I will edit and expand this thread as I have more time.
Cumulus Humilis- Heap Humble Also known as the Fair Weather Cumulus Cloud. This cloud occurs everywhere in New Zealand and is made by small pockets of warmer air rising and then condensing.
Cumulus Humilis is distinctive from Cumulus Mediocris as this cloud is wider than it is tall.
Cumulus Mediocris- Heap Moderate This Cloud occurs after Cumulus Humilis as stronger convection is present. This cloud occurs everywhere in New Zealand and is very common. The cloud is as wide as it is tall in this state but may extend a little taller than it is wide.
Cumulus Congestus- Heap Piled up Cumulus Congestus is that cloud occurs after the stage of Mediocris. This is due to much stronger convection and usually indicates atmospheric instability.
In summer this cloud is common over New Zealand and is associated with the term "Heat Shower".
Take note of when this cloud forms, if in the early hours of the afternoon it could lead to potential Thunderstorm activity later on in the day. Precipitation from this cloud is common.
Cumulonimbus Calvus- Heap Rain Bald Cumulonimbus Calvus is the developing stage of a Thunderstorm and requires atmospheric instability for it to develop. Cumulonimbus Calvus are fairly common in New Zealand in the Summer. Heavy Rain, Hail and Lightning can be produced from this cloud.
Pileus- Felt Cap Pileus also known as a 'cap' cloud can occasionally be seen in more rapidly developing convection (Cumulonimbus Calvus, Cumulus Congestus). The cloud is formed when a strong updraft within the convection hits a stable layer within the atmosphere. The portion of the stable air that is affected is then thrust up and then saturates. The convection will eventually overtake the cap and then disappear. Updrafts from within 32-48km/hr are usually required for this cloud to form. It is a relatively uncommon cloud as it usually doesnt last long as is it only associated with strong updrafts within convection.
Cumulonimbus Incus- Heap Rain CrownThe true king of all clouds. It usually signifies the presence of a mature thunderstorm as the cloud has reached the point in the atmosphere that it can no longer develop vertically.
This is due to Stratosphere (above the Troposphere) being extremely stable due to warmer temperatures in this part of the atmosphere. In some cases when updrafts within the cloud are very strong, parcels of cloud can breach the Tropospause and enter the lower Stratosphere. This is called an "Overshooting Top". This activity from the cloud is unsustainable as the cap is far too strong at this level of the atmosphere and will lead to the cloud retreating back to the Tropospause. Heavy Rain, Large Hail,Lightning and Tornadoes can form this cloud, but depends solely on the environment it develops in. I will discuss this later on. In New Zealand this cloud doesn't give a 100% chance of a storm occurring at the time.
Wall Cloud A Wall Cloud is a cloud feature that hangs below the base of Storm. In the U.S if wall clouds rotate that signifies potential Tornado Development due to rapid intake of air and can signify a greater feature called a Mesocyclone.
In New Zealand, Wall clouds are rare, but have been known to occur on very unstable days. They will typically occur in the Northern side of storm (as opposed to the Southern end in the U.S).
Mesocyclone A mesocylone is a feature within a Thunderstorm that indicates a rotating updraft. To a cloud observers prospective a Wall cloud (if it exists) can rotate, the storm can also contain striations which is a good indication of a mesocyclone. For confirmation access to a local Radar's velocity scan at upper levels is required. Look for an area of air moving towards and away from the radar within short distance also known as a couplet.
Supercell A supercell is a Thunderstorm that develops on an angle. Due to the storm developing on an angle the Storms updraft is less affected by rain, making the storm last much longer than it would have if it was a single or multi-cell standard storm. Supercells usually form in environments that have some form of shear.
Supercells are fairly rare in New Zealand, but are more likely to develop in the Canterbury Plains, Hawkes Bay area and areas of the Waikato.
Gust Front A Gust front is organized cooler outflow feature from a Thunderstorm but can develop on heavy Showers. It is usually associated with sudden gusts of cooler outflow from a storm. A gust front is a microscale cold front. Due to colder air separating the warmer ambient air (pre the gust front), the colder air will temporarily adjust the air pressure due to colder air being more denser than warm air, making a classic baro surge on weather graphs.
