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Solar-terrestrial indices for 20 May follow.
Solar flux 114 and estimated planetary A-index 8.
The estimated planetary K-index at 0600 UTC on 21 May was 2.33.

No space weather storms were observed for the past 24 hours.

No space weather storms are predicted for the next 24 hours.


Geo Magnetic Forecast:

NOAA Ap Index Forecast
Observed Ap 19 May 019
Estimated Ap 20 May 008
Predicted Ap 21 May-23 May 010-009-008

NOAA Geomagnetic Activity Probabilities 21 May-23 May
Active                35/45/35
Minor storm           05/10/05
Moderate storm        01/01/01
Strong-Extreme storm  01/01/01

NOAA Kp index forecast 21 May - 23 May
             May 21    May 22    May 23
00-03UT        2.67      2.67      2.33
03-06UT        2.00      3.67      2.33
06-09UT        2.33      2.00      2.33
09-12UT        2.33      0.67      2.33
12-15UT        2.33      1.67      1.67
15-18UT        2.33      1.67      2.00
18-21UT        2.33      2.33      2.33
21-00UT        2.67      2.33      2.33


Extended Three Day Forecast:

A. NOAA Geomagnetic Activity Observation and Forecast

The greatest observed 3 hr Kp over the past 24 hours was 3 (below NOAA
Scale levels).
The greatest expected 3 hr Kp for May 21-May 23 2026 is 3.67 (below NOAA
Scale levels).

NOAA Kp index breakdown May 21-May 23 2026

             May 21       May 22       May 23
00-03UT       2.67         2.67         2.33
03-06UT       3.67         3.00         2.67
06-09UT       2.33         2.00         2.33
09-12UT       2.00         1.67         1.67
12-15UT       1.67         0.67         1.67
15-18UT       2.33         1.67         2.00
18-21UT       2.33         2.33         2.33
21-00UT       3.00         2.67         2.33

Rationale: No G1 (Minor) or greater geomagnetic storms are expected.

B. NOAA Solar Radiation Activity Observation and Forecast

Solar radiation, as observed by NOAA GOES-19 over the past 24 hours, was
below S-scale storm level thresholds.

Solar Radiation Storm Forecast for May 21-May 23 2026

              May 21  May 22  May 23
S1 or greater    5%      5%      5%

Rationale: No S1 (Minor) or greater solar radiation storms are expected.


C. NOAA Radio Blackout Activity and Forecast

No radio blackouts were observed over the past 24 hours.

Radio Blackout Forecast for May 21-May 23 2026

              May 21        May 22        May 23
R1-R2           20%           25%           25%
R3 or greater    5%            5%            5%

Rationale: There is a slight chance for R1-R2 (Minor-Moderate) radio
blackouts on 21 May, increasing to a chance on 22-23 May due to regions
anticipated to rotate onto the visible disk in that interval.


Extended Space Weather Discussion:

Solar Activity

.24 hr Summary...
Solar activity continued at low levels during the past 24 hours, with
four active regions on the visible disk. The largest events were a C1.0
at 20/0443 UTC from the NE limb and a C1.0/Sf at 20/1017 UTC from
Region 4439 (N06E15, Hrx/alpha), that was accompanied by Type-III radio
sweeps. This region was responsible for the majority of the periods
activity, which otherwise included a B8.7 flare at 20/0332 UTC from
Region 4436 (N18W78, Csi/beta). Region 4441 (N07W30, Eai/beta) showed
some development during the period while 4443 (S16E23, Axx/alpha)
remained stable.

Coronal activity was observed in CCOR-1 imagery after 20/1700, but
additional data is needed for further analysis.

.Forecast...
Solar activity is expected to remain at low levels through 23 May, with
a slight chance for isolated M-class flares (R1-R2/Minor-Moderate) on 21
May, primarily due to the complexity of Region 4441 and the recent
flaring history of Region 4436. An increased in activity is anticipated
22-23 May as multiple active regions, tracked via far-side satellite and
helioseismology imagery, rotate into view.

Energetic Particle

.24 hr Summary...
The greater than 2 MeV electron flux at geosynchronous orbit remained at
high levels, reaching a peak level of 1716 pfu at 20/1615 UTC. The
greater than 10 MeV proton flux at geosynchronous orbit remained at
background levels.

.Forecast...
The greater than 2 MeV electron flux is expected to return to normal to
moderate levels on 21 May as current conditions wane. A return to
high levels is anticipated on 22-23 May following the geoeffective onset
of a new coronal hole high-speed stream. The greater than 10 MeV proton
flux is expected to remain at background levels through 23 May.

