Report

Space weather: solar flux 105, 10 below its 90-day average of 115. Propagation outlook: moderate — fair conditions on 20 through 40 meters. Estimated maximum usable frequency for mid-latitude paths is 22 megahertz. K index 1, very quiet. No significant flares. Data from NOAA.

Coronal holes become more common as the cycle declines, bringing geomagnetic activity that repeats about every 27 days, one solar rotation. If conditions are disturbed today, watch for a repeat in about four weeks.

Sun and moon, Pacific Daylight Time: sunrise 7:07 AM, sunset 6:50 PM, day length 11 hours 43 minutes. Moonset 2:56 PM at 304 degrees, west northwest. No moonrise today. Last quarter moon, 44 percent lit. The Orionid meteor shower peaks Wednesday, October 21, a meteor scatter opportunity on 6 and 2 meters. Moonbounce: the moon peaks tomorrow at 8:07 AM, 76 degrees high and 3 percent closer than average, a good time to listen for EME signals on 2 meters and up.

Rooftop solar inverters shut down at sunset, often lowering the HF noise floor for the evening. They come back on at sunrise.

Amateur satellite passes for the next four hours. AO7, linear transponder: at 8:12 PM rising in the south southwest, 31 degrees. SO 50, FM: at 8:20 PM rising in the north northwest, 44 degrees. PO 101, FM, on a schedule: at 8:31 PM rising in the north northeast, 87 degrees, overhead. AO 91, FM: at 9:35 PM rising in the north northeast, 41 degrees. For the next pass, SO 50: uplink 145.85 megahertz with a 67 hertz tone, downlink 436.795. Send a 74.4 hertz tone briefly first to start its timer. Frequencies and live status at amsat.org/status. Pass predictions at n2yo.com.

Satellite tip: rotate a handheld Yagi as the satellite passes to follow its changing polarization. A small twist can bring back a fading signal.

DX activity, via the cluster network and hamqsl.com. None spotted by West Coast stations right now. No aurora or 6 meter E-skip. Good HF conditions on 80 to 40 meters, 30 to 20 meters. Fair conditions on 17 to 15 meters. Poor conditions on 12 to 10 meters.

Tropospheric ducting, from balloon soundings 3 hours ago: No ducting strong enough for amateur VHF or UHF bands over Oakland. K6EEG's experimental tropo forecast, based on NOAA atmospheric model data, for the next 12 hours. Bay Area coast, peaking around 4 AM: ducting expected on 70 centimeters, 85 percent; a chance of ducting on 2 meters, 45 percent. Southern California coast: ducting likely on 70 centimeters, 75 percent; a slight chance of ducting on 2 meters, 25 percent. Nothing toward Hawaii.

Events. The California QSO Party, now under way, California stations in demand. IARU Region 1UHF/Microwaves Contest, now under way. IARU Region 2 Area GHFSSB Contest, now under way.

Club and community announcements. The SF Amateur Radio Club meets on the third Friday of each month, 7 PM at the Randall Museum. Visit sfarc.org for more details.

Current weather conditions at San Francisco International Airport: All values in SI units. Mostly Clear. Temperature 27 degrees Celsius. Dew point 12 degrees Celsius. Relative humidity 41 percent. Wind calm. Barometric pressure 1008 hectopascals, low pressure. Visibility 16 kilometers.

National Weather Service forecast. Values converted to SI units. Tonight: Mostly clear, with a low around 17 degrees Celsius. West wind 0.0 to 4.0 meters per second. Sunday: Partly sunny. High near 28 degrees Celsius, with temperatures falling to around 24 degrees Celsius in the afternoon. Northwest wind 0.4 to 4.5 meters per second. Sunday Night: Mostly clear, with a low around 16 degrees Celsius. West southwest wind 0.9 to 4.0 meters per second.

Tide predictions for today at the San Francisco Embarcadero gauge. High tide at 7:11 AM, 1.35 meters. Low tide at 11:12 AM, 1.08 meters. High tide at 5:11 PM, 1.77 meters.

Ocean and bay conditions. No marine advisories in effect. From the San Francisco buoy, 18 nautical miles west of the Golden Gate: significant wave height 1.1 meters, slight seas, dominant period 9 seconds, from the west northwest. Wind at the buoy 5 meters per second from the west northwest. Ocean water temperature 16 degrees Celsius. San Francisco Bay water temperature 20 degrees Celsius. Golden Gate currents: maximum ebb 1.7 meters per second at 9:40 PM, then slack water at 3:01 AM, then maximum flood 1.0 meters per second at 5:40 AM.

If you feel a strong or long-lasting earthquake near the coast, move to high ground immediately. Don't wait for an official tsunami warning.

Air quality for field operations, from the Bay Area Air District's San Francisco Arkansas Street monitoring station. Fine particulate matter, PM2.5, is 6 micrograms per cubic meter, rated good. Ozone is 37 parts per billion. Nitrogen dioxide is 6 parts per billion. For more information visit the Bay Area Air District or openaq.org on the web.

Sign up for your county's emergency alerts, such as Alert SF in San Francisco. Hams are often among the first to relay that information.

Seismic awareness for emergency communicators: no Bay Area earthquakes of magnitude 2.5 or greater in the past 24 hours. Largest in California in the past 24 hours: magnitude 2.9, near South Lake Tahoe. No earthquakes of magnitude 6 or greater worldwide. Seismic data from earthquake.usgs.gov.

After a strong earthquake, check in on your local emergency net, and keep transmissions brief to leave room for emergency traffic.