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HAWAII

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HAWAII

Hawai‘i is the only U.S. state located in the tropics. Almost half of the state’s land area is within five miles of the ocean, which provides a moderating effect on the state’s climate. August is the warmest month, with an average temperature of about 78°F, while the coldest month, February, averages around 72°F. Major geographic variations in temperature occur due to the state’s high elevations. For example, at elevations of less than 1,000 feet, winter temperatures rarely fall below 50°F, whereas lows can reach less than 20°F at the peaks of Mauna Kea and Mauna Loa. Hawai‘i is, however, the only state to have never recorded sub-zero Fahrenheit temperatures.

Figure 1

Observed and Projected Temperature Change

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Observed and projected changes (compared to the 1951–1980 average) in near-surface air temperature for Hawai‘i. Observed data are for 1905–2014. Projected changes for 2006–2100 are from global climate models for two possible futures: one in which greenhouse gas emissions continue to increase (higher emissions) and another in which greenhouse gas emissions increase at a slower rate (lower emissions). Temperatures in Hawai‘i (orange line) have risen about 2°F since the beginning of the 20th century. Shading indicates the range of annual temperatures from the set of models. Observed temperatures are generally within the envelope of model simulations of the historical period (gray shading). Historically unprecedented warming is projected during the 21st century. Less warming is expected under a lower emissions future (the coldest years being about as warm as the hottest year in the historical record; green shading) and more warming under a higher emissions future (the hottest years being about 8°F warmer than the hottest year in the historical record; red shading). Source: CICS-NC and NOAA NCEI.

Since 1950, temperatures across the Hawaiian Islands have risen by about 2°F, but the warming has leveled off in the most recent two decades (Figure 1). Temperatures in Honolulu have increased by 2.3°F over this period and have consistently been above the 1951–1980 average since 1975 (Figure 2). Both the number of hot days (days with maximum temperature above 90°F) and number of warm nights (days with minimum temperature above 75°F) have been near to above average since 1980 (Figures 3 and 4). The rate of temperature increase is greatest at high elevations, far exceeding the global average rate of change. The annual number of days below freezing is decreasing over time, as is the diurnal temperature range, largely due to nighttime warming. Historically, temperatures in Hawai‘i have been tightly coupled to the decadal variability of the atmospheric circulation and underlying ocean in the Pacific Basin (known as the Pacific Decadal Oscillation), however, since the 1970s, increasing temperatures are more consistent with an increase in the frequency of the trade wind inversion, and a decrease in trade wind frequency.

Observed Temperature Change

Observed Temperature Change

Figure 2: Observed changes (compared to the 1951–1980 average) in annual near-surface air temperature for four stations in Hawai‘i: Līhu‘e, Kaua‘i (red line), Honolulu, O‘ahu (blue line), Kahului, Maui (yellow line), and Hilo, Island of Hawai‘i (green line). Data are for 1950–2015. Temperatures across the islands have increased since 1950, at rates of between 0.2°F and 0.4°F per decade. Temperatures in Honolulu have increased by 2.3°F over this period and have consistently been above the 1951–1980 average since 1975. Source: CICS-NC and NOAA NCEI.

Observed Number of Hot Days

Observed Number of Hot Days

Figure 3: The observed number of hot days (annual number of days with maximum temperature above 90°F) for 1950–2014, averaged over 5-year periods; these values are averages from seven long-term reporting stations. The number of hot days has increased since the 1950s, being consistently high throughout the 1980s and 1990s. The dark horizontal line is the long-term average (1950–2014) of 6.5 days per year. Source: CICS-NC and NOAA NCEI.

Observed Number of Warm Nights

Observed Number of Warm Nights

Figure 4: The observed number of very warm nights (annual number of days with minimum temperature above 75°F) for 1950–2014, averaged over 5-year periods; these values are averages from seven long-term reporting stations. The number of very warm nights has increased since the 1950s, remaining above the long-term average since the 1980s. The dark horizontal line is the long-term average (1950–2014) of 23.9 days per year. Source: CICS-NC and NOAA NCEI.

