[RSM] W3LPL: Mostly normal thru Thursday/28

Wed Jul 28 12:10:51 EDT 2021

From: donovanf at erols.com
To: PVRC <pvrc at mailman.qth.net>
Cc:
Bcc:
Date: Wed, 28 Jul 2021 00:46:51 -0400 (EDT)
Subject: [PVRC] Mostly normal propagation is likely through Thursday 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 Thursday.

Propagation crossing the auroral ovals and polar regions is likely

to be mostly normal on Wednesday gradually improving to normal

on Thursday.

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

Click *here* <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

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

disk with five very small 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

Thursday. 40 meter short path propagation to south Asia at about

0015Z is expected to be mostly normal on Thursday. 40 meter

short path propagation from North America to east Asia after

about 0930Z is likely to be mostly normal through Thursday.

30 meter propagation through the auroral ovals and polar regions

is likely to be below normal on Wednesday gradually improving

to normal on Thursday. 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 below normal on Wednesday

gradually improving to normal on Thursday. 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 slightly improve due to increased ionizing

solar radiation in the northern high latitude regions caused by

increased sunspot activity, high solar elevation angles and long

summer 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 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, then gradually

improving to slightly enhanced on Thursday. The geomagnetic field

is likely to be quiet to unsettled 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 gradually improving to mostly quiet

with a chance of unsettled intervals on Thursday. There is a slight

chance of a minor geomagnetic storm on both Wednesday and Thursday.

Solar flares strong enough to affect HF propagation are not likely

through Thursday.

Mid-latitude northern hemisphere sunset is now 14 minutes earlier

and daylength is 37 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 *here* <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 *here*
<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 *here* <http://sidc.oma.be/products/meu/> for today's SIDC Daily
Bulletin on Solar and Geomagnetic Activity updated at 1230Z daily.

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

Click *here* <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