[RSM] W3LPL forecast Wed-Thur, Mar 31 - Apr 1

Wed Mar 31 06:04:29 EDT 2021

From: donovanf at erols.com
To: PVRC <pvrc at mailman.qth.net>
Cc:
Bcc:
Date: Wed, 31 Mar 2021 02:05:38 -0400 (EDT)
Subject: [PVRC] Mostly normal propagation through Thursday

Long distance propagation forecast for Wednesday and Thursday, March
31-April 1

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

Thursday. Auroral oval and polar propagation 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 remain at about 75 thoug

 at least Thursday There are no sunspots on the visible disk.

We are in the most disturbed weeks of the March-April geomagnetic

storm season when the earth passes 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 at about 0200Z is likely to be

mostly normal through Thursday. 80 and 40 meter short path

propagation from North America to east Asia is likely to be mostly

normal with below normal intervals through Thursday.

40 and 30 meter long path propagation from North America to

southeast Asia at about 2330Z is likely to be normal through

Thursday.

30 meter auroral oval and polar propagation is likely to be mostly

normal with below normal intervals 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 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 no sunspots on

the visible disk.

20 meter daytime auroral oval and polar propagation is likely to be

mostly normal with below normal intervals through Thursday. 20 meter

northern hemisphere trans-polar propagation within a few hours of

sunrise and sunset will steadily improve with gradually increasing

electron density in the polar cap F2 region through June. Night time

20 meter long distance propagation in the northern hemisphere continues

to be very unreliable because of insufficient residual F region electron

density due to no sunspots on the visible disk.

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 no sunspots on the visible disk. 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 relatively infrequent through

at least late 2021. 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 an 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 return to background levels during Wednesday and

remain at background levels on Thursday. Geomagnetic storms and

solar flares strong enough to affect HF propagation are not likely through

Thursday.

Mid latitude northern hemisphere sunset is now 11 minutes later and

daylength is 28 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. Daylength at northern polar latitudes is approximately

18 hours and increasing by 30 minutes per day until it reaches

24 hours on April 7th, significantly 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/

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