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Hurricane Dorian Winds Of 185 MPH Don’t Stand Up To Scrutiny

September 16, 2019

By Paul Homewood

 

 

 

I have some updated data for Hurricane Dorian which is relevant to my earlier post, Hurricane Dorian–The Facts v The Myth.

 

Just to re-cap from that post:

1) Claims of 185 mph winds were based solely on hurricane hunter aircraft data.

2) Based on central pressure of 910 mb, wind speeds would be expected to be 165 mph. This is how wind speeds were calculated prior to aircraft and satellite data.

3) Satellite data for Dorian indicated winds of about 140 mph.

4) The figure of 185 mph appears to have been derived from Stepped Frequency Microwave Radiometers (SFMR), which are known to artificially increase windspeeds in areas of shallow waters, such as are present around the Bahamas.

 

One reader got hold of the dropsonde data, which appeared to back up the SFMR readings:

image

https://notalotofpeopleknowthat.wordpress.com/2019/09/06/hurricane-dorian-the-facts-v-the-myth/#comment-143977

 

This is the data from the dropsonde, when the storm was at its peak. (To replicate it, you need to use the decoder):

image

However there is a big problem here.

Wind speeds used under the Saffir Simpson scale must be 1-minute sustained speeds. Given that dropsondes are falling at a rate of about 3000 ft per minute, clearly they can only measure peak winds, as the dropsonde data page actually states:

image

 

Wind gusts can easily be 40 mph greater than sustained speeds, so the data from the dropsonde is essentially worthless for deriving the latter.

 

It does appear that the National Hurricane Center are keen to paint the worst picture every time a hurricane comes along, for whatever reason.

Every single fact about Dorian however suggests that it was less powerful than the official reports have made out.

References

1) The NHC dropsonde archive data is here:

https://www.nhc.noaa.gov/archive/recon/2019/REPNT3/

2) The decoder is here:

http://tropicalatlantic.com/recon/recon.cgi?page=decoder

12 Comments
  1. A C Osborn permalink
    September 16, 2019 12:33 pm

    The devestation on Abaco was consistent with other Category 3 & 4 past Hurricanes.
    The BBC “Scientists” are now saying that Climate Change caused Dorian to “stall”, I wonder how CO2 managed that?
    Of course blocking highs etc are nothing unusual.

    • A C Osborn permalink
      September 16, 2019 12:47 pm

      ps Scientist was David King.

    • JimW permalink
      September 16, 2019 1:17 pm

      I am very sorry for the Haitians living in Mudd, the shanty town on Abaco, many lost their lives and Mudd was devastated.
      However it was devastated because it was a shanty town and right next to the shore line so bore the brunt of the surge. Next door, structures had some damage, further inland, not so much. Looks like a Cat 2/3 at 10m height. Surge also seems to have caused most damage in Freetown on Grand.
      The problem is getting accurate info/photos from the whole of the islands as the media just concentrate on the worst of the devastation. Like the NHC/NOAA info its all designed to support the ‘climate emergency’ nonsense. And of course anyone effected, including the Bahamian govt are going to say ‘climate change!’, knowing that is the best way to get most money, its a self-perpetuating situation.

  2. john cooknell permalink
    September 16, 2019 2:23 pm

    The Abacos islands were at risk, partly due to geography, part political (they want independence from the Bahamas, so no investment for hurricane protection).

    If you look at any picture of Hope Town, Abacos you can see why it did not fare well.

    Freeport is the main town on Grand Bahama, my understanding is hurricane protection was better as investment was encouraged.

    Dorian was a hurricane, and perhaps there is evidence of confirmation bias in the NHC forecasting and recording, but the severe damage was done! The strongest hurricane EVAH recorded(Patricia) caused almost no damage, go figure! At the height of the strongest cyclone EVAH, coastal residents were pictured walking down the street holding umbrellas.

