Summary
Marcia was the first cyclone of the 1974/75 tropical cyclone season to operate in the Northwestern Australian Region. It was a small system of only moderate intensity and maximum winds associated with it are estimated to have reached about 90 km/h on 20th October.
From 17th to 19th October a secondary system, a small tropical depression, was located near 10°S 100°E but this did not develop into a mature tropical cyclone. At 1200 GMT 18th October the ship Alkuwait reported that between 0830 and 1030 GMT 18 October it had experienced a "heavy storm" with W/SW winds of force 10/12.
These winds of almost hurricane force occurred while Marcia was in its developing phase. The winds estimated using the cloud photograph are considerably lower than those mentioned in this report.
Only one other report of the gale force winds was received. This was from the ship Cape Wrath at 0600 GMT 19 October when it was some 48 km west of the cyclone centre. The wind estimated at 63 km/h was probably caused by a temporary tightening of the pressure vicinity for two other ship reports do not confirm this speed.
The maximum wind recorded at Cocos Island was 39 km/h at 0400 GMT 21 October. As the cyclone was then some 320 km to the westsouthwest this wind speed indicated that the gale force winds generated by "Marcia" did not extend far from the centre.
The 'heavy storm" which affected the Alkuwait at about 0830 GMT 18th October also caused the seas to rise 3 m. Further west in the southeasterly stream the Cape Wrath reported the swell to be 5 m on several occasions, the last time being 0600 GMT 19 October. This was the heaviest swell reported form the vicinity of Marcia .
