Conditions leading up to Cyclone Tracy in 1974.

[tgsnoopy]

As I understand it, reading a little... (True, not a lot)

In 1974 an unusual situation existed ahead of Cyclone Tracy in that a very cold Artic flow had formed above Siberia that flowed out towards Japan and South West into the Pacific. This column of cold air got pulled into the monsoon trough, warming as it crossed the Java Sea and accross the Equator. This formed an unusually dense cloud structure which eventually became Cyclone Tracy and grew in strength dramatically when it was fed with very warm moist air over the Gulf Of Carpentaria.

So I have to wonder...

Is a very dense cloud required in advance to form one the strength of Tracy?

Is this very cold flow from Siberia feeding it necessary to form such a dense cloud to start with?

Will any Cyclone heading over the very warm water of the Gulf of Carpentaria gain strength dramatically?

What actually caused Tracy to hang a left and go to Darwin the way it did?

Theories or further info most welcome... Constructive style, lets all learn a little more, type discussion appreciated.

[PaulM]

Heya TG -

The surge of cold air from Siberia is part and parcel of our monsoonal weather & trough and what drives the Hadley cell.

Cyclogenesis for Tracy appears standard - i.e. cluster of storms banding together, coriolis starts it spinning etc.

The unusual thing about Tracy was the left-hand turn and the weather preceding her - i.e. there was a weak TC that went by that caused some complacency. As I understand it, prior to Tracy there was a period of unusually hot weather.

Good topic though - some more digging required!

[PaulM]

Good sumnmary from Wikipedia too (BTW the then Director, Ray Wilkie, is an Aus met legend having written a number of books on weather in Australia too - not sure if he's related to Alan Wilkie the famous Tv Met).

On 20 December 1974, the United States' ESSA-8 environmental satellite recorded a large cloud mass centered over the Arafura Sea about 370 kilometres (230 mi) northeast of Darwin. This disturbance was tracked by the Darwin Weather Bureau's regional director Ray Wilkie, and by senior meteorologist Geoff Crane. On 21 December 1974, ESSA-8 showed evidence of a newly formed circular centre near latitude 8° south and longitude 135° east.[6] The meteorological duty officer at the time, Geoff Crane, issued the initial tropical cyclone alert describing the storm as a tropical low that could develop into a tropical cyclone.
Later in the evening, the Darwin meteorological office received an infrared satellite image from the National Oceanic and Atmospheric Administration's satellite, NOAA-4, showing that the low pressure had developed further and that spiraling clouds could be observed. The storm was officially pronounced a tropical cyclone at around 10 p.m. on 21 December, when it was around 200 kilometres (120 mi) to the north-northeast of Cape Don (700 km or 435 mi northeast of Darwin).[7] Over the next few days, the cyclone moved in a southwesterly direction, passing north of Darwin on 22 December. A broadcast on ABC Radio that day stated that Cyclone Tracy posed no immediate threat to Darwin. However, early in the morning of 24 December, Tracy rounded Cape Fourcroy on the western tip of Bathurst Island, and moved in a southeasterly direction, straight towards Darwin.[8]
By late afternoon, the sky over the city was heavily overcast, with low clouds, and was experiencing strong rain. Wind gusts increased in strength; between 10 p.m. local time and midnight, the damage became serious, and residents began to realize that the cyclone would not just pass by the city, but rather over it. Despite Tracy's small size, the cyclone passed directly over Darwin after midnight, with its eye centered on the airport and northern suburbs. The wind gauge at Darwin Airport officially recorded winds of 217 km/h (135 mph) before being blown away itself.[9] Unofficial estimates suggested that the wind speed had reached 300 km/h (185 mph). The Bureau of Meteorology's official estimates suggested that Tracy's gusts had reached 240 km/h (150 mph).[10] The winds and torrential rain continued until early dawn.[8]

[PaulM]

Interesting satpic as well - note the total lack of any convective activity around her?! Not one storm cluster within thousands of k's.

