An unusual disturbance has appeared on Jupiter at the interface of the South Equatorial Belt (SEB) and the Equatorial Zone (EZ). It's visible as a very elongated bluish feature, highlighted in the center image above. The feature's bluish hue is more pronounced when it's near Jupiter's limb but is quite subtle when crossing the central meridian.
This disturbance was first detected on February 26, 2004, by European amateurs. On the 29th the new feature was some 40° long (in longitude) and was transiting Jupiter's central meridian about 2.5 hours before the Great Red Spot (GRS). Based on this estimate, you can use our GRS calculator to determine the approximate transit times of this disturbance on the next few nights. The time difference between the new feature and the GRS will increase slowly because features in Jupiter's EZ rotate slightly faster than the GRS.