  3. Ivan permalink
    September 16, 2019 2:56 pm

    Maybe 185mph wind claim can’t be sustained, but I remain satisfied by the Cat 5 categorisation. Every hurricane with a minimum pressure of 915 hPa or less is a Cat 5 hurricane. https://en.wikipedia.org/wiki/List_of_the_most_intense_tropical_cyclones
    There are indeed plenty of pictures of houses with intact roofs. This is not surprising. Building standards in the Bahamas are to survive Cat 4 hurricanes. But there are also pictures of well-built houses (not storm surge affected) with destroyed roofs.
    For example, although this drone video mostly shows storm surge damage, around 1m and towards then end you also see very badly wind-damaged properly on higher ground. https://www.youtube.com/watch?v=SN4jgJX0OP8
    Anecdotal, but storm chaser Josh Morgerman sat through Hurricane Dorian in Marsh Harbour, and said it was the strongest he has ever experienced, and he has been in the eye of several Cat 5 hurricanes. He measured 913 hPa in the eye, and reported catastrophic wind damage.
    https://www.smh.com.au/world/north-america/a-storm-chaser-went-silent-as-dorian-hit-he-reemerged-with-a-harrowing-story-20190905-p52o3i.html
    https://en.wikipedia.org/wiki/Josh_Morgerman

    • john cooknell permalink
      September 16, 2019 9:31 pm

      I have been many times to the Bahamas, mainly I went to Nassau where 75% of the population live safe from Hurricanes, and although there is a building code for Nassau, I am not sure any sort of building standard applied to houses damaged in the Abacos islands.

      The Abacos islands are remote, and the islanders are independently minded and my observation was they were at risk from Hurricanes. Real Estate was cheap!

      However if you were a poor person in the Bahamas, would you live on an island that most of the time was paradise and take your chance with a Hurricane, or would you take your chance with the drug dealers in downtown Nassau.

  4. September 16, 2019 5:59 pm

    “Every single fact about Dorian however suggests that it was less powerful than the official reports have made out.”

    Well, there’s one other fact to be considered; that being that Dorian was very slow moving as it made it’s first landfall in the Bahamas, and then slowed until it stalled for about 36 hours over Grand Bahama (no – I do not buy into the shrill that this was caused by AGW).

    Even at 145mph, +/- max sustained winds, what they went thru is unimaginable. The time element, in the end, makes Dorian one of the worst hurricanes in history ‘for those impacted.’

    Would be interesting to calculate the ACE for the time frame that it was over the Bahamas (Calling Phil, or Ryan). I was in Cozumel, MX for Hurricane Gilbert on Sept 14, 1988. Gilbert was a much larger Cat 5, with a broad double eye wall when it struck, with a pressure of 892 (at landfall – so Landsea told me). Was moving rather quickly, but because of it’s size it did indeed seem to last forever – but not 36 hours – probably more like 12-14 hours of Hurricane force winds – including gusts in the 200-225mph range which some in short 10-15 second pulses.

    • September 18, 2019 12:13 am

      “I do not buy into the shrill that this was caused by AGW” – garyh845

      Right.

      Basically, it’s due to steering currents resulting from weather patterns it encounters (also not caused by CO2 or fictional AGW), as discussed at various points in the excellent video commentaries here.
      https://www.tropicaltidbits.com/blog/2019/08/

  5. JKintheUSA permalink
    September 16, 2019 8:10 pm

    https://www.wmo.int/pages/prog/www/tcp/Meetings/HC31/documents/Doc.3.part2.pdf provides some helpful conversion factors for converting gust speeds to 1 minute average speeds. At sea conversion rate from 1 minute average speed to gust speed is only 1.11.

    https://www.nhc.noaa.gov/aboutwindprofile.shtml provides insight into wind speeds at different altitudes. It appears to that the data provided in Table 1 and Figure 1 does not line up – Table 1 shows a conversion factor of 1.31 from surface to 1,000 ft (eye wall speeds). The maximum conversion factor for eye wall speeds in Figure 1 is approximately 1.22.

    • September 16, 2019 9:59 pm

      Interesting to note that GPS based dropsondes only started in 1997!

  6. September 17, 2019 11:51 pm

    Technical Detail

    “…dropsondes are falling at a rate of about 3000 ft per minute…”

    Terminal velocity is 2200 fps, and the dropsondes are equipped with a small handkerchief sized “parachute,” which while slowing their descent will enable them to be carried laterally by the wind.

    Otherwise, yeah.

    Kudos to JKintheUSA! Nice find!

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