[Nino-X33]

She was an interesting Lady
"her eye was 15km dia off the coast, decreasing to 8km over the town, destructive winds over 25km, the slow speed 8km/h exposed Darwin to destructive winds for 6-8h , baro fell to 950hPa" Linacre and Hobbs 1977
I have mates i work with who reckon there were tornadoes involved but I am a sceptic of that, more died than the official record (many long grassers and people hiding in town from south were never accounted for), a fleet of taiwanese? boats were wrecked and two mass graves exist at east point and berrimah as the morgues could only keep bodies for 2-3 days. mmm I love a good conspiracy lol)

I also note from their book there was 17 cyclones in the 73/74 season (Tracey was 74/75) in Oz waters with 9 crossings, 4 in 73 - 3 off WA, 1 over the NT with the WA & NT ones crossing, the rest occurred in 74 half, 13 with 9 on the east coast, 1 on the NT and 3 on WA- numbers could be one off as the map I have is intricate and small lol)
I will post a pic of the map later
6 cyclones occurred in March 74 from 6th - 30th with 3 being active on the 25th!! (Numbers might be one out as one did a Steve crossing CS to WA
Quite a season and March would have had a billion hits if NAC existed lol

I spent many hours at the Uni library hiding from the Lismore heat, very similar to our build up, we called town the wok due to its location surrounded by hills
I read a lot of the old newspapers on file for the year preceding, Jan 74 - Dec 74
Even though the same conditions would not produce the same event Qld was an inland sea from flooding in early 74 much like now
I thought last years floods there may have been similar but I think the conditions now are much more similar

54 and 74 down there are epic years for the Lismore locals with a 54 storm ex cyclone the one that did Bris devastating a section of rain forest to the NW of Kyogle, the damage is still apparent to the trained eye
I think Lismore had its historic 74 flood in April?May? and the location of the markers on the telegraph poles around town is mind blowing up to 10m high near the intersection of the CBd and the ovals/ van parks, over 2 story buildings
I seem to recall a huge storm (maybe a east coast low that bombed down from the north) reeking havoc with huge swells entering Brisbane Waters the waterway around Gosford devastating the boaties jetties; and also removing all the sand from most beaches back to the bedrock
I shall look back into it when i have a moment free

But the period of hot weather proceeding Tracy sounds great and would be great to have similar weather soon to amp up the atmosphere, still next year could be better but the season has awhile to run, cyclogensis is poor at the moment so maybe the end of the wet will provide
Its all a chaotic system so anything is possible anytime and hard to clutch accurately at lol

[tgsnoopy]

Good stuff... I have lots of reading ahead of me by the looks. Please, here's a chance for everyone to throw in a bit, we no doubt all have others opinions to consider and potentially learn from.

One thing though, you all seem keen to experience another cyclone... But are you sure your dwelling is up to it?

[hooverdamsel]

The fact is tgsnoopy, most of our dwellings would be blown away in a four or a five, but as Orebound was saying in another thread that there is such a thing as being cost effective and balancing it with the risk of a cyclone hitting. Most of us have a plan for if a cyclone hits (see the December thread) and know where we would be going to in the event of a cyclone. I think though that noone really wants to go through the aftermath even though we like the excitement precursing it.

[looselipslou]

I know plenty of folk that can give eye witness accounts. My father work at Casuarina Australia Post and I believe that was a make sift morgue, my 'uncle' was one of the poor bugger that had to man it. He was a simple postie. We were in Nakara and had already lost over half the roof and exterior wall before the eye. Mum and Dad both tell me that the eye was over very quickly and some areas never really experienced the eye at all. As for the conditions, I have read the same as what Paul posted but either way, I will never put myself through that again.

[Nino-X33]

Saw this article and thought it was worth a read.

I think it might have been this one that she was referring to:

http://www.ntnews.com.au/article/2011/0 ... tnews.html

Just thought I'd place this here as well

[Mick K]

[quote="crystallan"]hi all my name is crystallan i am from newyork happy to come here meet you





Then why are you posting in the cyclone Tracy thresh?
And why do you have 3 URL's as your signature?
Are they related to weather?.

I think you should be deleted because you really aren't one bit interested in weather and are only using this site to pedel your handbags.
Prove me wrong!!!!