How (and why) do hurricanes spawn tornadoes?

[Liberal]

It seems like their rapid lateral speed and wide area turbulence would suppress the formation of localized low pressure vortices.

[Polycarp]

My impression is that the turbulence you note in the OP is what’s responsible for the tornadoes. Nobody seems to have a definite handle on the exact reasons that tornadoes form anywhere, but rapid wind moving turbulently can lead to localized areas of low pressure along the edges of cyclonic systems, which can develop into vortices. Such vortices can, in turn, turn into tornadoes.

I hope someone with more background in meteorology can explain this better or refute my impression and clarify exactly what does happen.

[Liberal]

I guess that’s possible, Poly, but when air is moving laterally at hurricane speeds, I don’t understand how a spiraling vortex is able to form. It seems like the hurricane itself would blow the forming vortex away.

[Jabba]

This site gives some information and does say “the full details of how tornadoes form are not well known.”

[Zebra]

As the the ‘why’
Because they can!

[slortar]

Sounds like a Fox special: “When Hurricanes Form Tornadoes and EXPLODE”

shows footage of elephants stampeding through a mall

[Liberal]

Thanks for the link, Jabba. Unfortunately, it deals with the formation of tornadoes from mesocyclones, which seems a reasonable way that they might form. But in a hurricane, with air moving laterally at a hundred miles per hour or more, it looks to me like tornado formation would be disrupted.

[Jabba]

This site says:

An important precondition linked to tornado formation in severe thunderstorms is the development of a mesocyclone that forms in the updraft of the thunderstorm. As the narrowing column of rotating air stretches downward, a rapidly spinning funnel cloud may emerge from a slowly rotating wall cloud. If the funnel cloud makes contact with the surface, it is then classified as a tornado

[Liberal]

How are you thinking that might apply for hurricanes, Jabba? There is no mesocyclone, and the drafts are decidedly lateral.

[Jabba]

I’m still working on that one. In my part of the world (UK) we don’t get much experience of hurricanes and tornadoes. Are we sure that purely laterally moving hurricanes can actually create tornadoes?

[tanstaafl]

Yet another site with information…

What they say that looks relevalent is:

Abundant low level moisture is necessary to contribute to the development of a thunderstorm, and a “trigger” (perhaps a cold front or other low level zone of converging winds) is needed to lift the moist air aloft.

Well, hurricanes certainly have moisture associated with them and the winds around the edges are converging. Also…

Finally, tornadoes usually form in areas where winds at all levels of the atmosphere are not only strong, but also turn with height in a clockwise, or veering, direction.

Again, conditions you would find around hurricanes.

[Jabba]

I’ve also found this site, which says:

Hurricanes and tropical systems have no fronts.
Hurricane winds weaken with height
The centers of hurricanes are warmer than their surroundings
Hurricanes and tropical systems form under weak high-altitude winds.
Air sinks at the center of a hurricane
Hurricanes’ main energy source is the latent heat of condensation
Hurricanes weaken rapidly over land

[Liberal]

You’re good Dopers. Thanks for sharing your abilities to find pertinent information. I wish I could put it all together and make sense of it.

Jabba, after landfall, hurricanes quickly lose their characteristic eye and eyewall. It is then that they begin spawning tornadoes. When I say the winds are lateral, understand that most hurricanes are hundreds of miles in diameter, and local winds are such that even the rain blows sideways.

I’ve been through a bunch of them. During Hugo, the wind blew pine needles into the brick of my house. It looked like a porcupine!

[Liberal]

For those interested, I saw a special today on Hurricane Andrew.

A fellow from the National Weather Service said that a hurricane’s eye-wall consists of thunderstorm clouds and is highly charged with lightning and the whole works. When the system hits landfall and loses its eye, the thunderstorm clouds disburse across the land and spawn tornadoes.

That makes sense to me.

[barbitu8]

When I say the winds are lateral, understand that most hurricanes are hundreds of miles in diameter, and local winds are such that even the rain blows sideways.

This is not true. Hurricane force winds usually extend outwards from the eye no more than 20-30 miles. What was unusual about Isadore was that it was so widespread. However, it was not a hurricane after it got entrapped in the Yucatan, and never was able to regain hurricane winds even in the GOM because dry air from the west was invading it. The tighter (smaller) the eye, the greater the potential for devasting major hurricane winds.

Feeder bands can extend outwards quite a ways, sometimes hundreds of miles, but there are no hurricane force winds with them, although there will be wind gusts.

A fellow from the National Weather Service said that a hurricane’s eye-wall consists of thunderstorm clouds and is highly charged with lightning and the whole works. When the system hits landfall and loses its eye, the thunderstorm clouds disburse across the land and spawn tornadoes.

That makes sense to me.

Makes no sense to me. Thunderstorm clouds and sometimes lightning will be present in the feeder bands also.

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Finally, tornadoes usually form in areas where winds at all levels of the atmosphere are not only strong, but also turn with height in a clockwise, or veering, direction.

Again, conditions you would find around hurricanes.

Not true. The lower level winds in a hurricane in the northern hemisphere are counterclockwise. The higher altitude winds are clockwise since at a higher level, a hurricane needs high pressure. (High pressure = sinking air, which is found within the eyewall.)

How are you thinking that might apply for hurricanes, Jabba? There is no mesocyclone, and the drafts are decidedly lateral.

Thunderstorms have updrafts, which can form “supercells” or “mesocyclones” necessary for spawning of tornadoes. The feeder belts contain thunderstorms sometimes.

I guess that’s possible, Poly, but when air is moving laterally at hurricane speeds, I don’t understand how a spiraling vortex is able to form. It seems like the hurricane itself would blow the forming vortex away.

But the tornadoes do not form in the hurricane force winds. They form in the feeder belts which have strong gusts but underlying decidedly normal winds.

[Liberal]

So, your answer to the question is…?

[barbitu8]

Your premise is incorrect. Tornadoes occur in areas in the tropical storm system (doesn’t have to be a hurricane, and they usually are not once they reach land) wherein the winds are the same as in any superstorm. Turbulence is a necessary ingredient for the spawning of tornadoes. You can’t have them without turbulence.

Irrespective of the winds, it’s the turbulence that spawns tornadoes. Hurricane-force winds do not, after all, interfere with the eyewall. The dynamics involved in the formation of tornadoes are not hindered by winds. The tornadoes ride through the winds like a knife through butter.