<div class="eI2">Fog Stability Index</div> This is a stability index for fog formation. It is from 2WW/TN-79/008, "A New Technique for Forecasting the Occurence of Fog and Low Stratus Ceiling by Use of a Flow Chart".<br> The equation for the index is:<br> <b><i>Fog Stability Index</i> = 2*(t<sub>s</sub> - t<sub>850</sub> + t<sub>s</sub> - t<sub>ds</sub> ) + W<sub>850 </sub>=</b><br> =4t<b><sub>s</sub> - 2(t<sub>850</sub> + t<sub>ds</sub>) + W<sub>850</sub></b><br> <table width="200" cellspacing="0" cellpadding="0" border="0"> <tr height="30" bgcolor="#E5E5E5"><!-- Row 1 --> <td colspan="3"><font size="3" face="Arial, Helvetica" color="#0000FF">Fog risk (FSI)</td> </tr> <tr height="30"><!-- Row 2 --> <td width="33%" valign="top"><center>high</center></td> <td width="33%" valign="top"><center>middle</center></td> <td width="33%" valign="top"><center>low</center></td> </tr> <tr height="30"><!-- Row 2 --> <td width="33%" valign="top"><center>FSI < 31</center></td> <td width="33%" valign="top"><center>31 < FSI < 55 </center></td> <td width="33%" valign="top"><center>FSI > 55</center></td> </tr> </table> </div>