Short-term Prediction Research
and Transition Center

Lightning - North Alabama Lightning Mapping Array

The North Alabama Lightning Mapping Array (LMA) provides additional information on storm kinematics and updraft evolution that offers the potential to improve severe storm warning lead time by up to 50% and decrease the false alarm rate (for non-tornado producing storms). Our prior studies suggest a rapid increase in the "in-cloud" lightning frequency is associated with the invigoration of the storm updraft followed by a rapid decrease in lightning activity associated with the weakening of the storm updraft and descent of the storm angular momentum from aloft.

Latest LMA Lightning Image
Central Florida Tornadic Storm July 11, 1997 (AVI Movie)
Central Florida Tornadic Storm February 23, 1998 (AVI Movie)

A new multiple Doppler radar network and lightning mapping network in northern Alabama will provide the needed data for this study.

The North Alabama 3-D VHF regional LMA consists of ten VHF receivers deployed across northern Alabama and a base station located at the National Space Science and Technology Center (NSSTC), which is on the campus of the University of Alabama in Huntsville. The LMA system locates the sources of impulsive VHF radio signals from lightning by accurately measuring the time that the signals arrive at the different receiving stations. Each station records the magnitude and time of the peak lightning radiation signal in successive 80 µs intervals within a local unused television channel (channel 5, 76-82 MHz in our case). Typically hundreds of sources per flash can be reconstructed, which in turn produces accurate 3-dimensional lightning image maps (nominally <50 m error within 150 km range).

The solid green dots are the 10 antennae that receive incoming lightning signals. The open green circles are the repeater stations (note that two of them are co-located with antennae). The open green circle with the blue box inside is the location of the central processing unit at the NSSTC. The red dot is the location of a planned, future antenna.

A 3-D gridded total lightning data set, updated every 2 min provides full coverage of the Huntsville and Nashville NWS warning areas, as well as partial coverage of five other NWS offices. The lightning source density grids have a horizontal extent of 460 by 460 km with a resolution of 2 km by 2 km centered on the NSSTC. The vertical grid resolution is 1 km from 0-17 km. The NWS Local Data Acquisition and Dissemination (LDAD) system ingests these near real-time VHF source density grids, which are then provided to the Advanced Weather Information Processing System (AWIPS) forecaster workstation that is used to integrate varied weather data and issue forecasts and warnings. Forecasters can interrogate the data on any of the 17 horizontal levels or examine the cumulative source density maps that contains all levels. Forecasters can also readily dither between NEXRAD and LMA maps and loop multiple frames to enhance situational awareness during severe weather episodes.

LMA gridded source density product region. The yellow outlines denote the warning areas for the various National Weather Service Forecast Offices.

Example of gridded source density map incorporated with other data in an AWIPS display.

One Hour Density

Previous LMA lightning imagery