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Posted
  • Location: Western Isles
  • Location: Western Isles

    their is most likely an obvious answer to this.

    how come northern hemisphere hurricanes seem to be more potent and longer last then southern hemisphere storms?

    we seem to barely scrapping the barrel for any major storms in the south and I can't remember any last year?

    surly we getting to the peak for southern hemisphere?

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    Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset
    their is most likely an obvious answer to this.

    how come northern hemisphere hurricanes seem to be more potent and longer last then southern hemisphere storms?

    we seem to barely scrapping the barrel for any major storms in the south and I can't remember any last year?

    surly we getting to the peak for southern hemisphere?

    I wouldn't say that there is any difference in the potency of southern hemisphere storms to northern hemisphere storms, we've had a couple big storms this year- Billy, Fanele and Gael being good examples but must admit it has been a little quiet so far. Last year we had Daman, Hondo, Ivan, Jokwe, Funa, Gene and Kamba which were all cat 3 and above. However, there is a difference in the number of storms yes. In the southern hemisphere, we have two basins where tropical cyclones can form- South Indian Ocean and South Pacific. In the north, there are four basins- Atlantic, East Pacific, West Pacific and North Indian Ocean. There is a larger expanse of tropical waters in the northern hemisphere thus there are generally more storms.

    If we are talking catastrophic landfalls then a similar thing can be said. In the Southern Hemisphere the two main landmasses than cyclones strike are Madagascar and Australia (and the east coast of Africa). The south Indian Ocean has a large expanse of open waters meaning cyclones are more likely to stay out to sea. In the northern Hemipshere, this is not the case. Think of the Atlantic, for example, you don't have large areas of open waters (apart from the eastern half of the basin) instead, plenty of land for TC's to strike. Similar thing in the North Indian Ocean, you have India and all the neighbouring countries at risk of landfalling TC's. In the West Pacific, you have Japan, China, the Philippines and Taiwan all at risk from the TC's here which move generally northwestwards towards land. Therefore, you tend to get more deadly storms in the northern Hemsiphere for this reason.

    Sorry if that's a bit waffly, but those are just some ideas I have in regards to your question. It's a simplistic view and there may be more behind it, but that goes above my level of understanding.

    You are right about this season being quiet though. South Indian Ocean is only running slightly below average (you have to remember last year was above average so expectation can't be quite so high) but the South Pacific has been extremley quiet, I would have thought that we are heading for one of the quietest seasons on record. Take a look at the tracks of the storms in 1997/8 for the South Pacific:

    ause97_8.gif

    It was a bumper season with well above average activity. As apposed to this year:

    track.gif

    You can clearly see the difference. I do not know why the South Pacific has been so quiet. Around 9 cyclones were forecast at long range, so far we've had two very weak and short lived affairs (Hettie and Innis, Charlotte and Ellie are Australian storms), and nothing brewing at the moment. So you've raised a very interesting point. I do not know the answer, but it would be great if anyone has any ideas?

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    Posted
  • Location: City of Gales, New Zealand, 150m ASL
  • Location: City of Gales, New Zealand, 150m ASL

    Just a few thoughts: whilst there has been nothing wrong with the SSTs so far this season, we have been in a persistent situation since about November of stronger than normal trade winds. I don't know directly whether this has an impact on the formation of TCs, but given that strong trade winds are a winter phenomena, and TCs don't form in winter.....maybe there is something there.

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    Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset
    Just a few thoughts: whilst there has been nothing wrong with the SSTs so far this season, we have been in a persistent situation since about November of stronger than normal trade winds. I don't know directly whether this has an impact on the formation of TCs, but given that strong trade winds are a winter phenomena, and TCs don't form in winter.....maybe there is something there.

    I guess the trades create a highly sheared environment, which would disrupt TC development? Interesting to note that this has occured for the Southern Pacific summer, any ideas why?

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    Posted
  • Location: City of Gales, New Zealand, 150m ASL
  • Location: City of Gales, New Zealand, 150m ASL
    I guess the trades create a highly sheared environment, which would disrupt TC development? Interesting to note that this has occured for the Southern Pacific summer, any ideas why?

    That is possible, but it would depend on the streamlines higher in the atmosphere to see how much shear there would be. But it does make sense.

    However, one would assume that stronger trades create a stronger SPCZ and also a stronger ITCZ. Both those convergence zones are good for spawning tropical cyclones...

