[RSM] W3LPL forecast Thu-Fri Apr 22-23

Thu Apr 22 09:18:12 EDT 2021

From: donovanf at erols.com
To: PVRC <pvrc at mailman.qth.net>
Cc:
Bcc:
Date: Thu, 22 Apr 2021 02:21:24 -0400 (EDT)
Subject: [PVRC] Mostly normal propagation through Friday

Long distance propagation forecast for Thursday and Friday, April 22-23

My propagation forecast derived from today's NOAA/SWPC web

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

Propagation at low and mid-latitudes is likely to be normal through

Friday. Propagation crossing the auroral oval and polar regions is

likely to be mostly normal with below normal intervals through Friday.

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.

The solar flux index (SFI) is likely to be about 78 through Friday.

Three active regions containing a total of 17 mostly tiny sunspots

are having minimal effects on HF propagation.

We are exiting the most disturbed weeks of the March-April

geomagnetic storm season when the earth is passing through the

part of the interplanetary magnetic field (IMF) with the most

frequent, longest duration southward oriented IMF. Approximately

twice as many brief minor and moderate geomagnetic storms occur

during March and April compared to the quieter IMF during June

and July. Brief minor to moderate geomagnetic storms may be

triggered with little warning when the IMF rotates to a southward

orientation and persists for several hours *coincident with* the effects

of earth directed coronal hole high speed streams and coronal mass

ejection (CME) enhancements in the solar wind.

160 and 80 meter short path propagation from North America to

VK/ZL is likely to be normal through Friday. 80 and 40 meter

short path propagation to south Asia is likely to be mostly normal

at about 0030Z Friday. 80 and 40 meter short path propagation

from North America to east Asia after about 0900Z is likely to be

mostly normal with below normal intervals through Friday.

30 meter propagation through the auroral ovals and across polar

regions is likely to be mostly normal with below normal intervals

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

propagation is likely to improve slightly through Friday due to

solar flux index of 78.

20 meter daytime and evening propagation through the auroral ovals

and across polar regions is likely to be mostly normal with below

normal intervals through Friday. 20 meter northern trans-polar

propagation within a few hours of sunrise and sunset will steadily

improve with gradually increasing electron density in the polar F2

region through June. 20 meter night time long distance propagation

in the northern hemisphere is likely to improve slightly through Friday

due to solar flux index of 78.

17 and 15 meter daytime long distance propagation in the northern

hemisphere is likely to improve slightly through Friday due to solar

flux of 78. 12 and 10 meter daytime long distance propagation is

likely to be mostly unreliable and limited to propagation from North

America to Southern Africa, South Atlantic, South America and

South Pacific regions.

Geomagnetic disturbances *caused by coronal hole high speed streams*

are likely to remain mostly brief, minor and less frequent through

at least late 2021. The north-south (Bz) component of the IMF plays

a crucial role in triggering brief minor to moderate geomagnetic

storms when it persists in a southward orientation (-Bz) with enhanced

field strength for several hours *coincident with* the effects of earth

directed coronal hole high speed stream or CME enhancements in

the solar wind.

IMF field strength, solar wind speed near earth and geomagnetic

activity are likely to be at close to background levels through Friday

with a possible enhancement late Friday due to coronal hole high

speed stream effects. There is a slight possibility that an M-Class

solar flare may cause a brief sudden ionospheric disturbance and

short-wave fadeout on the sun facing side of the earth late Thursday.

Geomagnetic storms and earth directed CMEs strong enough to affect

HF propagation are not likely through Friday.

Mid latitude northern hemisphere sunset is now 32 minutes later and

daylength is 81 minutes longer than it was on the March 20th.

Daylength is increasing by two minutes per day which is steadily

lengthening the duration of common daylight between distant

locations in the northern hemisphere. Solar elevation in the northern

polar region is increasing about three degrees per week, steadily

improving 20 meter northern trans-polar propagation through June.

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

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