Precipitation varies greatly by both season and location. Hawai‘i experiences a drier season from May through October, in which warm, steady trade winds cause frequent light-to-moderate showers, and a wet season from November through April, with weaker and less frequent trade winds and a significant amount of rain from storms. The mountainous terrain, persistent trade winds, heating and cooling of the land, and other factors interact to result in dramatic differences in average rainfall over short distances. Annual total rainfall sometimes exceeds 300 inches along the windward slopes of mountains, but less than 20 inches in leeward coastal areas and the highest mountain slopes. Despite great variability in precipitation amounts across the islands over the past century, annual rainfall has decreased throughout the island chain (Figure 5), particularly during recent years. The Island of Hawai‘i has experienced the largest significant long-term declines in annual and dry season rainfall, with annual total precipitation in Hilo decreasing the most among four major airports: a decrease of almost 20 inches since 1950 (Figure 6). An increase in the frequency of the trade wind inversion is also linked to a decrease in precipitation at high elevations. The number of consecutive dry days across the major Hawaiian Islands has become longer since 1950s. An increase in drought conditions has been seen in recent years, particularly at high elevations. In 2010, more than 40 percent of the Hawaiian Islands experienced severe, extreme, or exceptional drought conditions. Such conditions lead to a lack of useable water and increased risk of fire. On the other side of the coin, the number of extreme precipitation events has been below average in recent years (Figure 7), with areas at the highest elevations experiencing the strongest downward trend. Regionally, extreme rainfall events have become less frequent for O‘ahu and Kauai, but more frequent for the Island of Hawai‘i.

Time Series of HRI Anomalies

Time Series of HRI Anomalies

Figure 5: Time series of Hawaii Rainfall Index (HRI) for 1905–2010 as derived from 27 long-term gauges from Kaua‘i, O‘ahu, and Hawai‘i. This index represents rainfall variations over different climate regions of the Hawaiian Islands. A normalization technique is applied to each individual station, and a regional index is then computed as the arithmetic average of all station indices. The vertical axis is the regional standardized anomalies. Source: Chu and Chen 2005.

Observed Precipitation Change

Observed Precipitation Change

Figure 6: Observed changes (compared to the 1951–1980 average) in annual precipitation for four stations in Hawai‘i: Līhu‘e, Kaua‘i (red line), Honolulu, O‘ahu (blue line), Kahului, Maui (yellow line), and Hilo, Island of Hawai‘i (green line). Data are for 1950–2015. Annual precipitation varies greatly from year to year, however, overall amounts have decreased since 1950 at all four stations. The greatest decrease has been seen in Hilo, where annual precipitation has decreased by almost 20 inches across the period of record. Source: CICS-NC and NOAA NCEI.

Observed Number of Precipitation Events

Observed Number of Precipitation Events

Figure 7: The observed number of days with extreme precipitation events (annual number of days with precipitation greater than 3 inches) for 1950–2014, averaged over 5-year periods; these values are averages from 33 long-term reporting stations. The dark horizontal line represents the long-term average. The number of days with extreme precipitation has been variable over time, with the two most recent decades experiencing a below-average number of events. The dark horizontal line is the long-term average (1950–2014) of 2.6 days per year. Source: CICS-NC and NOAA NCEI.

The North Pacific High, a semi-permanent area of high pressure, has a strong influence on Hawai‘i’s weather. It is responsible for the trade winds which dominate during the dry season. During the wet Hawaiian winter, however, the North Pacific High is diminished, and the middle latitude jet stream shifts southward, providing an occasional opportunity for cool winter storms known as Kona storms. They usually affect the state for a week or more, and occur on average two to three times per year. Kona storms often result in flash flooding (and associated landslides), a common occurrence due to the state’s steep terrain, and the leading cause of direct weather-related deaths in Hawai‘i, far exceeding the toll due to high wind events and tropical cyclones. Kona storms can also produce additional hazards such as hail, heavy mountain snows, waterspouts, and high surf events—the leading cause of indirect weather-related deaths.

Hawai‘i is also susceptible to tropical storms, most often occurring between June and November. Such storms bring heavy rains, high winds, and high waves to the islands. Hurricanes rarely affect the state, with many dissipating into tropical storms or tropical depressions as they approach the islands. Fewer than 40 hurricanes have affected Hawai‘i since 1949, with only a handful making landfall. The number of tropical cyclones formed in the Central North Pacific has been variable over time, with a greater number of tropical cyclones forming during El Niño years. The year 2015 was the most active hurricane season on record in the Central Pacific, with eight hurricanes and six additional tropical storms reported. It is projected that Hawai‘i will see an increase in the frequency of tropical cyclones, due to storm tracks shifting northwards in the Central North Pacific.

