Date:  March 25, 2017

FROM: 90 North Shore Surfers

TO: Governor Ige, Hawai‘i State Senate, Hawai‘i House of Representatives, Hawai‘i’ PUC, Hawai‘i DBEDT, Mayor Kirk Caldwell, Honolulu City Council, HECO, Senator Brian Schatz, Representative Tulsi Gabbard, Save the Waves Coalition and Other Surf Conservation Partners, and Federal and State Agencies Responsible for Environmental Analysis and Compliance of Wind Farms

CC:  Na Pua Makani Wind Farm, Kahuku Wind Farm, and Kawailoa Wind Farm

Subject:  Please Conserve North Shore Surf: Adverse Wind Farm Effects to Swells and Offshore Surfing Wind Conditions on the North Shore of O‘ahu

Please employ your available means to minimize wind farm harm to North Shore O‘ahu’s surf conditions.  Although our letter addresses adverse effects of wind farms to surf, the social and environmental injustices of BOEM’s proposed Ka‘ena Point (O‘ahu North) and the proposed Na Pua Makani Wind Farm in Kahuku are of even graver concern than effects of those wind farms to surf.  The North Shore’s September 20 to April 20 surf season is internationally-renowned because our tropical waters receive ocean swells 80 percent of days and on 60 percent of those days, wave faces are groomed by offshore, easterly winds.  Large floating wind platforms should not be permitted in North Shore waters (Figure 1) during surf season where they would diffract incoming ocean swells.  Since 2005, engineering literature has documented turbulence in the air and increased ground temperatures extending more than 10 miles downwind from wind turbines; the air disturbances of the proposed, relatively inefficient, turbines far exceeds the relatively small amount of energy the turbine harvests.   Wind turbine wake turbulence is a double-whammy to our offshore wind flow: it disrupts our prevailing east winds, and, by contributing to warmer land temperature, exacerbates development of upslope onshore winds that are extremely detrimental to surf conditions.  To minimize these adverse wake turbulence effects to important offshore winds, any wind turbine situated upwind from a North Shore surf break should be required to shut down when ocean swells are reaching the North Shore (see Figure 1).

Surf_NorthShore with 1000m depth
Figure 1. North Shore O‘ahu areas of ocean swell and wind conservation needs.

Wave Disruption:  In May 2016, the Bureau of Ocean Energy Management (BOEM) concluded North Shore waters are suitable for wind development and in July 2016, they offered “Oahu North” for wind farm lease development (Figure 2).  The offshore wind farm leases under consideration would entail complex floating structures that would diffract waves (Figure 3, See Figure 1).

Figure 2. Ocean areas under consideration for BOEM wind farm development.
diffraction to upload
Figure 3. Large structures in the water would diffract incoming ocean swells.

Wind Farm Disruption of Offshore Winds:  Downwind wake air turbulence of conventional, inefficient, wind turbines results in significant disturbance in downstream winds.  Their air disturbance far exceeds the small amount of energy extracted by the wind turbine (Figures 4 and 5).  Since at least 2005, scientific engineering journals have documented significant changes in wind speed and direction, increased air turbulence, and increases in on-land air temperature extending distances 10 miles and farther downwind from wind farms.

Figure 4. Wake turbulence, far exceeding the relatively small amount of energy harvested from these very inefficient wind turbines, extends more than 10 miles downwind from the wind farm.
Remote Sensing of Environment October 2005 Denmark
Figure 5. Wind speed [meters/second] map based on the ERS-2 satellite. The Horns Rev wind farm, Denmark is indicated (white trapezoid) and a wind wake is seen as dark pixels downstream of the turbines, 25 February 2003, wind direction = 110⁰, wind speed 6.0 meters/second (m/s) (13 mph) (Christiansen and Hasager, Remote Sensing of Environment, October 2005).
Wind Farm Downwind Effects 20 km
The typical length-scale of the wind farm wakes is approximately 20 km (12.4 miles) that is independent of the size of the wind farms as well as background meteorology.” (Baidya, J. of Wind Engineering and Industrial Aerodynamics. In Press).

