When Is Tsunami Season In Hawaii?

Hawaii’s tropical location in the Pacific Ocean unfortunately leaves it vulnerable to the threat of tsunamis. If you’re planning a trip to the Hawaiian islands, you may be wondering what time of year is most at risk for destructive tsunami waves.

If you’re short on time, here’s a quick answer to your question: While tsunamis can strike Hawaii at any time, the official tsunami season recognized by NOAA is from October through April when seismic activity is highest in the Pacific Basin near Hawaii.

In this comprehensive guide, we will cover key details around tsunami risks in Hawaii including typical seasons, historical records, geographic factors, current warning systems, and preparedness tips for visitors.

Tsunami Seasons in Hawaii

Official Tsunami Season (October to April)

The official tsunami season in Hawaii runs from October through April each year. This period coincides with hurricane season in the Pacific and sees an increased threat of tsunamis triggered by seismic activity.

According to the National Weather Service, nearly 90% of tsunamis affecting Hawaii occur during this 6 month period.

The most common causes of tsunamis in Hawaii during official tsunami season are:

• Distant earthquakes – 90% of tsunamis affecting Hawaii are triggered by earthquakes at distances greater than 1000 miles away.
• Seismic activity along the Aleutian Islands arc in Alaska.
• Seafloor displacement following major storms and hurricanes in the Pacific.

October through April is considered the prime time for earthquakes in the Pacific region that can generate deadly tsunamis. Though the odds of a large tsunami making landfall in Hawaii may be low, residents must stay prepared as even small wave surges can be dangerous.

Summer Months Also Pose Some Threat

While tsunami risk drops off during summer, Hawaii isn’t entirely free from the threat. Around 10% of recorded tsunamis have occurred between May and September.

Potential summer tsunami triggers include:

• Seismic activity off the western coast of Mexico and Central America.
• Volcanic eruptions and earthquakes across the vast Pacific Ocean seafloor.
• Hurricanes that take erratic paths closer to Hawaii.

The chance may be lower, but Hawaii residents must stay prepared year-round. Having emergency kits and knowing evacuation routes reduces injury risk if any tsunami occurs.

Historical Tsunami Impacts in Hawaii

1946 April Fools Day Tsunami

On April 1, 1946, a magnitude 8.6 earthquake off the Aleutian Islands in Alaska generated a devastating tsunami that slammed into Hilo, Hawaii. This tsunami, sometimes called the April Fools Day tsunami, killed 173 people, made 1,800 homes uninhabitable, and caused $26 million (equivalent to $376 million in 2023) in damage in Hilo alone – making it one of Hawaii’s worst natural disasters.

The waves reached up to 55 feet high and destroyed Hilo’s downtown area. As the water rapidly retreated after the first wave, many residents went to the shore to investigate. This led to many people being swept away by the second incoming wave which was even larger.

Some incredibly sad stories emerged, like the iconic photo of a clock stopped at the exact time the tsunami hit – 1:04 AM.

1960 Chilean Tsunami

On May 23, 1960, a magnitude 9.5 earthquake off the coast of Chile generated a Pacific-wide tsunami. In Hilo, the waves reached 35 feet high, destroying buildings and infrastructure. Although the death toll was lower than the 1946 tsunami, at 61 people, the tsunami caused around $23 million (equivalent to $204 million in 2023) in damage.

Notably, this was the largest earthquake ever recorded and remains in the top three most powerful quakes. It unleashed extreme shaking and devastation along Chile’s coast and the ensuing tsunami traveled not only across the Pacific but also to as far away as Japan and even California.

Scientists credit improvements to Hilo’s warning system and protective seawall for preventing more loss of life compared to 1946.

2011 Tohoku Tsunami

On March 11, 2011, a magnitude 9.1 earthquake occurred off the Pacific coast of Tohoku, Japan. It triggered powerful tsunami waves throughout the Pacific, including in Hawaii where waves flooded low-lying areas and caused an estimated $30 million in damage to harbors and marinas.

While less damaging than previous tsunamis, the Tohoku event served as another reminder about tsunami risks even from distant seismic events. It also spurred more improvements to Hawaii’s warning systems.

New solar-powered sirens were installed in remote areas and protocols updated to include more channels like social media alerts.

Geographic Factors Influencing Hawaii’s Tsunami Risk

Location Along the Pacific Ring of Fire

Hawaii’s location makes it vulnerable to tsunamis triggered by earthquakes and volcanic eruptions. The islands sit along the Pacific Ring of Fire, an area encircling the Pacific Ocean characterized by active volcanoes and frequent seismic activity.

