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Hawai'i Sea Level
Elevated water levels and potential flooding expected this summer 2017
The Hawai‘i Sea Grant Center for Coastal and Climate Science and Resilience (Hawai‘i Sea Grant CCSR), University of Hawai‘i Sea Level Center (UHSLC), and Pacific Islands Ocean Observing System (PacIOOS) together at the University of Hawai‘i have been tracking unusual high tide levels and are advising that the State will likely continue to experience unusually high tide levels through the summer.
Data from NOAA tide stations around Hawaiʻi show that observed water levels have been 3–6 inches above predicted tidal heights since early 2016. In late April, levels peaked at more than 9 inches above predicted tides at the Honolulu Harbor tide gauge, resulting in the highest daily mean water level ever observed over the 112-year record. The combination of elevated water levels, seasonally high tides, and a large south shore surf event resulted in flooding on April 28, 2017.
Ocean models generated by the UHSLC indicate that elevated water levels are likely to persist through the summer. Record high water levels are expected around the upcoming highest astronomic tides of the year, known as “king tides,” occurring over a few days around the new moons on May 25-26, June 23-24, and July 21-22 in Hawai‘i. Actual water levels along exposed coasts will largely depend on wave heights during the high tides.
Figure: Plot showing highest ever daily water level recorded in Honolulu, April 28, 2017. The blue line represents predicted tide heights and green actual tide heights (NOAA Center for Operational Oceanographic Products and Services).
Why do we have elevated water levels?
- Unusual combination of:
- Pacific-wide variability associated with the Pacific Decadal Oscillation and El Nino
- Ocean eddies with high centers moving through the islands
- Global sea-level rise due to climate change
- Further exacerbated by:
- Highest high tides of the year (‘king tides’) around May 26, June 23, and July 21.
- Wave action including potential swells or storm surge
NASA Satellite image of high ocean levels in the Central Pacific. Red shading indicates higher than usual water levels in mm above the long-term average. Ocean Surface Topography From Space, NASA’s Jet Propulsion Laboratory, Latest El Niño/La Niña Watch Data https://sealevel.jpl.nasa.gov/science/elninopdo/latestdata/
How long is this expected to last?
- Model forecasts and satellite observations from the UH Sea Level Center and National Oceanic and Atmospheric Administration (NOAA) show water levels continuing through the the summer of 2017.
- The greatest potential for flooding is around the highest high tides of the year, known as “king tides,” for a couple days around the new moons on May 26, June 23, and July 21.
What are the potential impacts?
Localized impacts may include:
- Coastal erosion
- Wave over-wash
- Temporary nuisance flooding in low-lying areas and around storm drain systems.
Impacts may be more severe if the upcoming king tides coincide with an elevated surf event, which occur most often on south and east-exposed coasts this time of year,and/or during heavy rains.
How can the community prepare and respond?
- The Hawai‘i Sea Grant CCSR is asking residents to help document high water levels and related impacts through the Hawai‘i and Pacific Islands King Tides “citizen science” project by submitting photos online through the program’s smartphone app or website.
- Check the PacIOOS' Six-Day High Sea Level and Wave Run-up Forecasts on a regular basis to be prepared for impacts from higher than normal sea levels and potential wave run-up.
- Consider removing electronics, vehicles or other valuables from basements or low lying areas if you are at a low elevation or near the coast.
- Secure boats in anticipation of higher than usual water levels as needed.
- Coastal drainage issues may occur related to high water levels, especially if it rains.
- Property owners who have faced flooding and erosion problems in the past, particularly those on south and windward shores, should anticipate impacts similar to those experienced during the high tides of late April.
- Boaters and ocean recreationalists such as paddlers and fishers may experience unusual water levels and currents in addition to navigation hazards associated with the increased water levels.
For more information please contact: (808) 956-3013
For media inquiries, please contact Cindy Knapman: (808) 956-7410
Read more at University of Hawaii News
- NOAA Tide Gauges- View predicted and observed water heights from more than 30 NOAA tide gauges around the Hawaiian Islands.
- Hawaii Sea Grant Pacific Islands King Tides Project- Learn how you can help document high water impacts on local shorelines and contribute to efforts to better understand and prepare for rising sea levels.
- PacIOOS Wave Run-up Forecast- View the predicted height for the highest waves along the shoreline for the next six days.
- PacIOOS Six-Day High Sea Level Forecast- View the predicted sea level height for various locations in the State of Hawai‘i for the next six days.
- University of Hawaii Sea Level Center- Learn more about global sea level trends and access data on recent sea level observations from satellites and a global network of tide gauge stations.
- National Weather Service- Surf Forecast- Latest surf forecast for the Hawaiian Islands
- NOAA Sea Level Rise Viewer- Visualize the potential local impacts of sea level rise (up to 6 feet above average high tides) using this interactive mapping tool.
- NASA’s El Niño/La Niña Watch Data, 17 Apr 2017- Monthly sea level observations from satellites.