Forecast Discussion

Product: Forecast Discussion Issued: 2021 May 16 1230 UTC Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
Solar Activity
.24 hr Summary… Solar activity was very low. Region 2822 (N16W42, Hsx/alpha) was in decay and Region 2823 (S23 L=326) reached plage. No Earth-directed CMEs were observed in available coronagraph imagery.
.Forecast… Solar activity is expected to be very low over 16-18 May.
Energetic Particle
.24 hr Summary… The greater than 2 MeV electron flux was normal to moderate and the greater than 10 MeV proton flux remained at background values.
.Forecast… The greater than 2 MeV electron flux is expected to reach moderate levels and the greater than 10 MeV proton flux is expected to remain at background levels over 16-18 May.
Solar Wind
.24 hr Summary… Solar wind parameters, as measured by the DSCOVR spacecraft, were at near background conditions. Total magnetic field strength was at or below 5 nT and no significant periods of southward Bz were observed. Solar wind speeds were in a declining trend, ending the period near 350 km/s. Phi angle was predominantly oriented in the negative sector.
.Forecast… Solar wind parameters are expected to continue at near background levels over 16 May. Enhanced conditions are expected due to influence from a negative polarity CH HSS on 17 May. On 18 May, the anticipated arrival of the periphery of a CME that left the Sun on 13 May is likely to further enhance the solar wind environment.
Geospace
.24 hr Summary… The geomagnetic field was quiet.
.Forecast… The geomagnetic field is expected to continue at mostly quiet levels on 16 May. On 17 May, an increase active conditions are likely in response to the onset of coronal hole influence. Modeling of a CME that left the Sun on 13 May suggests passage by Earth on 18 May. The resulting geomagnetic response is likely to be active to G1 (Minor) storm levels.
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NOAA 3-Day Forecast

Product: 3-Day Forecast Issued: 2021 May 16 1230 UTC Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
A. NOAA Geomagnetic Activity Observation and Forecast
The greatest observed 3 hr Kp over the past 24 hours was 2 (below NOAA Scale levels). The greatest expected 3 hr Kp for May 16-May 18 2021 is 5 (NOAA Scale G1).
NOAA Kp index breakdown May 16-May 18 2021
May 16 May 17 May 18 00-03UT 1 2 3 03-06UT 0 2 3 06-09UT 1 1 2 09-12UT 2 1 3 12-15UT 1 2 3 15-18UT 1 3 3 18-21UT 2 4 4 21-00UT 2 4 5 (G1)
Rationale: A CME that left the Sun on 13 May is likely to further enhance ongoing influence form a negative polarity CH HSS on 18 May. The resulting geomagnetic response is likely to reach active to G1 (Minor) geomagnetic storm conditions.
B. NOAA Solar Radiation Activity Observation and Forecast
Solar radiation, as observed by NOAA GOES-16 over the past 24 hours, was below S-scale storm level thresholds.
Solar Radiation Storm Forecast for May 16-May 18 2021
May 16 May 17 May 18 S1 or greater 1% 1% 1%
Rationale: No S1 (Minor) or greater solar radiation storms are expected. No significant active region activity favorable for radiation storm production is forecast.
C. NOAA Radio Blackout Activity and Forecast
No radio blackouts were observed over the past 24 hours.
Radio Blackout Forecast for May 16-May 18 2021
May 16 May 17 May 18 R1-R2 1% 1% 1% R3 or greater 1% 1% 1%
Rationale: No R1 (Minor) or greater radio blackouts are expected. No significant active region flare activity is forecast.
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Geoalert

:Product: GEOALERT :Issued: 2021 May 16 0330 UTC # Prepared by the U.S. Dept. of Commerce, NOAA, # Space Weather Prediction Center. # Geoalert WWA136 UGEOA 20401 10516 0330/ 9930/ 10161 20161 30161 99999 UGEOE 20401 10516 0330/ 15/00 99999 UGEOI 20401 10516 0330/ 15/// 10024 20730 3008/ 4///0 50000 62608 74304 80002 90060 99999 UGEOR 20401 10516 0330/ 15/24 16102 12822 20000 30000 43312 50050 60003 43516 01000 12823 20000 30000 41001 50010 60001 32523 00000 99999

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Solar & Geophysical Activity Summary (SGAS)

