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The following is the weekly propagation bulletin from W1AW / ARRL (posting on 20210814 00:04 UTC):
QST de W1AW
Propagation Forecast Bulletin 33 ARLP033
>From Tad Cook, K7RA
Seattle, WA August 13, 2021
To all radio amateurs
SB PROP ARL ARLP033
ARLP033 Propagation de K7RA
Solar activity continues to be very weak, and the latest 45-day
outlook seems to indicate more of the same.
Sunspots only appeared on three out of the seven days in our
reporting week (August 5 to 11) and they were not consecutive.
Average daily sunspot numbers actually rose a little, from 6 to 9.9.
Average daily solar flux softened from 74.8 to 73.7. Average daily
planetary A index went from 8 to 6.3, while middle latitude averages
were 7, down from 8.7 last week.
Predicted solar flux over the next few weeks shows a predicted
maximum of only 75 on just one day, September 11. The solar flux
forecast from USAF and NOAA shows 73 on August 13 and 14, 72 on
August 15 to 19, 73 on August 20, 74 on August 21 through September
1, then 73, 72, 72, 74 and 74 on September 2 to 6, 73 on September 7
to 10, 75 on September 11, 72 on September 12 to 15, 73 on September
16, and 74 on September 17 and beyond.
Predicted planetary A index is 8 on August 13 to 15, 5 on August 16
to 22, 8 on August 15 and 16, 5 on August 17 to 22, then 8, 12 and 8
on August 23 to 25, 5 on August 26 through September 1, then 8 and
12, on September 2 and 3, then 8 on September 4 to 6, 5 on September
7 to 11, then 12, 10, and 10 September 12 to 14, and 5 on September
15 to 18.
Strangely, the planetary A index for September 5 is listed as 58,
which I was certain was an error. This outlier value was repeated
in Thursday's forecast. Wednesday's prediction was done by Stover
and Houseal and Thursday's was from Trost and Houseal. I have not
checked earlier forecasts to see when this value first showed up.
New forecasts appear daily at
ftp://ftp.swpc.noaa.gov/pub/forecasts/45DF/
OK1HH is gone for another week, so we present geo-forecasts from two
of his colleagues:
'Solar activity forecast for the period August 13-August 19, 2021
Activity level: mostly very low
X-ray background flux (1.0 to 8.0 A): in the range A3.5 to A7.0
Radio flux (10.7 cm): a fluctuation in the range 70 to 75
Events: class C (0 to 2/period), class M (0/period), class X
(0/period), proton (0/period)
Relative sunspot number (Ri): in the range 0 to 55
Geomagnetic activity forecast for the period August 13 to 19,
2021
Quiet: August 13 to 16, 19
Unsettled: August 16 to 18
Active: possible August 16 and 17
Minor storm: 0
Major storm: 0
Severe storm: 0
Geomagnetic activity summary:
Next week, we expect quiet to unsettled conditions generally. Till
the next Sunday, August 15, we expect the quiet to unsettled level
closer to the lower level.
Since Monday, August 16, more unsettled conditions are possible.
Between Monday, August 16, and Wednesday, August 18, more unsettled
conditions are probable. Within this interval, an isolated active
event is also possible.'
Interesting item from Southgate Amateur Radio News:
https://bit.ly/3sd5LNr
For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation and the ARRL Technical Information
Service at http://arrl.org/propagation-of-rf-signals. For an
explanation of numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere.
An archive of past propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation. More good
information and tutorials on propagation are at http://k9la.us/.
Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins .
Sunspot numbers for August 5 through August 11, 2021 were 36, 0, 0,
11, 0, 0, and 22, with a mean of 9.9. 10.7 cm flux was 74.3, 74.4,
73.7, 73.5, 73, 73.3, and 73.8, with a mean of 73.7. Estimated
planetary A indices were 3, 7, 11, 5, 5, 7, and 6, with a mean of
6.3. Middle latitude A index was 3, 9, 9, 6, 6, 9, and 7, with a
mean of 7.
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