SB PROP @ ARL $ARLP015
ARLP015 Propagation de K7RA
QST de W1AW
Propagation Forecast Bulletin 15 ARLP015
From Tad Cook, K7RA
Seattle, WA April 11, 2014
To all radio amateurs
SB PROP ARL ARLP015
ARLP015 Propagation de K7RA
Average daily solar flux weakened over the past seven days, and so
did the outlook for the near term, at least until Thursday, April
10. Average daily solar flux declined from 149 to 142.2, while
average daily sunspot numbers remained about the same, moving from
130.4 to 129.3
From the NOAA/USAF 45 day forecast, predicted solar flux is 140 on
April 11-12, 145 on April 13-15, 150 on April 16-18, 140 on April
19, 135 on April 20-23, 130 on April 24-27, 125 on April 28 through
May 3, and 140 on May 4-6.
In yesterday's ARRL Letter we reported the prediction from
Wednesday, April 9 showed an average daily solar flux of 133.3 over
April 10-15. But just two days earlier, on Monday April 7 the
predicted average for the same period was 142.5, and back on March
30 the prediction for April 10-15 showed an average solar flux of
145.8. The predicted solar flux for April 10 was 150 on March 30,
140 on April 7 and 130 on April 9, which indicated a progressively
However, the April 10 prediction showed higher values. For April
11-18, average solar flux is predicted at 145.6, ten points higher
than the prediction for the same eight days on April 9, which was
Predicted planetary A index is 5 on April 11, 8 on April 12, then 12
on April 13, 8 on April 14-15, 5 on April 16-18, 8 on April 19, then
5 on April 20 through May 5, and 8 on May 6-7.
OK1HH predicts a quiet geomagnetic field on April 11-13, mostly
quiet April 14, quiet to unsettled April 15-16, quiet to active
April 17, quiet April 18, mostly quiet April 19-20, quiet to active
April 21, quiet to unsettled April 22, mostly quiet April 23, quiet
on April 24, mostly quiet April 25-26, quiet April 27, mostly quiet
April 28, quiet on April 29, mostly quiet April 30, quiet May 1-2,
mostly quiet May 3, quiet to unsettled May 4, quiet May 5, quiet to
unsettled May 6, and back to quiet again on May 7-8.
A week ago (but too late for this bulletin) NASA released their
monthly Solar Cycle prediction, little changed from the March
The forecast begins, "The current prediction for Sunspot Cycle 24
gives a smoothed sunspot number maximum of about 70 in the late
summer of 2013. The smoothed sunspot number reached 73.1 in
September 2013, so the official maximum will be at least this high."
The March forecast said "The current prediction for Sunspot Cycle 24
gives a smoothed sunspot number maximum of about 69 in the late
summer of 2013. The smoothed sunspot number reached 68.9 in August
2013, so the official maximum will be at least this high."
These are smoothed numbers, averaged over a year, so that is why the
numbers from the end of last summer changed, because recent higher
activity is now averaged in.
Here is an interesting article, "Small Groups, Big Flares" from
Belgium's Solar Influences Data Center:
Wayne Starnes, KU4V of Cary, North Carolina sent an email concerning
the radio blackout mentioned in last week's bulletin:
"Yes I also experienced the blackout during the CQ WPX, but do not
actually recall the time it happened. I was running on 10M as I
recall and BOOM 20+ atmospheric noise on the band! I then checked
10m-160m and it was the same intensity on every band. I have never
heard anything like it.
"Then, after a few minutes, it stopped and the bands seemed to be in
better shape actually.
"Then, Sunday 30-Mar at 1503 UTC while running 10m, YB2DX calls me,
very weak but we made it. At 1522 UTC YC0IEM calls me, again very
weak but we made it. At 1547 UTC 4Z5ML called.
"After the contest, 31-Mar after 0200 I worked the TX5 guys on 10
"Amazing and interesting propagation this past weekend."
Chris Wreck, K2HVE of Bayonne, New Jersey wrote: "Yes! It was the
same at my station, K2HVE. I am located in Hudson County, 1.5 miles
SW of the Statue of Liberty and 2.5 miles SW of WTC in lower
Manhattan. I was on 20 meters during the CQ WPX Contest on Saturday
29 March working EU and Russian stations one after another when
around 1750 UTC the whole band was wiped out. Nothing but noise at
an S3 level. It was like somebody pulled my antenna wire out. I
began checking antenna connections on my IC-7600 and found nothing.
"Very shortly a NOAA SWPC alert came through noting the solar flare.
The disturbance lasted about 30-45 minutes, then slowly the US
Stations came back up and shortly after the EU Stations. In an hour
it was like nothing had ever happened. In all the years I never had
anything so sudden happen at my QTH regarding Ole' Sol."
Jon Jones, N0JK sent a correction concerning working long path on
"Fred, KH7Y made the first 6 meter Hawaii to Europe TPL (trans-polar
longpath) contact of solar cycle 24 with IT9 on February 28. But it
was TPL going southeast of Hawaii. It took place in the early
afternoon HST (Hawaii Standard Time).
"I think I made the first Hawaii to Europe TPL contact of Solar
Cycle 24 going southwest of Hawaii March 30 with S57RR. It was
around midnight HST for me."
Jon also reported, on April 10: "During the last week many contacts
were made in the afternoon from the Gulf Coast and southern parts of
the Midwest to CX, LU and PY in South America on 6 meters. A few
fortunate hams in AR, MO and OK worked the Falkland Islands. The
propagation mode is 'afternoon TEP.' This link has information about
this propagation mode:
heard CE4WJK working CO2QU on April 6 at 2100 UTC on 50.140 MHz.
"Today April 10 heard the K5AB/b 50.060 MHz on Es at 2350 UTC."
Scott Craig's Solar Data Plot Utility has an updated data file,
useful if you are just starting out with the program. Otherwise you
update it auto-magically weekly with this bulletin.
You can find it at http://www.craigcentral.com/sol.asp .
This program runs on Microsoft Windows, but I've never been able to
use it on Windows 7 computers, so I've used a virtual XP mode or
just my old XP machine. Now I see Microsoft has ended support for
This weekend is the Japan International DX CW Contest. See details
at http://jidx.org/ .
If you would like to make a comment or have a tip for our readers,
email the author at, firstname.lastname@example.org.
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 the
numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past
propagation bulletins is at
information and tutorials on propagation are at http://k9la.us/.
Monthly propagation charts between four USA regions and twelve
overseas locations are at http://arrl.org/propagation.
Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins.
Sunspot numbers for April 3 through 9 were 137, 174, 172, 127, 106,
94, and 95, with a mean of 129.3. 10.7 cm flux was 153, 156.9,
142.1, 140.9, 139.9, 132, and 130.6, with a mean of 142.2. Estimated
planetary A indices were 6, 6, 14, 5, 11, 5, and 5, with a mean of
7.4. Estimated mid-latitude A indices were 7, 5, 11, 3, 10, 4, and
5, with a mean of 6.4.