The ERA5 database is comparable to the SEAFINE database in terms of data length, temporal resolution and spatial resolution for extreme significant wave height analysis. The extreme value analysis from the SEAFINE database is approximately 33% to 200% higher than ERA5 for a 1-yearly return period and 25% to 100% higher for a 100-yearly return period in most western and central Indonesian seas. The developed extreme significant wave height maps based on SEAFINE and factored ERA5 analysis results showed a good fit between both databases.  Field measurements are required to further verify the analysis results.

The SEAFINE-based extreme significant wave height ranges from 4.5 to 5.5 m near the northern part of Natuna island for a 1-year return period and is approximately doubled for a 100-year return period. In the Indonesian inner seas such as the Java Sea, the significant wave height ranges from 0.5 to 2.5 m for a 1-year return period and 1.5 to 5.0 m for a 100-year return period. The SEAFINE-based 1-year and 100-year extreme significant wave heights are approximately 25% lower than that from ISO in intersecting regions.