[RSM] W3LPL forecast Wed-Thur Apr 21-22

[Art Boyars]

From: donovanf at erols.com
To: PVRC <pvrc at mailman.qth.net>
Cc:
Bcc:
Date: Wed, 21 Apr 2021 01:12:55 -0400 (EDT)
Subject: [PVRC] Propagation is likely to be mostly normal through Thursday

Long distance propagation forecast for Wednesday and Thursday, April 21-22


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

Thursday. Propagation crossing the auroral ovals and polar regions

is likely to be mostly normal with below normal intervals through

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.



The solar flux index (SFI) is likely to be 80 or higher over the next

week. Three active regions containing a total of 24 mostly tiny sunspots

are slightly improving HF propagation.



We are beginning to exit 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 Thursday. 80 and 40 meter

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

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

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

mostly normal through Thursday.



30 meter propagation through the auroral ovals and across polar

regions is likely to be mostly normal through 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 propagation is likely to improve

slightly through Thursday due to solar flux of 80 or higher.



20 meter daytime and evening propagation through the auroral ovals

and across polar regions is likely to be mostly normal through Thursday.

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 Thursday due to solar flux of 80 or higher.



17 and 15 meter daytime long distance propagation in the northern

hemisphere is likely to improve slightly through Thursday due to

solar flux of 80 or higher. 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 Thursday. Geomagnetic

storms and earth directed CMEs and solar flares strong enough to affect

HF propagation are not likely through Thursday.



Mid latitude northern hemisphere sunset is now 31 minutes later and

daylength is 79 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 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