Topic: Monsoonal activity 2006/07 season

[Mike]

Our monsoon is due to arrive in Darwin and coastal areas on Thursday 11 Jan.  It's been building for the last two weeks and is almost upon us.  We've also got a weak 1006Hp low imbeded in it just to the N of the Tiwi Islands, but it's not expected to form into anything as such within the next three days at least. With the combination of the two it's been storm chase heaven - I just can't sleep!

We've had a superb buildup to the monsoon over the last week  Friday 5th through to Sunday 7 Jan 07 saw many decent HP storms roll through.  Significant rainfalls in most areas.  My home area was hit with two large HP storms within an hour and at a guess with 35-40knot winds accompanying both of them.

There are daily storms around the skyscape and generally coming in during the afternoon without fail to-date.

So looks like the Top End is at last 'going off', I'm particulary pleased as you would all imagine - the only frustrating thing is in which direction to go to get shots - but the city is still favoured!

 If none of the members have seen the skyscape with a monsoon on the horizon i'll get some shots and post them, quite a cool sight with grey-green skies with white immature Cb's in the foreground - worth photographing!



Regards, Mike.

[Mike]

Jimmy, here;s your answer re monsoonal storms.

There are two regimes during the monsoon. (1) the monsoon trough is near Darwin then thunderstorms tend to be frequent, slow moving and can sometimes lead to flash flooding (warning current now)
(2) the monsoon trough is south of Darwin and Darwin is experiencing fresh to strong Nw winds thunderstorms will become in off the water, often in successive lines and can be associated with strong gusts, sometimes damaging.

The main differences with buildup thunderstorms tend to be: 

- generally (but not always) lower CAPEs often in the 1000s to 2000s rather than 3000 +j/kg.

- timing: often overnight and into the morning, rather than in the afternoon/evening.

- less electrically active, with just one or two claps of thunder rather than the buildup activity (sometimes there is no thunder at all IE deep showers rather than thunderstorms)

- direction of movement - come to Darwin off the water rather than inland.
- height: cloud tops tend to be lower than the buildup specimens.

I think that would cover it all.

[Jimmy Deguara]

Hi Mike,

Now that is interesting information given the specified differences. Personally, I didn't know that although I knew there were night and morning activity coming from the ocean and the storms that come in from the south or southeast. I take it this would result from the position of a surface low or monsoonal trough? Upper level winds woud need to be generally different to create the difference in movement.

Regards,

Jimmy Deguara

[Mike]

Indeed, Jimmy. Mid-level winds impact on our monsoon and tropical storms all the time.  Watching the storms today you can see the way they are coming in off the water - with the NW flow around that low to our NW, you can see the waterborne storms moving NE across the islands, but the other storms moving in from the NE.  It's weird to watch but interesting!

There is little or no lightning as i said, perhaps there's just too much moisture and cool air in and around the storms that inhibits it.

I always thought that upper level winds directed our cyclones, but it's the mid-levels that steer them from the East.  Having watched the monsoon troughs bobble up and down and watching the lows steer westward all the time, I've often asked why our cyclones end up in WA all the time.  It's not from a NW flow into the systems, but the steering winds at mid-levels from the east that push them NW

 There's still enough low level stuff to feed them - as with Monica last year was a good example - although her splatial size was mainly over land, she still had enough mass over the warm waters to have her retain her strength - and even now the met people are looking into that very thing.  Maintaining a CAT5 right up until her eye crossed the coast with such a  large percentage of her feeding 'off the land' so to speak.  It just didn't make sense at the time considering the models.

I think it's one of those areas that perhaps i'll look into more as far as monsoonal processes are concerned - 'tis certainly keeping me busy!

[Mike]

Jimmy further to your questions - sorry i've misunderstood you and confused myself a tad :

Yes, the convection is directed by upper level winds - good indicator is wind at 700hPa/3km.

Also re surface low, yes, a surface low will be positioned within the monsoon trough being the lowest pressure in the linear area of low pressure.

Jeez sorry about that.   I believe i've amended my mistake!

[Mike]

The monsoon is a bit lame at the moment i must say!  There have not been the constant squally showers that is normally experienced, but only the odd shower - light and heavy at times.  We had a few storms last night and this morning but there's too much daylight!  The forcast was for monsoonal showers/storms till Saturday, but now it's showers/storms.  The trough is at the base of the NT but will get pushed back up to us as that H in the bight moves east. The bureau says we should see the return of decent storms next week.

One consolation is that the newspaper here published three of my photographs with a half page story on the monsoon and subsequent weather.  Famous at last!

[Mike]

For those who would like to know...our monsoon or lack of it appears to reforming over the coming week, so hopefully by friday next in early Feb we should see some organisation.  We're about 260mm below our average for January to date, thanks to that deep low that stole our weather!  But on the positive side at least WA, Alice and SA got something out of it.

Just general inland storms predicted for the remainder - one can only hope they reach the city!  Soundings average, CAPE good each day but that's expected although our winds have gone from NW to SE and NE, which is good for storm development in the arvos. Everything else not in favour for anything significant.

