Propagation Forecast Bulletin #36 de K7RA:
W1AW Bulletin via the ARRL
September 9, 2017
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Propagation Forecast Bulletin #36 de K7RA:
QST de W1AW
Propagation Forecast Bulletin 36 ARLP036
>From Tad Cook, K7RA
Seattle, WA September 9, 2017
To all radio amateurs
SB PROP ARL ARLP036
ARLP036 Propagation de K7RA
Wow! What a week for solar activity. Although the solar cycle trend
is down over the past few years and moving toward a solar minimum
around the year 2020, we will still see notable upticks in activity,
such as this week's surprising events.
On August 31, http://www.spaceweather.com reported a G-1 Class
geomagnetic storm. Planetary A index was 59. The following day
Spaceweather.com reported geomagnetic unrest with a planetary A
index of 19. Planetary A index was 26 on September 2 when
Spaceweather.com reported sunspot group AR2674 "rapidly growing,
increasing in both area and sunspot count."
"As the sunspot grows, its magnetic field is becoming unstable,
posing a threat for M-class solar flares." Planetary A index was 9
on September 3, when Spaceweather.com reported two huge sunspot
groups facing Earth.
"Behemoth AR2674 has been growing for days, while newcomer AR2673
has suddenly quadrupled in size, with multiple dark cores breaching
the surface of the Sun in just the past 24 hours. This movie from
NASA's Solar Dynamics Observatory shows sunspot genesis in action:
On September 4, the planetary A index was 18, and Spaceweather.com
reported: "Huge sunspot AR2673, which materialized with shocking
speed over the weekend, is seething with activity.
A few days ago in Romania, solar photographer Maximilian Teodorescu
captured this snapshot of plasma currents surging inside the
sunspot's magnetic canopy, apparently on the verge of an explosion":
Note the recent emergence of large sunspot areas:
We also saw the largest solar flare in over a decade launch Thursday
Predicted solar flux is 115 on September 9, 105 on September 10, 90
on September 11-15, 85 on September 16-17, 88 on September 18, 92 on
September 19-21, then 95, 98, 100 and 105 on September 22-25, 110 on
September 26 through October 2, 105 on October 3-5, then 100, 95,
90, 85 and 80 on October 6-10, 85 on October 11-14, 88 on October
15, 92 on October 16-18, and 95, 98, 100, 105 and 110 on October
Predicted planetary A index is 30 and 10 on September 9-10, 8 on
September 11-12, then 28, 30, 20, 25 and 12 on September 13-17, 5 on
September 18-19, 8 on September 20, 5 on September 21-22, then 8, 5,
8 and 5 on September 23-26, 20 on September 27-29, then 12, 10, 8
and 5 on September 30 through October 3, 15 on October 4-5, 8 on
October 6, 5 on October 7-9, 25 on October 10-12 then 20 and 10 on
October 13-14, 5 on October 15-16, then 8, 5, 5, 8, 5, 8 and 5 on
Here is the latest geomagnetic activity forecast for the period
September 8 to October 4, 2017 from OK1HH:
"Geomagnetic field will be:
Quiet on September 20, 24
Mostly quiet on September 11, 21
Quiet to unsettled September 12, 19, 22, 25, October 2-4
Quiet to active on September 10, 15, 17-18, 23, 26-27, 30, October 1
Active to disturbed on September 8-9, 13-14, 16, 28-29
"Amplifications of the solar wind from coronal holes are expected on
September 8-10, 13-19, 27-28, October (1,) 2-4
"Remark: - Parenthesis means lower probability of activity
enhancement and/or lower reliability of prediction.
"F.K. Janda, OK1HH Czech Propagation Interested Group"
Lou, VK5EEE sent this, which I edited:
"Do not believe modern-day short-cut internet-gimmicks such as this
(he included a reference to an online tool predicting propagation
titled "HF Conditions").
"Have a listen to the propagation beacons, tune around the bands!
Remember there is NO SUCH THING generally speaking as a GLOBAL HF
one-size-fits-all-situation in spite of the modern trend to paint
that picture into their systems. Part of the world is in darkness,
part in light. There are many grey areas. The K index varies from
location to location. East-West and North-South paths are affected
differently by events.
