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kold weather

Tropical Cyclone Nicholas

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Another day and another system develops, this one 19S is close to NE Australia in an area with some very high heat content. This is showing with the convection being very deep indeed. There is also a very evident low level circulation center underneath the convection with the system and appears to be some inflow coming up from the ESE/E which is helping the system. Looks impressive and could be the one to watch over the next few days with fairly low shear present due to a developing upper high over the system next 24hrs, high heat content thanks to the very warm waters and no real obvious signs of dry air other then a little to the north but as long as the system doesn't injest too much into the middle layers it should fair just fine in the future with present forecasts going upto 90kts 10 min sustained winds in 72hrs which means development could well be pretty rapid, which to be honest wouldn't surprise me given the high heat content that could be used by the system, indeed I think it could well peak close to 100kts sustained 10 minute winds.

post-1211-1202850537_thumb.jpg

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Yes, conditions certianly look good and as I mentioned in the 17S thread, sea temps are very warm, near 32C in some spots. It's also worth noting that the cyclone is in a weak steering environment so it's not going to move much over the next couple days, and it is still highly uncertain just where this one will go after that. JTWC have a slow southwesterly motion setting in beyond 48hrs and BOM are thinking a southeastward motion will become established. Either way, the whole of the coast of NW Australia (particularly from Port Hedland eastward to Kalumburu) are at risk later this week. And as you say KW, this one has potential to be a biggie.

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Yes steering currents are weak though I've not really had a good look at the synoptic set-up and evolution around that part of the world so I won't comment too much about that side of things yet, other then that the forecast does prog the system to do a loop. After that the forecasting agencies differ with one idea being to take the system SE whilst another idea is for the system to be ejected westwards but carry on in the weak steering current. Much is going to depend on how strongly the high pressure neaby builds and even small changes in the heights of the high pressure can make all the difference bewteen a system taking different directions and often the models won't be certain even at 24hrs exactly how strongly a high will build.

Either way its going to come south eventually as the high is weak and so the cyclone is likely to be a reasonable risk to NW Australia and yeah given its current rate of organisation its going to end up being quite strong.

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Storm Alert issued at 12 Feb, 2008 18:00 GMT

Tropical Storm 19S is forecast to strike land to the following likelihood(s) at the given lead time(s):

Yellow Alert Country(s) or Province(s)

Australia

probability for TS is 75% in about 24 hours

Yellow Alert City(s) and Town(s)

Lombadina (16.5 S, 122.9 E)

probability for TS is 65% within 12 hours

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Nicholas looks like its being sheared a little from the east, its not too severe right now but igts preventing any strengthening right now. As soon as it starts to head south shear should start to reduce a little so in the short term I wouldn't expect much strengthening even when te shea does reduce it'll take a good 6-12hrs for the system to have reconsolidated again.

Long term I don't think shear is going to be a major problem as the upper high is bulding to the systems south right now, heat content is also pretty high though not exceptional despite the high SST's, probably because those high SST's don't extend below the surface...one thing that may slow down strengthening past 36hrs could be upwelling, the system looks like staying in a farly slack flow for at least the next 48hrs and this will reduce the heat content after a while. It all depend on how strong Nicholas gets, if it doesn't get too powerful due to whatever factor then it souldn't be a problem but if it gets down to say 920-930mbs in pressure then it could well become a real inhibiting factor

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Nicholas is at 45kts according to the JTWC, slightly up on this morning. Nicholas is currently in a competitive steering environment but this is expected to change as a break that should occur in the subtropical ridge allows Nicholas to move south. Both JTWC and BOM are now agreeing on a southward motion. Convection is currently sheared to the southwest but shear is expected to ease as KW says as an anticyclone builds near Nicholas. I've heard (from this Australian weather forum http://forum.weatherzone.com.au/cgi-bin/ul...?ubb=forum;f=12 ) that Northwest Australian coastal communities are already preparing for a likely landfall as Nicholas is expected to become fairly strong.

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Tropical Storm NICHOLAS is forecast to strike land to the following likelihood(s) at the given lead time(s):

Yellow Alert Country(s) or Province(s)

Australia

probability for CAT 1 or above is 15% in about 48 hours

probability for TS is 50% in about 48 hours

Green Alert City(s) and Town(s)

Lombadina (16.5 S, 122.9 E)

probability for TS is 45% in about 36 hours

Broome (18.0 S, 122.2 E)

probability for TS is 40% in about 48 hours

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Nicholas has started to track southwestward and has strengthened to 60kts accoding to the JTWC. Good outflow, low shear and warm sea temps will ensure Nicholas continues to strengthen as it heads generally southward.

