ninox33 Posted February 8, 2011 Share Posted February 8, 2011 A few more good pics arriving on Weatherzone p672 onwards if my link doesn't work Yasi General chat thread (EDIT) WZ P672 on Link to comment Share on other sites More sharing options...
HurricaneJosh Posted February 8, 2011 Author Share Posted February 8, 2011 Not yet mate, sorry. Should (and I repeat should) come out in a day or two. Bear with me. Sure, no prob. But until then, the landfall pressure as far as I'm concerned is 929 mb. You'll find we're a bit particular with regard to data sources here. And that value (922 mb) is so much lower than the two official readings in the eye that of course it needs to be qualified somehow in order to be accepted. I look forward to the details. Link to comment Share on other sites More sharing options...
HurricaneJosh Posted February 8, 2011 Author Share Posted February 8, 2011 This graphic from the BoM report shows the approximate extent of Yasi's winds. The map doesn't have a legend, but I assume the three color thresholds are as follows-- as per the BoM's categories): Damaging winds (Cat 1): Gusts >49 kt Destructive winds (Cat 2): Gusts >67 kt Very destructive winds (Cat 3): Gusts >89 kt So the "very destructive" winds covered Innisfail and Cardwell, and it looks like a very large section of the coast, including both Cairns and Townsville, had gusts over hurricane force. The cyclone's max winds would be a narrower zone (not depicted), within the red area: Link to comment Share on other sites More sharing options...
donsutherland1 Posted February 8, 2011 Share Posted February 8, 2011 Interim BOM summary with relevant figures, images and preliminary summary My link Many thanks for the link to the preliminary BOM report. Link to comment Share on other sites More sharing options...
Roger Smith Posted February 10, 2011 Share Posted February 10, 2011 I remember seeing that 922 mb pressure on the BOM map on their site, probably the 00z Coral Sea position. How they measured or estimated that, I don't know, but it was on the map before landfall. Link to comment Share on other sites More sharing options...
HurricaneJosh Posted February 10, 2011 Author Share Posted February 10, 2011 Check out this very silly bit of reporting: http://www.news.com.au/breaking-news/floodrelief/how-cyclone-yasi-compares-around-the-world/story-fn7ik2te-1225998762870 It's always funny the way the mainstream media (anywhere in the world) reports on weather events. This one superimposes Yasi over the USA and claims: The storm's scale of destruction is as shocking as it is inevitable. In the map above, the United States from Pennsylvania in the east to Nevada in the west, from Georgia in the south to Canada in the north and well into Mexico would be battered. The areas highlighted red would be worst hit, with up to 300km/h winds and up to one metre of rain. Completely incorrect. It's as if the writers of the article believe the outer reaches of a cyclone's circulation and the outflow fan have destructive winds. Also, even in a huge cyclone, the aerial coverage of maximum winds is very small in relation to the system as a whole. It's a narrow band and it only happens on the open coast. (This aside, the article's figure-- 300 km/hr-- contradicts the BoM's official estimate, which is lower.) Yasi was a huge cyclone-- but the media should not exaggerate and say things that couldn't be true of any cyclone. Mainstream media outlets should run their articles by qualified meteorologists before publishing them. Link to comment Share on other sites More sharing options...
HurricaneJosh Posted February 10, 2011 Author Share Posted February 10, 2011 Officially the bom is going to stick with 929hpa. However that is not from an official site but from a sugar mill that has a station approved by Bom. "Unofficially" 922hpa is not the lowest. But in the end it makes little difference until such time as the Bom expands its own stations and puts equipment in their existing ones that can cope with winds beyond 185kp/h (outside of major airports). You mean the 929 mb was taken at the sugar mill? Unfortunately, the highest winds in any cyclones are rarely sampled. We have the same problem in the USA. There just aren't enough stations to cover the coast thoroughly enough, so the wind max often slips between reporting stations. And when the wind max does pass over a station, of course the instruments might be damaged by flying debris. Link to comment Share on other sites More sharing options...
