Custom Meteorological Forecasts and Nowcasts in Support of Astronomical Operations at Mauna Kea in Support of Astronomical Operations at Mauna Kea

The summit of Mauna Kea is arguably the best site in the world for astronomical observations and the capital investment in telescopes on Mauna Kea has exceeded $500 million. The success of astronomical observations on Mauna Kea is strongly influenced by weather conditions. To facilitate the best possible use of good atmospheric conditions and to support operation safety on the mountain top, a new interdisciplinary research program has been initiated that provides custom weather forecasts/nowcasts and data to the Mauna Kea Observatories. The program called Hokukea (Hawaiian for white star) relies heavily on the Unidata software and data stream (http://hokukea.soest.hawaii.edu). Of the thirteen existing telescope facilities on Mauna Kea, seven telescopes have multiple instruments or detectors mounted simultaneously, including the recently dedicated Gemini telescope (NSF’s largest expenditure in astronomy). This permits the observation strategy to be tailored to take best advantage of the weather conditions each night. Temperature, moisture, and wind conditions from the summit upward all strongly impact image quality and even mirror longevity. Additionally, at an altitude of nearly 14,000’ (>4,000 m), the summit of Mauna Kea is subject to hazardous weather events, including blizzard conditions in winter. For these multiple reasons, an accurate weather forecast for Mauna Kea is highly desirable. The new Hokukea program utilizes Unidata software to process and display observational data (surface, satellite, radar, radiosonde, etc.) and the NCEP model output obtained via the Unidata IDD. The Unidata feed is supplemented by model output and satellite data from the NWS Forecast Office, which is collocated, with the Meteorology Department, at the University of Hawaii. High resolution (4 km) GOES-10 infrared satellite data are custom enhanced to differentiate between clouds above and below mountain top and are used in concert with 1 km visible imagery and summit in situ observations to generate custom short term forecasts and nowcasts of environmental variables and atmospheric conditions that impact telescope operations. These variables include seeing parameters, cloudiness, vertical profiles of water vapor, temperature, wind speed and direction, precipitation, pollution dispersion, and others as needs dictate. Additionally, output from the Global Spectral Model (AVN) is used as input for a nested-grid run of a mesoscale NWP model (NCAR/Penn State MM5) with 1 km resolution over Mauna Kea. Forecasts out to 48 hours are issued in a timely fashion daily to be of maximum value to operations at Mauna Kea. Meteorological data and custom products are made available in real-time to the observatories via the Internet using Unidata software and support, and a data archive is being maintained in the Meteorology Department to provide remote access to past data. A research component of the project will endeavor to improve forecast accuracy with time through improved understanding of the atmospheric processes impacting forecast variables.