Under a higher emissions pathway, historically unprecedented warming is projected by the end of the 21st century (Figure 1). Even under a pathway of lower greenhouse gas emissions, average annual temperatures are projected to most likely exceed historical record levels by the middle of the 21st century. However, there is a large range of temperature increases under both pathways, and under the lower pathway, a few projections are only slightly warmer than historical records. Rising temperatures will cause future heat waves to be more intense. This warming, accompanied by reduced rainfall in some areas, will stress native Pacific Island plants and animals, especially in high-elevation ecosystems with increasing exposure to invasive species, increasing the risk of extinctions. Increasing temperatures, combined with a growing human population and expanding invasive grass cover, are likely to continue the increase in wildfire occurrence that has been observed since the beginning of the 20th century.

Precipitation projections for Hawaii are particularly challenging due to the state’s high and steep topography, which leads to pronounced small-scale variations in climate. Projections of average annual precipitation are uncertain, with one likelihood that Hawai‘i straddles the transition between wetter conditions in the tropics and drier conditions in the subtropics (Figure 8). It is likely that the currently wet windward sides of the major islands will see an increase in rainfall, while the currently dry leeward sides will experience a decrease in rainfall. Future projections regarding both the frequency and magnitude of extreme precipitation events are also uncertain, with some climate models indicating increases and some decreases in heavy rainfall events. Even if average precipitation remains the same, higher temperatures will increase the rate of loss of soil moisture during dry periods, leading to increased intensity of naturally-occurring droughts.

Projected Change in Annual Precipitation

Projected Change in Annual Precipitation

Figure 8: Projected changes in annual precipitation (%) for the middle of the 21st century compared to the late 20th century under a higher emissions pathway. Average annual precipitation is projected to increase slightly across southern parts of the state, with the northernmost islands seeing a decrease in precipitation. These changes are small, however, relative to natural variability in Hawai‘i. Source: CICS-NC, NOAA NCEI, and NEMAC.

Increasing temperatures raise concerns for sea level rise in Hawai‘i. Since 1880, global sea level has risen by about 8 inches. It is projected to rise another 1 to 4 feet by 2100 as a result of both past and future emissions due to human activities (Figure 9). Rates of sea level rise in Hawai‘i vary between the islands, ranging from 0.6 inches per decade for Kaua‘i and O‘ahu to 1.3 inches per decade on the Island of Hawai‘i. Sea level rise across Hawai‘i is projected to rise another 1–3 feet by the end of the 21st century. Sea level rise has caused an increase in tidal floods associated with nuisance-level impacts. Nuisance floods are events in which water levels exceed the local threshold (set by NOAA’s National Weather Service) for minor impacts. These events can damage infrastructure, cause road closures, and overwhelm storm drains. As sea level has risen along the Hawaiian coastline, the number of tidal flood days (all days exceeding the nuisance level threshold) has also increased, with the greatest number occurring in 2002–2003 (Figure 10). Continued sea level rise will present major challenges to Hawai‘i’s coastline, through coastal inundation and erosion. Seventy percent of Hawai‘i’s beaches have already been eroded over the past century, with more than 13 miles of beach completely lost. Sea level rise will also affect Hawai‘i’s coastal water management system and could cause extensive economic damage through ecosystem damage and losses in property, tourism, and agriculture.

 

Past and Projected Changes in Global Sea Level

Past and Projected Changes in Global Sea Level

Figure 9: Estimated, observed, and possible future amounts of global sea level rise from 1800 to 2100, relative to the year 2000. The orange line at right shows the most likely range of 1 to 4 feet by 2100 based on an assessment of scientific studies, which falls within a larger possible range of 0.66 feet to 6.6 feet. Source: Melillo et al. 2014 and Parris et al. 2012.

Observed and Projected Annual Number of Tidal Floods for Honolulu, HI

Observed and Projected Annual Number of Tidal Floods for Honolulu, HI

Figure 10: Number of tidal flood days per year for the observed record (orange bars) and projections for two possible futures: lower emissions (light blue) and higher emissions (dark blue) per calendar year for Honolulu, HI. Sea level rise has caused an increase in tidal floods associated with nuisance-level impacts. Nuisance floods are events in which water levels exceed the local threshold (set by NOAA’s National Weather Service) for minor impacts, such as road closures and overwhelmed storm drains. The greatest number of tidal flood days (all days exceeding the nuisance level threshold) occurred in 2002 and 2003 at Honolulu. Projected increases are large even under a lower emissions pathway. Near the end of the century, under a higher emissions pathway, some models (not shown here) project tidal flooding nearly every day of the year. To see these and other projections under additional emissions pathways, please see the supplemental material on the State Summaries website (https://statesummaries.ncics.org/hi). Source: NOAA NOS.

