QST de W1AW
Propagation Forecast Bulletin 27 ARLP027
From Tad Cook, K7VVV
Seattle, WA July 2, 1999
To all radio amateurs
SB PROP ARL ARLP027
ARLP027 Propagation de K7VVV
Solar flux, and especially sunspot numbers, took a huge leap over the past week. Average sunspot numbers almost doubled, with a jump from 138.9 last week to 272. Sunday had the highest sunspot number, 341. Average solar flux was up almost fifty points to 198.6 compared to the previous week. Saturday and Sunday's big numbers were quite an event for Field Day weekend.
These numbers are a new record for this solar cycle. The last time sunspot numbers were any higher was on February 1, 1992, when the sunspot number was 363. Solar flux hasn't been this high since February 29, 1992 when it was 218.
The end of June was also the end of the second quarter for 1999. Average sunspot numbers for the last quarter of 1998 through the end of June were 99.1, 96.1 and 147.2. Average solar flux for the same three quarters was 136.9, 136.7 and 145. You can see a more dramatic rise in the monthly numbers over this quarter. April through June average sunspot numbers were 92.9, 140.6 and 208.3, and average solar flux for the same period was 117.2, 148.4 and 169.8. This indicates a great upward trend. Unfortunately, the last time we looked at these numbers in ARLP024 there was a bit of confusion regarding sunspot numbers. The monthly averages reported in that bulletin were for international sunspot numbers, which are lower than the NOAA Space Environment Service Center numbers always reported in this weekly bulletin.
The forecast for the next few days, Friday through Sunday has a solar flux of 195, 190 and 180, and planetary A index of 12, 10 and 8. Beyond the weekend look for flux values below 160 after July 8, rising above 160 after July 18 and above 180 after July 24.
Sunspot numbers for June 24 through 30 were 229, 260, 310, 341, 268, 259 and 237 with a mean of 272. 10.7 cm flux was 185, 200.8, 199.5, 207.4, 196.6, 191.3 and 209.5, with a mean of 198.6, and estimated planetary A indices were 6, 5, 17, 21, 26, 9 and 5, with a mean of 12.7.
The path projection for this week is from Seattle, Washington.