Tropical cyclone Nicholas formed from a low which developed within a broad band of monsoonal activity to the south of Sumatra, aftcr initially being located near 6.63°S, 102.2°E at 0000 UTC on 26 November 1985. The low moved south and then southwest before recurving onto an easterly track at 0600 UTC on the 28 November near 9.3°S, 100.9°E. At this stage it had just reached cyclonic strength.
After this recurvature and until peak intensity at 9.9°S,113.9°E (1200 UTC 3 December) the cyclone maintained a generally easterly track and a small but intensifying circulation. Although the cyclone passed through major shipping routes no reports of gales were received. One ship located the centre on radar at a distance of 55 km and reported northwesterly winds of 56 km/h. Dvorak analysis estimates of the winds at the centre were 160 km/h at that time.
At peak intensity (central pressure 945 hPa) Nicholas again changed direction and began to move on a more southerly track and weaken. Whilst the early easterly movement had been the result of upper-level westerly winds associated with a ridge across the equatorial Indian Ocean, the slower southerly track was associated with the passage of an upper trough to the south with accompanying northeasterly and then northwesterly upper-level winds.
Decay of the cyclone was comparatively rapid, despite the fact that it remained over warm water. A strong surface high, moving eastward following the upper trough, injected dry air into the low-level environment so that by 1800 UTC on 6 December at 14.7°S, 114.O°E the central pressure had risen to 998 hPa. The track of the cyclone was entirely maritime and all intensities were derived from Dvorak analysis techniques.
Track and intensity
All times in WST - subtract 8 hours to convert to UTC.