Tropical Systems Near The Equator

[michaelwmoss]

While observing the latest two storms in the Indian Ocean, a thought came across my mind:

Since in the Northern Heimsphere Storms spin Counterwise and in the Southern Heimsphere they spin Clockwise, what would happen if a storm in the Indian Ocean crossed the Equator? Would that cause the storm structure to totally be changed?

[HURAKAN]

I believe that if a tropical system cross from one hemisphere to the other, which is still unseen in the satellite era, the storm would keep its structure even though it will go against the norms of that hemisphere. I think is impossible for a system to change structure simply because it crossed a line.

[george_r_1961]

Im neither a met nor a physics expert but I dont see how a system crossing the equator and maintaining its identity could happen. Ripples in the ITCZ could bring the fringes of a circulation very near or just over the equator but theres no way the center could cross.

[Derek Ortt]

there would be no change in structure at all.

Based upon the equations of motion, the only thing that would occur would be that the corolis would be counter acted by the vorticity from the monsoon trough. The corolis is so close to 0 right now anyways that there would be no change if the corolis was acting against the rotation. The storm would continue to spin CCW just like before

[HurricaneBill]

My theory was that the storm would briefly move CCW and then degenerate into a disorganized wave and then reform moving CW.

[Aslkahuna]

Derek brings up an important point about total vorticity in a storm. Storm vorticity is comprised of a number of factors involving motions along a curved path in a moving coordinate system. These motions are brought about by a number of things including thermal differences (missing for the most part in a tropical system), tilt (also missing for the most part in the tropical system), divergence (yep) and shear both vertical (a no-no here) and horizontal (yep, yep) PLUS Earth's vorticity (always postive and what is known as the Coriolis Parameter). Within the monsoon trough we have regions of significant horizontal shear arising from the fact that on it's poleward side we have the Trade easterlies and on the equatorward or side facing the Winter Hemisphere we have cross equatorial westerlies that originate at some point in the WINTER Hemisphere. This will of its own set up rotation since for the most part the Earth's vorticity will be a smaller factor than the shear factor since when we move further away from the Tropics where the latter increases, the other factors will come into play. The major limiting factor for very low latitude formation of Tropical Cyclones is the fact that it is very seldom that we have the wind field aloft to provide the need outflow and high level divergence to result in the development and organization of a storm. As a result, most equatorial Lows (and they do exist) consist mainly of disorganized clusters of thunderstorms. This is where watching the Tropical regions all over the world comes into play for you see things that you would never think existed if all you know about is the Atlantic Basin. Tropical Meteorology is as, if not a more, complex a field of study as is mid latitude and Polar Met. Remember that the El Niño is a Tropical (and mostly Southern Hemisphere) Climate oscillation that affects weather worldwide. If you want to know weather, you have to know all of it not just some.

Steve

[cyclonaut]

My theory was that the storm would briefly move CCW and then degenerate into a disorganized wave and then reform moving CW.

Yep, thats what I was thinking.Interesting topic...

[Wnghs2007]

My theory was that the storm would briefly move CCW and then degenerate into a disorganized wave and then reform moving CW.

Yes that sounds like what it might do if it kept heading south or north respectivley and got far enough away from the equator for corolis to start having an effect.

[Derek Ortt]

It would have to get to at least 15S or so for the corolis to even start to play a role

[Wnghs2007]

It would have to get to at least 15S or so for the corolis to even start to play a role

Thanks for the info Derek

[michaelwmoss]

It would have to get to at least 15S or so for the corolis to even start to play a role

As for all of the posts as well! Thanks to everyone. I do have to ask what exactly a Corolis is. How is that pronounced exactly?

[isobar]

As for all of the posts as well! Thanks to everyone. I do have to ask what exactly a Corolis is. How is that pronounced exactly?

PLUS Earth's vorticity (always postive and what is known as the Coriolis Parameter).

Coriolis (kor-ee-oh-lis) is strongest at the poles, weakest at the equator, which is why TCs are extremely rare near the equator. It's described pretty well in this link: http://www.theweatherprediction.com/habyhints/27/

Great discussion Steve.

[isobar]

I think there was a system that crossed. Mike (SF) would know, it was discussed in a past thread.

[michaelwmoss]

Awesome information!! Thank ya!

I would assume this process is also used in the study of Tornadoes?