It is sometimes very difficult to see the outline of a large high – especially the entire way around one. However today’s satellite map shows this week’s very large high quite clearly.
The frontal clouds, from the weekend’s big rain system, still stretch up into the tropics where they connect to a separate system. However it does give the appearance of clouds being pushed along by the high as it moves in from the west…
The high (highlighted in red) moves into the Tasman Sea with a near perfect wall of cloud surrounding it / WeatherWatch.co.nz
High air pressure doesn’t always mean clear skies – and you can see that over the Tasman Sea where there are plenty of low level cloudy patches (in winter this low cloud can hang around with drizzle, becoming what we call “anticyclonic gloom”…a big high that brings gloomy weather, especially to coastal and low lying areas in the west).
However the start of a high moving in from the west often brings sunny, dry, weather to northern, western and inland areas of New Zealand – and cold nights to begin with. Why? This is because the wind flow on the right hand side of a high is generally southerly (anticlockwise around the high…southerlies on the right hand side, northerlies on the left hand side).
When the high is still centred in the Tasman Sea it tends to feed clouds and showers along the east coast (as it’s done so today).
By tomorrow the high will push further across the country – pushing those cold southerlies further out into the Pacific Ocean and allowing the east coast to start to warm up a bit.
The cloud to the south of the low marks more activity in the Southern Ocean – the next front is due to surge up and swipe the South Island late on Thursday in Southland, reaching Canterbury later on Friday. WeatherWatch.co.nz forecasters say it’s unlikely to have any of the oomph that this weekend’s southerly change had, although temperatures are likely to dip briefly in the south and east of the South Island on Friday and Saturday.