Question Box:

[wxmann_91]

I want a list of the different "systems" that Tropical Cyclones form from. Here is an example:

1. TC's can form from Tropical Waves
2. TC's can form from Ex-Tropical Low Pressure Systems
3. TC's can form from "" "" ""

If this is the question Cyclenall, I think I've already answered it, though maybe not:

TUTT's, decaying frontal boundaries, monsoon gyres (more frequent in the Indian and WPAC basins), there are probably more that I can't think of.

[wxmann_91]

Thanks WJS3 for the explanations.

[wjs3]

Sure thing!

[wzrgirl1]

also a mesoscale convective complex which is basically a large thunderstorm system

[Recurve]

Since I haven't seen it asked here, I'll pose a conceptual issue that's had me wondering:

How can pressure be both low and high at different layers of the atmosphere?

Since pressure is the weight of the atmosphere above a given location, it would seem to be naturally lower at increasing height. But we often speak of low pressure at the surface and high pressure above, or an upper-level low over a surface high.

Is it all relative? That is, a "high" can be above a "low" because of pools or layers of different air density -- pools that don't match what a straight linear pressure change going upward would produce?

Hope that's at least an understandable question.

[wjs3]

Recurve:

Not a bad answer to your own question--yes, different air temperature and density--relative to air at a particular level--can cause this. It of course can get more complex, but that's not bad. That's one reason you'll see people taking about height lines--height lines look at the situation realtive to a particular pressure level.

Specifically, do you "see" the mechanics of a Tropical Cyclone, with low pressure under high? That to me is the most blatant example of this phenomenon.

WJS3

[Cyclenall]

I want a list of the different "systems" that Tropical Cyclones form from. Here is an example:

1. TC's can form from Tropical Waves
2. TC's can form from Ex-Tropical Low Pressure Systems
3. TC's can form from "" "" ""

If this is the question Cyclenall, I think I've already answered it, though maybe not:

TUTT's, decaying frontal boundaries, monsoon gyres (more frequent in the Indian and WPAC basins), there are probably more that I can't think of.

Ok, I was missing a few of them though.

Another question, has a Tropical Cyclone ever spun the wrong way in the Atlantic ocean? I don't mean Hurricane Lenny.

Yet another question, what makes hurricanes larger or smaller? Is it just random chance or does something create the size?

[Brent]

Another question, has a Tropical Cyclone ever spun the wrong way in the Atlantic ocean? I don't mean Hurricane Lenny.

Spun the wrong way? As in clockwise? Not possible due to us being in the Northern Hemisphere.

[Cyclenall]

Another question, has a Tropical Cyclone ever spun the wrong way in the Atlantic ocean? I don't mean Hurricane Lenny.

Spun the wrong way? As in clockwise? Not possible due to us being in the Northern Hemisphere.

Well of course it's not possible but I'm asking if it has ever happened anyways.

[Audrey2Katrina]

Well of course it's not possible but I'm asking if it has ever happened anyways.

I've known the laws of nature and physics to be suspendable given extraordinary circumstances... but know of no case where the coriolis effect could have been defied on such a massive scale.

A2K

[Recurve]

Another question, has a Tropical Cyclone ever spun the wrong way in the Atlantic ocean? I don't mean Hurricane Lenny.

You mean rotating clockwise? Physics would say no in the northern hemisphere.

[wjs3]

No, all low pressure systems turn counterclockwise in the northern hemisphere. Now, if you literally mean the Atlantic Ocean, then yes, there have been tropical cyclones that turn clockwise in the South Atlantic.

Regarding size...I don't know! I would imagine that moisture availabe and atmospheric conditions have a lot to do with it, but am not sure beyond that. I don't recall hearing forecasts of storm size or windfield, so I'm not even sure if there's a lot of skill in this area. Anyone else know?

[Cyclenall]

I've known the laws of nature and physics to be suspendable given extraordinary circumstances... but know of no case where the coriolis effect could have been defied on such a massive scale.

A2K

Well I guess we may never see something like that happen in the North Atlantic ocean. That would be amazing if it ever happened.

