Developments in the nowcasting total lightning flash rates using GOES satellite infrared convective cloud information

Accurately forecasting the initiation and immediate impacts of thunderstorms and lightning remains a significant problem in various aspects of meteorology. This presentation will highlight satellite-based methods that improve upon our ability to nowcast (0-1 hour forecast) lightning initiation (LI) and perhaps assess the early trends in lightning intensity (in terms of flash numbers and intensity). This LI research rests on our current convective initiation (CI) nowcasting method relies on the use of infrared (IR) and visible (VIS) satellite data from GOES, and cloud-motion winds for tracking cumulus clouds. The CI technique develops relationships between VIS and IR data and cumulus cloud phase (e.g., first time glaciation of cumulus cloud tops), cloud growth and deepening, and is built with new and existing methods. Current results shows that 30-60 minute CI nowcasts (the first occurrence of a >35 dBZ radar echo) can be provided over large geographical regions in realtime, with PODs on the 1 km scale of about 63% when eight IR CI indicators are used.

Work underway at the University of Alabama in Huntsville (UAH) and the University of Wisconsin Cooperative Institute of Meteorological Satellite Studies (UW-CIMSS) is towards producing LI nowcasts in a manner similar to our GOES-based CI processing. Improved means of correlating VIS and IR fields from GOES and MODIS with rainfall (i.e. radar reflectivities greater than 35) are being developed. Relevant aspects of satellite-based CI research include: a) correlating radar echoes, satellite IR and total lightning flash rate data, as a way of predicting convective cloud properties (e.g., height, cloud-top microphysics) and growth rates (e.g., updraft widths and intensity), b) determining the relative importance of the various IR signals to the first occurrence of a 35 dBZ radar echo (e.g., the time trends in various IR temperatures for moving clouds), and c) developing a means to forecast LI and lightning flash rates and trends as related to changing satellite IR information.

The procedures that allow for the assessment, improvement and validation of our current CI techniques, namely the pixel-by-pixel comparison of GOES IR and WSR-88D level II radar fields, are expanded by the inclusion of Lightning Mapping Array (LMA) data from the North Alabama LMA network. Statistical correlations are made using these co-located data between changing GOES/MODIS IR information for moving cumulus, rainfall intensity changes, and lightning flash rates (for in-cloud, cloud-to-ground, and cloud-to-air lightning "sources"). This database is subsequently allowing us to gain further understanding of LI in various convective environments, as well as to assess the forecast lead times as a function of cumulus growth properties as observed by GOES. This presentation will highlight our current progress on this effort, as well as provide several examples and demonstrations of LI across mesoscale geographical regions.

This project's goals coincide with those of the FAA Aviation Weather Research Program (AWRP) efforts at the National Center for Atmospheric Research (NCAR) to nowcast CI and LI for the purpose of enhancing aviation safety over land and oceanic regions. As proven techniques are developed, they will be transferred into the forecast systems supported by the FAA for nowcasting convection.