Forecast track from BOM:

Nicholas

shows the areas BOM think are most at risk from Nicholas in the coming 24-48 hours.

Satellite image of Nicholas (northwestern Australia):

xxirgms5wbbm.jpg

Taken from CIMSS

You can see Nicholas is spinning up quite nicely in the favourable conditions. If the present rate of strengthening continues then Nicholas may pose a real danger to the areas highlighted in the BOM map.

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Just looking at the AVN loop it appears over the past 6hrs the shear has eased off, the system has condensed which to me suggests while there probably is some shea present (outflow on the western side still looks pretty fast) it appears to me that its eased off a little. This may be the start of the system developing faster we will wait and see.

Still some deep convection over the center though the loud tops have wamred quite a lot as you'd expect given the peak of heating shoiuld be occuring over that prt of the word right now, they should start to cool again in the next few hours I'd have thought. Inflow is ok but its not amazing it has to be said though outflow channel is decent as you'd expect given the shear.

Still looks like its heading for NW Australia, how strong depends on whether the shear has eased or not, ther eis still time for quick development though the forecasting agencies aren't calling or that and given its organisation at the moment I have to agree, tohugh Iwouldn't be surprised if it makes landfall in a strengthening phase, those for some reason always seem to be stornger then landfalling weakening storms...probably because the winds are carried down more effectivly in strengthening systems while in weakening systems the winds in the mid-level of the system isn't as effectivly carried down to the surface maybe because of factors like dry air etc.

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new update

Tropical Storm NICHOLAS is forecast to strike land to the following likelihood(s) at the given lead time(s):

Yellow Alert Country(s) or Province(s)

Australia

probability for CAT 1 or above is 20% in about 48 hours

probability for TS is 35% within 12 hours

Yellow Alert City(s) and Town(s)

Port Hedland (20.4 S, 118.6 E)

probability for CAT 1 or above is 10% in about 48 hours

probability for TS is 40% in about 48 hours

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Now its cat 2 and reaching cat 4 later tomorrow parallel coast!

Yup, could be a dangerous one as this article reflects:

http://www.news.com.au/heraldsun/story/0,2...5005961,00.html

(NOTE: the categories stated are Australian scale, not SS Scale)

Nicholas' landfall (or perhaps not! Nothing is certain yet) keeps being put further westward as Nicholas moves more westward rather than southward. The subtropical ridge to the south remains the primary steering influence and my guess is that the break in the ridge forecasted to occur which would let Nicholas push south has not materialised yet. JTWC have Nicholas at 65kt (cat 1 on SS Scale, 1 min sustained windspeed) and BOM have Nicholas at 50kts (cat 2 on Australian scale, 10 min sustained windspeed). Both agencies forecast further intensification and the BOM are warning of a severe cyclone event for the Pilbara Coast sunday into monday.

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I'm not entirely sure that it'll get quite as strong as they are predicting (I'd go for a cat-3 instead) as the structure seems a little off key to me right now, it seems to me that the system is having a hard time wrapping convection around its center on te soxuthern side, its probably taking in some slightly drier air from NW Australia as thats where the inflow is being drawn from and on top of that its still probably being hit by some shear hence why it looks a little odd a the moment.

Its still got 2 days over water and so I'd be surprised if doesn't eventually ramp up because saying all that it still looks like a decent system with strong deep convection on the northern quadrant which will probably help keep the system where it is right now.

IF it can get that convection wrapped around its southern side then a eye will proably rpaidly emerge from that deep convection and the system could well strengthen rapidly upto a cat-4 as is forecasted but the longer it takes to undertake this the lower its peak strength will be.

Whatever happens looks like being a fairly strong tropical cyclone heading into NW.australia, could well be a major hurricane on the Australia scale by the time it gets close to land. The exact landfall is tricky because the models still probably don't have a decent grip on both the TC and probably the weak high pressure system that is at the momen at least still guiding this system.