"Nor should we rely on advanced real-time programs such as VOAProp
by G4ILO. While useful, these also give sometimes wildly false
readings. For example, as I write this, bands including 10m are
having great propagation to all of America and to Asia, and perhaps
to other places too, while showing that even with 4kW and a big high
up Yagi at most S1 signals from a few isolated places north of
Australia would be possible. NOT. I just need to tune in to 28200 to
hear all the beacons coming in so nice and clear and they are
running 100W to simple Ground Plane antennas.
"What does the Australian government have to say about conditions
right now on the SWS website? 'Disturbed!'
"Again we may be tempted to take that at face value. 20-10m has not
been open much from VK in recent times with very low solar flux and
no sunspots at times. However right now, 10m is open. 12m is open,
15, 17 and 20m. Little activity but the beacons are clear, and Costa
Rica booming in on SSB on 20m even though the local time here is
high noon with the Sun high in the sky.
"If we look at the regional T index map,
"we see that in Australia and New Zealand conditions are actually
"If we look at the world map,
"we see that conditions in most of the world are ENHANCED, most of
the rest is NORMAL and only a few areas in parts of the Central
Pacific and near to the North Pole (parts of Canada, part of
Greenland) and northern Siberia are depressed. So why is there so
much alarm and DEPRESSED shown as a 'one size fits all' on simple
condensed gimmicks? Well, it is true for those few parts of the
world. And somewhere the K index is indeed 8, somewhere it is worse,
"Bear in mind that while over today and tomorrow there is a
possibility or even a probability of short wave fade-outs (not
worldwide but generally on the Sun side of the earth) but the Solar
Activity being high to very high means that when there is not a
fadeout conditions are most likely to be enhanced! We should be SO
HAPPY that solar flux is now well above 100, as that means HF
openings occur on higher bands more often.
"With the current predicament of those few radio amateurs who are
not hampered by various distractions, the LOCAL NOISE levels are
prohibitive on lower frequencies. When bands above 20m open up, we
should not be scared off by a glance at the RED/POOR prediction and
miss out on all the easy DX with simple antennas and low noise to be
had while the higher HF bands are wide open. Let us not forget the
IBP beacons, and to tune around and call CQ even when predictions
would encourage you do to otherwise."
Lou makes some excellent points. The various propagation models used
in the tools for predicting HF success are based on mean predicted
sunspot numbers for the month, and cannot predict real time HF
propagation. Lou included this URL: http://30cw.net/ .
On September 7, Mark Lunday, WD4ELG in North Carolina reported great
propagation to South America on 10 meters using the new FT8 mode.
More about FT8, which is from Joe Taylor, K1JT, can be found at:
Jon Jones, N0JK in Kansas wrote on September 4:
"10 Meters was back Sunday afternoon August 27 for intercontinental
"I had been working the Hawaiian QSO Party on 15 and noted spots for
Hawaiians on 10. I went to 10... unfortunately did not hear Hawaii
but logged WP4JW FK68 on 10 SSB at 2307z followed by LU5XP FF97
Argentina at 2310z. The QSO with WP4JW was probably double hop Es as
I saw many Es contacts spotted around this time on 10. The LU
contact may have been Es link to TEP. LU5XP was very loud for about
15 minutes then vanished abruptly. HK1MW was spotted via Es to W3,
W7 and W0.
"Stations in Hawaii did work North America on 10 meters August 27, I
saw Hawaiians spotted by stations in Florida, Texas, California,
Washington State, Oregon and New Mexico."
If you would like to make a comment or have a tip for our readers,
email the author at
For more information concerning radio propagation, see the ARRL
Technical Information Service web page at,
http://arrl.org/propagation-of-rf-signals. For an explanation of
numbers used in this bulletin, see
An archive of past propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation. More good
information and tutorials on propagation are at
Monthly propagation charts between four USA regions and twelve
overseas locations are at
Sunspot numbers for August 31 through September 6, 2017 were 59, 62,
71, 96, 122, 122, and 79, with a mean of 87.3. 10.7 cm flux was
91.9, 93.4, 100, 120.2, 140, 120.5, and 132.9, with a mean of 114.1.
Estimated planetary A indices were 31, 19, 26, 9, 18, 12, and 11,
with a mean of 18. Estimated mid-latitude A indices were 20, 17, 25,
10, 16, 11, and 18, with a mean of 16.7.
Source: W1AW Bulletin via the ARRL.
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