<div class="eI0"> <div class="eI1">Model:</div> <div class="eI2"><h2><a href="http://www.emc.ncep.noaa.gov/gmb/gdas/" target="_blank">GDAS</a>: "Global Data Assimilation System"</h2></div> </div> <div class="eI0"> <div class="eI1">Updated:</div> <div class="eI2">4 times per day, from 00:00, 06:00, 12:00 and 18:00 UTC</div> </div> <div class="eI0"> <div class="eI1">Greenwich Mean Time:</div> <div class="eI2">12:00 UTC = 13:00 CET</div> </div> <div class="eI0"> <div class="eI1">Resolution:</div> <div class="eI2">0.25° x 0.25°</div> </div> <div class="eI0"> <div class="eI1">Parameter:</div> <div class="eI2">Lifted Index</div> </div> <div class="eI0"> <div class="eI1">Description:</div> <div class="eI2"> <!--begin info text LI--> <p> The Lifted Index (LI) is defined as a rising parcel's temperature when it reaches the 500 millibars level (at about 5,500m or 18,000 feet asl), subtracted from the actual temperature of the environmental air at 500 mbar. If the Lifted Index is a large negative number, then the parcel will be much warmer than its surroundings, and will continue to rise. Thunderstorms are fueled by strong rising air, thus the Lifted Index is a good measurement of the atmosphere's potential to produce severe thunderstorms. </p> <p> <!--begin LI table--> <body> <table width="400" cellspacing="0" cellpadding="0" border="0"> <tr height="30" bgcolor="#E5E5E5"><!-- Row 1 --> <td colspan="4"><font size="3" face="Arial, Helvetica" color="#0000FF">The Lifted Index (LI)</td> </tr> <tr height="30"><!-- Row 2 --> <td width="17%" valign="top"><font size="1" face="Arial, Helvetica"><center>RANGE IN K</center></td> <td bgcolor="#E5E5E5" width="20%" valign="top"><font size="1" face="Arial, Helvetica"><center>COLOR</center></td> <td width="30%" valign="top"><font size="1" face="Arial, Helvetica"><center>AMOUNT OF INSTABILITY</center></td> <td widht="33%" valign="top"><font size="1" face="Arial, Helvetica"><center>THUNDERSTORM PROBABILITY</center></td> </tr> <tr height="25" bgcolor="#E5E5E5"><!-- Row 3 --> <td valign="top"><font size="1" face="Arial, Helvetica"><center>more than 11</center></td> <td valign="top"><font size="1" face="Arial, Helvetica" color="#00A1E6"><center>BLUE</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Extremely stable conditions</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Thunderstorms unlikely</center></td> </tr> <tr height="25"><!-- Row 4 --> <td valign="top"><font size="1" face="Arial, Helvetica"><center>8 to 11</center></td> <td bgcolor="#E5E5E5" valign="top"><font size="1" face="Arial, Helvetica" color="#00C7C7"><center>LIGHT BLUE</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Very stable conditions</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Thunderstorms unlikely</center></td> </tr> <tr height="25" bgcolor="#E5E5E5"><!-- Row 5 --> <td valign="top"><font size="1" face="Arial, Helvetica"><center>4 to 7</center></td> <td bgcolor="#E5E5E5" valign="top"><font size="1" face="Arial, Helvetica" color="#00D18C"><center>GREEN</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Stable conditions</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Thunderstorms unlikely</center></td> </tr> <tr height="25"><!-- Row 6 --> <td valign="top"><font size="1" face="Arial, Helvetica"><center>0 to 3</center></td> <td bgcolor="#E5E5E5"valign="top"><font size="1" face="Arial, Helvetica" color="#A1E633"><center>LIGHT GREEN</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Mostly stable conditions</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Thunderstorm unlikely</center></td> </tr> <tr height="25" bgcolor="#E5E5E5"><!-- Row 7 --> <td valign="top"><font size="1" face="Arial, Helvetica"><center>-3 to -1</center></td> <td bgcolor="#E5E5E5" valign="top"><font size="1" face="Arial, Helvetica" color="#E6DC33"><center>YELLOW</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Slightly unstable</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Thunderstorms possible</center></td> </tr> <tr height="25"><!-- Row 8 --> <td valign="top"><font size="1" face="Arial, Helvetica"><center>-5 to -4</center></td> <td bgcolor="#E5E5E5" valign="top"><font size="1" face="Arial, Helvetica" color="#F08229"><center>ORANGE</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Unstable</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Thunderstorms probable</center></td> </tr> <tr height="25" bgcolor="#E5E5E5"><!-- Row 9 --> <td valign="top"><font size="1" face="Arial, Helvetica"><center>-7 to -6</center></td> <td bgcolor="#E5E5E5" valign="top"><font size="1" face="Arial, Helvetica" color="#F00000"><center>RED</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Highly unstable</center></td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Severe thunderstorms possible</center></td> </tr> <tr height="25"><!-- Row 10 --> <td valign="top"><font size="1" face="Arial, Helvetica"><center>less than -7</td> <td bgcolor="#E5E5E5" valign="top"><font size="1" face="Arial, Helvetica" color="#FF00FF"><center>VIOLET</td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Extremely unstable</td> <td valign="top"><font size="1" face="Arial, Helvetica"><center>Violent thunderstorms, tornadoes possible</td> </tr> </table> <!--end LI table--> </p> <!--end info_text LI--> </div> </div> <div class="eI0"> <div class="eI1">GDAS</div> <div class="eI2">The Global Data Assimilation System (GDAS) is the system used by the National Center for Environmental Prediction (NCEP) Global Forecast System (GFS) model to place observations into a gridded model space for the purpose of starting, or initializing, weather forecasts with observed data. GDAS adds the following types of observations to a gridded, 3-D, model space: surface observations, balloon data, wind profiler data, aircraft reports, buoy observations, radar observations, and satellite observations. </div></div> <div class="eI0"> <div class="eI1">NWP:</div> <div class="eI2">Numerical weather prediction uses current weather conditions as input into mathematical models of the atmosphere to predict the weather. Although the first efforts to accomplish this were done in the 1920s, it wasn't until the advent of the computer and computer simulation that it was feasible to do in real-time. Manipulating the huge datasets and performing the complex calculations necessary to do this on a resolution fine enough to make the results useful requires the use of some of the most powerful supercomputers in the world. A number of forecast models, both global and regional in scale, are run to help create forecasts for nations worldwide. Use of model ensemble forecasts helps to define the forecast uncertainty and extend weather forecasting farther into the future than would otherwise be possible.<br> <br>Wikipedia, Numerical weather prediction, <a href="http://en.wikipedia.org/wiki/Numerical_weather_prediction" target="_blank">http://en.wikipedia.org/wiki/Numerical_weather_prediction</a>(as of Feb. 9, 2010, 20:50 UTC).<br> </div></div> </div>