QST de W1AW  
Propagation Forecast Bulletin 16  ARLP016
>From Tad Cook, K7RA
Seattle, WA  April 21, 2017
To all radio amateurs 

SB PROP ARL ARLP016
ARLP016 Propagation de K7RA

This just in from the Australian Space Forecast Centre at 2349 UTC
on April 20, 2017:

Recurrent coronal hole is expected to be geoeffective.

INCREASED GEOMAGNETIC ACTIVITY EXPECTED DUE TO CORONAL HOLE HIGH
SPEED WIND STREAM FOR 23 APRIL 2017

GEOMAGNETIC ACTIVITY FORECAST 23 Apr: Active to Minor Storm

Spaceweather.com reported old sunspot AR2644 returned after a 2-week
trip around the Sun, and exploded on April 18. The resulting CME
should miss Earth, but as this active region moves into a
geo-effective position we could see some geomagnetic disturbance in
the next few days.

Average daily sunspot numbers declined from 16.6 last week to 8.6 in
this reporting week, April 13-19. Average daily solar flux increased
from 73.8 to 76.5.

Geomagnetic indicators were lower this week. Average planetary A
index declined from 10.6 to 8, while average mid-latitude A index
was 6.3, down from 9.3 the previous seven days.

Predicted solar flux is 85 on April 21-27, 80 on April 28 to May 1,
75 on May 2-13, 83 and 88 on May 14-15, 90 on May 16-18, 85 on May
19-24, 80 on May 25-28, and 75 on May 29 through June 4.

Predicted planetary A index is 12, 8, 40 and 30 on April 21-24, 20
on April 25-27, then 15, 10, 5 and 20 on April 28 through May 1, 10
on May 2-4, 15 on May 5-6, then 5 and 8 on May 7-8, 5 on May 9-13,
20 on May 14, 15 on May 15-16, 10 on May 17, 5 on May 18-19, then
35, 25, 18, 20 and 25 on May 20-24, then 12, 8, 5 and 18 on May
25-28, and 10 on May 29 through June 4.

Franz K. Janda, OK1HH of the Czech Propagation Interest Group sent
us his geomagnetic activity forecast for the period April 21-May 17,
2017. 2017 marks the 40th year Franz has been writing these
bulletins.

'Geomagnetic field will be:
Quiet on April 22, 30, May 13
Mostly quiet on April 29, May 8
Quiet to unsettled April 21, May 3, 7, 10-12, 14-15
Quiet to active on April 24-25, 27-28, May 1-2, 4-5, 8, 16
Active to disturbed on April 23, 26, May 6, 17

'Increasing solar wind from coronal holes are expected on April
(21-22,) 23-28, May (1-4,) 7-8, (9-11,) and 18-19.

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

And from another Czech resource, a near term geo-forecast from
Thomas Bayer of the Budkov Observatory:

'Geomagnetic activity forecast for the period April 21-April 27,
2017:

'Quiet: Apr 21-22 
Unsettled: Apr 22-23, 25-27 
Active: Apr 23-25
Minor storm: possible Apr 23-24 
Major storm: 0 
Severe storm: 0

'Geomagnetic activity summary:

'Until the nearest Saturday, April 22, we expect quiet to unsettled
conditions. Between Sunday, April 23, and Monday, April 24, we
expect active episode arrival caused by present equatorial coronal
hole. During these two days, storming effect is possible.

'The following days, we expect at most unsettled conditions only with
isolated active episodes. The last day of the forecast period, we
expect geomagnetic activity decrease to quiet to unsettled level.

'Tomas Bayer RWC Prague Institute of Geophysics of the ASCR, Prague
Department of Geomagnetism Budkov observatory (BDV).'

According to this, we are due for more low solar activity, but there
is a chance of C-class and M-class flares:

www.spaceref.com/news/viewsr.html?pid=50058

Also from Spaceref, tomorrow a March for Science in Washington, DC:

spaceref.com/calendar/calendar.html?pid=9388

If you would like to make a comment or have a tip for our readers,
email the author at [email protected].

For more information concerning radio propagation, see the ARRL
Technical Information Service web page at,
arrl.org/propagation-of-rf-signals. For an explanation of
numbers used in this bulletin, see
arrl.org/the-sun-the-earth-the-ionosphere.

An archive of past propagation bulletins is at
arrl.org/w1aw-bulletins-archive-propagation. More good
information and tutorials on propagation are at k9la.us/.

Monthly propagation charts between four USA regions and twelve
overseas locations are at arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL
bulletins are at arrl.org/bulletins.

Sunspot numbers for April 13 through 19, 2017 were 12, 11, 11, 0, 0,
12, and 14, with a mean of 8.6. 10.7 cm flux was 73.5, 72.9, 73,
74.5, 75.2, 85.6, and 80.9, with a mean of 76.5. Estimated planetary
A indices were 5, 14, 7, 4, 4, 7, and 15, with a mean of 8.
Estimated mid-latitude A indices were 4, 10, 5, 4, 3, 6, and 12,
with a mean of 6.3.