GeminiFocus April 2019 - Page 21

Figure 4. For Gemini South (upper) and Gemini North (lower) the completion histogram for Semester 2018B. Horizontal axis shows the program completion in 10% bins, and vertically the colored bars show the fraction of programs in Bands 1, 2, and 3, which reached that completion percentage. Main features are described in the text. Credit: Andy Adamson Gemini North Survives Wild Weather Figure 5. The low-pressure system to the north of the Hawaiian Islands, on February 10, 2019, Hawaiian Standard Time. The circulation center is clearly visible in the lower-level cloud pattern (in grey). Image taken from the MKWC satellite archive; go there and select 11-Feb UTC to see animations. As we reported in our recent e-newscast, on February 10, 2019, a low-pressure sys- tem (Figure 5) subjected Maunakea to some of the highest wind speeds ever recorded. While there’s reason to be skeptical of the widely-reported peak gust speed of 191 miles per hour (mph), winds in excess of 150 mph (just below Category 5 Hurricane force) were reliably recorded on the summit on that day (Figure 6; following page). Winds of that speed at this elevation, push- ing on a structure of the scale of the Gem- ini dome, is sufficient to produce a force of around 280 tons sideways. The Gemini tele- April 2019 GeminiFocus 19