A NOTAM at Pensacola International Airport (KPNS) uses the phrase "CIRCLING CATS". What does this phrase mean?
"CIRCLING CATS" refers to a NOTAM element that applies to specific aircraft Categories (A,B,C,D, sometimes E). In the NOTAM (source: KPNS NOTAMs) shown below (Pensacola International Airport - KPNS), note the RNAV (GPS) RWY 8 instrument approach minimums for the circling approach pertaining to categories A/B and C/D.
It appears from this NOTAM that there is a temporary crane west of rwy 8 that has affected the published circling minimums.
KPNS A0519/22 RNAV (GPS) RWY 8, AMDT 2F... LNAV MDA 700/HAT 603 ALL CATS. CIRCLING CATS A/B MDA 700/HAA 579, CATS C/D MDA 860/HAA 739. VIS CAT C 2, CAT D 2 1/4. VDP NA. TEMPORARY CRANE 385FT MSL 1.79 NM WEST OF RWY 08 (2020-ASO-22425-OE). 08 AUG 14:16 2022 UNTIL 14 FEB 14:16 2023 ESTIMATED. CREATED: 08 AUG 14:27 2022
(emphasis is mine)
Below is the KPNS RNAV (GPS) RWY 8 Instrument Approach plate. (SAMPLE ONLY, NOT TO BE USED FOR NAVIGATION!)
A circling approach is one where you line up on one runway for the approach through the clouds, but once you break out of the clouds you circle around and land on a different runway due to winds. This will happen when the runway favored by the winds does not have a published instrument approach procedure.
Aircraft are grouped into different approach categories based on their final approach speed.
I haven't heard the specific term "circling cats" before, generally what you would hear instead is "circling mins". In other words, the minimum altitude you would fly the instrument approach down to before either expecting to see the airport and be able to land, or be expected to execute a missed approach procedure.
The minimum altitude would vary by approach category because a faster aircraft will have a larger turn radius during the circling portion of the approach, therefore they will need to be a bit higher to ensure terrain clearance.
If you happen to find the complete NOTAM please post it, I may be able to give a better answer with some context.