TABLE 4 ESTIMATES OF 13-MONTH SMOOTH SOLAR ACTIVITY FOR BALANCE OF CYCLE 24 WITH A MEAN CYCLE GIVEN FOR CYCLE 25 TIME SUNSPOT NUMBERS GEOMAGNETIC INDEX (Ap) PERCENTILE PERCENTILE 95.0% 50% 5.0% 95.0% 50% 5.0% 2018.2503 APR 10.8 9.1 6.5 8.5 7.8 6.9 2018.3337 MAY 11.1 8.3 3.5 9.1 8.0 6.1 2018.4170 JUN 11.8 7.9 1.9 9.6 8.2 5.8 2018.5003 JUL 12.4 7.5 0.5 10.2 8.4 6.1 2018.5837 AUG 12.6 6.8 0.9 10.7 8.5 6.0 2018.6670 SEP 13.5 6.4 0.3 11.2 8.4 6.0 2018.7503 OCT 14.7 6.2 0.0 11.4 8.5 6.4 2018.8337 NOV 15.8 6.5 0.0 11.5 8.5 6.8 2018.9170 DEC 15.6 6.5 0.0 11.5 8.5 6.7 2019.0003 JAN 14.9 6.1 0.0 11.0 8.4 6.5 2019.0837 FEB 14.7 5.5 0.0 10.4 8.4 6.5 2019.1670 MAR 15.0 5.1 0.0 10.4 8.5 6.5 2019.2503 APR 15.9 4.9 0.0 10.5 8.5 6.4 2019.3337 MAY 16.5 4.7 0.0 10.6 8.5 6.3 2019.4170 JUN 16.8 4.7 0.0 10.0 8.2 6.1 2019.5003 JUL 16.4 4.7 0.0 9.6 7.7 5.6 2019.5837 AUG 14.7 4.5 0.0 9.1 7.5 5.3 2019.6670 SEP 13.0 4.2 0.0 9.4 7.6 5.1 2019.7503 OCT 12.1 3.8 0.0 9.3 7.6 5.2 2019.8337 NOV 10.5 3.4 0.0 9.0 7.6 5.1 2019.9170 DEC 10.5 3.4 0.0 9.0 7.6 5.1 2020.0003 JAN 11.5 4.1 0.7 9.2 7.7 5.1 2020.0837 FEB 13.4 5.1 1.4 9.5 7.8 5.3 2020.1670 MAR 15.1 6.2 2.0 9.6 7.9 5.6 2020.2503 APR 17.7 7.2 2.8 9.8 8.0 5.7 2020.3337 MAY 20.6 8.5 3.2 9.9 8.1 5.7 2020.4170 JUN 25.4 10.0 3.9 10.0 8.2 5.5 2020.5003 JUL 29.0 11.6 5.0 10.1 8.3 5.4 2020.5837 AUG 32.7 13.3 5.4 10.5 8.5 5.3 2020.6670 SEP 38.3 15.4 5.5 10.8 8.8 5.2 2020.7503 OCT 45.4 17.7 5.8 11.2 9.1 5.4 2020.8337 NOV 55.9 20.6 5.7 11.7 9.5 5.8 2020.9170 DEC 64.9 23.9 5.9 12.5 9.8 6.0 2021.0003 JAN 71.9 27.1 7.0 13.6 10.0 5.9 2021.0837 FEB 82.1 30.8 7.1 14.1 10.3 5.9 2021.1670 MAR 93.4 34.8 7.1 14.3 10.4 5.8 2021.2503 APR 103.5 38.8 7.9 14.8 10.6 5.7 2021.3337 MAY 115.9 43.1 8.0 15.9 10.9 5.8 2021.4170 JUN 130.5 48.2 8.6 16.9 11.2 5.9 2021.5003 JUL 140.7 53.4 9.7 17.1 11.3 5.9 2021.5837 AUG 147.6 58.9 11.4 17.2 11.5 6.0 2021.6670 SEP 154.7 64.4 12.9 17.0 11.7 5.9 2021.7503 OCT 162.6 69.8 15.1 16.6 11.8 5.9 2021.8337 NOV 171.3 75.0 16.4 16.4 11.8 6.0 2021.9170 DEC 180.7 80.3 16.5 16.9 12.0 6.2 2022.0003 JAN 189.5 86.0 18.7 16.7 12.1 6.4 2022.0837 FEB 197.1 91.8 20.6 15.8 12.1 6.7 2022.1670 MAR 205.1 97.7 22.3 15.9 12.4 6.8 2022.2503 APR 209.9 103.4 24.2 16.4 12.5 6.9 2022.3337 MAY 