Staying Safe During Hawaii’s “Two Seasons”
(The following article courtesy National Weather Service Honolulu Office Website )
Hawaii’s Ocean Awareness Week: October 21st – 25th, 2013
Hawaii Governor Neil Abercrombie’s Proclamation for Ocean Awareness Week
Weather and surf are distinguished by two distinct seasons in Hawaii. The surf seasons generally follow the seasonal changes in the weather pattern across the North-Central Pacific Ocean. The dry season in Hawaii runs from May through September, while the wet season runs from October through April.
During the dry season, long period south swells are most common. These swells are generated by storm systems churning away in the southern hemisphere to the east of Australia and New Zealand. Two distinct zones of storm generation are favorable for south swell development. The most favorable location is in the area just east of New Zealand, while a second less consistent area is located between Australia and New Zealand. The south swells travel nearly 7,000 miles before reaching Hawaii, but still can produce large and dangerous surf.
Trade winds are most consistent during the dry season. In fact, trade wind weather accounts for around 90% of the days during this season. For those planning beach days this means that consistent off-shore winds should be expected for most southern and leeward sides of islands, with the only exception being leeward Big Island. These off-shore winds can be gusty and are enhanced by the terrain of the islands. Unsuspecting boaters, paddlers, swimmers, and surfers stand the chance of being pushed out to sea when the winds are strong.
Large northwest swells are common during the wet season between October and April. These swells are generated by storm systems in the North Pacific Ocean, and are generated much closer to the islands than southern hemisphere swells. This means the magnitude of the surf generated by these swells can be much larger. Each wet season, breaking surf with face heights between 20 to 40 feet or more is common along the north and west facing shores of most islands. Another thing to consider is that because the swell is generated closer to Hawaii, the waves themselves retain much of their energy as they approach the shore. This leads to more powerful and more dangerous waves.
As the swell and breaking waves impact the coast and shoreline, strong and consistent currents develop near shore. These currents sweep unsuspecting swimmers, surfers, and other recreationists away each year. In addition to currents, large breaking waves sometimes push water up onto coastal roadways and impact homes and infrastructure. Each year, tens of thousands of people flock to view the waves during large swell episodes, causing congestion along coastal roadways.
As you plan your visit to the beautiful beaches of Hawaii it is vitally important that you keep up to date with the latest wave and wind forecast. Beach specific information is available from Ocean Safety officials at oceansafety.soest.hawaii.edu, and broad scale weather patterns and surf forecasts are available from the National Weather Service at http://www.weather.gov/hawaii/pages/marine.php.
When surf is elevated and the danger to beach and oceangoers increases, the National Weather Service will issue High Surf Advisories and/or Warnings. Below is the criterion for these products.
It is recommended that you always recreate at beaches where lifeguards are present, and check with them before entering the water. Take a few minutes to watch the waves before you enter the water, and pay close attention to whether infrequent, but larger sets of waves are present. Only visit areas that are within your ability level, and remember, if in doubt…don’t go out.