:Product: Solar and Geophysical Activity Summary :Issued: 2021 May 16 0245 UTC # Prepared jointly by the U.S. Dept. of Commerce, NOAA, # Space Weather Prediction Center and the U.S. Air Force. # Joint USAF/NOAA Solar and Geophysical Activity Summary SGAS Number 136 Issued at 0245Z on 16 May 2021 This report is compiled from data received at SWO on 15 May A. Energetic Events Begin Max End Rgn Loc Xray Op 245MHz 10cm Sweep None B. Proton Events: None. C. Geomagnetic Activity Summary: The geomagnetic field was quiet to unsettled. D. Stratwarm: Not Available E. Daily Indices: (real-time preliminary/estimated values) 10 cm 073 SSN 024 Afr/Ap 008/008 X-ray Background A2.5 Daily Proton Fluence (flux accumulation over 24 hrs) GT 1 MeV 5.6e+04 GT 10 MeV 4.3e+04 p/(cm2-ster-day) (GOES-16 satellite synchronous orbit W75 degrees) Daily Electron Fluence GT 2 MeV 1.80e+06 e/(cm2-ster-day) (GOES-16 satellite synchronous orbit W75 degrees) 3 Hour K-indices: Boulder 3 2 3 2 2 2 1 1 Planetary 3 1 3 2 1 1 1 1 F. Comments: None.
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Solar Region Summary (SRS)

:Product: Solar Region Summary :Issued: 2021 May 16 0030 UTC # Prepared jointly by the U.S. Dept. of Commerce, NOAA, # Space Weather Prediction Center and the U.S. Air Force. # Joint USAF/NOAA Solar Region Summary SRS Number 136 Issued at 0030Z on 16 May 2021 Report compiled from data received at SWO on 15 May I. Regions with Sunspots. Locations Valid at 15/2400Z Nmbr Location Lo Area Z LL NN Mag Type 2822 N16W35 334 0050 Cao 04 03 Beta 2823 S23W25 325 0010 Axx 01 01 Alpha IA. H-alpha Plages without Spots. Locations Valid at 15/2400Z May Nmbr Location Lo None II. Regions Due to Return 16 May to 18 May Nmbr Lat Lo None
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Forecast Discussion

Product: Forecast Discussion Issued: 2021 May 16 0030 UTC Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
Solar Activity
.24 hr Summary… Solar activity was very low. Region 2822 (N16W35, Cao/beta) continued to decay and Region 2823 (S23W25, Axx/alpha) has almost become plage. No Earth-directed CMEs were observed in available coronagraph imagery.
.Forecast… Very low solar activity is expected, with a slight chance for C-class flares, on 16-18 May.
Energetic Particle
.24 hr Summary… The greater than 2 MeV electron flux was normal to moderate and the greater than 10 MeV proton flux remained at background values.
.Forecast… The greater than 2 MeV electron flux is expected to reach moderate levels and the greater than 10 MeV proton flux is expected to remain at background levels over 16-18 May.
Solar Wind
.24 hr Summary… Solar wind parameters, as measured by the DSCOVR spacecraft, reflected a slight enhancement early in the reporting period. Total magnetic field strength reached a brief peak of 10 nT before settling near 3 nT. Bz was +/- 4 during the latter half of the period. Solar wind speeds averaged near 425 km/s. Phi angle was predominantly negative.
.Forecast… Solar wind parameters are expected to trend towards background levels through 16 May. Enhanced conditions are expected due to influence from a negative polarity CH HSS on 17 May. On 18 May, the anticipated arrival of a CME from 13 May is expected to enhance conditions even further.
Geospace
.24 hr Summary… The geomagnetic field was at quiet to unsettled levels.
.Forecast… The geomagnetic field is expected to continue at mostly quiet levels, with isolated unsettled conditions, on 16 May. On 17 May, increase to unsettled levels are likely, with isolated active periods, in response to coronal hole influence. Mostly unsettled to active periods, with isolated G1 (Minor) storm periods are likely on 18 May due to the arrival of a CME from 13 May.
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NOAA 3-Day Forecast

Product: 3-Day Forecast Issued: 2021 May 16 0030 UTC Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
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 16-May 18 2021 is 5 (NOAA Scale G1).
NOAA Kp index breakdown May 16-May 18 2021
May 16 May 17 May 18 00-03UT 2 2 3 03-06UT 1 2 3 06-09UT 1 1 2 09-12UT 1 1 3 12-15UT 1 2 3 15-18UT 1 3 3 18-21UT 2 4 4 21-00UT 2 4 5 (G1)
Rationale: G1 (Minor) geomagnetic storm conditions are likely on 18 May due to negative polarity CH HSS influence and CME effects.
B. NOAA Solar Radiation Activity Observation and Forecast
Solar radiation, as observed by NOAA GOES-16 over the past 24 hours, was below S-scale storm level thresholds.
Solar Radiation Storm Forecast for May 16-May 18 2021
May 16 May 17 May 18 S1 or greater 1% 1% 1%
Rationale: No S1 (Minor) or greater solar radiation storms are expected. No significant active region activity favorable for radiation storm production is forecast.
C. NOAA Radio Blackout Activity and Forecast
No radio blackouts were observed over the past 24 hours.
Radio Blackout Forecast for May 16-May 18 2021
May 16 May 17 May 18 R1-R2 1% 1% 1% R3 or greater 1% 1% 1%
Rationale: No R1 (Minor) or greater radio blackouts are expected. No significant active region flare activity is forecast.
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Report of Solar Geophysical Activity (RSGA)

