[Ips-hf-warning] ASWFC HF DEPRESSION WARNING issued 2232 UT on 21 May 2023 [SEC=OFFICIAL]

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SUBJ: ASWFC HF RADIO COMMUNICATIONS WARNING 23/48
ISSUED AT 2232UT/21 MAY 2023
BY THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE.

HF communication conditions may be degraded over 22-24 May due 
to geomagnetic activity. Maximum usable frequencies (MUFs) may 
be depressed by 20%. Shortwave fadeouts are possible.

DEGRADED HF PROPAGATION CONDITIONS EXPECTED
FROM 22-24 MAY 2023
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
_____________________________________________________________
22 May:   87   normal/-20%      2  4  6  8  8 12 16 16
23 May:   87   normal/-20%      2  4  6  8  8 12 16 16
24 May:   87   normal/-20%      2  4  6  8  8 12 16 16

Note:
An SWS MUF depression HF Warning and SWS 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