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Due to a continued more westerly motion, landfall keeps being put further and further west. This afternoon, BOM were going for landfall between Port Hedland and Karratha, but this has now shifted towards Exmouth, right at the northwest tip of Australia. It is now increasingly possible that Nicholas may avoid a direct landfall entirely and instead scrape down the west coast of Aus though this soloution isn't currently considered by BOM or JTWC but if this general westward motion continues then it may be possible IMO. Either way, Nicholas has slightly longer over water and both JTWC and BOM are predicting Nicholas to be stronger than their last advisories. JTWC have Nicholas at 105kts at landfall which obviously could be very dangerous. Definitely one to watch.

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thanks for the updates guys

Tropical Cyclone NICHOLAS is forecast to strike land to the following likelihood(s) at the given lead time(s):

Red Alert Country(s) or Province(s)

Australia

probability for CAT 1 or above is 40% in about 48 hours

probability for TS is 75% in about 36 hours

Red Alert City(s) and Town(s)

Roebourne (20.8 S, 117.2 E)

probability for CAT 1 or above is 35% in about 48 hours

probability for TS is 70% in about 36 hours

Yellow Alert City(s) and Town(s)

Port Hedland (20.4 S, 118.6 E)

probability for CAT 1 or above is 15% in about 48 hours

probability for TS is 70% in about 36 hours

Pannawonica (21.8 S, 116.3 E)

probability for CAT 1 or above is 20% in about 48 hours

probability for TS is 60% in about 48 hours

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The westward shift of the track is good for both NW Aus. and also Nicholas. This mornings forecast had the system turning SSW by this point but a westward motion is stil in play. What has happened today is that the system has moved away from the more stable air from Australia and as a result the convection has deepened and has also become more widespread again as the inflow picks up a greater supply of moisture.

The system still has a strange asymertric look and the convection still hasn't banded round the center very well on that southern side however I fully expect the system to slowly wrap round over the next 36hrs, it'll never be totally perfect due to the nearby land but it will look better, indeed it has improved quite a lot since his morning.

Inflow is lookig less constrcited and outflow has improved quite a lot as well on that northern side, convection is still very deep indeed on the northern side and is starting to become wrapped around te center better and also outflow on that northern side looks more impressive, shear has evidently also weakened due to the better in/outflow channels.

Indeed I'd watch out for the shear now helping the system by fanning the outflow and helping to ventilate the system, if it can just wrap around the convection then this system could rapidly strenthen from here, big IF, but the further est it goes the better its chances of doing that are.

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Storm Alert issued at 16 Feb, 2008 6:00 GMT

Tropical Cyclone NICHOLAS is forecast to strike land to the following likelihood(s) at the given lead time(s):

Red Alert Country(s) or Province(s)

Australia

probability for CAT 1 or above is 45% in about 48 hours

probability for TS is 75% in about 24 hours

Red Alert City(s) and Town(s)

Onslow (21.7 S, 115.0 E)

probability for CAT 1 or above is 35% in about 48 hours

probability for TS is 60% in about 48 hours

Yellow Alert City(s) and Town(s)

Roebourne (20.8 S, 117.2 E)

probability for CAT 1 or above is 10% in about 36 hours

probability for TS is 70% in about 36 hours

Port Hedland (20.4 S, 118.6 E)

probability for TS is 55% in about 36 hours

Pannawonica (21.8 S, 116.3 E)

probability for TS is 55% in about 36 hours

Exmouth (22.0 S, 114.2 E)

probability for CAT 1 or above is 30% in about 72 hours

probability for TS is 55% in about 48 hours

Cardabia (23.0 S, 113.9 E)

probability for CAT 1 or above is 20% in about 72 hours

probability for TS is 40% in about 48 hours

Carnarvon (24.8 S, 113.8 E)

probability for CAT 1 or above is 10% in about 72 hours

probability for TS is 25% in about 72 hours

Gascoyne Junction (25.0 S, 115.2 E)

probability for CAT 1 or above is 10% in about 72 hours

probability for TS is 25% in about 72 hours

Note that

Red Alert (Severe) is CAT 1 or above to between 31% and 100% probability.

Yellow Alert (Elevated) is CAT 1 or above to between 10% and 30% probability, or TS to above 50% probability.

CAT 1 means Tropical Cyclone strength winds of at least 74 mph, 119 km/h or 64 knots 1-min sustained.

TS means Tropical Storm strength winds of at least 39 mph, 63 km/h or 34 knots 1-min sustained.

