Future geostationary hyper-spectral instruments such as the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) will have the sensitivity to resolve atmospheric features above and beyond the capabilities of today’s geostationary sounders. Although GIFTS data will most likely generate improvements in numerical forecast guidance out to 48 hours and beyond, a significant benefit will come from the use of GIFTS data in a real time objective nowcasting system designed to assist forecasters with identifying rapidly developing, small-scale extreme weather events. To satisfy nowcasting requirements such a system will need to detect and retain extreme variations in the atmosphere while assimilating large volumes of high-resolution asynoptic data from satellites. To accomplish this may require numerical techniques that are notably different from those used in numerical weather prediction where the forecast objectives cover longer time periods. A nowcasting system will need to place an emphasis on observation accuracy, require frequent updates and will have minimal interaction with numerical prediction models.

An objective analysis system for nowcasting is proposed that uses a LaGrangian approach to optimize the retention of information provided by multiple observing systems. The system is designed to preserve vertical and horizontal gradients in the observed fields, detect extreme variations in atmospheric parameters, and identify the onset of significant weather events. A proof-of-concept system is being tested at the Cooperative Institute for Meteorological Satellite Studies (CIMSS), University of Wisconsin. Analytical tests have been performed to test the ability of the method to retain gradients and extremes in meteorological fields. These tests show that the technique is computationally efficient and is able to retain sharp gradients, observed maxima and minima, and is capable of providing updates to forecast guidance provided by operational forecast models. Tests with real data are currently being conducted using full resolution (10 km) derived layer moisture products from the GOES-10/12 sounders. These tests focus on the ability of the proposed system to retain and capture details important to the development of convective instability.

Robert M. Aune 1225 W. Dayton St; Madison, Wisconsin 53706 Phone: 608-264-5325 Fax: 608-262-5974 Email: boba@ssec.wisc.edu