where the heaviest thunderstorms repeatedly move across the same areas.
So even though Edouard is going to be an extremely short-lived tropical storm, it can still produce significant impacts.
What's Interesting About The Setup?
Here's another thing that makes Edouard interesting.
The overall atmospheric pattern isn't exactly screaming, "Let's develop a tropical storm!"
The MJO isn't in an especially favorable phase for Atlantic tropical development, and the ongoing El Niño continues to produce substantial wind shear across the tropical Atlantic and Caribbean.
Yet here we are.
Another tropical storm developed anyway.
And, in some ways, this system was actually anticipated several days ago. The potential for something to develop in this general area started showing up in the guidance over the weekend.
So while the exact timing and intensity weren't necessarily nailed down, the atmosphere was giving us some clues that something could organize.
The Incredible Speed Of Tropical Development
That's what I find so fascinating about meteorology.
You can watch a cluster of thunderstorms move off the coast, and within hours the entire structure of the system can change.
The thunderstorms begin organizing.
The pressure begins falling.
The circulation develops.
The convection becomes concentrated.
And suddenly you've got a tropical storm.
That's Edouard.
A storm that may exist as a named tropical cyclone for less than a day.
It's a great reminder that tropical systems don't always need several days to develop. When you've got very warm water, tremendous moisture, and persistent deep convection, the atmosphere can sometimes organize itself incredibly quickly.
Edouard may be a very short-lived tropical storm, but meteorologically, it's giving us a pretty fascinating demonstration of how tropical cyclones can form.
And that's what keeps me watching the weather.
You never know what the atmosphere is going to do next!
🌴 The Madness continues.