Solar Wind

.24 hr Summary...
Solar wind parameters trended toward background conditions with speeds
reaching a peak of 542 km/s at 20/0222Z and then decreasing steadily
throughout the reporting period, ending at ~450 km/s. Total IMF reached
6 nT at 20/0158Z. The maximum southward component of Bz reached -5 nT at
20/0010Z, and the phi angle remained on the negative sector.

.Forecast...
Solar wind parameters are expected to continue trending toward nominal
conditions through early on 21 May. Mild enhancements are likely on 21
May from a solar sector boundary crossing, with more pronounced
high-speed stream conditions expected on 22-23 May due to the influences
of a positive polarity coronal hole high-speed stream (+CH HSS).

Geospace

.24 hr Summary...
The geomagnetic field has been at quiet to unsettled levels for the past
24 hours.

.Forecast...
Isolated active periods are likely on 21 May following an anticipated
sector boundary crossing and the onset of the approaching +CH HSS. Quiet
to unsettled levels are anticipated 22-23 May due to persisting +CH HSS
influences.


27 Day Forecast:

Date | Radio Flux | Planetary A Index | Largest Kp Index
2026 May 18     105          21          5
2026 May 19     110          21          5
2026 May 20     115           8          3
2026 May 21     115          10          3
2026 May 22     110           8          3
2026 May 23     112           5          2
2026 May 24     112           5          2
2026 May 25     115           5          2
2026 May 26     115           5          2
2026 May 27     115          12          4
2026 May 28     120          10          3
2026 May 29     125           8          3
2026 May 30     130           8          3
2026 May 31     135           8          3
2026 Jun 01     130           5          2
2026 Jun 02     130           5          2
2026 Jun 03     130           5          2
2026 Jun 04     125          12          4
2026 Jun 05     120           5          2
2026 Jun 06     115           5          2
2026 Jun 07     110           5          2
2026 Jun 08     105           5          2
2026 Jun 09     105          10          3
2026 Jun 10     100           5          2
2026 Jun 11      95          30          6
2026 Jun 12      95          25          5
2026 Jun 13      95          12          4


  • GRAPH OPTIONS: Learn more
    It is recommended that you start out with the default options. As you get used to AF you can disable additional information and combine data series' together to maxamise the use of screen space.

  • DATA SOURCES: Learn more
    Some data sources can only be enabled or disabled via the tick box. Others are disabled using the slider set to 0, or enabled by setting the slider from 0.5 to 4. This number also represents the thinkness of the line plot onto the graph.

  • 'The' Aurora Forecast Index: Learn more
    These are two good options for predicting Auroras.

    The Aurora Forecast Index takes into account many data sources. As a general rule if it stays high for many hours there is a good possibility of an Aurora present.

    Aurora Forecast website usage is also a good indicator, as visitors to the site come from many traffic sources. General internet and community chatter transplating to visits is a great indicator.

  • Planatary K Index (Kp): Learn more
    The Kp number is a system of measuring aurora strength. The range goes from 0 to 9 (0 being calm, 1 very weak, all the way up to 9, which would represent a major geomagnetic storm with strong auroras visible).

    Kp 5 and above is classified as a geomagnetic storm. Most Aurora Hunters consider prolonged 3+ or higher worth investigation.

  • Ovation (Model) Short Term Forecast (GW):' Learn more
    The Ovation-Prime Model produced by SWPC calculates the energy interacting with the Earths magnetic field. This is a good indicator for Aurora activity.
  • DSCOVR Observatory (L1): Learn more

    The DSCOVR or Deep Space Climate Obervatory sits 1.5 million Kilometers from Earth, between the Earth and the Sun in the L1 orbit point, the neutral gravity point between the Earth and the Sun. DSCOVR provides space weather readings, allowing for up to an hour of warning on weather events. This is why DSCOVR's data appears in the future on the graph.

    Strong negative Bz direction is linked to Aurora's because the solar wind magnetic direction is in direct oposition with the Earths magnetic field.

  • ACE Observatory (L1): Learn more

    ACE or Advanced Composition Explorer sits 1.5 million Kilometers from Earth, between the Earth and the Sun in the L1 orbit point, the neutral gravity point between the Earth and the Sun. ACE has now been replaced by DSCOVR, but the data is still useful for comparing to DSCOVR.
  • GOES Satalites: Learn more

    GOES or Geostationary Operational Environmental Satellites sit 46 Kilometers above the Earth in geostationary orbit. They provide local space weather data and are a good indicator for current geomagnetic conditions.

