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ARRL Propagation Bulletin ARLP019 (2017)

SB PROP @ ARL $ARLP019
ARLP019 Propagation de K7RA

ZCZC AP19
QST de W1AW  
Propagation Forecast Bulletin 19  ARLP019
From Tad Cook, K7RA
Seattle, WA  May 12, 2017
To all radio amateurs 

SB PROP ARL ARLP019
ARLP019 Propagation de K7RA

Average daily sunspot numbers this week (May 4-10) were 17.1, down
from 25.1 last week. Average daily solar flux declined from 76.9 to
71.5.

There were three consecutive days with 0 sunspots this week, May
9-11. Spaceweather.com noted that Thursday was the thirty-third day
with 0 sunspots in 2017, and through all of 2016 there were 32 days
with no sunspots. Being early May, this indicates an acceleration of
the decline of the current solar cycle.

Predicted solar flux is 71 on May 12-13, 70 on May 14-17, 80 on May
18-23, 77 on May 24-27, 75 on May 28 through June 1, 73 on June 2,
72 on June 3-4, 70 on June 5-8, 72 on June 9-10, 75 on June 11, and
80 on June 12-19.

Predicted planetary A index is 6 on May 12, 5 on May 13-16, 15 on
May 17-18, then 8, 15, 30, 20, 10 and 8 on May 19-24, 5 on May 25
through June 3, 8 on June 4, 5 on June 5-7, then 8, 5, 5 and 8 on
June 8-11, then 15, 30, 15 and 8 on June 12-15.

Both above Ap and 10.7 cm SF forecasts are from Wednesday May 10. As
of 1430 UTC Friday the Thursday May 11 forecast (normally out after
2100 UTC daily) was still unavailable.

You can check ftp://ftp.swpc.noaa.gov/pub/forecasts/45DF/ for daily
updates of predicted Ap (planetary A index) and solar flux
predictions.

OK1HH gives us his geomagnetic activity forecast for May 12-June 7,
2017.

"Geomagnetic field will be:
Quiet on May 14-15, June 1,
Mostly quiet on May 13, June 4
Quiet to unsettled May 12, 23-30, June 3, 5-7
Quiet to active on May 16, 20, 21-22, June 2
Active to disturbed on May (17-19, 31)

"Amplifications of the solar wind from coronal holes are expected
May 16-19 (and maybe about May 29-30 and June 3, 6, 7-8)

"Remark: - Parenthesis means lower probability of activity
enhancement and/or lower reliability of prediction.

"F.K. Janda, OK1HH Czech Propagation Interested Group OK1HH
compiling weekly forecasts since 1978."

If you would like to make a comment or have a tip for our readers,
email the author at k7ra@arrl.net.

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
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/.

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 May 4 through May 10, 2017 were 29, 31, 26, 23,
11, 0, and 0, with a mean of 17.1. 10.7 cm flux was 74.2, 73.5,
72.8, 71.7, 70.5, 68.9, and 68.6, with a mean of 71.5. Estimated
planetary A indices were 7, 6, 5, 8, 6, 6, and 6, with a mean of
6.3. Estimated mid-latitude A indices were 6, 5, 5, 7, 7, 5, and 6,
with a mean of 5.9.
NNNN
/EX