F/Sgt Stanley Spallin - 961 Barrage Balloon Diary

[Neil T.]

On Nov. 5, 1942, F/Sgt Stanley Spallin of 609 Squadron was killed when he flew his Typhoon into a barrage balloon moored above Dover Harbour during rainy weather. The Diary for 961 Barrage Balloon Squadron based at Dover contains the following entry for Nov. 5, 1942:
"Operational. 0.48 Fly Cats and Dogs 2500 ft. ROH 2500 ft. 18.23 Cats and Dogs 4500 ft. ROH 4500 ft.
Weather. Moderate winds, low cloud throughout day with almost continuous rain.
Balloon Casualties. Site 21. Breakaway Cable impact.
General. Typhoon A/C struck cable of Site 21 at approx. 1203 hours. A/C crashed into sea off breakwater. No trace of survivors."

The entry is straightforward but I do not understand the reference to "Fly Cats and Dogs" or "ROH". I'm assuming ROH might refer to something like 'regular operating height' but I don't know what is meant by Cats and Dogs - is it a reference to different types of balloons? I'd appreciate it if one of the forum members could explain the reference for me.

Thanks, Neil.