Report

Space weather: solar flux 105, 10 below its 90-day average of 115. Maximum usable frequency 17 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 20 meters, 17 meters and up closed. Critical frequency 5.8 megahertz, so 80 meters is good for NVIS, 60 meters marginal. Daytime absorption limits 160 and 80 meters to short range. K index 4, minor geomagnetic storm. 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, 35 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.

160 and 80 meters often peak right at sunrise on paths to the west, just before the D layer forms and absorbs them.

Amateur satellite passes for the next four hours. The ISS, FM crossband repeater, when active: at 5 PM rising in the northwest, 50 degrees. RS 44, linear transponder, SSB and CW: at 5:06 PM rising in the south southeast, 35 degrees. For the next pass, the ISS: uplink 145.99 megahertz with a 67 hertz tone, downlink 437.8. Frequencies and live status at amsat.org/status. Pass predictions at n2yo.com.

Satellite tip: satellite contacts count toward the ARRLVUCC satellite award for grid square chasers.

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 9 hours ago: 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 10 PM: ducting expected on 70 centimeters, 90 percent; ducting likely on 2 meters, 60 percent. Southern California coast: a chance of ducting on 70 centimeters, 30 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. 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.

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. Temperature 24 degrees Celsius. Dew point 17 degrees Celsius. Relative humidity 65 percent. Wind calm. Barometric pressure 1012 hectopascals, normal. Visibility 16 kilometers.

Batteries and radios in parked cars degrade in heat. Keep go-kit batteries somewhere cool.

National Weather Service forecast. Values converted to SI units. This Afternoon: Partly sunny. High near 32 degrees Celsius, with temperatures falling to around 27 degrees Celsius in the afternoon. West northwest wind 0.9 to 4.5 meters per second. Tonight: Mostly clear, with a low around 16 degrees Celsius. West southwest wind 0.0 to 4.0 meters per second. Monday: Sunny. High near 27 degrees Celsius, with temperatures falling to around 24 degrees Celsius in the afternoon. West northwest wind 0.0 to 4.5 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 4 meters per second from the west northwest. Ocean water temperature 16 degrees Celsius. San Francisco Bay water temperature 19 degrees Celsius. Golden Gate currents: slack water at 2:32 PM, then maximum flood 0.7 meters per second at 4:58 PM, then slack water at 6:58 PM.

Air quality for field operations, from the Bay Area Air District's San Francisco Arkansas Street monitoring station. Fine particulate matter, PM2.5, is 15 micrograms per cubic meter, rated moderate. Ozone is 39 parts per billion. Nitrogen dioxide is 14 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 2.4, near Alum Rock. 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.