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(NOTE: all photographs are my own unless otherwise credited and all are subject to copyright)
(shot taken from inside my car on a rainy storm night in 2008)
A STORM CHASERS HANDBOOK
This section will be divided into certain topics so you can browse through and find the areas you're most interested in and can scroll back and forth easily to locate them. Links will be included at the end of each bit of nonsense for the more technically minded so you can read explanations that give more in depth descriptions of the particular topics!
The wording will be easy to understand and I'll try to give as much detail as I can without too much text with the aid of graphics. To be a successful chaser you need to be patient, thorough and trust your instincts. You'll soon find out that chasing storms is not as easy as it may appear, a little knowledge of meteorology goes a long way and can help in deciding which area to chase and what to chase after.
Of course each country is different. Weather set ups in the USA are a ball park away from here in Darwin or England, but with time in viewing your own area's weather patterns and seasons you should be able to pick any storm days that are on the horizon. The information I'll give relates to what to look for with thunderstorms and, more importantly, what to expect here in Darwin relative to our tropical weather, but you will have to compare your own area's weather also and do some homework!
(photo above taken by me whilst a passenger when chasing inside a severe storm)
THE BASICS
It's important to set some reality checks first up. It aint gonna be easy! Sure you can jump in the car and head out to the storm and there it is, that's more convenience than anything else. The real satisfaction comes from doing the homework and putting it to practice. Even experienced storm chasers get it wrong a lot of the time, what they learn from all of the chases is knowing the quality storms to intercept, weeding out the rubbish and which ones will deliver the goods.
Yes, you can sit by the computer and watch the radar all day and night and as soon as a red blob appears you race out and realize that by the time you got there it's all dead and gone. Why? The answer is you did not put all the information together to evaluate whether it was going to get better or worse. Arm chair chasers guess the information and don't look at all the other current atmospheric models and 8/10 times get it wrong and usually don't even leave the comfort of their chairs to chase - hence the tag. Radar is a wickedly evil thing which will trick you all the time. Don't get me wrong, radar is a vital necessity and tool, but for you and I we have to know how to read it and what to look for to help us plan the chase. So here we go...
RADAR IMAGES for DARWIN
Interpretation of radar images is very involved and time consuming and would take many pages to even scratch the surface. So on this topic it will be basic and simple to understand.
Radar sends out a beam spread out several hundred kilometers and its interpretation is dependent on the reflectivity of the objects it 'bounces' off and thus returns the signal. Precipitation, including dust, carries a signature. The heavier the precipitation or hail the stronger the signature will be. The middle levels or from ground to 5,000ft of a thunderstorm is generally where most of the rain will fall and any hail within would be melting on the way down and give a stronger signature. Anything above this height would be in a colder environment further up from 5-30,000ft and above and would be ice crystals.
On most radar sites you'll see three main gradient colors. Green, yellow and red. The green color on radar shows a weak radar signature of light rain usually higher up and as the storm progresses the radar reflectivity changes color to yellow, orange and red - even to black - representing moderate to heavy rain or hail.
When looking at thunderstorms on radar you can tell which ones are producing high rainfall rates and maturing quickly and ones that are in the process of either maturing or not doing much at all. Most weather bureau sites give wind direction, dew point and humidity numbers and this helps greatly in determining where the storms are coming from and what environment they are in and going into. Strong storms will show coloring of oranges to reds to blacks and these are the ones to watch. Whilst a decent storm can still show on radar just as yellow, it is up to you to determine which storm you go after given what you see on radar.
Many things have to be taken into account. It's not simply a case of 'there's a nice orange radar cell coming this way' heading out and finding it's died on you. Radar has a delay of several minutes by the time the bean goes out and is sent back, so if a storm is say 40km from you it is more likely to be a little closer than that. Radar sites give times also and depending on where you live, you will have to calculate the time zone difference. Here in Darwin it is UTC time so we add 91/2 hours to what the radar time is which gives an approximate time. This way you can work out what the storm 'was' doing say ten minutes ago and figure out where it is heading.
I've found when viewing storms on radar heading for my area, I went outside to see what their progress was in relation to the radar image and it you'd be surprised to find out that things had changed dramatically. If storms have a life cycle of say half an hour or so then you have to know what you are viewing on radar is current or real time. Without doing this you'll be chasing old storms and missing on the best opportunity to intercept them.
Storms don't always behave in a predictable way either. A storm can seem weak on radar but as it goes through different atmospheric conditions it can be invigorated and liven up. Take your time to look at the radar images and work out for yourself which ones are likely to be the best option. Take into account the environment they are in, where they are heading and their stage of maturity. All these things are important. Observing the storms outside every ten minutes or so (if they are far enough away) AND going back to check the radar images will confirm your calculations on what they are doing.
