Report

Space weather: solar flux 105, 9 below its 90-day average of 114. Maximum usable frequency 10 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 40 meters, 30 meters marginal, 20 meters and up closed. Critical frequency 3.0 megahertz, too low for NVIS right now. K index 5, moderate geomagnetic storm. No significant flares. Data from NOAA.

Geomagnetic storms can open aurora on 6 and 2 meters. Point north and listen for raspy, buzzy signals. The declining phase of the solar cycle often brings some of the cycle's strongest flares and geomagnetic storms, so VHF aurora openings on 6 and 2 meters are still very possible.

Sun and moon, Pacific Daylight Time: sunrise 7:08 AM, sunset 6:48 PM, day length 11 hours 40 minutes. Moonrise 12:27 AM at 58 degrees, east northeast; moonset 3:40 PM at 299 degrees, west northwest. Waning crescent, 31 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 9:02 AM, 71 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. No passes above 30 degrees in the next four hours. Frequencies and live status at amsat.org/status. Pass predictions at n2yo.com.

Satellite tip: a small dual-band handheld Yagi is all you need for the FM satellites.

DX activity, via the cluster network and hamqsl.com. None spotted by West Coast stations right now. No aurora or 6 meter E-skip.

Tropospheric ducting, from balloon soundings 7 hours ago: Over Oakland, an elevated duct from 40 meters to 250 meters, trapping signals above about 150 megahertz, so 1.25 meters and up. A matching duct over Vandenberg suggests a possible path to Southern California on 1.25 meters and up. K6EEG's experimental tropo forecast, based on NOAA atmospheric model data, for the next 12 hours. Bay Area coast, peaking around 10 AM: ducting expected on 70 centimeters, 85 percent; a chance of ducting on 2 meters, 45 percent. Southern California coast, peaking around 1 AM: ducting expected on 70 centimeters, 95 percent; ducting likely on 2 meters, 70 percent. Pacific Northwest coast, peaking around 1 AM: ducting likely on 70 centimeters, 70 percent; a slight chance of ducting on 2 meters, 25 percent. Nothing toward Hawaii.

Tropo openings favor horizontal antennas. Calling frequencies, upper sideband: 144.2 and 432.1 megahertz.

Events. The California QSO Party, now under way, California stations in demand. VHF-UHF FT8 Activity Contest, on Wednesday. VHF-UHF FT8 Activity Contest-NA, on Thursday.

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. Clear. Temperature 19 degrees Celsius. Dew point 14 degrees Celsius. Relative humidity 73 percent. Wind calm. Barometric pressure 1014 hectopascals, normal. Visibility 16 kilometers.

National Weather Service forecast. Values converted to SI units. Tonight: Mostly clear, with a low around 16 degrees Celsius. West southwest wind around 2.2 meters per second. Monday: Sunny. High near 27 degrees Celsius, with temperatures falling to around 23 degrees Celsius in the afternoon. West wind 0.4 to 4.5 meters per second. Monday 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. Low tide at 12:34 AM, minus 0.02 meters. High tide at 8:16 AM, 1.42 meters. Low tide at 12:48 PM, 1.00 meters. High tide at 6:32 PM, 1.72 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 0.9 meters, slight seas, dominant period 15 seconds, from the south southwest. That's long-period ground swell. Wind at the buoy 5 meters per second from the northwest. Ocean water temperature 16 degrees Celsius. San Francisco Bay water temperature 20 degrees Celsius. Golden Gate currents: slack water at 4:09 AM, then maximum flood 1.1 meters per second at 6:50 AM, then slack water at 9:58 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 10 micrograms per cubic meter, rated good. Ozone is 19 parts per billion. Nitrogen dioxide is 8 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 2.5, near Pinnacles. No earthquakes of magnitude 6 or greater worldwide. Seismic data from earthquake.usgs.gov.

After an earthquake, listen before you transmit, and let emergency traffic through first.