HurricaneJosh Posted February 10, 2011 Author Share Posted February 10, 2011 Hey mate, Highly embarrassing (this has been out for a while now). I am media, and considering where this came from, I am in a difficult position. Despite that I have no hesitation in saying I was appalled when I saw it. Cheers OK, I am glad you agree! And don't feel embarrassed-- at least not here! The American mainstream media does the same exact thing. Link to comment Share on other sites More sharing options...
am19psu Posted February 10, 2011 Share Posted February 10, 2011 "a barograph at the Tully Sugar Mill recorded a minimum pressure of 929 hPa as the eye passed over suggesting wind gusts of about 285 km/h were possible." direct from the BOM. Now bear in mind Tully is about 25km inland and there is truckload of friction in regard to rainforest to get to, hpa must have been affected. 922hpa is conservative. Re the media... I do my own thing but get annoyed when collectively we are made to look foolish by those who do not know the reality. Why would friction affect the pressure reading? Link to comment Share on other sites More sharing options...
HurricaneJosh Posted February 10, 2011 Author Share Posted February 10, 2011 Is this a test? If Yasi has just crossed 25km of non feed it should be starting to dissipate (ever so slightly bearing in mind forest temps at that time of night well below 20 degrees)) friction would slow the system down at lower levels (ever so slightly causing any reasonably minded system to be starved of heat... it should also be noted he had already begun to slow). So in my basic lay person terms that equals a pressure rise between the coast and the sugar mill. Of course this all falls apart in some ways due to the sheer strength and size of the system. But.... bear in mind about 50km later it was Cat four and Catg 3 not long after. I don't think Adam (am19psu) is testing you-- but I think what he's suggesting is that friction doesn't have such an immediate effect on pressure. On winds, yes-- but the pressure usually rises much more slowly than the winds decrease as a cyclone moves inland. Also, since Yasi was 1) apparently strengthening at landfall and 2) moving briskly, that suggests to me that pressure readings in the eye just a short distance inland (for example, Tully) would be relatively close to landfall values. But I shouldn't speak for Adam. Link to comment Share on other sites More sharing options...
HurricaneJosh Posted February 10, 2011 Author Share Posted February 10, 2011 Fair enough, I am not being empirical. But you have to understand the topography and also see the damage differential between Tully and the coast. We are not talking about Yasi crossing sweeping plains but some of the oldest, densest rainforest in the world before it hit cane fields. It could have done nothing but slowed the system to the extent of tilting the core (going out on a limb on that one). No doubt windspeed was affected but pressure would also have to be. I've seen many cyclones on that coast and pressure drops quickly when it hits the mountains (Tully is a great example). So when it comes to pressure, friction at sea level cannot be anything but related, especially in this case. As i said I am a layperson... please correct me if I am wrong and I apologise to Adam. It's been a tense few weeks. Absolutely no need for apologies. It's good to discuss these things. We all learn something-- and, actually, I'm no expert on this topic, either. I'm curious what Adam thinks. Link to comment Share on other sites More sharing options...
am19psu Posted February 10, 2011 Share Posted February 10, 2011 I don't think Adam (am19psu) is testing you-- but I think what he's suggesting is that friction doesn't have such an immediate effect on pressure. On winds, yes-- but the pressure usually rises much more slowly than the winds decrease as a cyclone moves inland. Also, since Yasi was 1) apparently strengthening at landfall and 2) moving briskly, that suggests to me that pressure readings in the eye just a short distance inland (for example, Tully) would be relatively close to landfall values. But I shouldn't speak for Adam. Yeah, that's what I think. The eye would have reached Tully in about 70 minutes after landfall and the pressure would not have had time to react. I don't know the topography of that particular region, but I'd actually expect frictional convergence to slightly enhance the pressure gradient right at landfall before weakening due to the lack of an unstable boundary layer. Also, I'd consider that Yasi was slow to weaken as it moved across Australia. I'd expect that the 929 is representative of the strength at landfall. Now, if we're talking about winds, I absolutely agree that they will fall off quickly from landfall due to friction. Link to comment Share on other sites More sharing options...
