Question and Answer

By: Gorty , 2:39 AM GMT on August 31, 2010

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To become smarter in tropical meterology, I want to ask some questions and hopefully get some answers.

1. What does it mean when a tropical cyclone finds a weakness in a ridge?

2. Since we have a La Nina (at least I think) shouldn't there be little to no windshear for the rest of the season?

3. What is an eye wall replacement cycle? (Please, try make it simple, as I couldnt understand form when I looked it up).


4. Why does there have to be a west wind to close off the circulation?

5. I always have trouble trying to find a counter-clock wise rotation from a developing wave or low preassure system. How do you locate a rotation/center?

6. How does the out flow from a hurricane cause wind shear?

7. How come wind shear weakens thunderstorms over water but not over land?

8. How do you estimate the current movement speed of cyclone by looking at satallite alone?

9. Why does it depend on the strength of a cyclone to determine how it will get effected by a trof or a ridge?

10. How does upword motion helps a cyclone?

No need to for any of you to anwers all questions from one person, feel free to pick and choose which ones you want to asnwer. As I read about cyclones more, I will put up anothet set of questions.

Many thanks to anyone who answered these so i can be on my way of being way more knowledgble with tropical cyclones.

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2. Gorty
4:34 AM GMT on August 31, 2010
@Jeff,

Wow you are good! And thanks, it did help!
Member Since: November 8, 2008 Posts: 12 Comments: 1058
1. jeffs713
2:54 AM GMT on August 31, 2010
Lessee...
1. A weakness in the ridge is a "break" in the pressures of a high pressure ridge. Usually caused by a trough of low pressure that is "cutting into the ridge".
2. Wind Shear is always there. La Nina just creates conditions that reduces the average wind shear present. (it has to do with the pattern of upper lows and their related troughs).
3. Eye Wall Replacement Cycles (EWRC) are when the storm creates two eye walls. An inner one that is strong, but small, and then an outer one that is more spread out. Eventually, the inner wall collapses, and the outer one takes over, and shrinks down to a manageable size (size is dependent upon the storm's intensity and environment).
4. The "normal" winds in the tropics in the N hemisphere is out of the east. If you have a west wind, that means the low pressure is strong enough to force winds against the normal trade winds.
5. the RGB satellite loop is good, since low clouds are usually more yellowish. I'm not the best at this, I would suggest talking to Levi32, Drakoen, StormW, or Weather456 on this one. (among others)
6. A hurricane's outflow moves clockwise, and at opposing angles to the normal low-level flow. for an example, look at the position between Earl and Fiona. Earl's upper-level outflow is clockwise, which puts the mean flow to Earl's east coming from the north... a 90 degree angle off the "normal" flow at the low levels... which is from the west.
7. Wind Shear only weakens tropical systems, because they need a good outlet, or "exhaust". Normal storms don't need that outlet, because they are content with collapsing, which forms outflow boundaries and "arc clouds" of colder air. Those low-level outflow boundaries and arc clouds choke off a tropical system.
8. Its hard, but it is best to use lat/long lines, and track the *center* of the low-level circulation. Don't get distracted by the eye wall, or surrounding storms. Its an experience thing.
9. The more intense a cyclone, the deeper layer it is steered by. As a general rule, check out CIMSS steering layer maps for an explanation.
10. Upward motion helps a cyclone in that it fuels the storm. Cyclones generate energy by condensing water from the atmosphere. As humid air cools (and rises), it condenses, which releases energy. The more humid and warm the surface is, the more potential energy. This is the "dynamo" that powers all thunderstorms. Cyclones just have the advantage of a much deeper "pool" of humid air over the ocean to pull from, and organization to keep it going, and exhaust the drier, cooler air out the top.

Hope that helps! Feel free to ask me any other questions that come up via WUmail.
Member Since: August 3, 2008 Posts: 16 Comments: 5887

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About Gorty

Hey all! I live in New England and I love tropical cyclones.