The March 2019 RPM included the addition of a VIS/IR Sandwich RGB to AWIPS-II. To create the VIS/IR sandwich in the past, forecasters were required to overlay a semi-transparent IR over-top VIS. The RGB automates the creation of this image combination in AWIPS. The benefit of the VIS/IR Sandwich RGB is that it combines the high spatial detail apparent in VIS, with the temperature information of the IR.
In a convective scenario, for example, a forecaster can utilize the RGB to monitor a cu field and boundaries as they normally would, since only the visible imagery will be present up to the point of convective initiation. Once the clouds have cooled enough during convective initiation, the IR component will be combined with the visible, allowing a forecaster to continue to visualize the detail in the cloud top via the VIS component, but also now the temperature information/trends from the IR in the developing storm. Post initiation, this combination improves identification of cloud top features such as overshooting tops, above anvil cirrus plumes, and gravity waves. In the RGB, forecasters are unable to sample the IR temperature, so trends must be gleaned from the colors. However, forecasters can underlay the IR channel so that brightness temperatures can be sampled.
Figure 1 includes an example of rapid convective initiation to mature convection over the Texas Panhandle on 17 April 2019. In a little over one hour, the storm initiates and develops an overshooting top and above anvil cirrus plume. The rapid cooling is apparent in the imagery while the high detail of the VIS is maintained. Figure 2 shows the same storm a little later. One-minute imagery was available over the region to help forecasters monitor the evolution of convection. These storms produced large hail and tornadoes.
An example from 18 April 2019 of a large QLCS advancing east across Louisiana and the adjacent Gulf shows the ability of the product to highlight storm top features such as overshooting tops, above anvil cirrus plumes, and storm top gravity waves (Fig 3).
Bill Line, NWS