    My knowledge of tropical meteorology is relatively minimal unfortunately!

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    Posted
  • Location: City of Gales, New Zealand, 150m ASL
  • Location: City of Gales, New Zealand, 150m ASL

    As for "why"....

    It seemed that in November we had stronger than normal trades (positive SOI), but no substantial SST anomalies (neutral ENSO). So the atmosphere was "out of phase" with the SSTs. Eventually in late Dec/January we had our La Nina, where the SSTs in the eastern tropical Pacific starting to look as they should. We kept our strong trades.

    But now, the trades are apparently "normal", and the SSTs are heading that way too in the eastern tropical Pacific.

    So, who knows what this will bring.

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    Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset
    That is possible, but it would depend on the streamlines higher in the atmosphere to see how much shear there would be. But it does make sense.

    However, one would assume that stronger trades create a stronger SPCZ and also a stronger ITCZ. Both those convergence zones are good for spawning tropical cyclones...

    My knowledge of tropical meteorology is relatively minimal unfortunately!

    Thanks for the reply J. As for the last sentence, me too! I''ve tried to get hold of Kold but his PM box is full. Greatly appreciate your input though, certainly provides food for thought and a possible reason for the lack of TC development so far.

    We'll have to wait and see what happens. Trades and SSTs are normal, so if we don't see a pick up in activity there is some other mysterious factor at work here :lol:

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    Posted
  • Location: Western Isles
  • Location: Western Isles
    I wouldn't say that there is any difference in the potency of southern hemisphere storms to northern hemisphere storms, we've had a couple big storms this year- Billy, Fanele and Gael being good examples but must admit it has been a little quiet so far. Last year we had Daman, Hondo, Ivan, Jokwe, Funa, Gene and Kamba which were all cat 3 and above. However, there is a difference in the number of storms yes. In the southern hemisphere, we have two basins where tropical cyclones can form- South Indian Ocean and South Pacific. In the north, there are four basins- Atlantic, East Pacific, West Pacific and North Indian Ocean. There is a larger expanse of tropical waters in the northern hemisphere thus there are generally more storms.

    If we are talking catastrophic landfalls then a similar thing can be said. In the Southern Hemisphere the two main landmasses than cyclones strike are Madagascar and Australia (and the east coast of Africa). The south Indian Ocean has a large expanse of open waters meaning cyclones are more likely to stay out to sea. In the northern Hemipshere, this is not the case. Think of the Atlantic, for example, you don't have large areas of open waters (apart from the eastern half of the basin) instead, plenty of land for TC's to strike. Similar thing in the North Indian Ocean, you have India and all the neighbouring countries at risk of landfalling TC's. In the West Pacific, you have Japan, China, the Philippines and Taiwan all at risk from the TC's here which move generally northwestwards towards land. Therefore, you tend to get more deadly storms in the northern Hemsiphere for this reason.

    Sorry if that's a bit waffly, but those are just some ideas I have in regards to your question. It's a simplistic view and there may be more behind it, but that goes above my level of understanding.

    You are right about this season being quiet though. South Indian Ocean is only running slightly below average (you have to remember last year was above average so expectation can't be quite so high) but the South Pacific has been extremley quiet, I would have thought that we are heading for one of the quietest seasons on record. Take a look at the tracks of the storms in 1997/8 for the South Pacific:

    ause97_8.gif

    It was a bumper season with well above average activity. As apposed to this year:

    track.gif

    You can clearly see the difference. I do not know why the South Pacific has been so quiet. Around 9 cyclones were forecast at long range, so far we've had two very weak and short lived affairs (Hettie and Innis, Charlotte and Ellie are Australian storms), and nothing brewing at the moment. So you've raised a very interesting point. I do not know the answer, but it would be great if anyone has any ideas?

    thanks for getting back to me with a very interesting response. my only problem, is I have a short memory when it comes to remember storms and im still newish to the hurricane watching.

    thanks for the hard work :)

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    Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds. HATE:stagnant weather patterns
  • Location: Taunton, Somerset
    thanks for getting back to me with a very interesting response. my only problem, is I have a short memory when it comes to remember storms and im still newish to the hurricane watching.

    thanks for the hard work :)

    No problem Cookie. I do too really, which is why it's useful to have all these threads to look back on :)

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