[RSM] W3LPL forecast Fri-Sun Apr 23-25

[Art Boyars]

From: donovanf at erols.com
To: PVRC <pvrc at mailman.qth.net>
Cc:
Bcc:
Date: Fri, 23 Apr 2021 01:27:04 -0400 (EDT)
Subject: [PVRC] Mostly normal propagation through 0900Z Sunday followed by
a moderate geomagnetic storm

Long distance propagation forecast for Friday through Sunday, April 23-25



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

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



Low and mid-latitude propagation is likely to be normal through

about 0900Z Sunday. A G2 moderate geomagnetic storm (Kp=6)

is likely to significantly degrade mid-latitude propagation after about

0900Z Sunday followed by gradual recovery to mostly normal

propagation after about 2100Z.



Propagation through the auroral ovals and polar regions is likely

to be mostly normal through about 0900Z Sunday but interrupted

by below normal intervals from about 2100Z Friday through 0900Z

Saturday. Persistent below normal propagation is likely after about

0900Z Sunday followed by gradual recovery to mostly normal

propagation after about 2100Z.


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 84 through Sunday.

Two active regions containing a total of 11 mostly tiny sunspots

are having a minor effect on HF propagation.



We have nearly exited 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 Saturday and possibly

below normal after about 0900Z Sunday. 80 and 40 meter short path

propagation to south Asia is likely to be below normal at about

0030Z Saturday and normal at about 0030Z Sunday. 80 and 40 meter

short path propagation from North America to east Asia after

about 0900Z is likely to be mostly normal through Saturday

and below normal on Sunday.



30 meter propagation through the auroral ovals and polar regions

is likely to be mostly normal through about 0900Z Sunday but

interrupted by below normal intervals from about 2100Z Friday

through 0900Z Saturday. Persistent below normal propagation

is likely after about 0900Z Sunday followed by gradual recovery

to mostly normal after about 2100Z. 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 until

about 0900Z Sunday due to solar flux index of about 84.



20 meter daytime and evening propagation through the auroral ovals

and polar regions is likely to be mostly normal through about 0900Z

Sunday but interrupted by below normal intervals from about 2100Z

Friday through 0900Z Saturday. Persistent below normal propagation

is likely after about 0900Z Sunday followed by gradual recovery

to mostly normal after 2100Z. 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 until about 0900Z Sunday due

to solar flux index of about 84.



17 and 15 meter daytime long distance propagation in the northern

hemisphere is likely to improve slightly until about 0900Z Sunday

due to solar flux of 84. 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 close to background levels through about

2100Z Friday with possible enhancements through 0900Z Saturday

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 on Friday and Saturday. Geomagnetic storms and

earth directed CMEs strong enough to affect HF propagation

are not likely until about 0900Z Sunday when a G2 moderate

geomagnetic storm is possible due to expected arrival of an earth

directed CME.



Mid latitude northern hemisphere sunset is now 34 minutes later

and daylength is 86 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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