QST de W1AW
Propagation Forecast Bulletin 10 ARLP010
From Tad Cook, K7VVV
Seattle, WA March 5, 1999
To all radio amateurs
SB PROP ARL ARLP010
ARLP010 Propagation de K7VVV
Average sunspot numbers for the past week were up when compared to the previous week, while average solar flux was down. How could this be? If you look at a graph of the two indices at http://www.dxlc.com/solar/ or http://www.wm7d.net/hamradio/solar/, you can see that a recent minimum followed by a rise in solar flux lagged sunspot numbers. So the minimum solar flux of 115.1 occurred during the past week, while the minimum sunspot number of 38 was during the previous week.
Geomagnetic conditions have been active, with A indices in the double-digits over most of the past week. The worst day was Monday, when the planetary A index was 33 and the K index was four or five for most of the day. This is generally bad for HF, but often provides interesting VHF propagation. N5JHV received television signals from New Zealand, and V73AT was hearing California Highway Patrol around 42 MHz on Monday.
For the ARRL International DX Phone Contest this weekend, look for improving conditions with a rising solar flux of 150, 158 and 165 for Friday through Sunday. Geomagnetic conditions should settle down, indicated by a falling planetary A index of 18, 15 and 9 for those same days. The first day of the contest may be a little rough, with geomagnetic conditions possibly unsettled to active.
After the weekend expect the solar flux to peak near 200 around March 13, then drop below 170 five days later, then down to 130 on March 21, and 120 from March 23 until the end of the month. Days with possible unsettled to active geomagnetic conditions are March 10 and 11 and 27 and 28.
A couple of readers mentioned that the JA7SSB URL in ARLP009 was wrong because ip was written instead of jp. It should be http://www.roy.hi-ho.ne.jp/hamradio/.
Sunspot Numbers for February 25 through March 3 were 66, 70, 93, 145, 127, 143 and 148 with a mean of 113.1. 10.7 cm flux was 119.5, 115.6, 115.1, 123, 120.2, 129.9 and 137, with a mean of 122.9, and estimated planetary A indices were 7, 3, 5, 14, 33, 18 and 15, with a mean of 13.6.
Here are some path predictions for this weekend from New York City: