Drz1111 Posted August 17, 2011 Share Posted August 17, 2011 It's always struck me as very curious that tropical cyclones come in such an array of sizes. The same physical properties drive both the tiniest and largest storms, and you would imagine that there would be a stable "ideal" size for mature hurricanes. Instead we observe mature storms that differ in size by an order of magnitude. My question is, why? This can really be broken into two different questions: (1) Why do we observe different sizes in cases where the different sized storms originate in different ways, or in different basins? (2) More surprisingly, why do we observe different sizes among cyclones that arise out of virtually identical intial conditions? (i.e., why would two tropical waves crossing the Atlantic in quick succession might produce two wildly different sized tropical cyclones?) And as a follow-up: (3) Do tropical cyclones ever get smaller with time? Is the current size of a mature tropical cyclone only a "metastable" state, and with time and no change in environmental conditions, all tropical cyclones will grow with time? TYIA. Link to comment Share on other sites More sharing options...
hurricaneman Posted August 17, 2011 Share Posted August 17, 2011 The why happens to be the size of the circulation and the area of the moisture envelope, the examples are as follows Marco, smallest tropical cyclone on record small but really vigorous circulation Andrew, small tropical cyclone but epicly intense Ike, one of the largest tropical cyclones ever in the atlantic basin, had a large moisture envelope and a large circulation Tip, the largest tropical cyclone ever, it had a large circulation and a massive moisture envelope If im wrong, please tell me Link to comment Share on other sites More sharing options...
am19psu Posted August 17, 2011 Share Posted August 17, 2011 I don't know if I am going to get to answer this in detail or not, but start here and here for the seminal papers. Then watch this talk by Liz Ritchie from Tuscon. Link to comment Share on other sites More sharing options...
Anduril Posted August 18, 2011 Share Posted August 18, 2011 I don't know if I am going to get to answer this in detail or not, but start here and here for the seminal papers. Then watch this talk by Liz Ritchie from Tuscon. Reading through the first nine pages or so (probably should not do this after a long day of work and a few drinks but meh) I do have to ask a very basic question...does the development of pacific typhoons match that of Atlantic/gulf hurricanes for the most part? I'm very much a n00b in this respect but it doesn't seem like they exactly do. Pacific storms seem to intensify more quickly and become larger vs. Atlantic storms but again... I'm still very much a n00b with this EDIT: replaced exactly with "for the most part" Link to comment Share on other sites More sharing options...
wi_fl_wx Posted August 18, 2011 Share Posted August 18, 2011 Reading through the first nine pages or so (probably should not do this after a long day of work and a few drinks but meh) I do have to ask a very basic question...does the development of pacific typhoons match that of Atlantic/gulf hurricanes for the most part? I'm very much a n00b in this respect but it doesn't seem like they exactly do. Pacific storms seem to intensify more quickly and become larger vs. Atlantic storms but again... I'm still very much a n00b with this EDIT: replaced exactly with "for the most part" You are correct, the developmental stages are completely different. Northwest Pacific (NWP) storms generally form from the moonsoonal trough, which is a larger, less concentrated area of disturbed weather compared with the easterly waves/troughs in the Atlantic. You can see this if you parse through microwave imagery of tropical storms. By the time they reach hurricane, and especially major hurricane(super typhoon) stage, they all look the same, but the tropical storms do not look the same at all. Part of the reason for the difference is that there is more shear in the Atlantic, so the Atlantic tropical storms tend to show the shear pattern most frequently. Atlantic tropical storms are smaller because the disturbances they form from are smaller--which relates to the other reasons--there is more dry air in the Atlantic due to the Saharan Air Layer (SAL) and sea surface temperatures (SSTs) are colder in general in the Atlantic. So in the NWP you have much more favorable conditions for sustaining organized thunderstorm activity, allowing a larger storm to form. Not to mention other differences like overall lower environmental surface pressure in the NWP--so you may notice that the pressures for the Dvorak Technique have multiple scales, one for NWP and one for Atlantic. These differences make TC research challenging in all aspects of forecasting, modeling, satellite observations, etc. etc. If you calibrate or parametrize something to work in one basin, it might not be optimized for others. Same goes for small storms vs. large storms, you often see in forecast discussions that small storms are more likely to intensify/weaken quickly compared with a larger storm--this makes both conceptual and mathematical sense if you think about it. Link to comment Share on other sites More sharing options...
