Mike Broughton, weather forecaster/router for Dee Caffari on her Aviva Challenge takes a look at the sort of conditions she’s likely to expect over the next few days.

We will see glorious sailing conditions for Dee today (Thursday 22) as she benefits from strong northerly winds on the west side of a high-pressure system that has moved east from the River Plate to merge with the larger South Atlantic high-pressure that is in its normal position half way between Cape Town and Rio de Janeiro.
Blowing from the north, these winds will bring clear sunshine and possibly the last hot day prior to Aviva getting to the cooler conditions that look set for Christmas Eve.

Dee has done a good job of making ground to the south-west over the last couple of difficult days that have been dominated by tricky light winds and big rainsqualls.

Had she merely aimed south, she would have to contend with several days of very light winds, as the high pressure is expanding as it moves east and would have swallowed her up.

A big change is due for Christmas Eve as Dee makes her way south about 300 miles east of Argentina. The winds look set to increase from the south, as a low-pressure system from the Southern Ocean influences Aviva for the first time. What Dee will really feel is big temperature drop and she will experience the ‘delights’ of beating into strong winds and big waves.

So in today’s forecast for Dee, I have emphasised the importance of enjoying the heat whilst it lasts. Any southerly winds once you get to the south of 42 degrees south latitude is pretty cold, given the huge chilling effect of any winds from the direction of Antarctica. By way of comparison 42 degrees in the northern hemisphere is the same latitude/season as Rome in summer!

The fickle light winds of the tropics are now left behind. Instead of big breezes on the edges of billowing clouds and trough lines that quickly give way to capricious light zephyrs, the cold southerly winds will be much more steady and predictable. We can expect to see Aviva sailing to windward once again and the thermal layers called into action.

The sea quickly gets rough in the southerly winds, so if Father Christmas comes down the mast, he will need a sailing harness and a hard hat!

Mike Broughton