getting close and closer to November, and the MJO signal moving into phase 2 is exceptionally strong. be an interesting few weeks to see how strong it remains will moving across the indian ocean.
http://cawcr.gov.au/staff/mwheeler/maproom/RMM/phase.Last90days.html

If we get a massive high pressure system like we did this week in the monsoon season, the monsoon will get pushed back to the equator.

The latest Gradient Level Wind Analysis appears to show a slight cross equatorial flow into the area around that trough up near the Solomons. Could this lead to an early appearance of the MT like last year?

The position of the monsoon trough seems to have been pretty ill defined over the past week or so. On the current Gradient Wind Analysis (24/10 1200UTC) the only obvious cross equatorial flow seems to be in the area south of Sri Lanka where the North East Asian monsoon is converging with the flow from the Southern Hemisphere. Most of South and East Asia is dominated by NE Monsoon and the North Pacific trades. In fact convection over tropical East Asia has been very quiet lately as evidenced by satellite IR imagery. Despite this, October is still very early to see the MT in the Southern Hemisphere.

MJO Singnal is looking ok as it moves into the maritime continent. Bom says it is weakening, but there is plenty of cloud.
http://reg.bom.gov.au/climate/mjo/graphics/rmm.phase.Last40days.gif
http://www.bom.gov.au/climate/tropnote/tropnote.shtml
There is plenty of water vapour right across the indian ocean with storm activity from a low near Yemen to Jakarta.
http://tropic.ssec.wisc.edu/real-time/indian/images/xxwvm5bbm.jpg
Heavy rain is forecast for Jakarta for much of the next several days.
http://www.weatherzone.com.au/world/southeast-asia/indonesia/jakarta
Reasonable areas of high pressure across central asia, and lower pressure trough through north australia, helping draw the MJO this way.
http://www.bom.gov.au/australia/charts/viewer/?type=mslp-precip&tz=AEDT&area=G&model=G
Could be an early start to the monsoon, mid Nov looks interesting.

mjo signal weaked in phase 3 but is popping back up as it now moves into phase 4. going by the usual 40 day cycle, the next pulse should hit the maritime continent mid december, which is just about right on time to kick the monsoon off over northern WA and NT and into Qld by Christmas.

Just a quick question and might sound daft asking it....but....since all the severe flooding else where in the world eg. Thailand etc....does that mean the extreme rain will travel down our way....Just asking I am fairly new to the forum...cheers

After a flare up early in the week with a tropical storm in the South China Sea convection has again died off over most of SE Asia, even the equatorial region. This afternoon northern Australia has the most land based activity.

in my time following the weather i have never really looked a link personally. but i guess its the same when looking at the wet summer this country had last year and the failed rains on the african continent. i am a believer in that while its pouring on one side, its not on the other!
sorry it doesnt really answer your question, but i hope someone on here might have some info for you, maybe comparisions between busy typhoon and cyclone seasons maybe?

I am finding the The NOAA website a great resource- explains and forecasts the MJO.
NOAA Madden/Julian Oscillation MJO

The BOM has analysed the MT through the Soloman Islands/eastern PNG area on yesterdays and todays MSL charts. Not sure I agree with this though, maybe more like the South Pacific Convergence Zone. Looking at the 1200Z gradient wind chart of 12/11 I would say the MT is aligned ESE/WNW from northern Sumatra to Irian Jaya.

well if we believe this mornings charts, the monsoon trough runs from Katherine in the NT down to near Adelaide. but i see what you mean Nerd, agreed its a convergence zone, no cross equatorial flow so the real MT is still well north.

Latest surface chart from Thai Met Dept gives a good indication of where the trough may lie. Just follow the big (L)s

http://www.tmd.go.th/programs/uploads/maps/2011-11-14_TopChart_01.jpg

Am I correct in assuming that the fairly weak signal of the MJO in the western Pacific atm is what has kicked off this slight depression north of Fiji. And also that its weak strength will not help any development?
http://www.bom.gov.au/climate/mjo/graphics/rmm.phase.Last40days.gif

Mick:
On the 13/11 1200Z Gradient Wind Analysis the BOM have explicitly marked the position of the MT. A bit unusual for this chart. Almost as if they were reading this thread and and wanted to make a point ;-) Not impossible I suppose. That series of lows around 5-10 deg. north looks convincing as the main area of convergence though.

