This week is Severe Weather Awareness Week in Iowa with Wednesday's topic focusing on Tornadoes. There will be a statewide Tornado Drill at 10 AM. The primary mechanism the National Weather Service uses to analyze possible tornadoes is their NEXRAD Doppler RADARs. One of the products these RADARs produce is something called a Storm Attribute Table. The IEM maintains an archive of these with a download interface available. RADAR algorithms can generate a Tornado Vortex Signature (TVS) alert within this table output when rotation is detected with appreciable depth. The featured map presents a heatmap of these TVS reports with the individual NEXRAD locations denoted by a "X". This algorithm only works on RADAR information relatively close to the RADAR location, so thus why you see no-data gaps. There are other algorithms that can help diagnose possible tornadoes at further away distances, so the NWS is not completely flying blind over these areas. It is certainly much "easier" to see tornadoes on RADAR when it is close to the RADAR location.

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Tags:   nexrad