Wave Run-Up Forecast : Waikīkī, Oʻahu

ForecastAboutExamplesDetails

Attention: The forecast is not accurate when a tsunami, tropical storm or cyclone watch/warning is in effect. For these events, please seek information for either tsunamis or tropical storms/hurricanes. In case of a possible inundation event, please consult with local authorities and emergency responders to seek further information and direction.

SLpred graphic for Waikiki

The Solid Dark Blue Curve and Solid Cyan Curve display the Observed and Forecast Sea Level near Honolulu Harbor for the previous 3 days and the next 6 days, respectively, relative to Mean Low Low Water (MLLW, a typical NOAA datum).

The Dotted Dark Blue Curve shows the estimated maximum height reached by waves along the shore at Waikīkī for the previous 3 days, relative to MLLW. The Dotted Cyan Curve shows the forecast height for the highest waves along the shore at Waikīkī for the next 6 days, relative to MLLW.

If the forecast height expected for the highest waves exceeds the red line it is likely that the entire width of the beach will be periodically swept by waves at many locations along Waikīkī.

The PacIOOS Wave Run-Up Forecast is a tool to predict the potential occurrence of high sea levels and wave inundation impacting the shorelines of Waikīkī. Storm events, high waves, extreme tides, or a combination of these factors can lead to potential inundation.

The tool was developed to increase community resilience and enhance preparedness by providing decision-makers, agency representatives, hospitality industry, and community members with time to plan in advance of potential flooding events. The forecast is updated hourly and dates and times are shown in local time.

The PacIOOS Wave Run-Up Forecast does not serve as a warning system. In case of a possible inundation event, please consult with local authorities and emergency responders to seek further information and direction. A similar forecast is also available for Oʻahuʻs North Shore.

Contact

For more information, please contact Martin Guiles. The Wave Run-Up Forecast Tool was developed by M. Guiles, D. Luther, and M. Merrifield within the Department of Oceanography in the School of Ocean and Earth Science and Technology (SOEST) at the University of Hawaiʻi at Mānoa.

Shown below is an example of a very high wave run-up event at Waikīkī Beach in June, 2016.

Example of Waikiki Run-up 2016 Example of Waikiki Run-up 2016

Very high wave run-up at Fort DeRussy, Waikīkī, on June 5, 2016.
Photo Credit: HI Sea Grant King Tides Project.

Shown below is an example of a very high wave run-up event at Waikīkī Beach in July, 2009.

Example of Waikiki Run-up 2009 Example of Waikiki Run-up 2009

Very high wave run-up in front of the Sheraton Surfrider Hotel in the afternoon of July 22, 2009.
Photo Credit: Chris Conger, University of Hawaiʻi Sea Grant Program.

Description of Waikīkī Wave Run-Up Forecast

SLpred graphic for Waikiki

The Solid Dark Blue Curve and Solid Cyan Curve display the Observed and Forecast Sea Level at Honolulu Harbor (Pier 4) for the previous 3 days and the next 6 days, respectively, relative to Mean Low Low Water (MLLW, a typical NOAA datum). This tidal sea level variation and forecast captures most of the slowly changing sea level (without taking short period wind and swell waves into consideration) within 5 miles of Honolulu Harbor. The forecast is updated every 4 hours. Read more details about the components of the Observed and Forecast Sea Level.

The Dotted Dark Blue Curve shows the estimated maximum height reached by waves along the shore at Waikīkī (northeast of Waimea Bay) for the previous 3 days, relative to MLLW. The Dotted Cyan Curve shows the forecast height for the highest waves along the shore at Waikīkī for the next 6 days, relative to MLLW. These heights are equal to the Observed/Forecast Sea Level plus the Estimated/Forecast Wave Run-Up Height described below (estimated Black Dots; forecast Gray Dots).

If the forecast height expected for the highest waves exceeds the red line it is likely that the entire width of the beach will be periodically swept by waves at many locations along Waikīkī.

 

Components of Waikīkī Wave Run-Up Forecast

Off-Shore Wave Height and On-Shore Wave Run-Up Height for Waikiki

The Black Dots display the Estimated Wave Run-Up Height for the previous 3 days, measured relative to the Observed Sea Level described above. The Wave Run-Up Height is a simple, empirically-determined function of the three quantities plotted in the bottom plot and described below. All three quantities are estimated from the observed sea and swell Off-Shore Gravity Wave Height, shown as the Dark Violet Line in the above plot (note that the mean value of all—estimated plus forecast—gravity wave heights has been subtracted from the wave height variables in this plot to simplify the plot). Forecast and observed gravity wave height (denoted Hs) is the mean of the largest 1/3 waves recorded during the sample period.

The Gray Dots display the Forecast Wave Run-Up Height for the next 6 days, relative to the Forecast Sea Level described above. The Forecast Wave Run-Up Height is a simple, empirically-determined function of the three forecast quantities plotted in the bottom plot and described below. All three quantities are forecast from the sea and swell Forecast Off-Shore Gravity Wave Height, shown as the Light Violet Line in the above plot (note that the mean value of all—estimated plus forecast—gravity wave heights has been subtracted from the wave height variables in this plot to simplify the plot).

Inputs to the Calculation of the On-Shore Wave Run-Up Height

This plot displays estimates and forecasts of the three quantities that determine the Estimated and Forecast Wave Run-Up Heights shown in the previous plot. The estimated quantities are based on empirical formulas applied to the observed Off-Shore Gravity Wave Height for the previous 3 days, while the forecast quantities are based on these same formulas applied to the Forecast Off-Shore Gravity Wave Height for the next 6 days.

Dark Red (Pink) Dots – Estimated (forecast) sea level “set-up,” which we will call SU.

Dark Orange (Light Orange) Dots – Estimated (forecast) maximum short-period (2-30 seconds) gravity wave swash height, which we will call SGW.

Dark Green (Light Green) Dots – Estimated (forecast) long-period (2-20 minute) gravity wave height, which we will call LGW.

Given these quantities, the estimated and forecast wave run-up heights are calculated as follows.

Estimated Wave Run-Up Height equals

1.2 x ( SU + 0.5 x sqrt( LGW^2 + SGW^2 ) )

Forecast Wave Run-Up Height equals

1.2 x ( SU + 0.5 x sqrt( LGW^2 + SGW^2 ) )