Sandfly:
I've seen those charts before but find the analysis over the equatorial area a bit sus. If you have a close look some of plotted pressures don't correspond at all to the isobars. Also those lows seem too symetrical and perfect. A pity because otherwise it looks like a nice big clear chart.

I vote %50 to %50 chance December 2011 big wet or after the new year 2012 a big wet.

Nerd:
The Jap WV loop seems consistant with the Thai plot;
http://www.goes.noaa.gov/sohemi/sohemiloops/shwvgmsw.html

Last Qscat data has the convergence in the same area, am I missing something?
http://manati.orbit.nesdis.noaa.gov/datasets/QuikSCATData.php/QuikSCATData.php (sorry this does not seem to work - My Uni login prevents it's use)

Sandfly:
Yes the Thai chart does show a broad trough along approximarely 5 deg. N which is no doubt a real feature. My point was that I had doubts about the reality of the individual low centres depicted.

In any case this is not where the BOM has analysed the MT on their streamline chart and this is what I was referring to with Mick. I did note in my earlier post that a series of lows at 5-10 Deg. N looked a more likely candidate for the MT. This correponds to the eastern half of the broad trough on the Thai chart. Based on the BOM chart I reckon the MT at that time extended from central Borneo to south of the Philippines and then on to the aforementioned series of lows. The BOM doesn't agree with this as they have it about 10 deg further south through PNG and the Soloman Islands to a low north of Fiji.

To clarify, the BOM chart I'm referring to is the 1200z Gradient Wind Analysis (http://www.bom.gov.au/difacs/IDX0514.pdf) which although it depicts the wind as streamlines it also shows major lows and highs. There is a 0000Z chart as well but the 1200 chart is easier to read as it's manually drawn.

I did have a look at the Qscat site but couldn't make much sense of the wind imagery. Either the site's not working properly or I'm not using it properly.

The BOM are suggesting an early arrival of the Monsoon due to the rapid pace of the MJO. Early Dec is their call.

From the BOM

"The MJO heads into the Indian Ocean
Over the past couple of weeks, a fast moving Madden-Julian Oscillation (MJO) event has circumnavigated earth in just 30 days. A weak MJO is currently over Africa, heading east into the Indian Ocean. The majority of climate models surveyed by the Bureau of Meteorology suggest that if this MJO continues at the current speed, it will redevelop in the western Maritime Continent in early December.

Over the next week, decreased rainfall and tropical cyclone potential is likely in the northwest Pacific and the Maritime Continent, influenced by the current position of the MJO. However, an increase in cyclone potential is likely over the next week in the southwestern Indian Ocean.

Climatologically, the onset of the monsoon rains coincides with the Christmas holidays. Based on the current scenario, there is potential for an earlier onset of the monsoon across northern Australia".

http://www.bom.gov.au/climate/tropnote/tropnote.shtml

It may be quick but it is also very weak. Gonna have to really strengthen quickly to have a big impact as far as rain and cyclogenises goes.

The MJO is significant but it’s strength and location is far from the only influence on heavy rainfall and TC genesis for northern Aust. I tend to read that kind on statement a lot on these boards.

The MJO is really picking up in strength now. By the time it reaches the maritime continent we may be looking at a very sudden and intense onset of the 'wet' as it looks to be arriving around the same time as the monsoon trough. With La-nina still building(although somewhat gradually), it is starting to look like late December could be wetter than we were thinking a month or so ago.
MJO

A years worth of MJO.
http://www.youtube.com/watch?v=qh011eAYjAA&feature=relmfu

From the BOM
http://www.bom.gov.au/climate/tropnote/tropnote.shtml

The MJO strengthens in the Indian Ocean

During the past week, the Madden-Julian Oscillation (MJO) has gained strength over the Indian Ocean as it progresses eastwards towards Australia. The majority of climate models surveyed by the Bureau of Meteorology suggest that this MJO event will move into Australian longitudes during the first two weeks of December.

