[Ips-dhfpr] ASWFC Daily HF Prop Report - 18 May 25 issued 2330 UT on 18 May 2025 [SEC=OFFICIAL]

[Australian Space Weather Forecasting Centre]

SUBJ: ASWFC DAILY HF PROPAGATION REPORT
ISSUED AT 2330UT/18 MAY 2025
FROM THE AUSTRALIAN SPACE WEATHER FORECAST CENTRE
AUSTRALIAN REGION SUMMARY AND FORECAST

1. SUMMARY (18 MAY) 
Date   T index  Conditions    
18 May    94    Normal-fair    

Flares: none.

MUFs:
   Cocos Island Region:
      Near predicted monthly values during local day.
      Depressed by 20% during local night.
   Niue Island Region:
      Near predicted monthly values during local day.
      Depressed by 30% during local night.
   Northern Australian Region:
      Depressed by 15% during local day.
      Depressed by 15% during local night.
   Southern Australian Region:
      Mostly near predicted monthly values.
   Antarctic Region (Casey/Davis/Mawson):
      Depressed by 30% over the UT day.

PCA Event : No event.

Monthly T index:
Month  T index
Apr      123
May      113
Jun      111


2. FORECAST (19 MAY - 21 MAY)
Date   T index  Conditions       MUFs                              
19 May    95    Normal-fair      Near predicted values to 15-20% 
                                 depressed
20 May    95    Normal-fair      Near predicted monthly values 
                                 to 15-20% depressed    
21 May    95    Normal-fair      Near predicted monthly values 
                                 to 15-20% depressed   

COMMENT: ASWFC HF Communications Warning 48 was issued on 16 
May and is current for 17-19 May. ASWFC SWF HF Communications 
Warning 49 was issued on 18 May and is current for 18-20 May. 
Maximum usable frequencies (MUFs) in the Australian region on 
UT day 18-May were near predicted values to 15% depressed. Sporadic-E 
was observed in Cocos Islands and Darwin during local night hours. 
Spread-F was observed in Hobart. MUFs are expected to be depressed 
by 15-20% to near predicted values over 19-21 May due to ongoing 
coronal hole effects.

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For an explanation of some of the terms in this report, go to
https://www.sws.bom.gov.au, and follow links to Educational->
Glossary on Solar Terrestrial Terms.

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