Storms can either be single or multi or turn into squall lines (supercells not applicable here in Darwin) and these can be picked up on radar images you see just by viewing it for a while. There's no need to go rushing out as soon as you see a red signature because it's already happening! You want to get there before this happens and get the guts of the storm's activity.
So, as you look at the radar watch for the storms that show continual growth, strength and dominance during in a progressive stage. Look outside the main area of storms also to see if anything is firing up elsewhere, you never know what might happen. Some of the storms I've encountered have produced the best lightning simply due to the others dying out and I've chosen not to chase the obvious!
Follow the storms' progress and see how it all pans out. Look for continual growth and no cold pooling. A cold pool signature shows up as a weak 'bow' in front of the storms gust front. This shows that the cool outflow is pushing out strong and inhibiting any warmer air being fed into the storm. Cold pooling will kill off the storm quickly unless it finds alternate fuel sources to keep it alive. Sometimes the outflow of a storm can act as a trigger to actually push/circulate the warm air and give birth to new cells in front of it or behind it. This is just another thing you have to judge!
Some examples below of Darwin's storm radar images, what they are and what I did. (images courtesy Darwin Bureau of Meteorology)
The above image shows storms around 3:15pm. The large cell over the island to our north is Hector - (on the Hector page) and that's just not accessible at the drop of a hat! I saw that storms were brewing Annaboroo through to Humpty Doo, all within an hour's drive from where I live. I know that they are maturing simply because of the precip colors as by the gradient scale. Observing the storms at Humpty Doo I waited and then turned back and located near Middle Arm and followed the better storms back to Darwin this day. The white areas of the storm is outflow or spent areas, so no use going after them. The storms were tracking SE to NW so any area within the storms track would be ideal. I chose NW of Humpty Doo as my main observation point as I anticipated storms continuing in that area. There's areas of heavy rain (red) within some storms, so although that's a good indicator I did not go directly in the path of them but more around them to avoid being stuck in rain.
Radar image above shows many, many storms brewing in all areas. This is why Darwin is so great for chasing. Hector can be seen on the northern islands and is massive! You have so many cells to choose from and just by watching radar for a little bit you can then decide which way to head out to. From memory I drove to Noonamah and then followed a set back to East Point. I could tell from the radar which one's converged into larger cells, the cells at Batchelor and the Manton cells joined as a small squall line, but I chose to chase the maturing cells for the lightning back to Darwin. If I had gone further out given the timing I would have gotten lots of rain and missed the leading edge anyway.
The image might not look much but this storm squall line produces so much wild weather and lightning that I chased it for hours. The precip is light to moderate which indicated that it had already dumped quite a bit of rain in its path and the amount of cold air around the bottom line was not helping. I chased from home to Darwin City simply because the frontal storm system was still active and so I could get the coastal lightning from the line of storms heading out to sea. There's still some worry along the leading edge of the active storms on the coast as seen by the light precip or cooler air in front of it, but thankfully it did not hamper its development too much.
The image above is something very special! This is pre-TC George developing strongly as it crossed Darwin on his way to the western state that afternoon/night. This developing low was intensifying at a rapid rate and there was no need to chase this. It produced severe winds and a lightning rate of over 2,000 strikes in as many hours. The huge red and orange mass was the central region of the system and once it encountered even more warmer air it went ballistic. It was tracking nor'east to sou'west/west. I was at work looking out of the office window at the strikes - and yes, the camera was left at home.....
The things that need to be looked for on the radar are new cells with a progressive growth track. Look for new storms forming along side, behind or breaking away from older cells and show active growth. Avoid chasing in areas where the radar shows precip - not very handy for photographing and driving in rain looking for storms is a waste of time - you can't see anything anyway! It pays to be patient and not jump the gun as soon as you see a blob of red. Watch the skies, look at the radar and make a calculated decision on where you want to go. Your safety is paramount regardless so don't put yourself in the firing line of a severe storm. Better to locate around the storm for the best vantage point.
Use radar as a valuable tool but not the only tool! Radar can give 'false' readings and in time you'll be able to see what is worth chasing and what is better left to someone sitting in their arm chair chasing!
This site below has a wealth of information on radar, how to read it and so much more. You'll find it a handy site to keep bookmarked for reference material.
http://www.theweatherprediction.com/
SKEW-T PLOT or SOUNDING CHARTS
Just a small section on this because it does take a little time to understand how to read a skew-t chart and unless it is current then you'll be making calculations all day!
Basically the atmosphere is in constant change hourly. The weather services here send up 2-3 weather balloons each day to collect data - radiosondes or dropsondes. As the balloon rises the software records air temperatures, humidity, dew point level, wind speed and direction and a host of other things so that once collected, the observer draws up what is known as a 'sounding chart' This chart is valuable for chasers because it gives them a window to look into of what the atmosphere is doing or was doing at that particular recording time and can use the data on the chart to calculate what might happen or what potential the atmosphere has for instability and storm initiation.
