On May 17, Go detected a tiny white spot within SEB just preceding STrD-2 at II:178.5 deg. in longitude, -17.1 deg. in latitude. The spot emerged from a small barge in SEBs which was in progress of fading. This fact implies that the spot is convective cloud which is observed in initial stage of mid-SEB outbreak. This is a extremely unexpected event, because it was expected that such convective activity of white clouds in SEB which had lost with the termination of mid-SEB outbreak, would not be observed for one or two years until SEB fades away and SEB revival take place. After that, white cloud flowed out from the spot toward preceding-north direction as seen in mid-SEB outbreak, and several white spots were formed by the end of May. On the other hand, bluish filament appeared in following-south side of the spot. A part of the filament flowed into STrD-2 and made it temporarily darken, and the other part cohered as dark spots and began to retrograde beyond STrD-2. This motion indicates that SEBs jetstream is not completely blocked by STrD-2, and a part of it goes straight along SEBs. This activity extended to about 30 deg. long, and its bluish tint made it easy to distinguish from main part of SEB which was yellowish.

The major event took place on SEB is SEB Revival in which entirely faded SEB revives as dark belt, while dark SEB sometimes shows violent activities of white clouds which appears from the belt inside, known as mid-SEB outbreak. It seems that this activity has both characteristics, since it started before SEB faded away. At present, this activity of white cloud is weak, and is not likely to develop so intense as to make entire SEB darken. Moreover, it resembles mid-SEB outbreak with the fact that it took place following RS. Most of initial longitudes of old SEB Revivals are classified into three sources (A, B and C) whose rotation periods are close to System III (Reese's hypothesis). Though recent SEB Revivals in 1990 and 1993 started near source B, none of these sources corresponds to the white spot on May 17. However, dark spots emerged on SEBs can be regarded as activity of south branch of SEB Revival, also there is a instance of old SEB Revival which developed before SEB become faint (1949). Therefore, we have to keep careful watch on this activity for a while, since it is difficult to judge at present which phenomenon it is.

Two South Tropical Disturbances (STrD) were fading along with SEBs. Dark column at p. end of STrD-1 was at II:332.7 deg. (May 11, Kumamori), and gradually prograding. STrD-1 was gradually being overtook by BA due to a little slower drift rate, and dark column was deformed into inclined aspect, being dragged by BA. STrD-2 was at II:189.6 deg. (May 17, Go), and temporarily darkened with dark features on SEBs, as described above.

Dark NTB revived all round the planet by NTBs jetstreak outbreak. Rapidly prograding leading spot (LS1) reached at I:175.0 deg. on May 9 (Miyazaki), and disappeared at f. end of disturbed region of NTB. Late in May, NTB was dark and broad belt, though a sector between I:10 and 200 deg. was somewhat faint. Dark spots and shadings had decreased, and a few remained between I:100 and 200 deg.

RS was at II:118.8 deg. (May 12, Miyazaki). As no dark feature surrounded it, it was outstanding as reddish oval in bright STrZ. BA was also conspicuous as reddish doughnut, and white collar was formed between surrounding dark STB like Hollow. The diameter of the doughnut was about 9 deg. in longitude, but it reached to about 15 deg. when the surrounding Hollow was included. It was at II:324.8 deg. (May 11, Kumamori). Of the two large ovals in disturbed region of EZs, SED-1 having greater longitude had disappeared. Instead, SED-2 preceding it (I:313.1 deg., May 30, Fukui) became bright and prominent. It passed through north of disturbed region in SEB late May.

(2) Saturn

Saturn moved to south-west sky after sunset, passing eastern quadrature on May 9. This month, we have received observation listed below.

Yunoki and Vandebergh reported white spots etc. on Saturn this month too. Slight turbulence from SEBZ to SEBs between III:345 and 10 deg. on May 23 might be a real feature, because it was reported by both observers. In this sector, a light spot was also observed by Yunoki on May 15 (around III:0 deg.). Though it was a single spot without irregularity around, it is suspected of relationship to the feature observed on May 23.

(June 14, K. Horikawa)

(Translated on November 2)

[Fig.1] New activity started in fading SEB

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