:Issued: 2025 Nov 15 1301 UTC
:Product: documentation at http://www.sidc.be/products/presto
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# FAST WARNING 'PRESTO' MESSAGE  from the SIDC (RWC-Belgium)         #
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A halo coronal mass ejection (CME) was observed in SOHO/LASCO coronagraph data. It
was associated with the X4.1 flare (SIDC Flare 6063) that peaked at 08:30 UTC on 14
Nov 2025 from SIDC Sunspot Group 687 (NOAA AR 4274). The plane-of-sky speed in
SOHO/LASCO is about 1500 km/s, while STEREO-A indicates about 1300 km/s. A 3D
reconstruction gives a true speed of roughly 1650 to 1700 km/s. The apex is slightly
offset from the Sun-Earth line, so a direct impact is unlikely, but a flank encounter
remains possible. EUHFORIA modeling indicates a glancing blow early on 16 Nov with at
most a weak to moderate shock or compression, and geomagnetic activity up to active
or minor storm levels depending on the interplanetary magnetic field orientation
within the CME.
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