It is likely that this MJO event will spawn the first tropical cyclone for the Australian cyclone season, and the Bureau of Meteorology will be monitoring the situation very closely.

Whats the latest on the MJO?

It's passing Australian longitudes now and is forecast to weaken as it enters the Pacific Ocean. Looks as though it didn't result in the development of the monsoon trough over northern Australia as the Bureau suggested in their tropical climate note... But there was some cross equatorial flow in the vicinity of Cyclone Alenga.

What's the latest on its return?

Last I heard a few weeks back someone said it would be the 2nd or 3rd week of December for the Tropics to have their first MJO event.

Someone at work was saying how there is the high tide (the big big one) happening this year on Xmas day - 3metre waves ect. Any usually, in most years, the rains have started by this event. Anyone heard or noticed this? It cannot be far though, the atmosphere is busting and something has to give!!

it's bit odd that it didn't result in the formation of the monsoon trough, after all we are in a La Nina.

Drive..... pretty high for Cairns (not record high... but you would not like any wind on the back of it).
http://www.bom.gov.au/cgi-bin/oceanography/tides/tide_predications.cgi

So if the current MJO hasn't triggerd the onset of the wet, then would it be reasonable to suggest a late onset sometime in January?

From the BOM
Todays Trop Note http://www.bom.gov.au/climate/tropnote/tropnote.shtml

MJO influencing Australia's weather
Over the past week, a moderately strong Madden-Julian Oscillation (MJO) has moved into the Australian region, and as a response, conditions are getting wetter. The majority of climate models surveyed by the Bureau of Meteorology suggest that this MJO event will linger in Australian longitudes for the next week or two, but weaken in strength during this period.

The current MJO event spawned the first tropical cyclone for the Australian cyclone season, Severe Tropical Cyclone Alenga, which formed in the Indian Ocean last week.

The risk of tropical cyclone formation in the Australian region is likely to remain above average for most of December, with increased rainfall across northern Australia during this period.

There are early indications of the monsoon trough developing in the southern hemisphere, and as is typical for La Niña years, it is likely that the Top End will come under the influence of the monsoon before Christmas.

So does this mean the monsoon doesn't normally arrive until a week or two after the passage of the MJO signal? And that the MJO plays a role in setting up the right conditions for it?

Also the BOM 4 day chart is now showing a monsoon trough to the north of Darwin on Saturday.

we are also seeing a fairly solid high presure system building over nth china and russia. only around 1030hpa, might hopefully be the start of a cross equatorial flow. love to see that high getting to 1040hPa to be really happy and get rid of that area of low pressure on the nth side of borneo. but this large high up there could certainly help kick things along in the next few days.

The part of the surface trough extending from central QLD to northern WA could almost be considered a monsoon trough, at least from a surface perspective. It separates a hot humid airmass of northern hemisphere origin to its north from a drier trade flow to its south.

Mick10: What chart are you using for northern Asia?

a true monsoon trough has deep NW winds from the equatorial regions. sometimes you may see the bom using the MT line for this inland troughs but i just dont think the NW feed is there just yet.

MSLP chart for western pacific is here
http://www.bom.gov.au/australia/charts/darwin_MSLP_00z.shtml

Agreed. The true monsoon flow is deep but from a surface perspective what we've been having recently is about as equatorial as it's going to get. A chart that I look at occasionally is this one from Hong Kong: http://www.hko.gov.hk/cgi-bin/hko/dwm_e.pl

The one for 0800 HKT with observations is quite good especially if you choose normal rather than reduced size.

The monsoon trough is broken and messy atm. I don't agree with the computer generated MSLP depicting a solid continuous trough right across the area N of Aus, it will be well segmented. At best I can see it lasting a few days before weakening and clearing out. The first true monsoon will probably occur mid January with the next MJO.

