[RSM] W3LPL: Mostly normal likely through Wednesday July 28th

Tue Jul 27 08:15:06 EDT 2021

From: donovanf at erols.com
To: PVRC <pvrc at mailman.qth.net>
Cc:
Bcc:
Date: Tue, 27 Jul 2021 02:07:03 -0400 (EDT)
Subject: [PVRC] Mostly normal propagation is likely through Wednesday July
28th

My propagation forecast derived from today's NOAA/SWPC

web pages is published five days a week (M-F) in the Daily DX.

Propagation crossing low and mid latitudes is likely to be normal

through Wednesday.

Propagation crossing the auroral ovals and polar regions is likely

to be normal on Tuesday degrading to mostly normal on Wednesday.

Click https://services.swpc.noaa.gov/images/planetary-k-index.gif for today’s
latest planetary Kp Index, updated every three hours.

Click http://www.hamqsl.com/solar.html for N0NBH’s current HF Band
Conditions, updated regularly.

We are in the quiet geomagnetic activity season, only about half

as many geomagnetically disturbed days occur in June and July

compared to the more geomagnetically active equinox seasons.

Sporadic-E propagation will continue every day through late July

at mid-latitudes in the northern hemisphere making long distance

propagation up to 15,000 km sporadically available in the

17, 15, 12, 10 and 6 meter bands from sunrise through midnight

and occasionally somewhat later.

The solar flux index (SFI) is likely to be about 81 or less through

Wednesday. There are two small active regions on the solar visible

disk with four tiny sunspots.

https://sdo.gsfc.nasa.gov/assets/img/latest/latest_1024_0171.jpg

160 and 80 meter propagation from North America to VK/ZL and

the south Pacific is likely to be seasonably normal through Wednesday.

40 meter short path propagation to south Asia at about 0015Z

is expected to be mostly normal on Wednesday. 40 meter short path

propagation from North America to east Asia after about 0930Z is

likely to be normal through Wednesday.

30 meter propagation through the auroral ovals and polar regions is

likely to be is likely to be normal on Tuesday degrading to mostly

normal on Wednesday. 30 meter propagation is always significantly

degraded within a few hours of local noon because of E-region

blanketing of long distance F2 propagation. 30 meter night time

long distance propagation in the northern hemisphere is likely to

improve due to increased ionizing solar radiation in the northern

high latitude regions caused by increased sunspot activity, higher

solar elevation angles and short nights with no source of ionizing

solar radiation.

20 meter daytime and evening propagation through the auroral ovals

and polar regions is likely to be normal on Tuesday degrading to

mostly normal on Wednesday. 20 meter northern transpolar propagation

within a few hours of sunrise and sunset is improving with longer

duration solar ionizing radiation on the northern polar region caused

by increased sunspot activity and high solar elevation angles 24 hours

per day during the midnight sun season. 20 meter long distance

propagation is significantly degraded from mid-morning through

late afternoon at low and mid-latitudes in the northern hemisphere by

F1 region mid-day blanketing of low angle long distance propagation

during the summer. 20 meter late afternoon, nighttime and early

morning long distance propagation in the northern hemisphere

is likely to improve due to increased ionizing solar radiation in the

northern high latitude regions caused by increased sunspot activity,

higher solar elevation angles and short nights with no source of

ionizing solar radiation.

17 and 15 meter daytime long distance propagation in the northern

hemisphere is likely to improve due to increased ionizing solar

radiation in the northern high latitude regions caused by increased

sunspot activity, high solar elevation angles and long days.

17, 15, 12, 10 and 6 meter sporadic-E propagation up to 15,000 km

is likely to be sporadically available from sunrise through midnight

and occasionally later through late July.

Geomagnetic disturbances *caused by coronal hole high speed stream*

effects are likely to remain mostly brief, minor and somewhat less

frequent through at least late 2021. The southward oriented (-Bz)

component of the IMF plays a *crucial but unpredictable role* in

triggering all geomagnetic storms. Brief minor to moderate

geomagnetic storms may be gradually triggered when the IMF

persists in a southward orientation (-Bz) with enhanced IMF field

strength for several hours *coincident with* the effects of an Earth

directed *coronal hole high speed stream*. More frequent, longer

duration, minor to severe geomagnetic storms may be triggered

*suddenly* *and unpredictably *when the IMF persists in a southward

orientation (-Bz) with enhanced IMF field strength for several hours

or more *coincident with* the effects of an Earth directed fast CME.

The solar wind is likely to be near background levels on Tuesday

then slightly to moderately enhanced on Wednesday due to possible

minor coronal hole high speed stream effects and a slight chance of

effects of a glancing blow by a CME. The geomagnetic field is likely

to be quiet on Tuesday then quiet to unsettled Wednesday due to

possible minor coronal hole high speed stream effects and a slight

chance of effects of a glancing blow by a CME. There is a slight

chance of a minor geomagnetic storm on both Tuesday and

Wednesday. Solar flares strong enough to affect HF propagation

are not likely through Wednesday.

Mid-latitude northern hemisphere sunset is now 13 minutes earlier

and daylength is 35 minutes shorter than it was on the June 21st.

Daylength and solar elevation angle in the northern polar region

are steadily declining due to steadily diminishing summer solstice

effects.

Click https://www.spaceweather.gc.ca/solarflux/sx-4-en.php for today’s
Penticton 10.7 cm solar flux index updated at 1700Z, 2000Z and 2300Z daily.

Click
https://spaceweather.gfz-potsdam.de/fileadmin/ruggero/Kp_forecast/forecast_figures/KP_FORECAST_CURRENT.png
for today’s
three-day GFZ Planetary K Index forecast updated every three hours.

Click http://sidc.oma.be/products/meu/ for today's SIDC Daily Bulletin on
Solar and Geomagnetic Activity updated at 1230Z daily.

Click https://www.swpc.noaa.gov/products/forecast-discussion for today's
SWPC Solar Activity Forecast Discussion updated at 0030Z and 1230Z daily.

Click https://www.sws.bom.gov.au/Space_Weather/1/1 for today's Australian
Space Forecast Centre Summary and Forecast updated at 2330Z daily.

Perhaps the most useful HF propagation pages for DXers can be found at:

http://dx.qsl.net/propagation and http://www.solarham.net