Layers and streets of cloud

Clouds come in many different types and are characterised and named according to both their shape and height in the atmosphere.  While a single snapshot in time at a given location may only contain one type of cloud, there are many days when multiple cloud types can be observed in the sky at once. The satellite images below is a nice example of different cloud types sitting at different levels above Waikato. Here's what the satellite image looked like Saturday afternoon 3 July 2010, for southwestern parts of Waikato near Kawhia Harbour:

Predictability and popcorn

Among the most spectacular of meteorological phenomena are those associated with convection, particularly thunderstorms. Convection is all about the vertical motions that I mentioned in an earlier blog post, but confined to pockets or cells of strong up and down motion. These motions transfer heat through layers of the atmosphere on a local scale; this is why many showers and thunderstorms affect only small areas. But when the temperature differences are large, these storms can be very powerful.

Rain or Showers

We had an enquiry recently from an astute member of the public asking about the comings and goings of rain.  

They had noticed that in southerly weather the rain has a tendency to "come in bands (e.g., 20 minutes rain, 20 mins dry, 20 mins rain etc.) rather than as a more constant rain that comes with northerlies". They were wondering why this was. This is a good question and I will try to answer it here.  

A Lot of Rain

There has been a lot of rain in many parts of New Zealand over the past two weeks. One of the few places to escape this was the sunny West Coast of South Island - the days are clear and stunning there when the flow is southeasterly.