Report

Space weather: solar flux 105, 9 below its 90-day average of 114. Maximum usable frequency 13 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 30 meters, 20 meters and up closed. Critical frequency 4.4 megahertz, so 80 meters is good for NVIS. 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. 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.

VHF and UHF tropospheric enhancement is often strongest from sunset to early morning, when a nighttime temperature inversion forms.

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: AMSAT's live status page shows which satellites are working. Check before a pass, and log your own reports to help others.

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 100 feet to 800 feet, 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 11 AM: ducting expected on 70 centimeters, 85 percent; a chance of ducting on 2 meters, 45 percent. Southern California coast: ducting expected on 70 centimeters, 85 percent; a chance of ducting on 2 meters, 40 percent. Pacific Northwest coast, peaking around 2 AM: ducting likely on 70 centimeters, 75 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.

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: Clear. Temperature 64 degrees Fahrenheit. Dew point 57 degrees Fahrenheit. Relative humidity 77 percent. Wind calm. Barometric pressure 29.93 inches of mercury, normal. Visibility 10 miles.

National Weather Service forecast. Tonight: Mostly clear, with a low around 61. West southwest wind around 5 miles per hour. Monday: Sunny. High near 80, with temperatures falling to around 74 in the afternoon. West wind 1 to 10 miles per hour. Monday Night: Mostly clear, with a low around 60. West southwest wind 2 to 9 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 14 seconds, from the south southwest. That's long-period ground swell. Wind at the buoy 8 knots from the west northwest. Ocean water temperature 60 degrees Fahrenheit. San Francisco Bay water temperature 67 degrees Fahrenheit. Golden Gate currents: slack water at 4:09 AM, then maximum flood 2.1 knots at 6:50 AM, then slack water at 9:58 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 6 micrograms per cubic meter, rated good. Ozone is 17 parts per billion. Nitrogen dioxide is 10 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.

Set up an out-of-area contact for your family. Long-distance lines often work when local ones are jammed.