Lead Authors:
Laura E. Stevens, Rebekah Frankson, Kenneth E. Kunkel, and Pao-Shin Chu
Contributing Authors:
William Sweet
Recommended Citation:
Stevens, L., R. Frankson, K. Kunkel, P-S. Shin, and W. Sweet, 2017: Hawaii State Climate Summary. NOAA Technical Report NESDIS 149-HI, 4 pp.

Resources

  1. Chen, Y.R. and P.-S. Chu, 2014: Trends in precipitation extremes and return levels in the Hawaiian Islands under a changing climate. Int. J. Climatol., 34, 3913–3925.
  2. Chu, P.-S., and H. Chen, 2005: Interannual and interdecadal rainfall variations in the Hawaiian Islands. J. Climate, 18, 4796-4813.
  3. Chu, P.-S., W. Yan, and F. Fujioka, 2002: Fire-climate relationships and long-lead wildfire prediction for Hawaii. Int. J. Wildland Fire, 11, 25-31, http://dx.doi.org/1071/WF01040.
  4. Chu, P.-S., Y.R. Chen, and T.A. Schroeder, 2010: Changes in precipitation extremes in the Hawaiian Islands in a warming climate. J. Climate, 23, 4881-4900.
  5. Diaz, H.F., T.W. Giambelluca, and J.K. Eischeid, 2011: Changes in the vertical profiles of mean temperature and humidity in the Hawaiian Islands. Global and Planetary Change, 77, 21-25, http://dx.doi.org/10.1016/j.gloplacha.2011.02.007.
  6. Elison, T. O., M. Takahashi, T.W. Giambelluca, and H.F. Diaz, 2013: On the relation between large-scale circulation pattern and heavy rain events over the Hawaiian Islands: Recent trends and future changes. J. Geophys. Res., 118, 4129-4141, http://dx.doi.org/10.1002/jgrd.50314.
  7. Fletcher, C.H., B.M. Romine, A.S. Genz, M.M. Barbee, M. Dyer, T.R. Andderson, S.C. Lim, S. Vitousek, C. Bochicchio, and B.M. Richmond, 2012: National Assessment of Shoreline Change: Historical Shoreline Change in the Hawaiian Islands. U.S. Geological Survey Open-File Report 2011–1051, 55 pp. [Available online at http://pubs.usgs.gov/of/2011/1051]
  8. Frazier, A.G., and T.W. Giambelluca, 2016: Spatial trend analysis of Hawaiian rainfall from 1920 to 2012. Int. J. of Climatol. http://dx.doi.org/10.1002/joc.4862.
  9. Garza, J., P.-S. Chu, C. Norton, and T.A. Schroeder, 2012: Changes of the prevailing trade winds over the Islands of Hawaii and the North Pacific. J. Geophys. Res., 117, D11109, http://dx.doi.org/10.1029/2011JD016888.
  10. Giambelluca, T.W., H.F. Diaz, and M.S.A. Luke, 2008: Secular temperature changes in Hawai‘i, Geophys. Res. Lett., 35, L12702.
  11. Giambelluca, T.W., Q. Chen, A.G. Frazier, J.P. Price, Y.-L. Chen, P.-S. Chu, J.K. Eischeid, and D.M. Delparte, 2013: Online rainfall atlas of Hawai‘i. Bull. Am. Meteorol. Soc., 94, 157-160, http://dx.doi.org/10.1175/BAMS-D-11-00228.1.
  12. Keener, V. W., J. J. Marra, M. L. Finucane, D. Spooner, and M. H. Smith, Eds., 2012: Climate Change and Pacific Islands: Indicators and Impacts. Report for the 2012 Pacific Islands Regional Climate Assessment. Island Press, 170 pp.
  13. Keener, V.W., K. Hamilton, S.K. Izuka, K.E. Kunkel, L.E. Stevens, and L. Sun, 2013: Regional Climate Trends and Scenarios for the U.S. National Climate Assessment. Part 8. Climate of the Pacific Islands, NOAA Technical Report NESDIS 142-8, 44 pp. [Available online at https://www.nesdis.noaa.gov/content/technical-reports]
  14. Kruk, M.C., and D.H. Levinson, 2008: Evaluating the impacts of climate change on rainfall extremes for Hawaii and coastal Alaska. Proceedings, 24th Conference on Severe Local Storms, Savannah, GA, 27-31 October, American Meteorological Society.
