Using multi-spectral satellite remote sensing techniques to nowcast nocturnal convection initiation

Accurately forecasting convection initiation (CI) is an ongoing problem within meteorology. Mecikalski and Bedka (2005) have demonstrated with good success a process which nowcasts (0-1 hour) convection initiation during the daytime using GOES real-time satellite processing. Using 1 km visible imagery, temporal temperature trends using multiple wavelengths and band differencing, an algorithm was developed to select regions where cumulus clouds have ~60% or greater chance of precipitating within the next hour. An ongoing extension of this work is to advance daytime CI nowcasting to nighttime conditions. Since 1 km visible satellite is not available during the nighttime hours, one must rely on infrared channels with a spatial resolution of 4 km to monitor clouds. This can be challenging because 4 km is typically less than the cumulus horizontal spatial scale initially, and tracking cumulus at night is more difficult. As a corollary, during nighttime conditions the 3.9 micron near-infrared channel becomes available as an additional resource to use from the GOES instrument.

Recent research has shown that the 3.9 micron channel temporal temperature trends and difference fields will aid in the nowcasting of convection and provide additional information into cloud top microphysics. A data set of several cases has been analyzed and used to determine a critical value for using the 3.9 micron channel as a CI interest field. Thus, examples of cases with CI will be reviewed; statistics will be shown and MODIS data will be used when available to take advantage of improved spatial resolution and more available channels.

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 for the purpose of enhancing aviation safety. Thus, this presentation will highlight recent research progress on collaboration between the University of Alabama in Huntsville, the University of Wisconsin-Madison, Cooperative Institute for Meteorological Satellite Studies (UW-CIMSS) and NCAR to routinely diagnose convection over land and ocean regions. As proven techniques are developed through this collaboration, they will be transferred into the forecast systems supported by the FAA for nowcasting convection over land and oceans.