TC Marcia - Discrepancies and Inaccuracies

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• published: 21 Feb 2015
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The Bureau of Meteorology grossly misrepresented the strength of Severe Tropical Cyclone Marcia due to using the Advanced DVORAK Technique as opposed to using actual measurements available over the course of the Cyclones life. This creates complacency and the practice MUST stop. Like and Share if you agree. Why BoM? - http://forum.weatherzone.com.au/ubbthreads.php/topics/1311896/Re_Severe_Tropical_Cyclone_Mar#Post1311896 Summary: Maximum Figures Measured by Station Sustained : Gusts : Pressure : Category Creal Reef: 146km/h : 189km/h : 977.8hPa MSL : Cat 3 Middle Percy Is: 156km/h : 208km/h : 970.2hPa MSL : Cat 3 Samuel Hill: 98km/h : 170km/h : 977.3hPa MSL : Cat 3 Yeppoon: 120km/h : 156km/h : 985.4hPa MSL : Cat 2 Rockhampton: 82km/h : 113km/h : 985.5hPa MSL : Cat 1 Script: Tropical Cyclone Marcia began in the Northern Coral Sea as invest 98P while slowly drifting Eastwards. It gradually took a turn to the SW on the 17th, where the Buero of Meteroligy initialized it as a Tropical Low. It was expected to make landfall as a Cat 1 around 48 hours later. It was upgraded to cat 1 roughly as it became visible on the Mackay radar, and rapidly intensified to cat 4 before turning SSW and making landfall as a "cat 5" system, passing Middle Percy Island. Severe TC Marcia passed to the West of Yeppoon as a cat 4 system, then proceeded to pass directly overtop Rockhampton as a cat 3. However, upon investigation of official BoM recorded observations from stations on Middle Percy Island, Samuel hill, Yeppoon and Rockhampton, discrepencies between the recorded data and the official cyclone intensity become very clear. Actual recorded data would suggest the system never exceeded cat 3 strength, and weakened significantly faster than suggested by the BoM. The maximum wind speed recorded at Middle Percy Island shows a mid cat 3 system just before landfall. Upon moving further to the South and passing to the West of Yeppoon, wind speeds had declined to within category 2 strength. It is worthy to note that, although the system did not pass directly over Yeppoon, being situated on the coast would have possibly exposed it to higher windspeeds than would have been recorded further inland due to onshore winds, however no other stations were located in it's path. Marcia proceeded to cross directly over Rockhampton, with the highest official wind speeds only denoting a Cat 1 system. The BoM uses the advanced dvorak technique to estimate the strength of tropical cyclones where real life observations are not available. The Advanced Dvorak Technique (ADT) utilizes longwave-infrared, temperature measurements from geostationary satellites to estimate tropical cyclone (TC) intensity. The ADT is based upon the operational Dvorak Technique developed by Vern Dvorak of NOAA over 30 years ago. This step-by-step technique relies upon the user to determine a primary cloud pattern and measure various TC cloud top parameters in order to derive an initial intensity estimate. Various rules regarding TC development and intensity change over time are employed to guide the user in the scene selection process and govern the rate in intensity change over a given time period. The discrepencies in strength were due to the BoM reporting the ADT estimate rather than actual recorded data, which was available before, during and after the cyclone had passed multiple official stations. In some cases, these estimates were up to 70km/h higher than the actual recorded wind speeds. Photos of damage from Yeppoon do not justify a category 4 system, with only a few cases of severe structural and environmental damage, which was limited to older, exposed structures. This scenario will create complacency in the future, due to civilians misinterpreting potential damage of the actual category rating. References and Credits: Original Poster - Things/LPFThings https://www.youtube.com/user/LPFthings http://forum.weatherzone.com.au/ubbthreads.php/topics/1311774/Re_Severe_Tropical_Cyclone_Mar#Post1311774 Popeye - Weatherzone Forum http://forum.weatherzone.com.au/ubbthreads.php/topics/1311888/Re_Severe_Tropical_Cyclone_Mar#Post1311888 http://forum.weatherzone.com.au/ubbthreads.php/topics/1312004/Re_Severe_Tropical_Cyclone_Mar#Post1312004 Strongest TC in 25 Years Statement - Brisbane Times http://www.brisbanetimes.com.au/queensland/cyclone-marcia-to-hit-queensland-coast-at-10am-20150219-13jvis.html Radar Imagery - Weatherzone.com.au www.weatherzone.com.au/radar/ MIMIC - Microwave Imagery http://tropic.ssec.wisc.edu/real-time/mimic-tc/2015_13P/webManager/basicGifDisplay48.html Censored Middle Percy Obs http://jennifermarohasy.com/wp-content/uploads/2015/02/Middle-Percy-Obs-Now-Removed.pdf