World Weather API returns negative swell height

Question

I'm using the World Weather Online API and am getting some funky results. I can't find much documentation about how these readings work, but one weird thing I'm seeing is a swell height of -999 meters. I'm using a location in Mountain View, CA, which isn't super close to water, but I expect that the API will return results from the closest available station/ instruments. Here's an example response:

        <data>
        <script id="tinyhippos-injected"/>
        <request>
        <type>LatLon</type>
        <query>Lat 37.39 and Lon -122.09</query>
        </request>
        <nearest_area>
        <latitude>37.467</latitude>
        <longitude>-122.083</longitude>
        <distance_miles>5.4</distance_miles>
        </nearest_area>
        <weather>
        <date>2013-12-06</date>
        <maxtempC>10</maxtempC>
        <mintempC>-233</mintempC>
        <hourly>
        <time>0</time>
        <tempC>1</tempC>
        <tempF>34</tempF>
        <windspeedMiles>4</windspeedMiles>
        <windspeedKmph>6</windspeedKmph>
        <winddirDegree>193</winddirDegree>
        <winddir16Point>SSW</winddir16Point>
        <weatherCode>113</weatherCode>
        <weatherIconUrl>
        <![CDATA[
        http://cdn.worldweatheronline.net/images/wsymbols01_png_64/wsymbol_0001_sunny.png
        ]]>
        </weatherIconUrl>
        <precipMM>0.0</precipMM>
        <humidity>68</humidity>
        <visibility>10</visibility>
        <pressure>1021</pressure>
        <cloudcover>0</cloudcover>
        <sigHeight_m>-999.0</sigHeight_m>
        <swellHeight_m>-999.0</swellHeight_m>
        <swellDir>-999</swellDir>
        <swellPeriod_secs>-999.0</swellPeriod_secs>
        <waterTemp_C>12</waterTemp_C>
        <waterTemp_F>54</waterTemp_F>
        </hourly>

Is there some kind of problem with this reading? I'm assuming that it should just be a swell height of zero, which I can deal with, but I want to make sure that -999 doesn't mean something else (like the reading was not available at the time or something).

Answer 1

-999 is often used to represent missing data in weather feeds, as you feared. If that feed is not giving you the data you want, you might try the National Data Buoy Center, which collects wave height data worldwide with a focus on the US coast. They offer many ways to consume their data including KML download.