Whether you like dark brooding thunderstorms or lightning that flashes across the skies or strikes close by, Darwin has it all. On this page there's fantastic information about our tropical storms.
(Anvil crawler lightning stretches outward)
Thunderstorms in the Top End are usually termed 'short lived' and really do depend on a lot of atmospheric factors to maintain longevity, but that's not to say that the storms we get don't produce some spectacular lightning and they do stay around for a decent time span to get photos or just to watch on the beach! Storms here are tropical thunderstorms and what are commonly called pulse storms. These storms develop independent of other thunderstorms, that just means they go through their own lifecycle of maturity and dissipation. Pulse storms aren't tropical in reality, it just means that they are the most common types we get due to our weather conditions.
Pulse storms generally favour high CAPE ( which i'll go into on another page!) and weak wind/speed shear. Wind shear is the change in wind speed with direction and/or height. The stronger the wind speed with height the better - if you get change of direction of wind wind speed then the stronger the storm will be! Updraught strength determines what type of storms are produced and tropical storms are no different. We rarely get supercells, but they do occur with tropical depressions and cyclone activity and some storms do exhibit supercellular rotation but this may be caused by strong convergence.
( Pileus cloud)
Darwin experiences multicell systems and squall lines regularly which favour great lines of storms which make for beaut photographs. The squall or Gulf Lines often come way off from the Gulf of Carpentaria to our east and swing around toward Darwin.
(Two images above used with kind permission from Marty Pouwelse Australian photographer of a triple CG strike at Cullen Bay, Darwin and fabulous anvil crawler lightning also in Darwin December 2005) http://www.ozlandscapes.com/
Multicell storms favour good speed shear but where low level directional shear is weak. These storms are long lasting and basically tend to assist other cells next to each other by interrupting the colder downdraught from the original mature cell that would normally inhibit growth of another cell. In fact once the original cell dissipates another takes its place. These storms are fairly common also and they make for great viewing as they produce ample amounts of lightning within and outside the storms.
The monsoon troughs that arrive from Indonesia bring widespread showers, heavy rain and storms. If the trough has tropical lows embedded in them then that makes for even more activity - but the norm for monsoonal periods is for less full-blown classic thunderstorms than we'd otherwise get during 'build-up' or break period conditions with hot, humid days. There's just too much moisture and not enough daytime heating for the production of nice photogenic storms. Overcast rainy skies hinder storms and photographs!
(Wall cloud underneath a severe thunderstorm in Darwin)
Wall clouds do appear with strong storms but you'll only 'see' them during daytime storms with good effect. Generally they're associated with strong directional/speed shear and you'll need to check atmospheric soundings to see if there's any severe storms likely and if there are it's best to keep an eye out anywhere these storms are in view.
(lightning sequence credit to Sebastien D'Arco taken in Toulouse France)
They're called wall clouds because the updraught or inflow portion of the storm seems to 'lower' or create a thick, wall like structure underneath. It's just a huge amount of moisture and condensation that is drawn around this area and actually can seen to rotate if the shear is strong enough and can be a prelude to severe weather, both of strong winds and/or hail. In the USA they are a prelude to tornado development with supercell storms.
D
Tail clouds. Tail clouds is the visible line of air that is feeding the storm. You may have seen a thunderstorm and either to the left or right/front or rear (depending on which way it's heading) a long line of cloud that contains smaller cumulous cloud all strung in a line but of which its appearance growing larger toward the main storm tower. This is another sign of inflow - the fuel. Timelapse footage shows this well but if you watch for long enough you can see how it changes shape and length as the storms moves along. Warmer air is cooling much the same as scud but on a much larger scale.
on't confuse scud with being associated with a wall cloud. Scud is the loose, scraggly pieces of cloud that swirl and seem to be thrown around the base of the storm's inflow or outflow - but it's a good indicator of what the storm is doing and if you watch long enough. Generally it's seen in the inflow or rain shaft leading edge. Scud allows you to actually view in essence invisible air turning to condensation as the temperature changes from warm to cool near the storm - cloud in reality!
Tail clouds. Tail clouds is the visible line of air that is feeding the storm. You may have seen a thunderstorm and either to the left or right/front or rear (depending on which way it's heading) a long line of cloud that contains smaller cumulous cloud all strung in a line but of which its appearance growing larger toward the main storm tower. This is another sign of inflow - the fuel. Timelapse footage shows this well but if you watch for long enough you can see how it changes shape and length as the storms moves along. Warmer air is cooling much the same as scud but on a much larger scale.
Inflow fingers. A strange name but these can be viewed at the front of the storm at different heights, generally from the cloud base and upward - remember the storm is drawing air from the surface area below it. Higher *dew points (humidity) in the atmosphere the lower the cloud bases will be. When you see a storm very low to the ground that is an indication of high dew points. It's not how much humidity you read in the newspaper - for example 87%! .
*Dew point is a measure of atmospheric moisture, it is the temperature to which air must be cooled in order to reach saturation.
Ever wondered what the term 'calm before the storm' means? It's this: Was the storm near you when you noticed that the wind just disappeared? That's because you're more than likely in the updraught or inflow portion of it. As the wind is being drawn up into the storm it means that the height of that wind is above you - sometimes called AGL or Above Ground Level. If the inflow is above you then you won't feel it, hence the lull in wind, but as soon as the storm moves along you get the wind coming back? - that's the wind that is replacing what has been drawn up inside the storm - what's been taken has to be replaced remember!
