NOAA still expects a G2 storm Friday morning, and a second solar blast may reach Earth Saturday night

Note

NOAA’s Space Weather Prediction Center issued Watch WATA30, Serial 283, at 12:33 PM EDT on Oct 6, after sunspot Region 4549 produced an M1.4 flare and a halo coronal mass ejection with an Earth-directed part. It calls for a G2 (Moderate) geomagnetic storm on Oct 9 and is still the watch in effect. SWPC’s Forecast Discussion issued at 1230 UTC Oct 8 keeps that outlook: G1 to G2 storms are likely on Oct 9 with the arrival of the Oct 6 CME events. The 3-Day Forecast puts Kp at 5.00 (G1) from 0300 to 0600 UTC and 5.67 (G2) from 0900 to 1200 UTC on Oct 9. In Eastern time that is roughly 11 PM Thursday to 2 AM Friday, then about 5 to 8 AM Friday. A coronal hole high-speed stream is expected to follow, keeping the field unsettled to active through Oct 10. This is a moderate storm watch, not a severe storm forecast.

On Oct 7, Region 4549 produced a C7.9 flare at 1317 UTC, the largest of the day, followed by a CME seen off the Sun’s northwest edge in SOHO/LASCO C2 coronagraph images from 1500 UTC. SWPC says its modeling of that CME indicates an Earth-directed component arriving early on the Oct 11 UTC day, which is Saturday night into Sunday in the eastern U.S. SWPC has not issued a storm watch for that date. Region 4549 sits at N10W22 and is classed beta-gamma-delta, with opposite magnetic polarities crowded together, the kind of group forecasters watch for stronger flares. SWPC puts the chance of M-class flares at 40% per day through Oct 10 and of R3 (strong) or greater at 5%.

At 11:48 AM EDT Thursday an M6.7 flare peaked at N12W20, close to Region 4549’s reported position, and caused an R2 (Moderate) radio blackout, a limited loss of high-frequency radio on the sunlit side of Earth for tens of minutes. SWPC had not said whether it launched a CME as of 12:15 PM EDT.

High-energy electrons above 2 MeV at geosynchronous orbit, where many communications and weather satellites sit, crossed NOAA’s 1,000 pfu alert level at 1830 UTC Oct 5 and have stayed above it, peaking at 11,911 pfu at 1645 UTC Oct 7. SWPC expects high levels through Oct 9, easing after the CME arrives. Protons are at background, with a 10% chance of an S1 radiation storm through Oct 10.

Back-to-back CMEs from one complex region are the setup forecasters watch most closely, because a second cloud can arrive into a field already disturbed by the first. Arrival times usually carry an uncertainty of several hours either way, and the Oct 11 timing is first-pass modeling only. Nothing official says this week will go beyond G2.