Report

Space weather: solar flux 105, 9 below its 90-day average of 114. Maximum usable frequency 21 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 17 meters, 15 meters marginal, 12 meters and up closed. Critical frequency 6.7 megahertz, so 80 and 60 meters are good for NVIS. Daytime absorption limits 160 and 80 meters to short range. K index 6, 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. Strong geomagnetic storms can degrade GPS accuracy, affecting APRS positions and GPS disciplined timing. We're in the declining phase of Solar Cycle 25, which peaked in October 2024. Sunspots and solar flux are trending down toward the next minimum, expected around 2030.

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, 34 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.

Grayline enhancement on 80 through 40 meters is strongest within about half an hour of sunrise and sunset.

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, and at 6:59 PM rising in the south southwest, 49 degrees. AO7, linear transponder: at 7:11 PM rising in the south southeast, 74 degrees, overhead. FO 29, linear transponder, on a schedule: at 8:01 PM rising in the north northeast, 88 degrees, overhead. PO 101, FM, on a schedule: at 8:31 PM rising in the north northeast, 88 degrees, overhead. SO 50, FM: at 8:37 PM rising in the north northwest, 87 degrees, overhead. 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: 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 24 hours ago: Newer data is not yet available, and conditions may have changed. 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, peaking around 1 AM: a chance of ducting on 70 centimeters, 30 percent. Nothing toward Hawaii.

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: Temperature 82 degrees Fahrenheit. Dew point 54 degrees Fahrenheit. Relative humidity 37 percent. Wind calm. Barometric pressure 29.85 inches of mercury, normal. Visibility 10 miles.

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

National Weather Service forecast. This Afternoon: Partly sunny. High near 89, with temperatures falling to around 80 in the afternoon. West wind 3 to 10 miles per hour. Tonight: Mostly clear, with a low around 61. West southwest wind 0 to 9 miles per hour. Monday: Sunny. High near 81, with temperatures falling to around 75 in the afternoon. West northwest wind 0 to 10 miles per hour.

Tide predictions for today at the San Francisco Embarcadero gauge. Low tide at 12:34 AM, minus 0.1 feet. High tide at 8:16 AM, 4.7 feet. Low tide at 12:48 PM, 3.3 feet. High tide at 6:32 PM, 5.6 feet.

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 3 feet, slight seas, dominant period 8 seconds, from the west northwest. Wind at the buoy 8 knots from the west northwest. Ocean water temperature 61 degrees Fahrenheit. San Francisco Bay water temperature 67 degrees Fahrenheit. Golden Gate currents: maximum flood 1.3 knots at 4:58 PM, then slack water at 6:58 PM, then maximum ebb 3.1 knots at 11:14 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 6 micrograms per cubic meter, rated good. Ozone is 29 parts per billion. Nitrogen dioxide is 5 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.

Text, don't call. Text messages often get through when voice calls can't, and they keep lines open for emergency calls.