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast SDF Number 135 Issued at 2200Z on 15 May 2021
IA. Analysis of Solar Active Regions and Activity from 14/2100Z to 15/2100Z: Solar activity has been at very low levels for the past 24 hours. There are currently 2 numbered sunspot regions on the disk. IB. Solar Activity Forecast: Solar activity is expected to be very low with a slight chance for a C-class flare on days one, two, and three (16 May, 17 May, 18 May).
IIA. Geophysical Activity Summary 14/2100Z to 15/2100Z: The geomagnetic field has been at quiet to unsettled levels for the past 24 hours. Solar wind speed reached a peak of 479 km/s at 15/0949Z. Total IMF reached 9 nT at 15/0446Z. The maximum southward component of Bz reached -6 nT at 15/0543Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 192 pfu. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet levels on day one (16 May), quiet to active levels on day two (17 May) and quiet to minor storm levels on day three (18 May).
III. Event probabilities 16 May-18 May Class M 01/01/01 Class X 01/01/01 Proton 01/01/01 PCAF green
IV. Penticton 10.7 cm Flux Observed 15 May 073 Predicted 16 May-18 May 073/073/077 90 Day Mean 15 May 076
V. Geomagnetic A Indices Observed Afr/Ap 14 May 004/005 Estimated Afr/Ap 15 May 005/005 Predicted Afr/Ap 16 May-18 May 006/005-008/012-015/018
VI. Geomagnetic Activity Probabilities 16 May-18 May A. Middle Latitudes Active 15/35/35 Minor Storm 05/10/20 Major-severe storm 01/01/05 B. High Latitudes Active 15/15/10 Minor Storm 20/30/25 Major-severe storm 20/45/50
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NOAA 3-Day Forecast

Product: 3-Day Forecast Issued: 2021 May 15 1230 UTC Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
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 15-May 17 2021 is 4 (below NOAA Scale levels).
NOAA Kp index breakdown May 15-May 17 2021
May 15 May 16 May 17 00-03UT 3 2 2 03-06UT 1 1 2 06-09UT 3 1 1 09-12UT 2 1 1 12-15UT 1 1 2 15-18UT 1 1 3 18-21UT 1 2 4 21-00UT 2 2 4
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-16 over the past 24 hours, was below S-scale storm level thresholds.
Solar Radiation Storm Forecast for May 15-May 17 2021
May 15 May 16 May 17 S1 or greater 1% 1% 1%
Rationale: No S1 (Minor) or greater solar radiation storms are expected. No significant active region activity favorable for radiation storm production is forecast.
C. NOAA Radio Blackout Activity and Forecast
No radio blackouts were observed over the past 24 hours.
Radio Blackout Forecast for May 15-May 17 2021
May 15 May 16 May 17 R1-R2 1% 1% 1% R3 or greater 1% 1% 1%
Rationale: No R1 (Minor) or greater radio blackouts are expected. No significant active region flare activity is forecast.
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Forecast Discussion

Product: Forecast Discussion Issued: 2021 May 15 1230 UTC Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
Solar Activity
.24 hr Summary… Solar activity was very low. Region 2822 (N16W27, Cao/beta) continued to decay and Region 2823 (S23W18, Axx/alpha) has almost become plage. No Earth-directed CMEs were observed in available coronagraph imagery.
.Forecast… Very low solar activity is expected, with a slight chance for C-class flares, on 15-17 May.
Energetic Particle
.24 hr Summary… The greater than 2 MeV electron flux was normal to moderate and the greater than 10 MeV proton flux remained at background values.
.Forecast… The greater than 2 MeV electron flux is expected to reach moderate levels and the greater than 10 MeV proton flux is expected to remain at background levels over 15-17 May.
Solar Wind
.24 hr Summary… Solar wind parameters, as measured by the DSCOVR spacecraft, reflected a slight enhancement in the latter half of the reporting period. Total magnetic field strength reached a brief peak of 10 nT. Bz reached -6 nT between 15/0530-0600 UTC. Solar wind speeds gradually climbed to ~370 to ~460 km/s. Phi angle was predominantly negative.
.Forecast… Solar wind parameters are expected to trend towards background levels over 15 May and persist through 16 May. Influence from a negative polarity CH HSS is likely on over 17 May.
Geospace
.24 hr Summary… The geomagnetic field was at quiet to unsettled levels.
.Forecast… The geomagnetic field is expected to continue at mostly quiet levels, with isolated unsettled conditions, on 15 May. Quiet conditions are expected over 16 May. On 17 May, increase to unsettled levels are likely, with isolated active periods, in response to coronal hole influence.
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