Re: If they recorded a 102 mph on a surface observation with the plane...
Posted by
Chris in Tampa on 7/3/2014, 6:40 pm
If you look at the "Forecast Advisory" on the NHC front page for Arthur ( http://hurricanes.gov/ ) you will see inside it information about gusts.
Like this at 5pm:
ESTIMATED MINIMUM CENTRAL PRESSURE 977 MB
EYE DIAMETER 30 NM
MAX SUSTAINED WINDS 80 KT WITH GUSTS TO 100 KT.
That is gusts of 115mph right now. That is an important thing to note too. (Although given the storm's movement, those kind if gusts will likely remain offshore) A dropsonde falls from a plane with a little parachute. I forget the approximate rate of decent, but I imagine in strong winds it varies. What you see in a dropsonde, at the surface, is a gust. Perhaps a few seconds, I'm not sure how the data is averaged. There is more readings from a dropsonde than what is sent out in the message that my site processes for example. The dropsonde message text has specific data and some significant observations in it. I'm not sure how it is averaged from the original raw data of constant obs on the way down to what we get in the raw text product. But it definitely would not be anywhere close to 1 minute sustained.
You can see from the image I posted here:
https://canetalk.com/2014/07/1404419471_1404403517.shtml
That not that far above the surface, at the 979mb level, just 8mb from the surface, the wind was 85mph. (again, gust) At the 951mb level it was 112 mph. Perhaps they considered that the 102mph looked to be more of a gust, since SFMR readings, estimated by an instrument on the plane to estimate what the winds at the surface are, were not that high. Of course even SFMR is a 10 second surface wind estimate, still not 1 minute sustained. (although the NHC often uses those SFMR readings to set what they go with for 1 minute sustained, I guess somewhat assuming that the plane did not sample the strongest wind out there.)
One of the important readings from that sonde would probable be this decoded part from that sonde:
Average Wind Over Lowest Available 150 geopotential meters (gpm) of the sounding:
- Lowest 150m: 158 gpm - 8 gpm (518 geo. feet - 26 geo. feet)
- Wind Direction: 105° (from the ESE)
- Wind Speed: 82 knots (94 mph)
Still a bit above the 90mph they set it at, but assuming that the wind above the surface is a bit more, I guess 90mph would be a good estimate for the 1 minute sustained winds. |
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In this thread:
If they recorded a 102 mph on a surface observation with the plane... -
AquaRN,
7/3/2014, 5:22 pm- Buoy 41036 near eye wall - - DTB_2009, 7/3/2014, 8:52 pm
- Re: If they recorded a 102 mph on a surface observation with the plane... - Chris in Tampa, 7/3/2014, 6:40 pm
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