Although
receiving soundings online they may not be current to the hour. In
Darwin we can only view online one at 11:30pm and 11:30am, which is
fine for my purposes. A lot of the information on the sounding does not need to be looked at but there are some things that do need to be viewed and judged. Wind speed and direction at the 500mb area will give you storm direction or their dominant steering winds - on the sounding below it is from the NE at 10knots - not much in that but at least there's what's called speed shear before and after 500mb - this tells me what type of storms may form and whether they will be severe or not. The temperature and dew point lines are important also as they show if the air is moist or dry throughout the atmosphere. The chart below shows moist in the lowers, dry towards the mids. At 500mb it's moist and then the same going to 200mb. This is pretty good. It shows a balance of different air temps and moisture throughout the atmosphere and storms like this type of scenario - so long as the trigger is there - Too much dry air in the lowers or mids will not fire them up until they find an alternate moisture source ...here in Darwin anyway.
The grey line to the right of the temperature line in red is the give away. The
sounding below shows high levels of instability in the CAPE region and
the list tells us the CAPE is 3233j/kg (joules per kilogram).The blue lines are from the previous sounding taken earlier and the red is the latter sounding taken and plotted on the same graph to show comparisons. Soundings work millibars for height levels in the atmosphere.
On the left hand side you can see the millibar numbers and the associated height in feet. Millibars work from highest number - being ground level - to lowest number to the upper levels. So the surface would be from ground to 1000mb and 200mb being aloft and so on. The area of 500mb or 19,000 is the general area where most storm related information comes from. If you look at around 950mb you'll see the grey lines intersect? That's the lifted condensation level where the parcel of air no longer needs help to rise - you can tell if storms with either a low or high cloud base will happen from this point on the chart. The lower the LCL area the lower the storm base will be. High 'based' storms for Darwin are not uncommon, but thankfully not too regular!
Lapse rates are pretty vital also. Those dotted curved lines that swing to the left hand side as the it rises tells me that a parcel of air will find it's getting colder in the upper atmosphere. That's what you want to see, a cooling, not a warming. A thing called LI in the list is Lifted Index, a minus figure tells me the amount of instability up there, -6 is none too shabby! The other thing to watch is the CIN/CAP number. These values indicate the inhibition or 'lid' that suppresses storms from rising or even forming until that cap is burnt off by the sun or other variables. CIN of around 18 is low and great for showing me that there's a weak 'lid'. Even if the CIN was a high number, the instability will still cook so to speak. Once that lid breaks then all the energy has to go somewhere - upward! Once that happens it's this time when you get severe storms. All the pent up energy is finally released because the CIN or 'lid' has been taken away. Think of CIN as being a lid on a pot. You boil the pot and you can see the lid jumping around right? Take the lid off and what happens...all that steam is released and flies upward. Same scenario for storms. They need a free environment to be able to rise. The higher the better.
There's a whole gambit of information online on how to read soundings and it takes a long time to work it all out because so much information is put on the charts, but for my purposes I simply look at wind direction, sheer, temperature, instability and the lapse rate. The CIN level and CAPE numbers and any dry inversions that might be hampering storms.
Using the soundings, the radar and your eyes you can quickly work out what may happen or what is not happening and why. Soundings are a guide only as to what potential is in the atmosphere at that time, you have to work out with the information you have what is happening now!
This link will provide you with an in-depth explanation in easy terms as in interpreting a sounding chart. It's extremely informative and it deserves the time required to understand how sounding charts work and don't work!
http://www.downunderchase.com/storminfo/stormguide/guide07.html
TOOLS WHILE CHASING
I guess I've been fortunate enough that since chasing I have not used any technical aids whilst on the road to find the lightning I photograph, most of it comes from observation and some radar views before heading out and watching the storms whilst driving and also stopping here and there to see what's happening. If you have the funds and want to use these tools then you should consider having wireless internet, a lap top, GPS and a HAM radio as an option also.
The benefits in the USA for having these items is a given due to the large storm systems they get and how complex their supercells are. You need these tools to accurately track and predict where the big storms are going, what they are doing and if any tornado is likely to form.
Here in Darwin it's up to the chaser to use this equipment and in my view considering the amount of storms we get in the area it's not needed, Whilst in coverage at least logging on to the weather bureau and other related sites you can keep a check on what storms are doing, what the atmosphere was doing - I say 'was' because real time data is extremely scarce to rare for anything in Darwin which makes it difficult to chase if you want information in a 'nowtime' situation. Radar is about the only thing you can use here to track storms and lightning detection downloads that may assist. The biggest headache is the lack of coverage for the internet in Darwin. You can drive 40km's out of Darwin and drop out! So your new laptop is next to useless unless you have satellite feeds!
