ZCZC AP33
QST de W1AW
Propagation Forecast Bulletin 33 ARLP033
From Tad Cook, K7VVV
Seattle, WA August 13, 1999
To all radio amateurs
SB PROP ARL ARLP033
ARLP033 Propagation de K7VVV
Solar flux and sunspot numbers were way down this week, with the average solar flux off almost 60 points and sunspot numbers down by over 85 points compared to last week. This week was probably the low point in activity for the near term.
Currently the forecast for this weekend, Friday through Sunday, shows a predicted solar flux of 120, 124 and 126 and predicted planetary A index of 8, 6 and 6. Friday morning's solar flux reading at Penticton was 128.2, somewhat higher than forecast, so the weekend numbers could be correspondingly higher.
Next week look for flux values to rise to 150 by August 18, 175 around August 21, and peak around 205 from August 26-29. These present some hopeful numbers as we move away from the summer season and toward the fall equinox, always an exciting time for propagation.
This week there were some days with active geomagnetic conditions. The most active was August 9, when the planetary A index was 19 and the K index was 4 during most periods. During these periods the conditions tend to be worse at higher latitudes, and the A index measured in Alaska (the College indices) was 60, with a K index as high as 7. HF operators in the far north must have experienced awful HF conditions, because polar absorption would be so pronounced. At the same time VHF operators at lower latitudes would be enjoying auroral propagation.
Today, Friday morning UTC, the planetary K index was 4, which means that conditions are somewhat disturbed. The forecast for the weekend though is for stable geomagnetic indices.
Over the next few weeks look for moderately unsettled conditions around August 19, 27 and possibly September 4-6. Otherwise, the forecast is for stable conditions.
In last week's bulletin, ARLP032, it was stated that the solar flux should drop to 10 by August 10. The solar flux will never go that low, even with no sunspots. That should have read 130.
Sunspot numbers for August 5 through 11 were 187, 164, 149, 154, 118, 89 and 76 with a mean of 133.9. 10.7 cm flux was 177, 170.4, 153.3, 137.8, 138.1, 127.3 and 127.9, with a mean of 147.4, and estimated planetary A indices were 11, 13, 11, 7, 19, 7 and 8, with a mean of 10.9.