[Ips-hf-warning] ASWFC HF DEPRESSION WARNING issued 0447 UT on 02 Jan 2025 [SEC=OFFICIAL]

[Australian Space Weather Forecasting Centre]

SUBJ: ASWFC HF RADIO COMMUNICATIONS WARNING 25/02
ISSUED AT 0446UT/02 JANUARY 2025
BY THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE.

Due to recent geomagnetic activity, HF maximum usable frequencies 
are currently depressed by up to 40% and are expected to continue 
on 02-Jan. HF radio propagation conditions in the Australian 
region are also degraded, with periodic blackout conditions. 
The degradations are expected to ease by 03-Jan, but depressions 
are expected to linger over 03-04 Jan.

DEGRADED HF PROPAGATION CONDITIONS EXPECTED
FROM 02-04 JANUARY 2025
IF COMMS DIFFICULTIES EXPERIENCED TRY A LOWER FREQUENCY BAND
_____________________________________________________________

HF COMMUNICATIONS FORECAST (AUSTRALIAN/NEW ZEALAND REGION)
                                   FREQUENCY BANDS
       T-index      MUFs        2  4  6  8 12 16 22 26
_____________________________________________________________
02 Jan:   -9   normal/-40%      2  4  4  4  8  8 12 12
03 Jan:   55   normal/-20%      2  4  6  8  8 12 16 16
04 Jan:   71   normal/-15%      2  4  6  8 12 12 16 22

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