  15. Leong, J.-A., J. J. Marra, M. L. Finucane, T. Giambelluca, M. Merrifield, S. E. Miller, J. Polovina, E. Shea, M. Burkett, J. Campbell, P. Lefale, F. Lipschultz, L. Loope, D. Spooner, and B. Wang, 2014: Ch. 23: Hawai‘i and U.S. Affiliated Pacific Islands. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, T.C. Richmond, and G.W. Yohe, eds., U.S. Global Change Research Program, 537-556. http://dx.doi.org/10.7930/J0W66HPM.
  16. Li, T., M. Kwon, M. Zhao, J.-S. Kug, J.-J. Luo, and W. Yu, 2010: Global warming shifts Pacific tropical cyclone location. Geophys. Res. Lett., 37, L21804.
  17. Murakami, H., B. Wang, T. Li, and A. Kitoh, 2013: Projected increase in tropical cyclones near Hawaii. Nature Climate Change, 3, 749-754.
  18. NOAA Climate.gov, cited 2016: Drought Grips Hawaii in 2010, National Oceanic and Atmospheric Administration. [Available online at https://www.climate.gov/news-features/videos/drought-grips-hawaii-2010]
  19. NOAA, cited 2016: Climate at a Glance: U.S. Time Series, published May 2016, retrieved on June 3, 2016, National Oceanic and Atmospheric Administration National Centers for Environmental Information. [Available online at http://www.ncdc.noaa.gov/cag/]
  20. NOAA News, cited 2016: Below-normal Atlantic hurricane season ends; active eastern and central Pacific seasons shatter records, National Oceanic and Atmospheric Administration. [Available online at http://www.noaanews.noaa.gov/stories2015/120115-below-normal-atlantic-hurricane-season-ends-active-eastern-and-central-pacific-seasons-shatter-records.html]
  21. NOAA, cited 2016: Flash Floods in Hawaii, National Oceanic and Atmospheric Administration Pacific Region Headquarters. [Available online at http://www.prh.noaa.gov/hnl/pages/weather_hazards_stats.pdf]
  22. NOAA, 2013: Mean Sea Level Trends for Global Network Stations, National Oceanic and Atmospheric Administration Center for Operational Oceanographic Products and Services (CO-OPS). [Available online at http://tidesandcurrents.noaa.gov/sltrends/sltrends_global.shtml]
  23. NOAA, cited 2016: Central Pacific Hurricane Center: Tropical Cyclone Climatology, National Oceanic and Atmospheric Administration. [Available online at http://www.prh.noaa.gov/cphc/pages/FAQ/Climatology.php]
  24. Norton, C.W., P.-S. Chu, and T.A. Schroeder, 2011: Projecting changes in future heavy rainfall events for Oahu, Hawaii: A statistical downscaling approach. J. Geophys. Res., 116, D17110.
  25. Penn State University, cited 2016: Subtropical Cyclones. [Available online at https://courseware.eeducation.psu.edu/public/meteo/subtropical_cyclones.html]
  26. Trauernicht, C, E. Pickett, C.P. Giardina, C.M. Litton, S. Cordell, and A. Beavers, 2015: The contemporary scale and context of wildfire in Hawai'i. Pacific Science, 69, 427-444, http://dx.doi.org/10.2984/69.4.1.
  27. U.S. Fish and Wildlife Service, cited 2016: Climate Change in the Pacific Region. [Available online at http://www.fws.gov/pacific/climatechange/changepi.html]
  28. University of Hawai‘i at MŠnoa Sea Grant College Program, 2014:
    Climate Change Impacts in Hawai‘i - A summary of climate change and its impacts to Hawai‘i’s ecosystems and communities, 36 pp.
  29. Western Regional Climate Center, cited 2016: Climate of Hawaii. [Available online at http://www.wrcc.dri.edu/narratives/HAWAII.htm]
  30. Zhang, C., Y. Wang, K. Hamilton, and A. Lauer, 2016: Dynamical downscaling of the climate for the Hawaiian Islands. Part I: Present day. J. Climate, 29, 3027-3048, http://dx.doi.org/10.1175/JCLI-D-15-0432.1.
  31. Zhang, C., Y. Wang, K. Hamilton, and A. Lauer, 2016: Dynamical downscaling of the climate for the Hawaiian Islands. Part II: Projection for the late 21st century. J. Climate, 29, 3027-3048, http://dx.doi.org/10.1175/JCLI-D-116-0038.1.
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