  • Terrestrial Magnetometer Sources: Learn more
    Terrestrial or surface magnetometers detect fluctuations in the Earths magnetic field from the ground.
    These do not work as well as satalites as the magnetic field obsorbs some of the effects from the solar winds.
    There is a mix of govenment and citizen science stations listed here, including two run by Aurora Forecast in Hobart.
  • User Magnetometer ID's: Learn more
    If you have a TAFS Magnetometer and you want to add it to the graph you can do it here.
    Insent your Mag's Unique ID.

 

v4.16b

Aurora Forecast is free to use, however it takes a lot of time and effort to maintain. If you find it useful and are a regular user then please consider making a donation to keep it running. Feedback is always welcome.


v4.X Release 17th Dec 2020)
Fixed New GOES and HPI inputs from noaa for Json (17/12/20).
Addded the ability to add 2 custom Magnetometers in settings (comming soon) (18/10/19).
Improved Hobart Magnetometer code. (18/18/19)
Move all presets into their own pop out side menu. (19/06/19)
Added Composite weather maps (TAS, VIC and SA), thanks to Oz forecast! (19/06/19)
UI Upgrades, Name, Logo and Website Site Changes.
Added custom line widths for most items.
Added GOES Difference (#1 - #2)
Added Ovation-prime model outputs.

v3.8x
Various Updates, New AF Index Algo. (8/12/18)

v3.6x
Added more Presets. Disabled Presets overwriting graph views (6/7/18)
Added GeoSpace Kp Model Prediction. (3/7/18)
Added SWPC Kp Forecast + Observation. (2/7/18)
Removed WingKP and USKp. :( No longer Avaliable. (2/7/18)
Removed feed from www.dunedinaurora.nz (Unreliable). (2/7/18)
Updates to latest JQuery, JQuery Mobile and AmCharts etc. (2/7/18)
Enhanced Pro setting with Dynamic Preasure. (2/7/18)
Added Quickselect preset buttons to main page. (2/7/18)
 
v3.5x
Added Ruru Observatory Magnetometer. (25/4/28)
Added Forecast Sub Tabset. (1/3/18)
Added Extended Discussion Text, 27Day FC (1/3/18)
Removed Dial, and Added Forecast Report. (28/2/18)
Updated A few settings for better visilation. (28/2/18)
Updated Goes-13 is Now Goes-14 (15/2/18)
Improved Commmunity Activity for faster loads.
Consolidated Proton Density / Dynamic Preasure.
Added Additional Balloon Text.
Added TAFS Visual Probability in %.
User Interface Upgrades.
Add 'Dial' for the basics, with default support.
Added one click presets.
 
v2.1 - v2.49
Added 'Automatic Chart Update' option in settings.
Database caching enabled, significant load time improvements.
Extension to max 96 hours of data, up from 24.
Added ACE Bt,Bx and By for comparison.
Added More User Presets.
Fixed Orentation Change Alert.
Small layout changes.
Added Header Image.
Removed Top Header to fee up Space, Refresh added to Chart Tab.
Added Community Activity Indicator
Fixed MAG value issues in graph.
Added Second Hobart MAG Source.
Updated Comment Features (Disable).
 
v2.0
Fixed DSCOVR B? display bug.
Added MAG Stack Feature.
Upgrade to json feeds.
Feeds are timezone and forecast aware, making them super fast.
DB Optimisation, improved DB search times.
Charts are now zoomable, allow selection and export.
Added USAF Kp, Updated Wing Kp.
Added Ovation Aurora Short Term Forecast.
Added Macquarie Island MAG feed.
Added Mawson MAG Feed.
Added Canberra Feed.
Added MAG feed from www.dunedinaurora.nz (Portobello).
Added Brendan's experemental MAG feed (Hobart).
Fixed cookie bug, One Alert is enough for landscape mode.
 
> v1.0 (Started 20/10/2014)

  Mawson and Macquarie Island data is copyright Commonwealth of Australia (Geoscience Australia), and redistributed under Creative Commons v4.
Thanks to INTERMAGNET for promoting high standards of magnetic observatory practice in providing access to these feeds. (www.intermagnet.org).

Local Australian weather composite maps provided by Oz Forecast

Aurora Forecast is free to use, however it takes a lot of time and effort to maintain.
Why not make a donation to keep it running?
Feedback is always welcome. - ©2022 Brendan Davey