TS

From todays BOM tropnote. http://www.bom.gov.au/climate/tropnote/tropnote.shtml


The Australian monsoon trough intensifies
Over the past couple of days, a strengthening Madden-Julian Oscillation (MJO) has led to enhanced convection over much of the Maritime Continent. North of the Equator, Tropical Storm Washi intensified, rapidly causing flash floods over southern Philippines. TS Washi is expected to track southwest over the South China Sea during the next few days.

The majority of climate models surveyed by the Bureau of Meteorology suggest that this MJO event will remain active around the Maritime Continent, contributing to tropical rainfall activity over the next seven to fourteen days.

A weak monsoon trough intensified north of Australia over the weekend, leading to enhanced convection across northern parts of the continent. An intensifying monsoon trough and an active MJO in the Maritime Continent increases the potential for tropical cyclones in the Australian region, with some numerical models predicting the formation of a low over the Arafura Sea and another in the Coral Sea later this week.

The Australian monsoon trough intensifies
Over the past couple of days, a strengthening Madden-Julian Oscillation (MJO) has led to enhanced convection over much of the Maritime Continent. North of the Equator, Tropical Storm Washi intensified, rapidly causing flash floods over southern Philippines. TS Washi is expected to track southwest over the South China Sea during the next few days.
The majority of climate models surveyed by the Bureau of Meteorology suggest that this MJO event will remain active around the Maritime Continent, contributing to tropical rainfall activity over the next seven to fourteen days.
A weak monsoon trough intensified north of Australia over the weekend, leading to enhanced convection across northern parts of the continent. An intensifying monsoon trough and an active MJO in the Maritime Continent increases the potential for tropical cyclones in the Australian region, with some numerical models predicting the formation of a low over the Arafura Sea and another in the Coral Sea later this week. The Bureau of Meteorology will be monitoring the situation very closely.
http://www.bom.gov.au/climate/tropnote/tropnote.shtml

That's last weeks. New one still not up yet.

Here is the updated one, a little late in the day.

A strong soi continues in the Pacific
La Niña remains established in the Pacific with little change from last week. Atmospheric indicators of La Niña continued to intensify slightly, thanks to below average Mean Sea Level Pressures (MSLPs) at Darwin. The 30-day Southern Oscillation Index (soi) value was +23.1 to the 24th of December, with contributing pressure anomalies of +2.3 hPa at Tahiti and −1.9 hPa at Darwin. The monthly soi for November was +13.8, the highest monthly value since April. The 5-month running mean (centred on September) was +9.1.
Below average sea surface temperatures (SSTs) and sub-surface temperatures persist across the tropical Pacific Ocean. Data from the NINO3.4 region shows SSTs remain 0.8 °C below average, with no change form last week. Cloudiness near the International Date Line continues to be below average, but the area has expanded south of the equator. A well developed South Pacific Convergence Zone (SPCZ) extends from the Solomon Islands, over New Caledonia through to the south of Tonga. A large area of enhanced convection is evident from the southern tip of India, through northern Australia and the SPCZ.
Forecast models surveyed by the Bureau suggest this La Niña event is likely to persist for the majority of the north Australian wet season. It is unlikely that the current La Niña will be as strong as La Niña event of last wet season.
La Niña periods are typically associated with above average rainfall across northern Australia during the wet season, with an earlier monsoon onset in Darwin (which usually arrives around Christmas / New Year). Daytime temperatures are typically cooler from December onwards, and tropical cyclone activity is usually above average between November and April
See the Bureau's ENSO Wrap-Up which includes a compilation of ENSO computer model predictions.
Australian region nurtures first cyclones
Over the past couple of days, a strengthening Madden-Julian Oscillation (MJO) has led to enhanced convection over the southern Maritime Continent. An erratic MJO has been quasi-stationary around the Maritime Continent since early December.
The majority of climate models surveyed by the Bureau of Meteorology suggest that the MJO will remain active around the Maritime Continent, contributing to tropical rainfall activity over the next week as it propagates east.
Early last week, a tropical low developed over the Coral Sea into Tropical Cyclone Fina within the South Pacific Convergence Zone but lasted just a few days. Later in the week and with the monsoon trough over the Arafura Sea, a low gradually intensified into a tropical cyclone. TC Grant contributed to above average rainfall, flooding and strong winds across the Top End during Christmas. Now as low over land, ex-TC Grant is expected to travel east and may intensify again over the Gulf of Carpentaria later this week.  Above average rainfall and strong winds will continue across northern parts of the continent until early January.

