[RSM] W3LPL says mostly normal thru Fri/27

[Art Boyars]

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From: donovanf at erols.com
To: PVRC Submissions <pvrc at mailman.qth.net>
Cc:
Bcc:
Date: Thu, 26 Aug 2021 01:31:14 -0400 (EDT)
Subject: [PVRC] Propagation is likely to be mostly normal through Friday
August 27th

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 Friday.



Propagation crossing the auroral ovals and polar regions is likely

to be mostly normal through Friday.



Click here for today’s latest planetary Kp Index, updated every three hours.

Click here for N0NBH’s current HF Band Conditions, updated regularly.



We have transitioned into more frequent mildly active geomagnetic

activity during late August. The more geomagnetically active autumn

equinox season begins in September and runs through late October

with about twice as many geomagnetically active days as June, July,

December and January.



Sporadic-E propagation will be shorter in duration with much lower

MUFs and much less reliable at mid-latitudes in the northern

hemisphere during late August making long distance sporadic-E

propagation up to about 8,000 km intermittent and unreliable in the

17 and 15 meter bands from a few hours after sunrise until a few

hours after sunset.



The solar flux index (SFI) is likely to be 84 or less through Friday.

The sun’s visible disk has two active regions with nine small sunspots

having a small effect on HF propagation.

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 normal through Friday. 40 meter

short path propagation to south Asia at about 0015Z is likely to be

mostly normal through Friday. 40 meter short path propagation

from North America to east Asia after about 0930Z is likely to be

mostly normal through Friday.



30 meter propagation through the auroral ovals and polar regions

is likely to be mostly normal through Friday. 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 less reliable due to decreased ionizing

solar radiation in the northern high latitude regions caused by

lower solar elevation angles and longer 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 mostly normal through Friday.

20 meter northern transpolar propagation within a few hours of

sunrise and sunset is less reliable and shorter in duration due to

decreased ionizing solar radiation in the northern high latitude

regions caused by lower solar elevation angles and longer nights

with no source of ionizing solar radiation. 20 meter long distance

propagation is significantly degraded from mid-morning through

late afternoon at mid and especially low latitudes in the northern

hemisphere by F1 region mid-day blanketing of low angle long

distance propagation through late August. 20 meter late afternoon,

nighttime and early morning long distance propagation in the northern

hemisphere is likely to be significantly shorter in duration due to

decreased ionizing solar radiation in the northern high latitude regions

caused by declining elevation angles and longer nights with no source

of ionizing solar radiation.



17 and 15 meter daytime long distance propagation in the northern

hemisphere is likely to be shorter in duration due to decreased

ionizing solar radiation in the northern high latitude regions caused

by lower solar elevation angles and longer nights with no source

of ionizing solar radiation. 17 and 15 meter sporadic-E propagation

up to about 8,000 km is likely to be intermittent, short duration and

unreliable from a few hours after sunrise until a few hours after sunset

during late August.



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 interplanetary magnetic field (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 through Friday

due to coronal hole high speed stream effects and a slight chance of a

weak glancing blow by a passing CME on Friday. The geomagnetic

field is likely to be quiet to unsettled with active periods on Thursday

and mostly unsettled with active periods on Friday due to coronal hole

high speed stream effects and a slight chance of a weak glancing blow

by a passing CME. There is a chance of a minor geomagnetic storm on

Thursday and Friday with the greatest chance mid to late Friday. Solar

flares strong enough to affect HF propagation are not likely through

Friday.



Mid-latitude northern hemisphere sunset is now 49 minutes earlier and

daylength is 98 minutes shorter than it was on the June 21st. Daylength

and solar elevation angle in the northern polar region have significantly

declined due to the end of the midnight sun and the approaching autumn

equinox.



Click here for today’s Penticton 10.7 cm solar flux index updated at 1700Z,
2000Z and 2300Z daily.

Click here for today’s three-day GFZ Planetary K Index forecast updated
every three hours.

Click here for today's SIDC Daily Bulletin on Solar and Geomagnetic
Activity updated at 1230Z daily.

Click here for today's SWPC Solar Activity Forecast Discussion updated at
0030Z and 1230Z daily.

Click here 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