AWIPS provides an image combination option that automatically transitions imagery from IR to VIS and VIS to IR during the sunrise and sunset (Fig 1). This prevents the user from needing to change imagery/panels during the day/night transition, and provides pleasing imagery to share with the public.

Unfortunately, AWIPS does not make it easy to apply this option to RGB imagery. After some tinkering, I was able to get it to work.

The VIS/IR Sandwich RGB recently become available in AWIPS-II. Since this RGB is only usable during the day and primarily for monitoring convection, it makes sense to transition to IR alone at night. The example below shows mature convection driving south across central Texas during the afternoon into the evening of 9 June 2019 (Fig 2). The imagery automatically transitions from the VIS/IR Sandwich RGB to IR single-band imagery during sunset. Fig 3 provides a wider view.

The VIS/IR Sandwich RGB to IR transition provided an impressive view of the development and evolution of a prolific hail producing storm over Kansas during the early evening of 11 June (Fig 4).

Another useful transition is the cloud monitoring RGBs. Many blog posts have been written on the utility of the Nighttime Microphysics RGB for monitoring clouds at night, and the Day Cloud Phase Distinction RGB for doing the same during the day. This feature in AWIPS allows for a transition between the two RGBs within a single loop (Fig 5).

It should be noted that the transition feature can slow AWIPS, particularly if looking over a large area. Finally, feel free to reach out if you’d like the code to do this.

Bill Line, NWS