It's my understanding SST's in the CS and Gulf are above average (and clearly rising in the CS). And the fact that the MJO continues to waddle around indicates some interesting times over the few weeks.
http://reg.bom.gov.au/products/IDYOC049.shtml

MJO to weaken over Pacific
After a brief stall over the Maritime Continent last week, the Madden-Julian Oscillation (MJO) increased in strength and pushed eastward into the Western Pacific. The MJO added to the already enhanced convection within the SPCZ. Furthermore, enhanced westerly flow in the wake of the MJO encouraged monsoon activity over northeast Australia.
The MJO is forecast to weaken as it moves eastward throughout the rest of this week. It is typical for an MJO pulse to weaken over the Eastern Pacific during La Niña events; this is most likely due to cooler SSTs and enhanced easterly winds at lower levels.
When the MJO pushes into the central and eastern Pacific it typically allows for a break in the North Australian Monsoon. Even with a weakening MJO signal (meaning the MJO will be less of a factor in driving the monsoon) it is likely that monsoonal conditions over northern Australia will subside for the remainder of the week.
See the Bureau's MJO Monitoring for more information, including rainfall maps.
http://www.bom.gov.au/climate/tropnote/tropnote.shtml

An erratic MJO over the Pacific
Over the past seven days, a weak and erratic Madden-Julian Oscillation (MJO) remained in the western Pacific contributing, in some small measure, to convection within the northern flank of the South Pacific Convergence Zone (SPCZ).
The MJO is forecast to remain weak, but progress eastward throughout the next fortnight. During La Niña events, it’s typical for MJO pulses to weaken over the eastern Pacific as they encounter below-average SSTs and enhanced easterly winds at lower levels.
Drier than average conditions are expected over far northern Australia as the monsoon trough migrates north and extends from the Arafura Sea to the Coral Sea. These drier than average conditions are expected to last at least until late January. In contrast, northern WA and the south western NT can expect above average rainfall and gusty winds in the next few days as a trough draws in moisture from the tropics. A low pressure system over the North West Shelf is expected to intensify before heading south over land. At this stage, it is unlikely this low will develop into a tropical cyclone.
See the Bureau's MJO Monitoring for more information, including rainfall maps.
http://www.bom.gov.au/climate/tropnote/tropnote.shtml

The MJO has re-emerged into phase 5 after a period of dormancy. It will be interesting to see how it interacts with the developing monsoon trough.

Yeah definately keen to be watching what it does. Surprising its been so dormant when over near Madagascar they have two very active systems and the convection across Australias tropics is deepening more and more by the day. I would imagine there will be rapid deepening of that MJO signal over the next few days. Otherwise I will just be plain confusd if it doesn't.

australian continent is like a magnet for the mjo during lanina, finally the map is showing this

http://cawcr.gov.au/staff/mwheeler/maproom/RMM/phase.Last40days.html

very nice amplification there ... sooo looking forward to a good rain event
cheers

I have started a new thread here for any discussion of the NT monsoon low:

http://forum.weatherzone.com.au/ubbthreads.php/topics/1063985#Post1063985

The MJO signal is quite significant at the moment and is firmly in phase 5 atm. This has really kicked along the monsoon trough which has spawned several lows, including a monsoon trough over the NT which is forecast to interact with an upper trough and have a significant affect on central parts of Queensland and NSW.

