Developing methods to nowcast total lightning flash rates and convective initiation using satellite infrared convective cloud information
John R. Mecikalski, University of Alabama, Huntsville, AL; and S. J. Paech and K. M. Bedka
Accurately forecasting the initiation, temporal and spatial scales, and the immediate impacts of thunderstorms remains a significant problem in various aspects of meteorology. This presentation will highlight satellite-based methods that improve upon our ability to nowcast (0-6 hour forecast) convection initiation (CI) and assess the early trends in thunderstorm intensity. Our current 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 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 >25 dBZ radar echo) can be provided over large geographical regions in realtime, with accuracies on the 1 km scale of about 60-70%.
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 enhancing our GOES-based CI processing with lightning information, as well as with data from the MODerate resolution Infrared Spectrometer (MODIS). Improved means of correlating VIS and up to 20 IR fields from GOES and MODIS with rainfall (i.e. radar reflectivities greater than 25) are being developed. Specific 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., updrafts) and growth, b) determining the relative importance of the various IR signals to the first occurrence of a 25-30 dBZ radar echo (e.g., the time trends in 6.7-10.7 um Tb differences for moving clouds), and c) developing a means to forecast lightning flash rates and trends as related to changing satellite IR information. Developing the IR-based processing toward nighttime CI nowcasting, when VIS data are unavailable, is another long-term goal of this work. The procedures that allow for the validation of our techniques are engrained in our data processing.
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 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.
Extended Abstract (240K)
Poster Session 1, Poster Session 1
Monday, 10 January 2005, 2:30 PM-4:00 PM
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