QST de W1AW
Propagation Forecast Bulletin 49 ARLP049
From Tad Cook, K7RA
Seattle, WA November 29, 2004
To all radio amateurs
SB PROP ARL ARLP049
ARLP049 Propagation de K7RA
Because last week's bulletin was prepared Tuesday night, it didn't include the numbers that are always at the end of this bulletin. This is an extra bulletin put out after the Thanksgiving holiday to catch up on those numbers.
The reporting week that we use for the data runs Thursday through the following Wednesday, so we are reporting and comparing data from November 18-24 with the earlier seven-day period from November 11-17. The November 18-24 data is not much different than the earlier period. Average daily sunspot numbers are a little lower, and so are geomagnetic indices.
Currently early Monday morning a solar wind is up against earth's magnetic field, but so far the worst effect is a K index of 3, indicating unsettled conditions, but not active. Conditions over the weekend were a little rough, with both the mid-latitude and planetary K index as high as 5.
The current forecast shows a moderate A index of 10 over the next few days, but active geomagnetic conditions are predicted for December 2-3. Daily solar flux values around 110 are predicted through December 1, rising a bit higher through December 5.
The nights are longer now in the Northern Hemisphere, and will continue to lengthen through December 21, the Winter Solstice. This suggests an emphasis on the lower bands for communication, especially for those of us at a higher latitude. On December 21 Miami, Florida will have 10 hours and 34 minutes from sunrise to sunset, but Seattle, Washington will only have 8 hours and 40 minutes.
Plotting a 10 meter daylight path from Miami to Brazil on the Solstice using propagation software such as W6ELprop, shows a 4-hour longer opening than a path from Seattle to Brazil under the same conditions. Those in the southern states of North America frequently have longer and better openings to the rest of the world than operators further north.
If you would like to comment or have a tip, email the author at, firstname.lastname@example.org.
For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service propagation page at, http://www.arrl.org/tis/info/propagation.html.
Sunspot numbers for November 18 through 24 were 77, 61, 40, 27, 28, 45 and 72 with a mean of 50. 10.7 cm flux was 104, 102.2, 99.3, 100.9, 106.3, 106.9 and 107.3, with a mean of 103.8. Estimated planetary A indices were 3, 4, 18, 16, 10, 5 and 6, with a mean of 8.9. Estimated mid-latitude A indices were 4, 3, 12, 9, 6, 4 and 7, with a mean of 6.4.