Regarding size...I don't know! I would imagine that moisture availabe and atmospheric conditions have a lot to do with it, but am not sure beyond that. I don't recall hearing forecasts of storm size or windfield, so I'm not even sure if there's a lot of skill in this area. Anyone else know?

A question that can't be answered! Unless someone else comes up with one, when anyone gets the chance ask a pro or the NHC about it.

Does anyone have a satellite loop movie of Hurricane Lenny from 1999? I want to see what he looked like going the wrong way.

[wxmann_91]

Yet another question, what makes hurricanes larger or smaller? Is it just random chance or does something create the size?

There is a theory which a met presented on here that if a hurricane is exposed to shear in their formative stages, they might start out larger than the average cane, thus develop into bigger canes. Examining the satellite loops of Katrina and Rita, one can notice that at first, there are TUTT's near them that hinder them in the beginning, only to move away, but still provide good UL divergence. This allowed them to fan their clouds freely and become big and fat.

Time also has to do with it too. More time, the more time for fanning of the clouds, and the storm keeps getting larger during ERC's. Of course, 2005 being an exception. Ivan went through a ton of ERC's, allowing its windfield to expand each and every time, thus it became huge.

Speed of the storm, IMO, has something to do with it too. Think about it: if a hurricane travels at an extremely fast rate of speed, the storms on the outer fringes never develop because they will lag behind, sheared apart by the storm's outflow

(BTW, when I mention "fanning of the storm" I mean development of convection on the outer rainbands. That is key to bringing TS force winds to the sfc and thus expanding the windfield. How large a storm looks on sat is a poor indicator of the actual windfield.)

The surrounding atmospheric environment is important too. We had low atmospheric pressures across the basin in 2005, so thunderstorms easily developed on the outer fringes of the hurricane. If there were high pressure, the storm would be sort of suppressed, squeezed. Good example would be Andrew of 1992, which was kept small by a huge area of high pressure to the north (which of course drove Andrew into FL in the first place).

Just my thinking here.

Sat loop of Lenny: http://vortex.plymouth.edu/hur_dir/1999 ... 9_sum.html (scroll down to bottom)

[FritzPaul]

ITCZ.

What is it?

Inter
Tropical
Convergence
Zone

Hope this helps, Paul

[Cyclenall]

Thanks wxmann_91 for that huge amount of information you gave and loop of lenny. The loop of lenny is a bit to fast and there seems to be a chunk of the movie still during the first part. But that track is so rare, hurricanes just don't do that.

If anyone has a different loop of lenny then post it please.

[whereverwx]

This is what I was able to find:
http://jrscience.wcp.muohio.edu/movies/ ... u1700z.gif
http://rsd.gsfc.nasa.gov/goes/pub/goes/ ... .lenny.mov
http://jrscience.wcp.muohio.edu/movies/ ... 92200z.mov
http://www.aoml.noaa.gov/hrd/assessment ... ny_wnd.mov
http://jrscience.wcp.muohio.edu/movies/ ... 91015z.mpg

[Cyclenall]

This is what I was able to find:
http://jrscience.wcp.muohio.edu/movies/ ... u1700z.gif
http://rsd.gsfc.nasa.gov/goes/pub/goes/ ... .lenny.mov
http://jrscience.wcp.muohio.edu/movies/ ... 92200z.mov
http://www.aoml.noaa.gov/hrd/assessment ... ny_wnd.mov
http://jrscience.wcp.muohio.edu/movies/ ... 91015z.mpg

Big thanks. I could have searched myself but I was lazy and I forgot.

[angelwing]

If I remember last year I think someone was talking about a "1028" line? (I think that's the correct number) Could someone explain the significance of that?

Angelwing, that sounds like it may have been in reference to an Isobar--a line that marks places of equal pressure. That's pretty high surface pressure (1028 MB) and probably marked part of a surface high/ridge. I'm guessing here, but we normally watch that stuff because forecasting TC track often has to do with finding weaknesses in a ridge...or assessing the shape of a ridge/high. So knowing where particular isobars are located can help us in doing so.

Hope that helps.

WJS3

Thank you very much, it does!

[wjs3]

Sure thing!