Typhoon Meranti – The Real Facts v The Hype
September 14, 2016
By Paul Homewood
h/t AC Osborn
http://www.dailymail.co.uk/news/article-3788458/Super-Typhoon-Meranti-tears-Taiwan-wind-gusts-370km-h-sets-sights-China.html
Not for the first time in the last year or so, we find that a Pacific cyclone being grossly overhyped.
I must stress that this is not the doing of the media, they are simply being fed this information from official sources.
It is only in relatively recent years that cyclones have been monitored and measured by satellite, Before the 1980s, many would have been missed altogether as they often go nowhere near land. Others may only have been spotted by ship or land observation after they had reached maximum strength.
It is also important to understand that satellites do not actually measure wind speeds, speeds are estimated with the Dvorak technique using a variety of other information. It is well recognised that these estimates can be several mph out.
It is also relevant to point out the “actual” wind speeds, routinely reported in the media, are not “actual” at all, but the “operational warnings”, which are issued every six hours.
According to NOAA, Meranti peaked at 165 Kts (190 mph or 303 kph), for a six hour slot yesterday, based on the operational warning. However, when actual data from the Advanced Microwave Sounding Unit or AMSU, an instrument on NOAA operational polar-orbiting satellites, is used to estimate intensity, much lower wind speeds are obtained. Instead of 165 Kts, we actually get somewhere around 140Kts, or about 160 mph.
http://rammb.cira.colostate.edu/products/tc_realtime/products/storms/2016WP16/AMSUTSPL/2016WP16_AMSUTSPL_201609141200.GIF
While this would still make Meranti a Cat 5 storm on the Saffir-Simpson Scale, this would not be unusual for a mid Pacific typhoon.
It is no coincidence that we keep finding examples like this in the Pacific, where wind speeds have been grossly overstated. In the Atlantic, most strong hurricanes tend to hit land, where monitored wind speeds would soon tell the true story.
https://metoc.ndbc.noaa.gov/ProductFeeds-portlet/img/jtwc/products/wp1616.gif
JTWC now show Meranti tracking NW towards the China coast, with wind speeds of 125 Kts, or 144 mph, which would make it a Cat 4, with wind speeds forecast to weaken as it hits land.
This is still a major, and potentially damaging, storm, but nothing that does not come along regularly every year.
As I say, the Mail’s version of the story is covered by most of the media, including the Indian Express. However, they also quote Taiwan’s Central Weather Bureau:
Taiwan’s Central Weather Bureau warned that the Category 5 storm would threaten several southern and eastern cities, including Kaohsiung and Hualien, with strong winds, torrential rain and flooding.
Meranti, which grew in strength as it neared Taiwan, was carrying maximum winds of 216 km per hour (134 mph), meteorologists said.
This is 10 mph less than the JTWC figure.
One further point.
All the wind speeds mentioned are sustained winds over 1-minute. Often the media like to use gusts, as these sound much more scary. On this occasion, the Mail state, an enormous ‘super’ typhoon set to rip through China after leaving a trail of devastation in Taiwan has recorded wind gusts of up to 370 km/h .
As can be seen on the JTWC chart above, maximum gusts are only 150 Kts, or 172 mph.
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