216.4 108.9 25.1 17.0 12.8 7.2 2022.4170 JUN 217.8 113.7 26.1 17.5 13.2 7.6 2022.5003 JUL 218.3 118.3 27.1 18.2 13.6 7.8 2022.5837 AUG 223.6 122.2 27.8 18.2 13.7 7.8 2022.6670 SEP 226.1 125.5 28.5 18.2 13.7 8.0 2022.7503 OCT 228.6 129.2 28.5 18.4 13.8 8.2 2022.8337 NOV 231.8 132.9 27.9 18.7 14.0 8.7 2022.9170 DEC 234.2 136.7 27.3 19.1 14.0 9.3 2023.0003 JAN 240.6 140.1 28.0 19.2 13.9 9.8 2023.0837 FEB 248.2 143.0 29.0 19.3 13.7 9.5 2023.1670 MAR 253.1 146.0 31.1 19.5 13.7 9.4 2023.2503 APR 257.3 149.4 34.3 20.0 13.6 8.9 2023.3337 MAY 262.0 152.1 36.2 20.7 13.5 8.4 2023.4170 JUN 265.4 154.0 38.5 20.4 13.3 8.1 2023.5003 JUL 267.5 155.3 42.4 19.3 13.1 8.3 2023.5837 AUG 268.6 155.5 46.7 18.5 12.9 8.3 2023.6670 SEP 270.1 156.1 51.3 18.0 12.8 8.5 2023.7503 OCT 269.7 157.4 53.5 17.6 12.7 8.8 2023.8337 NOV 268.6 158.2 55.6 17.5 12.6 8.8 2023.9170 DEC 269.9 158.8 59.5 17.3 12.6 8.7 2024.0003 JAN 269.4 157.4 62.2 17.1 12.8 8.7 2024.0837 FEB 263.8 155.2 66.0 16.9 13.2 8.7 2024.1670 MAR 257.1 153.9 68.7 16.9 13.3 8.5 2024.2503 APR 251.1 153.3 71.3 17.4 13.2 8.0 2024.3337 MAY 247.6 153.2 73.2 18.3 13.3 8.4 2024.4170 JUN 245.8 152.9 72.9 20.0 13.6 8.9 2024.5003 JUL 244.2 152.4 72.1 21.3 13.9 8.9 2024.5837 AUG 242.9 151.7 73.3 21.9 14.0 9.1 2024.6670 SEP 240.8 150.7 76.5 23.1 14.3 9.3 2024.7503 OCT 239.2 150.0 76.7 23.6 14.5 9.5 2024.8337 NOV 237.2 149.0 75.1 22.8 14.5 9.7 2024.9170 DEC 236.0 147.8 74.0 22.7 14.5 9.9 2025.0003 JAN 233.6 146.5 74.9 21.9 14.4 10.0 2025.0837 FEB 229.3 144.1 75.7 20.0 14.4 10.0 2025.1670 MAR 224.2 140.9 73.7 20.3 14.5 10.2 2025.2503 APR 220.0 138.0 72.9 21.1 14.6 10.0 2025.3337 MAY 215.3 135.9 74.5 21.1 14.6 9.2 2025.4170 JUN 209.2 133.9 76.2 20.6 14.6 8.9 2025.5003 JUL 204.3 131.1 74.2 20.0 14.5 9.0 2025.5837 AUG 198.6 128.1 70.9 19.9 14.5 9.0 2025.6670 SEP 194.2 125.8 69.3 20.7 14.7 8.9 2025.7503 OCT 192.6 124.1 68.8 21.6 15.1 9.0 2025.8337 NOV 187.4 121.8 65.5 21.8 15.3 9.0 2025.9170 DEC 184.5 118.9 58.3 21.8 15.6 8.9 2026.0003 JAN 182.8 116.0 56.8 21.8 15.7 8.8 2026.0837 FEB 177.9 113.3 58.9 21.4 15.8 8.5 2026.1670 MAR 172.3 111.1 57.6 20.5 15.8 8.6 2026.2503 APR 166.6 109.2 54.5 20.7 15.8 8.8 2026.3337 MAY 161.0 107.5 52.9 21.0 16.0 9.6 2026.4170 JUN 156.3 105.3 51.5 21.1 