wxmx Posted February 10, 2011 Share Posted February 10, 2011 Yeah, that's what I think. The eye would have reached Tully in about 70 minutes after landfall and the pressure would not have had time to react. I don't know the topography of that particular region, but I'd actually expect frictional convergence to slightly enhance the pressure gradient right at landfall before weakening due to the lack of an unstable boundary layer. Also, I'd consider that Yasi was slow to weaken as it moved across Australia. I'd expect that the 929 is representative of the strength at landfall. Now, if we're talking about winds, I absolutely agree that they will fall off quickly from landfall due to friction. Agreed, also rainforest wouldn't make much difference...on near surface winds, yes, but not on central pressure, not even on above surface winds, which would diminish their strength just slowly. Remember, trees are relatively tiny with respect to the depth of a cyclone... Mountains, yeah, if high enough, they can kill the lower levels and have a sudden rise of pressure near the surface . The Yucatan, specially the central and southern portions have very dense rainforests, and we have seen time and time again how cyclones slowly weaken over it, with little to no pressure rise...especially if they are strengthening... some have even deepened over land, this very last season! They were relatively weak at the time, I agree, and a cat 4/5 would suffer quicker from lack of a steady inflow, but I think it's relevant to the point. Link to comment Share on other sites More sharing options...
aslkahuna Posted February 10, 2011 Share Posted February 10, 2011 You mean the 929 mb was taken at the sugar mill? Unfortunately, the highest winds in any cyclones are rarely sampled. We have the same problem in the USA. There just aren't enough stations to cover the coast thoroughly enough, so the wind max often slips between reporting stations. And when the wind max does pass over a station, of course the instruments might be damaged by flying debris. One main problem here in the US is that ASOS was not originally equipped with any backup in the event of a power failure and it is this more than anything else that prevents us from getting good wind obs from hurricanes. Our mesonet at FHU when I was there had battery backup and data storage which allowed the site to continue to collect data and us to retrieve the data after power was restored. This was how we were able to get the data on the passage of TS Lester after the power was restored the next day. Steve Link to comment Share on other sites More sharing options...
k*** Posted February 11, 2011 Share Posted February 11, 2011 shame on the christian science monitor http://www.csmonitor.com/World/Asia-Pacific/2011/0204/US-sized-Cyclone-Yasi-could-cost-Australia-more-than-2-billion Still, considering Yasi was a category five cyclone only a little smaller than the United States, analysts are saying Australia should consider itself lucky. Link to comment Share on other sites More sharing options...
OzTCchaser Posted July 25, 2011 Share Posted July 25, 2011 Very cool looking back over all the comments from our American friends regarding TC Yasi. Having chased this system I suppose my only regret is not choosing Cardwell over Ingham as our intercept point. Having checked Cardwell out the morning before landfall it was decided that storm surge issues and a night-time crossing were not a good combination so we re-located 45km south. I also had it very much in the back of my mind that Yasi would dip SW prior to landfall which it did do, but maybe an hour or two later than I had hoped. Was still a pretty rough night and alot of fun to chase although there were some pretty sad scenes to the south of the eyewall the following morning. I will certainly check out this forum and the views of it's users during the next big system we can spin up this upcoming summer. Some very insightful posts all round. We will be chasing as many as we can again this season and I shall attempt to stream as much back as I can through my forum and website although some of our Pilbara systems in Western Australia tend to make landfall in poor coms areas but we will certainly be getting plenty of video footage in any case. Again, great forum guys. Live Streaaming this summer @ www.xweatherlive.com Cheers Link to comment Share on other sites More sharing options...
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