[RSM] W3LPL Forecast Thur-Fri Apr 15-16

[Art Boyars]

Sorry I'm a little late with this one.
(Good thing this weekend is not a DX 'Test.)

From: donovanf at erols.com
To: PVRC <pvrc at mailman.qth.net>
Cc:
Bcc:
Date: Thu, 15 Apr 2021 01:52:16 -0400 (EDT)
Subject: [PVRC] Normal propagation through 0600Z Friday steadily degrading
to below normal after 1500Z

Long distance propagation forecast for Thursday and Friday, April 15-16


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

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



Low latitude propagation is likely to be normal through Friday.

Mid latitude propagation is likely to be normal through about 0600Z

Friday, mostly below normal after about 0600Z, then below normal

after about 1500Z. High latitude propagation is likely to be normal

through about 0600Z Friday, degrading to below normal after

about 0600Z.


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 74 through Friday.

A small sunspot region is slowly growing and now has

12 tiny sunspots having little effect on HF propagation.



We are in 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 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 normal on

Thursday and below normal on Friday.



30 meter propagation through the auroral ovals and across polar

regions is likely to be normal through about 0600Z Friday, degrading

to mostly below normal after about 0600Z, then below normal after

about 1500Z. 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 long distance propagation is

unreliable during most of the night in the northern hemisphere

because of insufficient residual night time F region electron density

due to 12 tiny sunspots on the visible disk having little effect on

HF propagation.



20 meter daytime propagation through the auroral ovals and across

polar regions is likely to be normal through about 0600Z Friday,

degrading to mostly below normal after about 0600Z, then below

normal after about 1500Z. 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. Night time 20 meter long distance propagation in the northern

hemisphere continues to be unreliable because of insufficient residual

F region electron density due to 12 tiny sunspots on the visible disk

having little effect on HF propagation.



17 and 15 meter daytime long distance propagation in the northern

hemisphere continues to be shorter in duration because of insufficient

F2 region electron density due to 12 tiny sunspots on the visible disk

having little effect on HF propagation. 12 and 10 meter daytime long

distance propagation is likely to be unreliable and mostly 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 background levels through about 0600Z

Friday, then mildly enhanced and disturbed by earth-directed

coronal hole high speed stream effects after about 0600Z, then more

strongly enhanced and disturbed after 1500Z. There is a slight risk

of a minor geomagnetic storm late Friday. CMEs and solar flares

strong enough to affect HF propagation are not likely through Friday.



Mid latitude northern hemisphere sunset is now 25 minutes later

and daylength is 65 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 3 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 1800Z, 2000Z and 2200Z 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