The monsoon only generated average rainfall around the place, nothing like persistant monsoonal showers as the norm of previous years, but there's plenty of time left for further activity.  The monsoon trough is above us, it just has to develop more and move further south - patience!

[Mike]

well the rebirth of the monsoon is about to come again with the trough gathering good strength compared to last time around Jan 11 '07.  Flood advices have been posted on BoM and there's another weak low 1008hpa expected to be in the gulf on Tuesday.  The weather today was great - high rates of humidity and skies just ripe for storm formation, you didn't need sounding charts - the sky told it all!

By about 6pm things got well underway atmosphere wise and by 7:30pm there was a fair amount of electrical activity.  Unfortunately constant steady rain hampered any vantage point without getting wet - I ran out of time being at dinner at work (again) when things started to get exciting and missed the opportunity to get some really good CG branching over the harbour by about 8pm. 

Forcast is for showers and storms for the next week, so now that i've got a weeks respite from my night work i'll be able to chase a bit more.  My daugher is quite the avid chaser now with me and enjoys seeing the lightning, but gives me a hard time when i'm setting up the camera and missing the good CGs - always the critic!

This second rebirth of the monsoon looks like it will be a bit more substantial, so I think all up here that chase will be pretty chuffed - that's if we can get some shelter from the rain to get some decent shots!

Mike

[Mike]

Things cooking up here.  We've got a 1002 low in the gulf and now a 1002 low above us (both heading east) and both are expected to deepen by Friday 2 Feb '07.

Went chasing last night and was not disappointed in the action.  I must admit since chasing seriously in the last year or so and not taking much notice of what types of lightning were about but I saw my first Stattaco bolt on the way into town - awesome!

There were plenty of cells around the Islands and along the north coast and found a perfect spot to capture some great shots.  Spent about 2 hours photographing until it all went further north.

There's still plenty to come and 'hopefully' the lows will develop into cyclones and come back our way - the chasers in Qld and North Sydney should see some of the overflow from these systems as they develop with storm activity - good hunting!

Mike

[tohnanon]

My first post - Hello storm watchers.
I am doing time in Gove NT and have enjoyed what nature has offer me in cloud formation and storm activity. Today we have been under Cyclone watch as the low has deepen to 1001hpa, so i may experience my first Cyclone.
I have found this tropical weather quite comforting, like a warm hug, and forever changing, I tend to star into the clouds alot and have seen some quite amazing formation including a water funnel and many nuclear type mushroom formations, one that had a halo on its peak. Here are some amature photos. Thanks for the great info

[Jimmy Deguara]

Welcome tohnanon,

Did the mushroom cloud put out lightning at any point or was it attached to the rain band?

Regards,

Jimmy Deguara

[Mike]

Welcome too Tahnanon!  You will find as I have there are many experienced people on this forum and you'll be educated beyond belief - so ask away if you need to know anything!

Yes, Gove and Nhulunbuy see a lot of cyclone activity as the majority of the NTs systems form from the Gulf area.  The system is expected to be Cat2 by Friday/Sat and models track it heading SW - but as unpredictable as they are, anything can happen.  Far North Queensland looks like getting widespread rain from that system and the other low over Cape York.

For myself personally and others interested perhaps you could keep posting some information on the weather over the next day or so and describe what is happening with the cyclone in the area?

Great shot of the thunderstorm also - beautiful colouring and shape!

Mike

[tohnanon]

Well here it is a calm night in the sky, light rain occasional lightning in the distance and a balmy light breeze. But preperations on the ground is very busy, I am an active member on the radio station www.govefm.com.au and we are putting out warnings and getting a 24 program ready in case things esculate. The community radio is a life line for communications to the public and we advise everyone to keep a radio and batteries on hand for updates and warning in case all else fails. So i was invovled in getting the generator prepared and at work we had to pack up all valueable equipment and cover other belongings in plastic. People here arent really in panic mode and alot say this is a safe area as we have had alot of close calls with Cyclone Monica and others. Ya never know and prevention is better than disaster. We have had a fair bit of rain but not as much as i would expect, coming in heavy but short downpours, with a uniform grey sky and not much wind. The mushroom cloud above was a morning storm from early last year and the lightning wasnt very visable but the distant thunder rumbled often. I do have 1 question regarding the cyclone - at what stage does a tropical low become catagorised as a cyclone?

[Mike]

Hi John.

 Now there's something I didn't know re Cat1 hurricanes - are they classified differently in the US?  Are our Cat5 systems equal to their Cat1 hurricanes?  I thought the systems were the same just differentiated by location and description (title)?  So if they had they had hurricanes with winds of 35k or 55k what category would it be then?  What you say re this would mean theyr'e not classified except as depressions!

Mike

[Michael Bath]

Hi Mike and all - you can find some TC scale comparisons here:

http://australiasevereweather.com/cyclones/intensity_scale.htm

regards, Michael