Monsoon returns to northern Australia
A deep and well organized trough formed last week over the Arafura and Timor seas and gradually migrated southwards towards central Australia, bringing an active monsoon to our latitudes. At the same time, the Madden-Julian Oscillation (MJO) gained strength and propagated east across the southern Maritime Continent. The MJO is currently positioned over the western Pacific Ocean. There is some degree of uncertainty on the positioning and amplitude of the MJO in the forthcoming weeks due to the influence of La Niña, but it is likely to contribute to enhanced storm activity within the SPCZ including the Coral Sea.
Over the next week, monsoonal conditions will prevail over northern Australia with above average rainfall and enhanced low-level westerly winds. The Monsoon trough is expected to migrate north and reach the base of Australia’s Top End later this week. Off the Western Australia coast Tropical Cyclone Iggy is expected to continue on a southwest track. Over the Australia’s eastern seaboard, a low is likely to develop over the Coral Sea by the end of the week although at this point it is too early to predict its strength or possible track.

YS, where is that story from? Please remember to provide a link to the source of the information.

the BOM must be seriously under staffed? i checked the weekly tropical climate note at 7 am this morning and it still had not been updated (it is normally updated every Tuesday) i checked it again an hour later and it had been updated, the funny thing about that is that the date on it had been backdated to "Tuesday" the 13th......but Tuesday was actually the 14th!


Drier conditions return to northern Australia
Drier conditions have prevailed over northern Australia as the North Australian Monsoon (NAM) remains in a break period. Agreement between the models continues, suggesting the MJO will remain strong over the next two weeks as it progresses from the Atlantic into the Indian Ocean. Current guidance suggests it will not be back in Australian longitudes until late February or early March.
Drier than average conditions are expected to continue across northern Australia for the next one to two weeks due to the break conditions of the NAM and the forecast track of the MJO. A pocket of dry air over most of northern Australia will ensure little rain for the coming days as daytime temperatures in central Australia climb to the high 30s and low 40s.
Over the Coral Sea, severe Tropical Cyclone Jasmine tracked in an east to southeasterly direction over the past week, bringing strong winds and torrential rains to parts of New Caledonia and Vanuatu. TC Jasmine reached category 4, the strongest so far in the 2011-2012 season. The Fijian meteorological service is monitoring TC Jasmine as it continues across the central Pacific. The chance of tropical cyclones forming in the Australian longitudes will remain below average over the next week.
See the Bureau's MJO Monitoring for more information, including rainfall maps.
http://www.bom.gov.au/climate/tropnote/tropnote.shtml

Noticed the monsoon trough is no where to be seen on the synoptic chart atm. It is well out of sight
Is that caused by the MJO or ?
What makes the monsoon trough inactive? It was only active for a very short time in january

a MT forms when monsoonal cross equatorial Nth West winds meet the SE trade winds from southern Australian highs. we have only had one real strong NW burst this season, in early February. We have lacked strong high pressure systems in the tasman sea especially this season. the Qld area being dominated by upper and surface troughs. so there has only been the one short window when the classic monsoon has formed to date.

the MJO is seperate to the MT. But also the same! The MT can be strong and bring good rain events to northern australia, seperate from an MJO event. While the MJO over northern australia will also increase monsoonal activity.

should also note, strong monsoonal NW winds are driven by large 1040+hPa highs over siberia. If there are no strong low pressure belts between mainland asia and Australia, thats when we get the best out of the MT. if your looking at models in summer, look at Asia and watch for very, very big high pressure system!

Thanks for that. Mick 10..
also
Does the N/west to ..s/east tropical infeeds ( cloud band) traveling toward the mid latitudes) come from the MJO position or quadrant
I noticed there have been no tropical cloud infeed since the MJO has shifted east.

For example the recent floods in QLD and NSW.
Was that because the MJO was near the gulf of Carpentaria where the persistent moisture laden cloud stream appeared to be emanating from?

In Victoria we have missed the N/west cloud bands this summer
Last the n/west incoming tropical cloud gave us some decent rain
Is the MJO in the wrong position for an infeed from the N/west corner of WA?

Oh well, not to worry, there is always next season.