Over 90% of the world’s earthquakes occur in this zone.

Powerful magnitude 8+ earthquakes in the Ring of Fire often disturb the ocean floor, generating dangerous tsunami waves. Since Hawaii protrudes up from the seafloor hotspot, waves emitted from seismic activity can easily reach and impact the islands’ shores.

Proximity to Seismically Active Deep Ocean Trenches

In addition to the Ring of Fire, Hawaii lies near multiple oceanic trenches with shifting tectonic plates. These include the Aleutian Trench (7,679 km away) and the closest, the Peru-Chile Trench (6,736 km away).

The 2011 Tōhoku earthquake in Japan demonstrated how tsunamis can travel great distances across the Pacific. This magnitude 9.1 event created waves over 130 feet high, causing significant damage in Hawaii after crossing over 6,800 miles of ocean.

With deep sea trenches on both sides, Hawaii remains vulnerable to far-field tsunamis originating well beyond the Ring of Fire zone. According to the National Weather Service, roughly 80% of destructive tsunamis affecting Hawaii are generated from distant earthquakes.

Hawaii’s Tsunami Monitoring and Warning Systems

Pacific Tsunami Warning Center

The Pacific Tsunami Warning Center (PTWC) in Ewa Beach on Oahu monitors seismic activity and sea level throughout the Pacific Ocean to detect potential tsunamis. They use a network of seismic stations, sea level gauges, and DART (Deep Ocean Assessment and Reporting of Tsunamis) buoys that provide real-time water level data.

The PTWC issues warnings and advisories for Hawaii and other locations when a possible tsunami threat is detected.

Emergency Sirens and Wireless Alerts

If the PTWC issues a tsunami warning, Hawaii has an extensive emergency siren system that will sound to alert coastal residents. The sirens are tested on the first working day of each month. The state also utilizes the Federal Emergency Management Agency’s Wireless Emergency Alert system, which sends warnings directly to mobile devices in affected areas.

Tsunami Signs and Evacuation Routes

Clearly marked tsunami evacuation route signs point inland and to higher ground from low-lying coastal areas. Residents and visitors should learn the nearest evacuation route in their area before a tsunami watch or warning is issued.

Maps of evacuation zones can usually be found through local emergency management agency websites. Being prepared and knowing where to go can save critical minutes during a life-threatening emergency situation.

How to Prepare for Tsunamis in Hawaii

Know Evacuation Zones and Emergency Plans

Living in Hawaii means the possibility of tsunamis is always present. According to the Pacific Tsunami Warning Center (PTWC), Hawaii has experienced over 70 tsunamis in the past 182 years, with nearly one-third causing significant damage.

Being prepared can save lives, so know your tsunami evacuation zones ahead of time.

Evacuation zone maps are available through local emergency management agencies. Determine if your home, school, workplace or frequently visited spots fall into inundation areas. Make an emergency plan with family members about where to meet if separated during a tsunami warning.

Prepare Emergency Supplies and Go Bags

Assemble disaster supply kits with essential items for each member of your family. Useful products include first aid supplies, flashlights, batteries, cash, copies of ID documents, extra medication and nonperishable foods.

Also prepare portable “go bags” that are easy to grab if you need to evacuate quickly.

Hawaii emergency management advises each person’s kit should contain at least 14 gallons of water, rated to last 14 days. Be sure to update kits every six months as needs change. Premade emergency bags with some basics can also be purchased online or in stores.

Sign Up For Warning Alerts and Stay Informed

The PTWC monitors earthquakes and sea level activity 24/7, issuing warnings to emergency officials if a tsunami poses a threat. Residents should sign-up for community warning systems so alerts are received promptly across multiple channels.

Options range from SMS text alerts to Wireless Emergency Alerts directly to mobile phones. Stay tuned to local news for official updates and guidance during emergencies. Social media can also provide useful real-time information, but rumors spread quickly too, so verify anything read online through trusted organizations.

Conclusion

Tsunamis remain an ever-present threat for the Hawaiian islands given surrounding seismic hazards. By understanding typical seasons, past events, warning systems, and preparedness steps, residents and visitors can help minimize risks.

While tsunamis can occur at any time of year, be especially vigilant during recognized seasons from October to April. But also stay alert in summer when many tourists visit Hawaii. Following safety tips and any evacuation orders is key to saving lives in the event of a tsunami.

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