ZCZC AP20
QST de W1AW
Propagation Forecast Bulletin 20 ARLP020
From Tad Cook, K7RA
Seattle, WA May 14, 2004
To all radio amateurs
SB PROP ARL ARLP020
ARLP020 Propagation de K7RA
Sunspot activity has been in the doldrums, which is expected at this stage of the declining solar cycle. Average daily solar flux and sunspot numbers have hardly changed over the past week. Now, both numbers are rising modestly due to quickly expanding Sunspot 606, which is squarely aimed at Earth. There's also some good news from the sun's far side, where helioseismic holography has detected another sizable sunspot group. Both sunspot and solar flux numbers have topped 100. The lowest recent sunspot count was 30 on May 6, and the solar flux dropped to 85 the following day.
Solar flux values should rise over this weekend, with the Friday through Monday, May 14-17, solar flux predicted at 105, 110, 115 and 115. Solar flux should stay in the vicinity of 115 through Thursday, May 20. The predicted planetary A index indicates unsettled conditions for Saturday, May 15, with the Friday through Monday planetary A index predicted at 12, 15, 12 and 8.
A new issue of the NOAA Space Environment Center Preliminary Report and Forecast includes some solar cycle predictions on pages 12-13. The forecast for the bottom of the cycle still looks to be around the end of 2006 or early 2007. For the higher HF bands, declining sunspots mean fewer or even no openings on 10, 12 and 15 meters, and probably a greater reliance on 20 or 17 meters for worldwide propagation during daylight hours.
Sunspot numbers for May 6 through 12 were 30, 34, 37, 57, 55, 46 and 83, with a mean of 48.9. The 10.7 cm flux was 86.4, 85.2, 87.2, 93.2, 93, 90.2 and 98.8, with a mean of 90.6. Estimated planetary A indices were 8, 17, 10, 6, 7, 10 and 11, with a mean of 9.9. Estimated mid-latitude A indices were 10, 13, 7, 3, 5, 8 and 9, with a mean of 7.9.