Looking at the satellite imagery it looks like a return to November i.e. widespread convection over South East Asia and sporadic isolated convection over northern Australia. The depression in the South China Sea is apparently receiving a bit of impetus from a NE monsoonal surge. Hopefully that surge will give us a bit of activity in a week or so.

Crikey ,
NW infeeds into VIC are typically an Mid Autumn - Early Summer Gig . They will be influenced by an MJO , but not the MT as much .
BUT all of this ( position of MT and MJO Peaks ) has all to do with the IOD ( Indian Ocean's version of ENSO [ so to speak ] ) .
There is a Thread in the General weather section that will explain IOD . Or if your lucky , PM ROM . Generally i think it would be wise to read that Thread first then Fire questions at himself or if he's busy ( AGW fighting ) then I can try and answer any questions you have .

Link " http://forum.weatherzone.com.au/ubbthreads.php/topics/42457/The_Indian_Ocean_Dipole_and_th#Post42457 "

Looks like the stuff from the east is approaching to our waters. Looks like another monsoonal burst ahead from that massive thick cloud east of PNG moving westwards. No wonder why COLA is suggesting heavy falls most of the tropics.

http://wxmaps.org/pix/prec7.html

Thanks for that info Southern oracle. Quite a strange phenomena.the MJO. I read somewhere you can spot 'it' on the world satellite pic re : convection./cloud but l am yet to find 'it'
LOL

Oh my Matthew T. just had a look at the forecst rainfall and looks like QLD and NSW are in for some more heavy rain after the last floods?
Is that related to the MJO position or is the monsoon trough heading southward over the mainland again?
Another n/west tropical infeed moving over QLD/NSW from near the GOC?

is the BOM going back in time? last week the backdated the tropical note to tuesday and this week they have updated it with the Tropical note from the 7th of Feb?
Weekly Tropical Climate Note

Issued on Tuesday 7 February 2012
soi eases further, but La Niña persists
The Southern Oscillation Index (soi) eased slightly over the past week, falling below +10 for the first time since late November. The current (4 February) 30-day soi value stands at +8.3. The contributing atmospheric pressures were 0.8 hPa above normal at Tahiti and 1.0 hPa below normal at Darwin. The monthly soi for January was +9.4. The 5-month running mean (centred on November) was +13.0.
Oceanic indictors remain at La Niña levels with below average sea surface temperatures (SSTs) and sub-surface temperatures persisting across the central and eastern tropical Pacific Ocean. The NINO3.4 index is currently at -1.1. Cloudiness near the Date Line continues to be below average south of the equator. Enhanced convection remained dominant across the western Maritime Continent and extended through far north Queensland and the South Pacific Convergence Zone (SPCZ).
Forecast models surveyed by the Bureau suggest this La Niña event will gradually decline over the coming months. However, it will remain a dominant climate driver until the end of the north Australian wet season (end of April).
La Niña periods are typically associated with above average rainfall across northern Australia during the wet season. Daytime temperatures are typically cooler than normal from December onwards, and tropical cyclone activity is usually above average between November and April.
See the Bureau's ENSO Wrap-Up which includes a compilation of ENSO computer model predictions.
Monsoon eases across northern Australia
After a wet end to January, drier conditions have returned to far northern Australia as the North Australian Monsoon (NAM) retreated north and weakened. The Madden-Julian Oscillation (MJO) continued to gain strength and has maintained a steady eastward progression over the Pacific Ocean. There is a good degree of agreement between models, suggesting this MJO will remain strong over the next two weeks as it progresses across the western hemisphere. Current guidance suggests the MJO will not be back in the Australian longitudes until late February.
Drier than average conditions are expected across northern Australia for the next one to two weeks due to the break conditions of the NAM and the forecast track of the MJO. Southeasterly winds will gradually spread across most of northern Australia by the end of the week, with strong winds expected across central parts of the continent. Remnants of the NAM remain over a region from the Cape York Peninsula to Vanuatu, but it is expected to weaken by the end of the week. Tropical Cyclone Jasmine is expected to continue on an east track and gain intensity before crossing the island nation of Vanuatu on Wednesday and continue east towards Fiji.
See the Bureau's MJO Monitoring for more information, including rainfall maps.
Next update expected by 14 February 2012 | Product Code IDCKGEWOOO
For more information please contact climate.nt@bom.gov.au
http://www.bom.gov.au/climate/tropnote/tropnote.shtml

