Report

Space weather: solar flux 105, 9 below its 90-day average of 114. Maximum usable frequency 12 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 30 meters, 20 meters and up closed. Critical frequency 3.9 megahertz, so 80 meters is marginal for NVIS. K index 4, active. 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 7:08 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.

After sunset the D layer fades, and 160, 80, and 40 meters open for long distance contacts, while 15 through 10 meters close as the F layer weakens.

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: keep FM satellite contacts short, callsign and grid square, so everyone gets a turn.

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 18 hours ago: Newer data is not yet available, and conditions may have changed. over Oakland, a duct at 250 to 330 meters, good for 33 centimeters and up. No matching ducts along the coast or toward Hawaii, so the enhancement is likely local. K6EEG's experimental tropo forecast, based on NOAA atmospheric model data, for the next 12 hours. Bay Area coast, peaking around 9 AM: ducting expected on 70 centimeters, 80 percent; a chance of ducting on 2 meters, 35 percent. Southern California coast, peaking around 12 AM: ducting expected on 70 centimeters, 95 percent; ducting likely on 2 meters, 70 percent. Pacific Northwest coast: ducting expected on 70 centimeters, 90 percent; a chance of ducting on 2 meters, 30 percent. Nothing toward Hawaii.

Tropo openings favor horizontal antennas. For CW, try 144.05 to 144.1 megahertz on 2 meters, and 432.1 on 70 centimeters.

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

Current weather conditions at San Francisco International Airport: All values in SI units. Clear. Temperature 20 degrees Celsius. Dew point 14 degrees Celsius. Relative humidity 68 percent. Wind calm. Barometric pressure 1013 hectopascals, normal. Visibility 16 kilometers.

Know how long your backup power lasts. Test it under real load, not just with a meter.

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 west northwest. Ocean water temperature 16 degrees Celsius. San Francisco Bay water temperature 20 degrees Celsius. Golden Gate currents: maximum ebb 1.6 meters per second at 11:14 PM, then slack water at 4:09 AM, then maximum flood 1.1 meters per second at 6:50 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 8 micrograms per cubic meter, rated good. Ozone is 30 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.

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