Last week saw some unsettled conditions due to the effects of a coronal hole.
Its associated high speed solar wind stream actually hit the Earth a day earlier
than predicted, resulting in poor HF conditions during the International Marconi
Day event on Saturday, 21 April.
The planetary K-index hit six
the night before and we were left with noisy bands and poor propagation. HF
openings were predominantly to Europe, although Australia and the US were worked
by GB0CMS from Caister in Norfolk. While conditions improved slightly through
the week the K-index remained steadfastly high.
There were highlights though.
The A25UK Expedition to Botswana was worked from the UK on bands as high as 10
metres. As this is a North-South path, signals didn’t have to go through the
unsettled auroral oval.
There were a couple of sunspots
that helped push the solar flux index to more than 80, but next week NOAA
predicts the SFI will be around the mid to high 70s, with unsettled geomagnetic
conditions at times. The K-index could hit five on Bank Holiday Monday, but then
decline to three or four for the rest of the week.
We should soon start to see the
start of the sporadic E season, which may bring good short-skip opportunities on
the upper HF bands. Keep an eye on the 10 metre beacons from around 28.150 to
28.330MHz for openings.
VHF and up:
Low pressure will bring showery
rain into western Britain later in the weekend, with prospects for GHz bands
rain scatter. This will soon be replaced by a ridge of high pressure extending
south from a large high over Scandinavia. The ridge may bring the possibility of
some tropo conditions towards the east across the North Sea.
That said, the quite strong
easterly wind over southern areas may not be the best for good tropo, since it
is likely to be a dry flow and thus there may not be a good moisture contrast
between the surface and the dry air above any temperature inversion. If tropo
turns out to be not such a strong player, there are good reasons to hope for
some sporadic E as we move into the first week of May. This is usually regarded
as the start of the main sporadic E season, so the main periods to check are
late morning and late afternoon.
As we said earlier, start with
10m and then move higher in frequency as any opening develops. The openings can
eventually reach 2m.
Moon declination is high and
losses still low this weekend but declination falls and losses increase as the
week progresses.
A week today, before dawn, the
Eta Aquarids meteor shower peaks, but the shower’s radiant never gets very high
above the horizon for observers in the Northern Hemisphere.