Weekly Tropical Climate Note
Issued on Tuesday 21 February 2012

La Niña continues, but the Pacific warms
Sea surface temperatures (SSTs) in the tropical Pacific Ocean have continued to warm during the previous week. Despite this, the typical La Niña pattern remains, although weaker, with the NINO3.4 index currently at –0.5 °C.

The 30-day Southern Oscillation Index (soi) also weakened over the past week dropping from last’s week +12.0 value to +8.0 on 18 February. The contributing atmospheric pressures were 0.9 hPa above normal at Tahiti and 0.7 hPa below normal at Darwin. The monthly soi for January was +9.4. The 5-month running mean (centred on November) was +13.0.

Although both oceanic and atmospheric indices show signs of weakening, cloudiness near the Date Line continues to be below average, while convection across the South Pacific Convergence Zone (SPCZ) was greatly reduced over the past week. In contrast, enhanced convection was dominant over the South China and Philippines Seas.

Forecast models surveyed by the Bureau suggest this La Niña event will gradually decline over the coming months. However, it will continue to play a mayor role on Australian climate until the end of the north Australian wet season (end of April).

La Niña periods are typically associated with above average rainfall across northern Australia during the wet season. Tropical cyclone activity is usually above average between November and April, with six named systems across the Australian longitudes since November 2011.

See the Bureau's ENSO Wrap-Up which includes a compilation of ENSO computer model predictions.

The monsoon looms as drier conditions continue
Drier conditions continued over northern Australia as the North Australian Monsoon (NAM) remains in a break period. Agreement between the models continues, suggesting the MJO will remain strong over the next fortnight as it progresses across the Indian Ocean. Current guidance suggests it will not be back in Australian longitudes until the last few days in February or early March.

Over the next week and under the current scenario, drier than average conditions are expected to continue across northern Australia. Humidity levels across far northern Australia are expected to increase while daytime temperatures in central Australia continue to hit the high 30s and low 40s.

A weak trough is now developing over the southern Maritime Continent. A stronger signature of the NAM is expected to develop over the eastern Indian Ocean and the Coral Sea next week. With a developing NAM, the chance of tropical cyclones forming in the Australian longitudes is expected to increase over the next fortnight.

See the Bureau's MJO Monitoring for more information, including rainfall maps.

Next update expected by 28 February 2012 |

An active Northern Australia Monsoon
An active MJO has slowly propagated eastwards over the past week across the Maritime Continent. This event is forecast to remain active and continue its eastward propagation across Australian longitudes over the next days, enhancing convection over the region. Model guidance suggests this MJO will move into the western Pacific Ocean later this week.
Over the past week, above average convection was observed over the eastern Indian Ocean, the Maritime Continent and most of northern Australia. Below normal cloudiness continued from New Guinea to the Date Line, with a weaker than usual South Pacific Convergence Zone (SPCZ) in the western Pacific.
A monsoon trough over the Timor and Arafura seas is expected to strengthen and migrate southwards over the coming days. Winds will shift west-northwest with monsoonal showers and storms developing over the far north of Australia. Central Australia will remain in east-to-northeasterly flow which could be strong at times over the weekend.
With the MJO currently moving across the Maritime Continent and a strengthening Northern Australian Monsoon (NAM), the risk for tropical cyclone formation and above average rainfall across tropical Australia will be high, more so over the northwest. A tropical low is currently being monitored over the Timor Sea, while a low off the coast of the Pilbara is likely to achieve tropical intensity later in the week. Next week, the risk of tropical cyclone formation over the Coral Sea will increase to moderate, as the MJO enters the Pacific.
See the Bureau's MJO Monitoring for more information, including rainfall maps.
Next update expected by 20 March 2012 |