Can TS's go backwards?

[Stormavoider]

Here is an all together different question. On occasion tornadoes develop with an anticyclonic spin in the northern hemisphere. Has a tropical system ever done this?

[Frank2]

I've never heard of it happening in either hemisphere, at least as far as a tropical cyclone is concerned. If it does start to happen, we'd all be in big trouble, because it would mean something has gone very wrong with the Earth's rotation...

Frank

[SCHurricane]

They cannot spin the opposite way in the northern hemisphere. Contrary to what you may believe, the coriolis force does not dictate which way the water goes down your toilet, but it does dictate what way a tropical system will spin.

[mtm4319]

The only time I can think of was with Cyclone Agni.

Read more on that here (original discussion on the storm) and here (why, as a developing cyclone that originated in the northern hemisphere, it crossed the equator into the southern hemisphere but still kept spinning counterclockwise).

[destro34]

lennin. i do not remember date,but i heard that cyclone lennin did.

[Cyclenall]

The only time I can think of was with Cyclone Agni.

Read more on that here (original discussion on the storm) and here (why, as a developing cyclone that originated in the northern hemisphere, it crossed the equator into the southern hemisphere but still kept spinning counterclockwise).

I asked a question a long time ago about "has a tropical cyclone ever spun the wrong way?" and I got "NO". Thank you for the information! That is really neat.

[Cyclenall]

lennin. i do not remember date,but i heard that cyclone lennin did.

There is no such thing as Cyclone Lennin. Google can't even show up anything.

[mtm4319]

lennin. i do not remember date,but i heard that cyclone lennin did.

There is no such thing as Cyclone Lennin. Google can't even show up anything.

I'm guessing he means Hurricane Lenny, which went eastward through the Caribbean while most of them go westward.

[gilbert88]

Don't mean to be nitpicky, but that map shows Cyclone Agni dissipating before crossing the Equator.

[mtm4319]

Don't mean to be nitpicky, but that map shows Cyclone Agni dissipating before crossing the Equator.

Advisory 1 is where it was first considered a named storm. It went WNW toward the African coast before dissipating ("14A"). It crossed over the equator and back in its formative stage, before Advisory 1.

[ncweatherwizard]

A circulation, cyclonic or anticyclonic, cannot survive a trip across the equator. Coriolis works because areas at higher latitudes have higher linear speeds to "keep up" with the equatorial regions. As such, coriolis effect is dependent directly on latitude, and its value is 0 at the equator. With no coriolis, air moves linearly instead of converging to or diverging from a circulation center, and any circulation that may have existed will weaken if it gets too close to the equator and be nonexistent at the equator. This will *usually* be the case, but it does assume only coriolis dictates air flow at the equator.

[Hurricanehink]

A circulation, cyclonic or anticyclonic, cannot survive a trip across the equator. Coriolis works because areas at higher latitudes have higher linear speeds to "keep up" with the equatorial regions. As such, coriolis effect is dependent directly on latitude, and its value is 0 at the equator. With no coriolis, air moves linearly instead of converging to or diverging from a circulation center, and any circulation that may have existed will weaken if it gets too close to the equator and be nonexistent at the equator. This will *usually* be the case, but it does assume only coriolis dictates air flow at the equator.

Wouldn't Agni negate this?

[tgenius]

Has there ever been a case where a storm has moved south over FL? I had a dream last night that a storm was coming in through JAX and coming down the state... is that even possible? lol

[Recurve]

Has there ever been a case where a storm has moved south over FL? I had a dream last night that a storm was coming in through JAX and coming down the state... is that even possible? lol

Absolutely. Betsy (1965) moved from north to south and hit Key Largo. It had almost two complete loops in its track before then.
Katrina entered the east coast north of Miami and went southwest to exit the southwest corner of the peninsula. I can't think of a track exactly from Jacksonville to Naples, say, but it's not impossible exactly.

[Hurricanehink]

Has there ever been a case where a storm has moved south over FL? I had a dream last night that a storm was coming in through JAX and coming down the state... is that even possible? lol

Actually, yes. A hurricane moved across the state in 1906, looped, and hit the state again from the north near Jacksonville.

[Ptarmigan]

It has happened. Hurricane Lenny of 1999 was known as "Wrong Way" Lenny because it went from west to east.

[tgenius]

Is that a zany track or what?!

[Derek Ortt]

Scott,

A storm can cross the equator theoretically

Absolute vorticity is relative plus planetary. The planetary would work against it, but if a monsoon circulation was intense enough, it would probably be able to support an equatorial cross

Agni basically has 0 help from the Earth when it spun up, all from the monsoon circ

[DrCloud]

Coriolis works because areas at higher latitudes have higher linear speeds to "keep up" with the equatorial regions.

It's true that the Coriolis torque is zero at the equator, but this speed statement is not. Toward the poles, parallels of latitude, being closer to the axis of rotation, are shorter, yet they rotate around once a day, just like the equator. The "linear speed" is obviously fastest at the equator.

What this does is to give equatorial parcels of air the greatest "planetary" angular momentum; parcels toward the poles have less. And it's the change of this planetary angular momentum with latitude that's related to the Coriolis torque. No change just at the equator means no Coriolis torque at the equator. The fastest change with latitude is at the poles, where the torque is greatest. You can use this reasoning and geometry to work out for yourself that it's proportional to the sine of the latitude. HPH