kwilcox
Active Member
I've been playing with this WX data for a few days and thought I would share some of my findings.
First let me say that METAR information is really useful! What would you think about being able to do these sorts of things in your automation system?
If its overcast out, enable the home light sensors 1 hour before sunset otherwise enable them a half hour before sunset.
or perhaps:
If its overcast with low cloud cover, enable the light sensors. Disable them again when the clouds lift.
Here's one that irks me:
If its time to water the lawn and its raining outside, don't do it!
Or, how about this:
If there's a tornado sighted and everyone's asleep, turn on all lights in the house and flash the master bedroom lights.
Well, METAR data is a way to help do this.
METAR data is maintained by automated weather stations at most airports. These stations generally transmit this information to airplanes. What's nice is that NOAA automatically collects this information every hour and makes it available via FTP. The METAR content itself is a string that can be parsed for interesting information. Sooo, all you have to do is fire up an FTP request for your closest METAR station Weather data then have fun with the results. Here's a link to get you started on the format of METAR data:
Metar Help
The Metar string from the example they use is from Chicago O'Hare Airport and in its raw state looks like this btw:
KORD 041656Z 19020G26KT 6SM -SHRA BKN070 12/08 A3016 RMK AO2
You can pull that Airport's current data by following this link:
ftp://tgftp.nws.noaa.gov/data/observation...ations/KORD.TXT
When you're ready to pull your own METAR data, here's a link that you can use to find the closest METAR station to your location:
http://www.faa.gov/asos/map/map.htm
Once you find your station's call letters then just insert it into the ftp link above in place of KORD.
Now, how to use this data in the above examples? I'm keying in on the WX and SKY data which would contain unique identifiers for various conditions. In the above example, this data is "-SHRA BKN070" which decodes to "light rain showers ovserved", "broken clouds at 7,000 feet". However, if you get a hit on "+FC" anywhere in the METAR string then you've got a tornado situation. While better than nothing, this data can be up to an hour old since NOAA only updates their info once per hour. Much more useful would be finding "RA" which is a rain indicator in WX data or "OVC" in SKY data. In my example above, "OVC" triggers early sensor mode and "OVC" followed by a number less than 100 triggers "sensor now" mode.
Several automation systems have a built in ability to pull METAR data which frees you up from having to program the FTP pull and import logic. I use HCA which has direct support for METAR data. Unfortunately, they don't currently decode WX or SKY data into their WeatherConditions variable. Hopefully, I'll be able to convince the tech group at Advanced Quonset to start doing this in future releases; I had suggested that they simply place the WX and SKY strings into WeatherConditions and let us parse away. Perhaps other posters can speak to their system's WX and SKY capture capabilities.
Anyway, this is pretty neat stuff and the biggest advantage of all is that its FREE! Paid for by our taxpayer dollars. Have fun with it!
First let me say that METAR information is really useful! What would you think about being able to do these sorts of things in your automation system?
If its overcast out, enable the home light sensors 1 hour before sunset otherwise enable them a half hour before sunset.
or perhaps:
If its overcast with low cloud cover, enable the light sensors. Disable them again when the clouds lift.
Here's one that irks me:
If its time to water the lawn and its raining outside, don't do it!
Or, how about this:
If there's a tornado sighted and everyone's asleep, turn on all lights in the house and flash the master bedroom lights.
Well, METAR data is a way to help do this.
METAR data is maintained by automated weather stations at most airports. These stations generally transmit this information to airplanes. What's nice is that NOAA automatically collects this information every hour and makes it available via FTP. The METAR content itself is a string that can be parsed for interesting information. Sooo, all you have to do is fire up an FTP request for your closest METAR station Weather data then have fun with the results. Here's a link to get you started on the format of METAR data:
Metar Help
The Metar string from the example they use is from Chicago O'Hare Airport and in its raw state looks like this btw:
KORD 041656Z 19020G26KT 6SM -SHRA BKN070 12/08 A3016 RMK AO2
You can pull that Airport's current data by following this link:
ftp://tgftp.nws.noaa.gov/data/observation...ations/KORD.TXT
When you're ready to pull your own METAR data, here's a link that you can use to find the closest METAR station to your location:
http://www.faa.gov/asos/map/map.htm
Once you find your station's call letters then just insert it into the ftp link above in place of KORD.
Now, how to use this data in the above examples? I'm keying in on the WX and SKY data which would contain unique identifiers for various conditions. In the above example, this data is "-SHRA BKN070" which decodes to "light rain showers ovserved", "broken clouds at 7,000 feet". However, if you get a hit on "+FC" anywhere in the METAR string then you've got a tornado situation. While better than nothing, this data can be up to an hour old since NOAA only updates their info once per hour. Much more useful would be finding "RA" which is a rain indicator in WX data or "OVC" in SKY data. In my example above, "OVC" triggers early sensor mode and "OVC" followed by a number less than 100 triggers "sensor now" mode.
Several automation systems have a built in ability to pull METAR data which frees you up from having to program the FTP pull and import logic. I use HCA which has direct support for METAR data. Unfortunately, they don't currently decode WX or SKY data into their WeatherConditions variable. Hopefully, I'll be able to convince the tech group at Advanced Quonset to start doing this in future releases; I had suggested that they simply place the WX and SKY strings into WeatherConditions and let us parse away. Perhaps other posters can speak to their system's WX and SKY capture capabilities.
Anyway, this is pretty neat stuff and the biggest advantage of all is that its FREE! Paid for by our taxpayer dollars. Have fun with it!
