YOU WILL FIND LOTS OF INFORMATION ON THIS PAGE SO GRAB A COFFEE AND ENJOY THE READ.
I HAVE INCLUDED A FANTASTIC DESCRIPTION OF OUR WEATHER FROM THE DARWIN BUREAU OF METEOROLOGY WHICH CAN BE FOUND AT THE END OF THIS PAGE.
Darwin's thunderstorms are typically tropical if you have not guessed that by our location! They are generally pulse or air mass thunderstorms of the variety commonly found in locations such as Florida for example. Darwin also is home to just about every other type of thunderstorm except for supercells, so most of the other common storm characters are daily items, with severe storm systems being on the cards also. For regular lightning displays you really can't beat Darwin. When the storms are frequent and active the nighttime sky really does come alive with all sorts of lightning...some a little too close for comfort whilst dining out!
Pulse storms generally favor 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.
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. The photo above was taken in Darwin Harbor whilst photographing another severe storm to the left and and I noticed this wall cloud to my right. Wall clouds are created by condensation forming around the updraft area of the storm and this gives the impression of 'lowering' by the cloud base. Usually they are precursors to tornadoes.
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 cumulus 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. Time lapse 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.
*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 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 special storm that regularly occurs during the transitional period between dry and wet seasons, commonly known as the 'build-up' is Hector, a very large thunderstorm that is visible NE of Darwin each afternoon.
If you visit any of the northern beaches you can see him towering on the horizon. As high as 72,000 feet to be exact, but he's visible from any location around Darwin.
(high dew points show the inflow tail in this photo and notice how low the cloud base is?)
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 or 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!
Darwin Bureau of Meteorology's summary of Darwin's weather and storms
Courtesy...http://www.bom.gov.au
The climate of Darwin and the Top End is distinctly different from those of
southern Australia, and the familiar division into spring, summer, autumn and
winter is less applicable. For example, the Gagudju people of western Arnhem
Land, to the east of Darwin, describe six seasons, where each season is linked
to weather conditions and associated changes in flora and fauna. Nowadays Darwin
residents recognise two seasons, the "wet" (October to April) and the "dry" (May
to September). In recognition of the change between these seasons, transition
periods are also referred to, with the transition from the dry to the wet
commonly referred to as the "build-up".
Most afternoons the sea breeze brings in slightly cooler air. Sea breezes arise due to differences between land and sea surface temperatures. The air over the land heats up and rises, drawing in cooler ocean air. Sea breezes can occur at any time of year in Darwin, though they tend to be strongest during the build-up months when the land-sea temperature contrast is greatest.
During the wet the monsoon trough varies in position from off the Australian north coast to well inland. The "intensity" of the trough also varies depending on the strength of the two airstreams. This results in periods of "active" monsoon weather, typically lasting from a few days to several weeks, interspersed with "break" periods. Break periods usually last longer than active periods. The active phase produces cloudy conditions and frequent periods of rain, at times quite heavy. Conditions are then very humid but relatively cool. Westerly winds can often be quite strong and persistent at these times. During break periods, conditions are similar to those experienced during the build-up.
Click here for a graph showing average and extreme temperatures.
Return to top
Normally there would be 2 or 3 active monsoon bursts during a typical wet season over northern Australia. Usually scattered to widespread areas of rain and storms. Low cloud is prevalent in moist westerly flow as well as with precipitation.
Tropical cyclones and Tropical lows that occur over or near Darwin may result in extended periods of widespread rain and low cloud. Tropical cyclones develop off the coast during the cyclone season of November to April (inclusive), usually forming in an active monsoon trough. Heavy rain and gale force (or stronger) winds can be experienced along the coast if a cyclone is in the vicinity. On average there are 7.7 days each year when a cyclone exists over the waters around the Northern Territory. Darwin has been severely damaged by three major cyclones: in 1897, 1937 and 1974 (Cyclone Tracy). Cyclone Tracy is well remembered by Australians as probably the worst natural disaster in our history. Since Tracy twelve cyclones have passed within 200km of Darwin. Two of these, Max (1981) and Gretel (1985), caused minor damage. In December 1998 severe tropical cyclone Thelma moved near Darwin. Over 430mm was recorded at the airport over a 48 hour period.
Darwin is not a particularly fog prone location, on average about 2 days a year, though there have been fogs recorded on 6 days in a month. They are predominately a dry season (May to September) phenomenon. Typically you need a light east to northeast synoptic wind pattern, with a sea-breeze the afternoon before, that is strong enough to feed sufficient moisture in the low levels, while maintaining very dry conditions aloft.
The atmosphere in Darwin is favourable for storms on most days in the wet season, and there are a number of phenomena that will trigger their onset and/or movement over Darwin. They typically move with the winds at the 10,000 to 14,000 ft level. Very active days occur when upper divergence and lower convergence are present.
Storms triggered on the front of the sea-breeze are common, and these are the variety that develop on location during the early afternoon, or move in from the east/southeast in the mid to late afternoon. The occurrence of these storms reaching Darwin is dependent on many factors including position of the front, strength of the sea-breeze and direction and strength of the steering level winds.
Numerous other events can trigger storms remote from Darwin that subsequently move over the city, which means they can occur at most times of the day. The relatively quiet time is the daylight morning hours.
Storms that are triggered inland (usually originating near the Arnhem escarpment) can occasionally form an organised squall line. With easterly steering of 20+ kt these may reach Darwin late evening or early morning. Lines of storms that form over Cape York Peninsula (commonly known as Gulf lines) and move westward may often trigger these squall lines.
Gulf line activity may seem to dissipate over the eastern Top End late afternoon and overnight. However these lines may trigger isolated storms near Darwin, usually over water, in the early morning. With favourable steering these may move over Darwin.
Situations that favour enhanced activity are:
* Large amplitude upper trough about 10/20 deg to the west with divergence into the left entrance of the Sub-tropical Jet.
* Upper trough retrogressing westward across the Top End.
* Surface trough with marked 'dry line' over the Top End and moving northward ahead of a southeast surge.
* Heavy rainfall. Rainfall rates of up to 200mm/hr can occur, resulting in flooding, poor visibility and low cloud.
* Lightning. With the high frequency of thunderstorm activity in the Darwin area in the wet season, there is the high incidence of lightning strikes.
* Severe turbulence is assumed with thunderstorms.
Hail may be a problem at higher levels in large convective clouds. It is rarely a problem in Darwin because it tends to melt before reaching the surface.