Weather Alert Script for your Home Server

2010-05-23
Weather Alert Script for your Home Server

With the often active tornado season in Middle Tennessee I've been meaning to buy a weather radio. But first I wanted to see if my home server could do the job for me. Using beep, cron, and the weather API from Weather Underground, I've crafted a homebrew weather alert system.

How it works: Utilizing cron, a PHP script is run every ten minutes retrieving the number of active weather alerts for a specific zip code. On most days the alert count is zero. However, if an alert is active, (a severe thunderstorm watch or a tornado watch, for example) cron starts running a separate PHP script every 1 minute looking specifically for severe thunderstorm warnings or tornado warnings.

If a watch is active, the server uses beep to send out a specific sound.


beep -f 75 -l 3000

If a warning is active, beep outputs a different sound.


beep -f 900 -l 1500 -r 4

As it happens, our server is just off the kitchen, so we can hear the beeping from the main part of the house.

Here is the code:


< ?php
function pullWXAlerts() {
  $zipCode = 37086; // Your Zip Code
  $wxAlerts = "http://api.wunderground.com/auto/wui/geo/AlertsXML/index.xml?query=".$zipCode; // Weather Underground API

  $xml = simplexml_load_file($wxAlerts);
  $alertCount = count($xml->xpath('//AlertItem')); // Counting the number of active alerts.

  echo "\nActive Alerts: ".$alertCount."\n\n";

  $alerts = array();
  if ($alertCount > 0) {
    echo "The following alerts are active for ".$zipCode.":\n";
    foreach($xml->xpath('//description') as $alert) {
      $alerts[] = $alert;
      echo $alert."\n";
    }
    shell_exec('beep -f 75 -l 3000'); // Beep if an alert exists
    $wxAlerts = print_r($alerts,true);
$mailBody=<<<_order_ the="" following="" alerts="" are="" active="" for="" $zipcode="" zip="" code:="" $wxalerts="" _order_;="" mail('user@domain.com','wx="" alerts',$mailbody);="" }="" echo="" "\n";="" if="" exist,="" start="" checking="" additional="" warnings="" every="" minute.="" $lsresult="shell_exec('ls" etc="" cron.minutely');="" $f="strstr($lsResult,'wx-warn');" (($alertcount=""> 0) && ($f == false)) {
    echo "Copying warning script to /etc/cron.minutely.\n";

    // Copy our script to be run once a minute into /etc/cron.minutely
    shell_exec('cp /home/user/wx-alerts/wx-warn-min /etc/cron.minutely/');
  } else if (($alertCount == 0) && ($f == true)) {
    echo "Removing script from /etc/cron.minutely\n";

    // If no alerts exist, remove our script from /etc/cron.minutely
    shell_exec('rm /etc/cron.minutely/wx-warn-min');
  }
}

pullWXAlerts();

?>

Above is the script that looks for watches every ten minutes. If watches exist, a second script is copied over to to the cron folder and is run every minute. I've added the functionality to also email myself if an alert exists.

This is the script that runs every minute if a weather alert is active:


< ?php
function pullWXAlerts() {

  $zipCode = 37086; // Your Zip Code
  $wxAlerts = "http://api.wunderground.com/auto/wui/geo/AlertsXML/index.xml?query=".$zipCode; // Weather Underground API

  $xml = simplexml_load_file($wxAlerts);
  $alertCount = count($xml->xpath('//AlertItem')); // Counting the number of active alerts.

  echo "\nActive Alerts: ".$alertCount."\n\n";

  $alerts = array();
  if ($alertCount > 0) {
    echo "The following alerts are active for ".$zipCode.":\n";
    foreach($xml->xpath('//description') as $alert) {
      $alerts[] = $alert;
      echo $alert."\n";
      if ($alert == "Tornado Warning" || $alert == "Severe Thunderstorm Warning") {
        shell_exec('beep -f 900 -l 1500 -r 4');
	echo "Beeping 4 times for ".$alert."\n";
        $warn = true;
	$warning = $alert;
      }
    }
    $wxAlerts = print_r($alerts,true);

    if ($warn == true) {
$mailBody=<<<_order_ the="" following="" warnings="" are="" active="" for="" $zipcode="" zip="" code:="" $warning="" _order_;="" mail('user@domain.com','wx="" warning="" alert',$mailbody);="" }="" echo="" "\n";="" pullwxalerts();="" ?="">

Once again we're getting an alert count. If an alert exists and it's either a thunderstorm warning or a tornado warning, beep takes over and starts sounding the alarm.

I had to customize my crontab in order for the system to run a job every ten minutes as well as every minute. There is a lot of info about crontab on the interwebs.

Once cron is set up, you can call these files from a bash script like so:


#!/bin/bash

php /home/user/wx-alerts/pull-wx-alerts.php

A word of caution: While this system may work well for some, it's likely not ideal for everyone. Some system beeps are very quiet. You're also relying on computers to get the alert out. Not to mention your internet connection and power company. Personally, I'll still be investing in a real weather radio, but this can act as a decent failsafe.