A long-term plant study records mean spring temperature and first flowering day of year. Use the accompanying scatterplot with these values: 8.5 degrees C: day 128, 9.1: day 123, 9.8: day 119, 10.4: day 113, 11.0: day 109, 11.6: day 104. Which statement best describes the overall trend, pattern, plateau, peak, or periodicity in the data?