Thunderstorms tend to roll in around lunch or late afternoon but that of course depends on the weather at the given day but in 2007 it was no different and most tended towards this time and was very annoying as they weakened by nightfall! If there's a decent amount of daytime heating and enough instability to cause convection then you're assured some great storm activity.
The city skyline makes for great backdrops and depth as there's a decent amount of open area between the buildings. If you're keen you can keep an eye on the radar and satellite photos that day/night and if you've been reading the sounding for that day for storm direction you can watch them rumble in to wherever you're located at the time.
(fantastic strike with natural colours.)
A unique feature of the Northern Territory's northern Tiwi Islands is an event that happens generally during the buildup transition period from about October through to Nov/December and is referred to as 'hector convection' with one notable storm affectionately known as the convection suggests - 'Hector ' . He grows to massive proportions during his maturity. Many scientific studies are done by countries hiring aircraft to fly in and around this spectacular storm to conduct many experiments. Hector is probably more known for his size, on most days when he forms the thunderstorm reaches heights of 20km - truly one of the tallest single storms in the world that eventuates so regularly. The storm can be seen from anywhere in Darwin and is best viewed on the coastal areas where you can sit and watch this monster grow before your eyes.
Hector produces spectacular lightning - sometimes up to one lightning strike every minute for several minutes or strikes regularly throughout the storm's life cycle, usually some hours! Massive anvils and a huge tower make for excellent photography shots. Hector (see Hector page on this site) is part of a sea breeze convergence and due to the topography of the Tiwi Islands and the sea. These conditions are favorable for his formation almost every day in the months of November and December. He is also part of what's called a MCS or Mesoscale Convective System that arrives due to low pressure lines or squall lines to our north or from the Gulf of Carpentaria to the east of Darwin that move westward along the islands. Although the term MCS is very broad and wide ranging, some may disagree, but there's enough literature around to say that it is in fact hector convection which occurs not only here but on the African coast, parts of Eastern USA and other countries.
This image below shows the immense size of the storm over the islands 75km to Darwin's north. There are not too many daytime storms in Darwin that can out-do Hector on a good day, but I have been through storms inland that have reached up to 23km - truly immense! I intend on capturing some regular photographs of Hector during the 2007/09 wet season and will post them on the hector page once I get them.
Below are two images courtesy of the Japanese Meteorological Satellite that show low pressure convection and large storms to the north and over the Islands.
As far as supercells go we don't see a lot of them, in fact hardly ever and this is due to our conditions being tropical in nature. (anyone that tells you different is a liar!) Our storms may be within the mid-lattitude realm but Darwin is in the tropics not in Central Australia. The Bureau class our storms as tropical, they class mid-lat storms as being in the middle of the country, period. Added to that that most scientific research is related to tropical convection and conditions whenever they are done.
Our weather conditions would only support supercells if there is cyclonic activity or close developing tropical lows in the area which would produce some. Added to that the amount helicity, vorticiy, cold and warm fronts converging to enable rotation just does not happen in Darwin. You need CAPE and strong directional/speed shear and be significant to initiate them - which cyclonic activity has a lot of!
How many storms does Darwin receive compared to the rest of Australia? Here's a map from the Bureau of Meteorology. You can see that we average around 80 thunderstorm days a year and is the highest in the country.
Contrary to popular belief Darwin does not hold the record for being the most active lightning hot spot on the planet even though our thunderstorm days are numerous. There are places in the US, South Africa, etcetera that have more lightning active days. I have read that Tamba Bay in Florida and Africa's Congo region are well known for extremely vigorous thunderstorms.
(high dew points show the inflow tail in this photo and notice how low the cloud base is?)
Around 90% of the time we get pulse or air mass storms, severe pulse storms with periods of mutlicell squall lines during the morning/evening. Gulf lines are common and produce some great cluster cells. When the monsoon arrives there's less storm activity but more rain and there's too much moisture in the atmosphere and not enough daytime heating to initiate storms. From what I have experienced chasing, good strong storms accompany tropical lows in the area as instability increases and it pays to keep an eye on the tropical weather maps!
There is still a lot to be researched on our storms. Although the textbook type pulse storms prevail, it's important to observe and report any out of the ordinary storm systems or types that might be seen. There is a lot of interest in Darwin's storms and as a chaser I'm always on the look out for anything significant.
We do have waterspouts regularly with conditions favour strong speed and directional wind shear. Sometimes a thunderstorm will promote shear within its own environment. Water spouts are in fact classed as tornadoes, just on a much smaller scale and rarely cause damage unless they make landfall.
Hail is virtually non-existent simply due to any hail melting before it even reaches halfway through the storm's tower. You need extremely cold temperatures in the upper levels and an extremely persistent, vigorous storm to produce hail. I've seen hail in the city with one-off storms, but the most intense was in Katherine 300km to our south. Pea sized hail or larger with a ferocious storm that lasted 6 hours and displayed supercell type characteristics during its maturity.
The 2008 storm season was a little disappointing. Although we were under the influence of a La Nina weather pattern, which was supposed to bring extreme weather and increased cyclones, it did not bring the wild weather. No fault of the bureau or anything else! It's the weather and conditions change. The east coast of Australia received some very serious flooding and supercell storms with very large 8cm hail and tornadoes! It seems they got all the action this time.
In a nutshell, Darwin provides the opportunity to view all types of storms. Mild to severe and multicellular are the norm, so charge the battery in that camera or fill that stubby cooler. A wine glass that needs to be topped up and sit back, relax along the coast...you'll see some of the world's best lightning shows whilst spending time with friends.
It's what we all do as locals.......!