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Nicholas is now moving southwestwards but the anticipated south-southwestward turn is not materialising as the cyclone continues to track along the northwest periphery of a subtropical steering ridge to the southeast. This ridge was predicted to weaken but as it has remained fairly strong it hasn't allowed Nicholas to begin a more southerly motion. As KW said, this is good for NW Aus and for Nicholas; it means that Nicholas will have slighlty longer over water and not so much land will be affected by the worst of Nicholas. Having said that, the Pilbara Coast and Karratha westwards towards Exmouth are still in real danger of some very severe weather as Nicholas makes landfall. I'm not saying areas east of Karratha won't experience some heavy rains and strong winds but the worst conditions should be further west.

BOM have upgraded Nicholas to a cat 3 storm (Aus scale) with sustained winds of 70kts, and the JTWC have Nicholas at 80kts which is a high end cat 1 on the SS scale. Nicholas is expected to continue intensifying before landfall as sea temps remain favourable and shear could possibly ease a little. BOM are expecting Nicholas to be a cat 4 on the Aus scale when it makes landfall.

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Nicholas just keeps heading west and it's now fairly likely there won't be a direct landfall at all although the areas I mentioned yesterday are still at risk of some adverse weather. Nicholas is tracking around the periphery of a subtropical ridge to the southeast and it seems it will pass west of Exmouth then remain over water as it travels down the west coast of Aus. Nicholas is still likely to weaken however at this point as waters cool with decreasing latitude. Nicholas has weakened a little over the past 12 hours as shear has a negative impact on the system. Shear is expected to ease which may allow for a little intensification before the arrival at cooler waters but BOM have now tapered off strengthening it to a cat 4 (Aus scale) and predict a nothing more than a cat 3 and JTWC only peak it at 80kts, which Nicholas has already been.

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Storm Alert issued at 17 Feb, 2008 12:00 GMT

Tropical Cyclone NICHOLAS is forecast to strike land to the following likelihood(s) at the given lead time(s):

Red Alert Country(s) or Province(s)

Australia

probability for CAT 1 or above is 40% in about 36 hours

probability for TS is 95% within 12 hours

Yellow Alert City(s) and Town(s)

Exmouth (22.0 S, 114.2 E)

probability for CAT 1 or above is 30% in about 24 hours

probability for TS is 85% in about 24 hours

Onslow (21.7 S, 115.0 E)

probability for CAT 1 or above is 10% in about 36 hours

probability for TS is 75% in about 24 hours

Cardabia (23.0 S, 113.9 E)

probability for CAT 1 or above is 20% in about 48 hours

probability for TS is 70% in about 36 hours

Green Alert City(s) and Town(s)

Carnarvon (24.8 S, 113.8 E)

probability for TS is 45% in about 48 hours

Pannawonica (21.8 S, 116.3 E)

probability for TS is 40% in about 24 hours

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new update

Tropical Cyclone NICHOLAS is forecast to strike land to the following likelihood(s) at the given lead time(s):

Red Alert Country(s) or Province(s)

Australia

probability for CAT 1 or above is 45% in about 24 hours

probability for TS is 100% within 12 hours

Yellow Alert City(s) and Town(s)

Exmouth (22.0 S, 114.2 E)

probability for CAT 1 or above is 25% in about 24 hours

probability for TS is 100% within 12 hours

Onslow (21.7 S, 115.0 E)

probability for TS is 85% within 12 hours

Cardabia (23.0 S, 113.9 E)

probability for CAT 1 or above is 20% in about 24 hours

probability for TS is 85% in about 24 hours

Carnarvon (24.8 S, 113.8 E)

probability for CAT 1 or above is 10% in about 72 hours

probability for TS is 60% in about 72 hours

Green Alert City(s) and Town(s)

Useless Loop (26.3 S, 113.4 E)

probability for TS is 40% in about 48 hours

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Thanks for the alert Cookie. It shows that places further south down the west coast are more at risk now as Nicholas is only expected to slowly weaken as it continues southwestward then veers south as it rounds the periphery of the subtropical ridge over Australia. Shear will eventually win over Nicholas though but not before it gives some gales and possibly heavy rains to more western regions over the coming days. The latest BOM forecast map shows the track close to land nicely.

http://www.bom.gov.au/products/IDW60285.shtml

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