Weather & Climate

Rainfall Atlas of Hawaii

Rainfall Atlas of Hawaii WebsiteThe 2011 Rainfall Atlas of Hawai‘i was developed by the University of Hawai‘i at Manoa (UHM), Department of Geography, as part of an agreement between the Commission on Water Resource Management and the U.S. Army Corps of Engineers, Honolulu District. This project is a major update of the original Rainfall Atlas first published in 1986. The Rainfall Atlas of Hawai‘i is comprised of maps of the spatial patterns of rainfall for the major Hawaiian Islands and represents the best estimates of the mean rainfall for the 30-year base period 1978-2007. The UHM Geography Department has developed an easy-to-use and informative website hosting the Rainfall Atlas report, an interactive map, GIS layers, tabular data, and more.

Rainfall Atlas of Hawai‘i Website

The video below is a presentation by Dr. Thomas Giambelluca, Professor of Geography at the University of Hawaii Manoa, discussing the methodology and findings of the investigation that went into developing the 2011 Rainfall Atlas of Hawaii.


The original 1986 Rainfall Atlas of Hawaii was also developed by Dr. Thomas Giambelluca, et al. with support from the Department of Land and Natural Resources, Division of Water and Land Development. The 1986 Atlas has served as the rainfall standard for the past 25 years.

Report R76, Rainfall Atlas of Hawaii, June 1986 [17.7 MB]

Estimation of Evapotranspiration in Hawaii

Waikamoi, MauiIn order to better estimate ground and surface water availability, a comprehensive assessment of evapotranspiration (ET) in Hawaii is needed. To fulfill this need, the Commission is partnering with the U.S. Army Corps of Engineers and the University of Hawaii to conduct the first comprehensive analysis of ET for Hawaii. Evapotranspiration is the combined loss of water from the land surface through the process of evaporation and plant transpiration. In this project, remote sensing data from satellites will be used to estimate net radiation, air temperature, relative humidity and wind speed. These elements will be combined to produce unprecedented digital maps of estimated mean monthly and annual evapotranspiration. The project is expected to be completed in mid-2013 producing a suite of maps of potential and actual ET estimates for each major island in the State.

The video below is a presentation by Dr. Thomas Giambelluca, Professor of Geography at the University of Hawaii Manoa, discussing the status of a current project to establish evapotranspiration rates in the State of Hawaii. Dr. Giambelluca is the principal investigator on this joint effort between the Commission and the U.S. Army Corps of Engineers.


Other Evapotranspiration Resources

USGS Scientific Investigations Report 2008-5163, The Significance of Accounting Order for Evapotranspiration and Recharge in Monthly and Daily Threshold-Type Water Budgets, Delwyn S. Oki.

Report R74, Pan Evaporation: State of Hawaii, 1894-1983 [10.3 MB]

Climate Change in Hawaii

Center for Island Climate Adaptation & PolicyClimate is defined as the long-term average of weather conditions such as temperature, precipitation, and cloudiness. Long-term trends in these weather elements are used as an indication of climate change. While causes of climate change have been linked to human activities, mainly the increase in carbon dioxide due to the burning of fossil fuels, some climate change can also be attributed to natural causes. Global climate change can affect precipitation patterns, ocean temperatures, and sea levels, and in turn impact human health, agriculture, forests, water resources, coastal areas, freshwater ecosystems, coral reefs, species diversity, and natural areas. Consequently, potential impacts to Hawaii’s surface and ground water resources due to global climate change need to be considered when planning for water resource protection in Hawaii.

UH Sea Grant’s Center for Island Climate Adaptation & Policy Website

The video below is a presentation by Richard Wallsgrove, who works with the Center for Island Climate Adaptation & Policy. He is the co-author of the report entitled “Water Resources and Climate Change in Hawaii: Adaptive Tools in the Current Law and Policy Framework” (link to report below).


Water Resources and Climate Change Adaptation in Hawai’i: Adaptive Tools in the Current Law and Policy Framework [2.7 MB]

Weather Resources on the Web

Many gonvernment agencies and educational institutions, often in collaboration, collect, analyze, and disseminate weather and climate information. Listed below are a few internet resources that will aid in learning more about Hawaii’s climate and weather.

National Weather Service Honolulu

National Weather Service Honolulu Climate Page

Western Regional Climate Center

National Integrated Drought Information System

U.S. Drought Monitor

U.S. Seasonal Drought Outlook