See this site for some locations on Oahu. It’s where they count the whales.
Here are the results from each location by date
From https://hawaiihumpbackwhale.noaa.gov/about/welcome.html
The Hawaiian Islands Humpback Whale National Marine Sanctuary was created by Congress in 1992 to protect humpback whales and their habitat in Hawai`i. The sanctuary, which lies within the shallow (less than 600 feet), warm waters surrounding the main Hawaiian Islands, constitutes one of the world's most important humpback whale habitats.
Through education, outreach, research and resource protection activities, the sanctuary strives to protect humpback whales and their habitat in Hawai`i.
From https://hawaiihumpbackwhale.noaa.gov/involved/ocwelcome.html
The Sanctuary Ocean Count project offers the community a chance to monitor humpback whales from the shores of Oʻahu, Hawaiʻi and Kauaʻi. The count is held the last Saturday of January, February, and March (during peak whale season) of each year from 8:00 a.m. to 12:15 p.m.
The 2020 Ocean Counts are scheduled for the following Saturdays: January 25, February 29, and March 28, 2020. Registration for 2020 can be found at https://oceancount.org/
Not only has this proven to be a fun volunteer activity for residents and visitors, but it also helps to provide important information on humpback whales around the Hawaiian Islands.
NOTE: Maui has a separate organization that runs their count
https://www.pacificwhale.org/research/great-whale-count/