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General Discussion >> Hurricane Ask/Tell

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Random Chaos
Weather Analyst


Reged: Sat
Posts: 1024
Loc: Maryland
Felix Dropsondes
      #77811 - Sun Sep 02 2007 09:47 PM

Not sure the best spot for this post, so I'm sticking it in the Storm Forum so hopefully people will see it.

I've coded up a Dropsonde decoder and it needs testing. Anyone that wants to plug in dropsondes on Felix from http://twister.sbs.ohio-state.edu/text/tropical/atlantic/UZNT13.KNHC have fun.

Location: http://aewww.firstones.com/dropsonde_decoder.php5

Please let me know via PM if you have any difficulties with the app or think something important is missing from the decoder. I decode almost everything, but I don't actually display everything in the final output. I've tested it with a half dozen dropsondes from past storms, but there might always be something I forgot .

Once it's fully tested, I'll email it to MikeC to stick on this site.

I based my development of it mostly on these sources:
- http://www.storm2k.org/phpbb2/viewtopic.php?f=29&p=1610668
- http://www.wunderground.com/about/reconreport.asp?MR=1

Enjoy!
--RC

Edit: I know the current dropsonde works - I'm mostly interested in future ones

(Post moved to a more appropriate Forum.)

Edited by Ed Dunham (Sun Sep 02 2007 11:05 PM)


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Random Chaos
Weather Analyst


Reged: Sat
Posts: 1024
Loc: Maryland
Re: Felix Dropsondes [Re: Random Chaos]
      #77837 - Mon Sep 03 2007 12:30 AM

One thing I'm a little stumped by in the app is figuring out the heights for the fixed pressure readings. They only record 3 digits of the heights. So if it says 850m, it might actually be 1850m, but I can't see any way that you know it is 1850 and not 2850 (you'll probably know it can't be 850 because you'll have seen a 900 before).

Can anyone help me out with this?

This is what I'm reading on it (3 different sources):

1:
P1P1hhh...the first mandatory pressure level data follows, with
00 being 1000 mb, 85 being 850 mb, 70 being 700 mb, etc.
hhh is the height of this level in meters above sea level.

2:
the standard isobaric level height is listed, in geopotential meters. At and above 500mb, heights are in decameters, with any thousands or tens of thousands omitted. For 1000mb and 925mb heights than are negative, 500 is added. When the pressure is less than the isobaric level, slashes are encoded. (SLP = 950mb: 00/// ///// /////.)

3:
h1h1h1 – Heights of the standard pressure level in geopotential meters or decameters above the surface. Encoded in decameters at and above 500mbs omitting, if necessary, the thousands or tens of thousands digits. Add 500 to hhh for negative 1000mb or 925mb heights. Report 1000mb group as 00/// ///// ///// when pressure is less than 950mbs.


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Random Chaos
Weather Analyst


Reged: Sat
Posts: 1024
Loc: Maryland
Re: Felix Dropsondes [Re: Random Chaos]
      #77943 - Tue Sep 04 2007 10:50 PM

Found a few bugs with some of the dropsondes (bad day data, not loading latitude/longitude from alternate sources, etc.). None of these are critical, so I'm not going to upload a patch yet (hopefully I'll find more stuff to improve).

Still looking into the height stuff. DanielW sent me some good reference, but I'm still trying to figure out how to transform that into code in a "smart" manner.

--RC


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Random Chaos
Weather Analyst


Reged: Sat
Posts: 1024
Loc: Maryland
Re: Felix Dropsondes [Re: Random Chaos]
      #78066 - Sat Sep 08 2007 11:45 AM

I've finalized the project. Hopefully all dropsondes decode right; if not, I'll have to play with the code some more.

You can grab it here: http://www.vorklift.com/temp/dropsonde_decoder.txt

Requires PHP5 and can be embedded into any XHTML page.


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