The solar wind environment at the ACE spacecraft began to reflect
disturbed conditions over the past 24 hours. Around 26/2100 UTC, phi
began to shift from a positive orientation as wind speed and density
increased. Wind speed rose slightly from near 280 km/s to 300-310 km/s.
The total magnetic field which had been less than 10 nT began rising
gradually around 27/0143 UTC, climbing from near 6 nT to 15 nT by
27/0900 UTC. Bz became mostly negative after 27/0031 UTC and continued
declining to reach -14 nT by 27/0900 UTC. These conditions suggested
the arrival of the anticipated CME.