HF
propagation conditions during last weekend’s IOTA contest were pretty dire. This
was due to a perfect storm of typical summer conditions, a fairly low sunspot
count and poor geomagnetic conditions, reflected in a Kp index of three. This
was due to the arrival of material from a coronal mass ejection and the onset of
a weak high speed solar wind stream from a coronal hole. One contestant said
that he worked no stations outside of Europe at all in the IOTA contest, which
just about sums it up!
Over the next week the solar flux index is
predicted to be in the range 100-110 with the Ap index in the range five to
sixteen. The third, fourth and fifth are predicted to be the most settled days
geomagnetically, with Sunday, 2 August and next weekend predicted to be very
unsettled with the chance of the Kp index hitting five. This means that you may
be better off hunting DX during the week as next weekend may see a return of
unsettled conditions with poor maximum usable frequencies in terms of F layer
propagation and low DX potential.
As we are now in August, make sure you
use the new smoothed sunspot number of 51 for your VOACAP-based prediction
programs.
VHF and up propagation news:
This will be another week
of mixed, but not really strong indicators. Tropo-wise there are likely to be
periods when there is a weak ridge of high pressure over southern parts of
Britain and this could mean slightly enhanced prospects at times, both across to
the Baltic, and south across Biscay towards Spain.
Unfortunately, for
much of the week, there will be a large area of low pressure near north-western
Britain and this will mean its only rain scatter on offer for many north-western
areas of the UK.
For sporadic-E, the prospects are reasonable on two
counts. Firstly there is a very non-summer jet stream, albeit weaker than last
week, over the British Isles and into northern Europe. Jet streams are good
places to generate the wave motion in the air that can propagate vertically to
make sporadic-E.
Secondly, we are approaching the interesting part of the
year for the Perseids meteor shower, which peaks around 12 August and meteors
are generally regarded as the raw materials of sporadic-E. For a day-by-day
update on the jet stream check out the sporadic-E blog on RSGB Forums.
It
is also less than two weeks to the Perseids meteor shower, peaking around 12
August.
With EME, the moon declination is increasing and losses are
lowest today and Monday.
