Incremental Analysis Updating with Variable-Dependent Timing Applied in a Real-Time High Resolution Forecast System

The Dallas/Ft. Worth Urban Testbed (D/FW Testbed) has been established as a site for evaluating real-time observing systems, data analysis and short-term forecasting over an urban area.   A number of high density observing networks are being tested in the region, including X-band Doppler radars, citizen weather observations, mobile sensors, and ground based profilers.  These systems along with the federal surface and radar networks comprise the diverse data that CAPS is using in our real-time analysis, nowcasting and short-term numerical weather prediction (NWP) efforts. We are utilizing a 3DVAR with complex cloud analysis system with 400-m grid spacing and a Numerical Weather Prediction system with 1-km grid spacing for 2-hour forecasts with low latency.  Besides providing real-time information for local governments and the National Weather Service Forecast Office in Fort Worth, the system can be used as a basis for the testing of observation system impacts, including Networks of Networks that are being integrated into the National Mesonet Program.

This work describes the Incremental Analysis Updating with Variable-Dependent Timing (IAU-VDT) assimilation method that is now being now using to assimilation the analysis increments in the real-time forecasts.  The IAU-VDT allows the timing of the introduction of analysis increments to differ for each variable. This allows for the development of updraft structures to support rain and hail before introducing the hydrometeors.  Other recent improvements to the analysis scheme are also described.  Real time analysis and forecasting products from the 26 Dec 2015 tornadoes in the D/FW metro area are presented as sample results.