B737 flight crew reported receiving a GPWS terrain alert on approach to mkjs.

Attributes
ACN	1590405
Time
Date	201810
Local Time Of Day	1801-2400
Place
Locale Reference	MKJS.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737 Next Generation Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument
Events
Anomaly	Deviation - Track / Heading All Types Inflight Event / Encounter CFTT / CFIT

Narrative:

Lenar 4 arrival for ILS DME runway 07. Cleared to omaxi descending to 3;000 ft. Cleared for the approach. Intercepted omaxi on LNAV and selected 1;800 ft for anapa crossing. Selected localizer as we crossed omaxi (waited until between sia 278 and 218 radials per note on 10-7B-1). Received a warning caution terrain. Disconnected autopilot and verified aircraft position. We were slightly north (left) of localizer and above 1;800 feet for anapa crossing. Continued to hand fly a visual approach; intercepted glide slope at anapa and landed runway 07. We are unsure why we received a warning when we were at proper altitudes and north of localizer which should have kept clear of all terrain.

Original NASA ASRS Text

Title: B737 flight crew reported receiving a GPWS terrain alert on approach to MKJS.

Narrative: LENAR 4 Arrival for ILS DME RWY 07. Cleared to OMAXI descending to 3;000 FT. Cleared for the approach. Intercepted OMAXI on LNAV and selected 1;800 FT for ANAPA crossing. Selected LOC as we crossed OMAXI (waited until between SIA 278 and 218 radials per note on 10-7B-1). Received a warning CAUTION TERRAIN. Disconnected autopilot and verified aircraft position. We were slightly north (left) of localizer and above 1;800 feet for ANAPA crossing. Continued to hand fly a visual approach; intercepted glide slope at ANAPA and landed RWY 07. We are unsure why we received a warning when we were at proper altitudes and north of localizer which should have kept clear of all terrain.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.