QST de W1AW
Propagation Forecast Bulletin 31 ARLP031
From Tad Cook, K7VVV
Seattle, WA July 30, 1999
To all radio amateurs
SB PROP ARL ARLP031
ARLP031 Propagation de K7VVV
Sunspot numbers and solar flux took a big leap upward this week, and the trend continues until the weekend. Average sunspot numbers were up almost 55 points over last week, and average solar flux was up almost 42 points. The high solar flux reading of 197.8 on Wednesday continued on Thursday at 202.4. This is much higher than forecast last week. Solar flux on Friday is predicted to be around 200, and 190 and 180 on Saturday and Sunday. Planetary A indices for Friday through Sunday are predicted to be ten for all days.
Beyond the weekend, solar flux should drop to 170 around August 4, 160 by August 8, and 140 around August 12. Flux levels are expected to be back above 200 by August 19 and possibly 210 around August 21. By that date 10 meters should be quite exciting.
Many positive responses to last week's bulletin about the meaning of the solar and geomagnetic indices, and among the mail was a tip from K9MIF about http://hamradio-online.com/1998/jun/wwv.html, which was created by KC7LVZ. This web page has some nice explanations for the various solar numbers, and what they mean to hams. N6RT sent along a pointer to http://dx.qsl.net/propagation/, which he created to show solar information from a number of sources in one handy location.
Scott Craig, WA4TTK has an update to his solar plotting program. This freeware takes data directly from this bulletin and plots it on your computer. If you aren't running it yet, now is a good time to download it, because the data files have been updated through July 24. You can add to it by taking the data out of these bulletins, which the program can do automatically. Go to http://edge.net/~scraig/sol.htm for the download.
Sunspot numbers for July 22 through 28 were 127, 158, 173, 183, 150, 161 and 218 with a mean of 167.1. 10.7 cm flux was 152.8, 193.7, 184.2, 182.3, 172.4, 174.5 and 197.8, with a mean of 179.7, and estimated planetary A indices were 24, 12, 12, 8, 7, 6 and 9, with a mean of 11.1.
Path projections for this week are from the center of the contiguous 48 states of the USA.