[Ips-hf-warning] ASWFC HF SHORTWAVE FADEOUT WARNING issued 2323 UT on 04 Jul 2026 [SEC=OFFICIAL]

[Australian Space Weather Forecasting Centre]

SUBJ: ASWFC HF RADIO COMMUNICATIONS WARNING 26/63
ISSUED AT 2322UT/04 JULY 2026
BY THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE.

Active sunspot region (AR) 4479 has produced a high number of 
flares, causing a range of R1-R3 conditions in previous days. 
While this region is due to rotate out of sight in the coming 
days, a new region 4482 is rotating into sight which is showing 
signs of high potential for flaring. For this reason, solar flare 
activity is expected to be R1-R2 over the next few days.

DEGRADED HF PROPAGATION CONDITIONS EXPECTED
FROM 05-06 JULY 2026
IF COMMS DIFFICULTIES EXPERIENCED TRY A HIGHER FREQUENCY BAND
_____________________________________________________________

SOLAR ACTIVITY FORECAST       HF COMMS FADEOUTS
05 Jul:  R1-R2                Probable
06 Jul:  R1-R2                Possible

Note:
An ASWFC MUF depression HF Warning and ASWFC shortwave fadeout 
HF Warning are both current. Shortwave fadeouts degrade 
lower shortwave radio frequencies first (through increased 
ionospheric absorption) and the usual strategy during shortwave 
fadeouts is to try a higher frequency. In contrast, during 
periods of ionospheric MUF depression, the upper frequencies 
are degraded first and the usual strategy is to use a 
lower frequency. 

In general use a lower frequency if you are having trouble
with your normal workable frequency.

If a shortwave fadeout occurs during a period when ionospheric 
MUFs are depressed the available HF bandwidth will be "squeezed", 
with increased absorption raising the lowest usable frequency 
and the ionospheric depression lowering the highest usable 
frequency. Under such conditions it is suggested that the 
HF communicator operates on the highest usable frequency, 
even though this may well be in fact lower than what is normally 
supported for that particular circuit.

Australian Space Weather Forecasting Centre
Bureau of Meteorology
ASWFC at bom.gov.au
www.bom.gov.au | www.sws.bom.gov.au