16.2 10.1 2026.5003 JUL 153.0 102.7 49.0 20.4 16.4 10.2 2026.5837 AUG 147.8 99.6 46.2 19.6 16.2 10.3 2026.6670 SEP 138.8 96.1 44.6 19.2 16.0 10.5 2026.7503 OCT 130.5 92.3 44.0 19.7 15.7 10.6 2026.8337 NOV 129.3 89.2 44.4 19.7 15.5 11.5 2026.9170 DEC 127.8 86.4 42.9 20.1 15.5 11.3 2027.0003 JAN 123.5 84.0 40.5 20.5 15.6 11.0 2027.0837 FEB 119.0 81.6 40.7 20.3 15.4 11.2 2027.1670 MAR 114.3 79.0 39.7 20.3 15.1 10.9 2027.2503 APR 108.9 76.3 37.9 20.6 14.8 10.7 2027.3337 MAY 108.0 73.8 36.4 20.9 14.5 10.3 2027.4170 JUN 109.0 71.2 34.0 21.4 14.2 9.4 2027.5003 JUL 107.5 68.4 31.6 22.1 14.0 8.7 2027.5837 AUG 106.1 65.6 27.8 22.8 13.9 8.9 2027.6670 SEP 103.7 63.7 24.8 23.3 13.9 8.9 2027.7503 OCT 99.7 61.7 22.9 23.5 13.9 8.8 2027.8337 NOV 95.8 59.7 19.9 23.4 13.9 8.9 2027.9170 DEC 92.5 57.5 17.3 22.9 13.8 9.2 2028.0003 JAN 91.7 55.2 15.8 21.9 13.6 9.3 2028.0837 FEB 90.6 53.0 14.5 21.0 13.5 9.5 2028.1670 MAR 87.6 50.9 13.2 20.5 13.6 9.4 2028.2503 APR 83.7 48.8 13.0 20.1 13.7 9.3 2028.3337 MAY 78.6 46.4 13.2 19.7 13.9 9.4 2028.4170 JUN 76.9 44.6 12.6 19.3 13.9 9.6 2028.5003 JUL 77.2 43.2 12.5 18.7 13.8 9.6 2028.5837 AUG 74.2 41.6 12.3 17.9 13.5 9.5 2028.6670 SEP 69.7 39.6 11.9 18.0 13.4 9.3 2028.7503 OCT 65.9 37.3 10.9 18.1 13.2 8.9 2028.8337 NOV 62.1 35.7 10.7 17.8 13.0 8.3 2028.9170 DEC 60.5 34.3 10.1 17.4 12.8 7.8 2029.0003 JAN 57.9 32.6 9.1 16.9 12.7 7.3 2029.0837 FEB 56.7 30.9 8.6 16.2 12.7 6.8 2029.1670 MAR 55.3 29.3 7.7 15.3 12.6 6.1 2029.2503 APR 54.4 27.9 6.4 15.3 12.4 5.7 2029.3337 MAY 53.0 26.2 5.9 15.4 12.3 5.8 2029.4170 JUN 51.1 24.7 5.8 15.5 12.3 6.0 2029.5003 JUL 49.0 23.3 5.5 15.5 12.2 6.4 2029.5837 AUG 46.8 21.9 5.4 15.7 12.1 6.7 2029.6670 SEP 43.9 20.3 4.2 16.0 12.0 6.7 2029.7503 OCT 40.7 18.8 3.2 15.9 11.8 6.7 2029.8337 NOV 36.2 17.5 2.7 15.6 11.5 6.6 2029.9170 DEC 30.7 15.9 2.5 15.3 11.2 6.7 2030.0003 JAN 27.0 14.1 2.1 14.2 10.8 6.6 2030.0837 FEB 25.2 12.2 1.4 12.8 10.4 6.5 2030.1670 MAR 24.1 10.6 1.1 11.8 10.0 6.5 2030.2503 APR 23.7 9.4 0.9 11.9 9.6 6.4 2030.3337 MAY 23.0 8.3 0.9 11.6 9.2 6.4 2030.4170 JUN 22.3 7.3 0.6 11.1 8.9 6.1 2030.5003 JUL 20.0 6.4 0.4 10.9 8.5 5.6 2030.5837 AUG 17.4 5.6 0.3 10.6 8.3 5.3 2030.6670 SEP 15.5 4.8 0.1 9.8 8.2 5.5 2030.7503 OCT 13.8 4.0 0.0 9.3 8.0 5.3