Offshore winds are important on the North Shore because they groom wave faces, hold wave faces up to allow them to build taller and steeper before they break, and contribute to hollow larger longer barrels.  Onshore winds ruin surf conditions because they result in bumpy wave faces.  The four year-old Kahuku Wind Farm (in full-time operation since February 2014) is disturbing the prevailing east (offshore) winds and increasing the prevalence of onshore winds at Sunset Point surf spots situated 3.4 miles downwind from the wind farm.  Winds from 90⁰, when the wind moves “behind the wind farm”, are inconsistent, less filled-in, gustier, and more onshore when the wind turbines are operating.  When prevailing winds are from 95 and 100 degrees directions Sunset Point winds are normal, unaffected, not “blocked” or disturbed by the Kahuku Wind Farm and cool down-valley air is not affected because wake turbulence stays offshore from surf spots.  Review of data from the Federal, scientific-grade weather station located one mile east (upwind) from the wind farm ( confirms the east (90⁰) winds are still there during periods they’re disturbed at Sunset Point; therefore the degradation of the 90⁰winds at Sunset Point can’t be attributed to natural variability or climate change.  The Kawailoa Wind Farm is having the same direct effect to offshore wind flow at Chuns Reef and Laniakea surf breaks and the double-whammy is the wind farm’s exacerbation of land heating and development of onshore winds.  The proposed Na Pua Makani Wind Farm would be five miles directly upwind from Pipeline (Figure 6), 58% taller than the largest Hawai‘i wind farm, and with each rotor sweeping an area 1.8x (almost 2x) those of the existing Kahuku Wind Farm.  Offshore winds are of critical importance to Pipeline, which is among the most important waves in the world.  When we expressed concern regarding the adverse effects the Na Pua Makani Wind Farm would have to Pipeline’s offshore winds, the wind developer refuted our concerns (March 7, 2017 Pacific Business News).  Since these direct wind farm effects to wind flow and indirect effects to wind direction due to land heating have been documented in the literature since 2005, these adverse effects of Na Pua Makani to Pipeline’s surf conditions would be expected even in the absence of local observations.

NaPuaSurfWind with Waimea
Figure 6. Surf breaks in relation to existing Kahuku Wind Farm and proposed Na Pua Makani Wind Farm wake turbulence and increased air temperature zones under prevailing east, 90⁰, wind.

On March 15, 2017, Sunset Beach Community Association unanimously agreed to ask for a county law requiring wind turbines situated upwind from the Velzyland to Waimea Bay surf breaks (see Figure 6) to feather their blades so the blades are oriented parallel to the wind, not catching the wind, shut down, during the day, when the most recent swell reading on the NOAA Waimea buoy (Station 51201) is 8-feet, 14-seconds or higher.  These are large barrel conditions with wave faces breaking double-overhead, 12-feet (Hawaiian).  These swells occur approximately six percent of year-round hours (day and night).  When daylight and wind direction are accounted for, this North Shore wind farm shut-down for surf winds would affect fewer than three percent of the hours of the year.  To reduce the adverse effect of wind farm wake air turbulence to North Shore surf conditions, it should be illegal, at a bare minimum, for a wind turbine to be operating upwind from a North Shore surf break when these largest, internationally-important, swells occur.  To avoid the adverse effect completely, turbine shutdown would need to extend to swells 4-feet, 11-seconds and larger.

Please don’t allow bulky in-water structures to diffract incoming North Shore swells between September 20 and April 20; please require wind farms upwind from the North Shore’s important surf breaks to shut down when swells are reaching the North Shore; and please discontinue use of North Shore wind farms by utilizing less harmful clean energy alternatives as quickly as possible.  Ua mau ke ea o ka ʻāina i ka pono.

For additional information please contact Carol Philipps, Tamayo Perry, Chris Bruns, Eddie or Makauakai Rothman, Dan Moore, Shane Weldon, or Mike Takahashi via (808) 927-4602 and for wind data, please see

Sincerely [90 North Shore Surfers, Signatures Attached to Hard Copy Letter]