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Aussie (& S-Hemisphere) Cyclone Action 2011-2012


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Thanks, guys, for posting those images while I was out last night!

Looking at the data and the radar imagery, I suspect Heidi was actually a Severe Tropical Cyclone (Cat 3) as it crossed the coast. (Cat 3 = winds of at least 65 kt (10-min).)

First off, the radar signature looked good, with a small, tight core, and the center seemed to contract as it neared the coast. Secondly, Port Hedland had 53 kt (10-min) with gusts to 71 kt, with a solid hour and a half of sustained winds over 50 kt. Those data are impressive-- especially given that the station was on the right (weaker) side and several miles inland, and therefore most certainly didn't sample the strongest winds. The lowest pressure (978.2 mb) occurred at 5:00 am-- within an hour of the max wind (4:07 am).

While the BoM might have slightly underestimated it, rather stunning to me is the JTWC's assessment of it in Warning No. 5 (2100Z), issued as the center was about to make landfall:

TROPICAL CYCLONE (TC) 06S (HEIDI), LOCATED APPROXIMATELY 11 NM NNE OF PORT HEDLAND, AUSTRALIA, HAS TRACKED SOUTH-SOUTHWESTWARD AT 05 KNOTS OVER THE PAST 06 HOURS. ANIMATED INFRARED SATELLITE IMAGERY REVEALS THAT TC 06S HAS BEEN STEADILY WEAKENING OVER THE PAST 12 HOURS AND IS ABOUT TO MAKE LANDFALL ALONG THE WESTERN COAST OF AUSTRALIA. THE LOW LEVEL CIRCULATION CENTER IS CLEARLY DISCERNIBLE ON THE PORT HEDLAND COMPOSITE REFLECTIVITY RADAR LOOP. AN 1118Z SURFACE OBSERVATION AT THAT STATION REPORTS WINDS OF 44 KNOTS,GUSTING TO 55 KNOTS FROM THE SOUTH-SOUTHEAST.

I don't usually criticize the official agencies, but this is just silly. They assessed an intensity of 45 kt (1-min) based on a reading of 44 kt (10-min) that was taken well inland, relatively far from the center, on the weaker side, more than 2 hr before the highest winds arrived. I'm sorry, but that doesn't even make sense. The actual intensity was probably more like 75 kt (1-min). And what is this about weakening?

I'm just at a loss to understand this analysis.

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Well... You've always been a bit harsh Re: them. :D But that is the most inexplicable operational intensity estimate I've ever seen, from any agency.

You just don't pay attention in the NIO or the WPAC. This isn't out of the ordinary for them. I forget which storm it was earlier this year (or maybe even last year?), but SATCON had something analyzed as a Cat 5 in the WPAC, JMA had 135 kts (10-min), SAB had T7.0 and JTWC only analyzed it at 110 kts. I swear, YOU, an enthusiast, are better at identifying intensities of TCs from satellite images than their trained Dvorak specialists.

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