Report

Space weather: solar flux 105, 10 below its 90-day average of 115. Maximum usable frequency 16 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 30 meters, 20 meters marginal, 17 meters and up closed. Critical frequency 4.8 megahertz, so 80 meters is good for NVIS. K index 3, active. No significant flares. Data from NOAA.

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 7:07 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, 42 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. 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: passes above 30 degrees are the easiest. Low passes mean longer paths and more obstructions.

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: 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 11 AM: ducting likely on 70 centimeters, 75 percent; a chance of ducting on 2 meters, 30 percent. Southern California coast: a chance of ducting on 70 centimeters, 35 percent. Nothing toward Hawaii.

Events. The California QSO Party, now under way, California stations in demand. IARU Region 1UHF/Microwaves Contest, now under way. VHF-UHF FT8 Activity Contest, on Wednesday.

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.

Keep your FCC license information current in the ULS, including your email address. The FCC sends license notices by email. Many handhelds can receive NOAA Weather Radio. Program the local channels.

Current weather conditions at San Francisco International Airport: All values in SI units. Clear. Temperature 23 degrees Celsius. Dew point 13 degrees Celsius. Relative humidity 53 percent. Wind calm. Barometric pressure 1010 hectopascals, normal. 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 2.2 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. 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: slack water at 3:01 AM, then maximum flood 1.0 meters per second at 5:40 AM, then slack water at 9:03 AM.

Air quality for field operations, from the Bay Area Air District's San Francisco Arkansas Street monitoring station. Fine particulate matter, PM2.5, is 11 micrograms per cubic meter, rated good. Ozone is 19 parts per billion. Nitrogen dioxide is 19 parts per billion. For more information visit the Bay Area Air District or openaq.org on the web.

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.

If you smell gas, leave first. Use radios and phones only after you're at a safe distance.