am19psu Posted August 18, 2011 Share Posted August 18, 2011 Reading through the first nine pages or so (probably should not do this after a long day of work and a few drinks but meh) I do have to ask a very basic question...does the development of pacific typhoons match that of Atlantic/gulf hurricanes for the most part? I'm very much a n00b in this respect but it doesn't seem like they exactly do. Pacific storms seem to intensify more quickly and become larger vs. Atlantic storms but again... I'm still very much a n00b with this EDIT: replaced exactly with "for the most part" As the poster above me mentioned, no they do not form in the same way. However, my master's degree was on storm size in the Atlantic and I found similar results to W&G. Link to comment Share on other sites More sharing options...
phil882 Posted August 18, 2011 Share Posted August 18, 2011 I don't know if I am going to get to answer this in detail or not, but start here and here for the seminal papers. Then watch this talk by Liz Ritchie from Tuscon. For some reason the two papers would not load for me, but the talk was very interesting. It does make some intuitive sense that increased shear would cause a tropical cyclone to grow in size, because we see quite a few examples of that phenomena taking place in reality such as Alberto 2000, Isaac 2000, Karl 2004 among many others. Link to comment Share on other sites More sharing options...
am19psu Posted August 18, 2011 Share Posted August 18, 2011 For some reason the two papers would not load for me, but the talk was very interesting. It does make some intuitive sense that increased shear would cause a tropical cyclone to grow in size, because we see quite a few examples of that phenomena taking place in reality such as Alberto 2000, Isaac 2000, Karl 2004 among many others. Search Google Scholar for Weatherford and Gray Link to comment Share on other sites More sharing options...
phil882 Posted August 18, 2011 Share Posted August 18, 2011 Search Google Scholar for Weatherford and Gray I had the same problem with Google Scholar with the pdf's not loading, but I was able to find the papers on AMS journals online since both papers were published in the Monthly Weather Review. Good for a late morning read! Link to comment Share on other sites More sharing options...
phil882 Posted August 18, 2011 Share Posted August 18, 2011 Ok I perused through the papers. A point made in the first paper that relates to this threat was that storm size tends to be correlated with latitude. As a storm increases in latitude, it interacts with more baroclinicity which tends to increase the size of the system until it has become an extra-tropical entity with a very large radius of maximum winds (RMW). The second paper is very interesting because of a couple of plots showing storm size while the minimum central pressure stays about the same and while minimum pressure is decreasing. The general rule of thumb I am getting from this paper is that storms tend to experience larger changes in size if they stay at the same pressure for a long period of time, while a decrease or increase in pressure tends to not have a huge impact on the overall storm size. Interesting stuff because that's not really very intuitive since you would think a stable tropical cyclone would also have a stable radius and not the other way around. My guess is that the latent heat during these periods of little intensity change go towards increasing the size of the storm rather than continuing to intensify the inner core. Link to comment Share on other sites More sharing options...
Drz1111 Posted August 18, 2011 Author Share Posted August 18, 2011 You are correct, the developmental stages are completely different. Northwest Pacific (NWP) storms generally form from the moonsoonal trough, which is a larger, less concentrated area of disturbed weather compared with the easterly waves/troughs in the Atlantic. You can see this if you parse through microwave imagery of tropical storms. By the time they reach hurricane, and especially major hurricane(super typhoon) stage, they all look the same, but the tropical storms do not look the same at all. I've noticed that cyclones in the South Pacific in particular, even setting aside the different direction of rotation, really have a different "look" than their Atlantic (or even N. Pacific ) counterparts . . . Link to comment Share on other sites More sharing options...
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