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World ARC Weather - Leg 7

World ARC Weather - Leg 7

Issued 25 May 2010

Weather situation

A weakening trough with a cloud band around 150nm wide containing scattered showers with a couple of clusters of thunderstorms lies from 15S 177W to 20S 167W and is moving towards the east at around 10 knots. This cloud band is weakening but some pockets of squally winds are possible in the regions east and southeast of the thunderstorms that lie just ahead of the wind change.

Winds shift from a Moderate NE direction near Suwarrow to a freshening northerly south of 15S with winds tending NW for a few hours ahead of the wind change. The wind change is a weak southwest then southerly that should gradually shift SSE. The system should move eastwards and largely dissipate as Wednesday progresses.

A moderate but somewhat erratic SE then ESE trade wind regime should then become established along the race route to Nuie and onwards to Tonga. This erratic trade wind patter should continue through Thursday and Friday. Only very well separated showers are expected in this trade wind flow.

The weather of concern is the band of scattered showers with thunderstorm clusters that lies along and just ahead of the trough system. Local wind squalls with the thunderstorm activity remains a possibility until the change has moved through, although this activity will be weakening quickly during the next 12 to 18 hours. Behind the trough system very widely spaced showers can be expected with fine weather being the normal conditions. Wind gusts should be fairly low with these showers.

Winds: Note: All forecasts will be given according to the local time zone of the fleet.

Tuesday 25th
North of 15S: NE winds shifting NNE mostly 8/13 knots but becoming more variable in the evening.
South of 15S: Winds northerly 15/20 knots shifting NW 13/18 knots for 3 to
4 hours, gusty at times near showers, ahead of a rapidly weakening SW then southerly change. Winds dropping back to 8/13 knots within a few hours following the change. The strength of the winds either side of the change should progressively weaken through this evening as the system overall will be weakening.

Wednesday 26th
Winds north of 17S generally variable below 10 knots apart from patches of gusty winds associated with remaining showers ahead of the trough. Winds gradually shifting southerly 5/10 knots through the afternoon and turning SE 8/13 knots in the afternoon and evening.
South of 17S: SE winds mostly 8/13 knots, although locally around 15, briefly 18, knots near Nuie til noon. Winds then tending SE to ESE mostly 10/15 knots, although weakening progressively between 20S and Tonga.

Thursday 27th
North of 20S: ESE winds freshening to 13/18 knots during the morning then holding this range throughout the remainder of the day.
South of 20S: Winds easterly to ESE mostly 8/13 knots, although with a few small patches to 15 knots but weaker areas towards Tonga.

Prepared by: Bruce Buckley (Weather Australia)

Note: This forecast covers the expected weather between Suwarrow past Nuie and on to Tonga.