Re: Harvey Battling Dry-Air Entrainment
Posted by
Chris in Tampa on 8/24/2017, 9:23 pm
The chart I have on this page:
http://hurricanecity.com/recon/recon.cgi?basin=al&year=2017&storm=Harvey&product=sonde
Has a column called "Maximum Wind from Significant Wind Levels".
When the sonde drops through the atmosphere it constantly collects wind, pressure, temperature and dewpoint data and relays that back to the plane. Then a text message is created with lots of various data, including winds at various levels as the sonde fell from the plane.
Here is a decoded sonde with highest winds to date in the storm:
http://hurricanecity.com/recon/recon.cgi?basin=al&year=2017&product=sonde&storm=Harvey&mission=15&agency=AF&ob=08-24-2341-05-981-93-65
"Surface and Standard Isobaric Surfaces" has info at standard levels. Further down there is "Significant Wind Levels". That is where you can find some of the highest winds. Highest in bold. And then there is this caveat:
"Winds at a particular level are peak winds since a dropsonde only records momentary slices of data at each level as it falls through the atmosphere. These winds are not 1 minute sustained."
A program called Aspen (https://www.eol.ucar.edu/software/aspen ) creates messages in the WMO format from the original data which measured data either every half or quarter of a second, I forget. I don't know how the winds are averaged in a message, such as if it varies. But it is not 1 minute sustained. (sonde is falling to Earth, not in one place)
You can see the average of the wind near the surface:
Average Wind Over Lowest Available 150 geopotential meters (gpm) of the sounding:
- Lowest 150m: 155 gpm - 5 gpm (509 geo. feet - 16 geo. feet)
- Wind Direction: 80° (from the E)
- Wind Speed: 79 knots (91 mph)
But it can give you an idea of what the winds are at the surface. I like to see if higher winds are just above the surface that might mix down too. |
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