A GPS unit is pretty much the standard gizmo for chasers when they have a wide road network to cover and many towns to drive through. Again, here in Darwin once you drive just 100km's out the road network becomes a little scarce and if there are any they are dirt roads which prove to be pretty rough! In saying that though, there are sealed roads around the rural areas and it's all not a lost cause. The major thing is not being able to 'get to' those rural storms that are large simply due to a lack of access. A lot of the storms are close enough to get right under them and the rural storms generally fall within a road network of some sort as they cross them. Getting lost is very difficult if you have come from Darwin...there's only one main highway into and out of Darwin and all sealed roads you find head you back to that highway! It's a personal thing and if you have one it might be handy to keep a log of where you've encountered storms on a regular basis, given that your brain should be able to retain where you drove to and where you stopped!
A HAM radio is probably a good thing if you are chasing as a group with other cars. That way you can keep in touch with each other and relay info back and forth about cloud structures and the like. The most important thing I see would be for safety concerns or break-downs. At least you have a means to which you can call someone for help if required.
Once you become accustomed to storm structure here in Darwin at least you can use the mentioned tools to assist you. For me, like I said, I just check the obs, models and radar. Then use my eyes and my own local knowledge to then decide which way to head out and when. Sometimes it pays off, sometimes it does not - that's nothing to do with bad nowcasting, it's a matter of the storms not doing what you expected simply because - well - they can do what they like!
Remember that forecasting is not the same as nowcasting. If you want to chase storms in two days time, in a certain area, then that is forecasting and you have to be pretty good at it to be confident that what you forecast is going to happen. Professional chasers spend days - even weeks - forecasting the models to go after big storm systems.
In Darwin forecasting storms is not required because you 'know' it's the storm season and the majority of them will be daily pulse storms. The storms form so fast here that you could look at models for the next two days and forecasting 'something', yet the next day things have changed dramatically. Let the weather bureau forecast and you do the rest. Even when storms are forecast, they sometimes don't even appear. That's why in the early hours of the morning while everyone is sleeping, I'm up looking at radar and satpics to see if, at that moment, there is a sneaky squall line forming and heading for Darwin - which is a common trick our weather plays on us!
If you want to forecast then over a period of weeks watch tropical storms form into depressions and then into cyclones. Forecast that from start to finish and accurately make informed predications and calculations on when the cyclone forms, wind speeds, lengevity and direction and you're on the money. It's always too easy to say you forecast things when in fact you've just nowcast and have no basis for the information you are trying to relay. A bit like believing your own BS!
You should be using satellite images to accurately show you what clouds are forming, if there are any fronts or convergence lines, text book set ups that give you a clue as to when, where and what will come to you or which is close enough for you to chase in time. Any serious chaser worth his or her salt will be using this. How else can you determine what the atmosphere is actually making away from you otherwise? You can even use satpics to see hours ahead what setups are being formed before they get to you, used with radar you can nowcast more accurately and see what is happening to clouds.
Satellite images show you small storm clouds, cumulous cloud fields, large thunderheads, anvil flow/storm direction and overshooting tops which tell you there's healthy, strong storms evident. Combining radar, sounding charts, models like GFS, satellite pics and your own eyes you can really get a handle on how to nowcast and kind of 'forecast' a few hours ahead. A little preparation and homework really will pays off when you get it right. Luck plays a bit role also as we don't have control over Mother Nature!
Winds
An overlooked but vital thing to look at. Wind direction, speed and at which height all play a vital role in thunderstorm development. Differing winds can either help or hinder storms. Jet streams that travel in the lower portions of the atmosphere as well as upper jets all play a role also. Whilst I won't give too many secrets away...you need a good convergence and divergence of lower and upper winds respectively. Lower winds to carry adiabatic winds (horizontal) with moisture, some drier air in the mid levels and moist again up top. Divergence helps spread and dissipate the anvil wash that sometimes can linger and hamper other storms temperature wise. Convergence is a meeting of winds from opposing directions into one line, a boundary of sorts which storms form on.
A trough is a convergence of winds, both moist and dry - combine the two and you have instability, which in turn creates convection & storm initiation. The 500mb area is the most useful area and preferred area in fact when determining storm formation. Up higher to 300mb is heading towards the upper atmosphere - colder of course and where you see anvils spread out. Steering winds are also around the 500mb range, so it's handy to know what direction and what speed that are traveling to determine where to go. Wind speed is also a factor to determine. Does speed change with height? Does the direction change with height? Where do all these happen right to the upper levels from the surface? Winds determine storm character in conjunction with instability levels. It can mean the difference between pulse storms and supercells!
