Everyone knows the sunspot cycle. A cycle that is there with a timespan of about 11 years. The amount of sunspots gives you an idea of propagation on the HF bands. Anything around 100 or above is good. At the moment we just had a peak of suncycle 24 and sunspots are going down. With the decline of cycle 23 back in 2004/2005 I already noticed another cycle. It is the rotation of the sun in about 27 days. That could mean that "good" or actually better propagation is appearing every 27-28 days as well as any active sunspots will appear again within that time. This can especially be noticed when in the solarcycle minimum. I've been searching for this phenomenon on the internet but only little can be found. Though I noticed it several times through the low sunspot years and others probabely did as well. But it is not known by many HAM radio operators.
Find some excellent written info understanding HF propagation here:
A day by day International Sun Spot Number can be found here:
Best 10m propagation this month was at 16 February when I worked 7P8C with only 5W on 10m. At least, that was my best day. Several HAM radio operators noticed that commonly best 10m propagation occurs after a sunspot peak. Counting 27 days from the peak whe see at the day by day plot the next peak could appear around 1-3 March, it doesn't mean that the propagation will be excellent those days but expect better propagation at the end of next week. Last week propagation was low. I've been calling with 5W to obtain some new DXCC for the 100 DXCC in 100 days QRP challenge but unfortenately signals were too low and there were only a few weak spots from my signal. So instead I switched to the new 60m band which was open for a short moment. I worked MM0GGI John from north of Scotland. And then for a new DXCC on 60 TF1EIN Heimir was calling me. Of course this were 100W contacts. Signals were not that good on 60m either.