south pacific Severe Tropical Cyclone Lusi

[Vorticity0123]

A new tropical cyclone has developed in the southern Pacific basin, to the west of Fiji. The cyclone is currently pretty well organized, with a healthy amount of convection, along with some banding features apparent to the north. THe current intensity estimate is 35 kt (from JTWC). Unlike Hadi and Gillian, 18P doesn't appear to be struggling with high wind shear. Still, there seems to be some easterly shear impinging on the cyclone.

 

Below is a visible loop of 18P, showing the well-organized structure:

 

 

The cyclone is forecast to move initially eastward, before recurving to the south (toward New Zeeland), and strenghten up to 70 kt (as of the JTWC), before undergoing extratropical transition as the cyclone encounters cooler water. The forecast track from the JTWC can be seen below:

 

 

 

Of note is that the GFS is rather agressive on 18P, especially in its extratropical phase. It may impact New Zeeland as a potent extratropical storm.

 

 

The GFS expects the cyclone to attain a minimum pressure around 970 hPa once it arrives near New Zeeland.

 

Another important point is that this cyclone might increase westerly winds near the Equator, and have a possible positive effect on an El Nino developing in the summer. This is all very speculative, though.

 

Sources:

http://www.ssd.noaa.gov/PS/TROP/floaters/18P/18P_floater.html

http://www.usno.navy.mil/JTWC/

http://moe.met.fsu.edu/cyclonephase/gfs/fcst/archive/14030912/7.html

Edited May 8, 2014 by Somerset Squall

[Somerset Squall]

Your topic tag says the southern Indian ocean not Pacific lol.

 

I reckon 18P has the potential to get stronger than 70kts. As you say, shear is not so much of an issue and 18P looks really well organised already.

 

EDIT: Just been named Lusi by Fiji Met.

Edited March 10, 2014 by Somerset Squall

[Somerset Squall]

Lusi has steadily strengthened over the last 24 hours, and now has winds of 45kts. Lusi remains in a weak steering environment, trapped between two ridges. Ridging to the northeast is expected to win out, and is expected to accelerate Lusi to the south over the next few days. Relatively low shear and good outflow will allow Lusi to continue to strengthen until it reaches colder waters. The cyclone is likely to be a potent extratropical storm as it tracks towards the north island of New Zealand.

[Somerset Squall]

Lusi has strengthened a little more as it moves through the islands of Vanuatu. Winds are up to 50kts according to JTWC. Convection remains persistant over the LLCC, with a strong spiral band of convection wrapping around the southern and eastern sides of the cyclone. Conditions favour some further intensification before Lusi slips south into coolder water.

[Somerset Squall]

Lusi is quite a large system, and as a consequence, is strengthening quite slowly despite the favourable outflow and low shear. Winds are up to 55kts according to both JTWC and Fiji Met.

 

 

Latest satellite image of Lusi:

 

[knocker]

Cyclone Lusi may bring severe weather to New Zealand

 

The Ministry of Civil Defence & Emergency Management is advising people to prepare for possible severe weather this weekend.

 

The Director of Civil Defence Emergency Management, John Hamilton, said the Ministry and the MetService are working together, monitoring Tropical Cyclone Lusi as it moves from Vanuatu, past Fiji to New Zealand.

 

At this stage, computer models expect Lusi to arrive over northern New Zealand on Saturday or early Sunday, and then to track southwards over central New Zealand before moving out to sea east of the South Island on Monday.

 

Cyclone Lusi is expected to transition into a sub-tropical weather system as it approaches New Zealand, but it is still expected to be a dangerous storm. Severe weather is likely to affect many regions during this event, especially over the weekend from Northland down to Canterbury.

 

http://www.scoop.co.nz/stories/PO1403/S00128/cyclone-lusi-may-bring-severe-weather-to-new-zealand.htm

Edited March 11, 2014 by knocker

[Somerset Squall]

Lusi has turned south and continued to strengthen. Winds are at 65kts according to JTWC. Lusi has developed a large, ragged eye overnight, in the middle of a more firmly established central dense overcast. Lusi has another 24hrs to further intensify before it begins extratropical transition.

[tropicbreeze]

TROPICAL DISTURBANCE ADVISORY NUMBER A14 ISSUED FROM RSMC NADIMar 12/0745 UTC 2014 UTC.TROPICAL CYCLONE LUSI CAT 2 CENTRE 975HPA WAS LOCATED NEAR 18.7S 171.5E AT 120600 UTC.  POSITION FAIR  BASED ON MTSAT VIS/IR IMAGERY AND PERIPHERAL SURFACE REPORTS. CYCLONE MOVING SOUTHEAST AT ABOUT 09 KNOTS.  MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT ABOUT 60 KNOTS.EXPECT WINDS OVER 47 KNOTS WITHIN 60 NAUTICAL MILES OF CENTRE.EXPECT WINDS OVER 33 KNOTS WITHIN 150 NAUTICAL MILES OF CENTRE IN SOUTHERN SEMI-CIRCLE  AND WITHIN 180 NAUTICAL MILES OF CENTRE IN NE QUADRANT AND WITHIN 120 NAUTICAL MILES OF CENTRE IN NW QUADRANT..OVERALL ORGANISATION HAS IMPROVED PAST 24 HOURS. DEEP CONVECTION REMAINS PERSISTANT. PRIMARY BANDS WRAPPING TIGHTLY AROUND LLCC. SYSTEM LIES SOUTH OF AN UPPER RIDGE IN A LOW SHEARED ENVIRONMENT. OUTFLOW GOOD TO THE SOUTH AND FAIR TO THE NORTH. SST AROUND 29 DEGREES CELCIUS. SYSTEM IS BEING STEERED TO THE SOUTHEAST BY THE NEAR EQUATORIAL RIDGE LOCATED TO THE NORTHEAST. DVORAK ANALYSIS BASED ON 1.1 WRAP IN VIS ON LOG10 SPIRAL YEILDING DT OF 4.0, MET AND PT AGREE. FT BASED ON MET THUS, T4.0/4.0/D1.0/24HRS.GLOBAL MODELS AGREE ON A SOUTHEASTWARD MOVEMENT WITH FURTHER INTENSIFICATION.FORECASTS :AT 12 HRS VALID AT 121800 UTC 20.2S 172.9E MOV SE AT 10 KT WITH 70 KT CLOSE TO CENTREAT 24 HRS VALID AT 130600 UTC 22.4S 174.1E MOV SSE AT 12 KT WITH 75 KT CLOSE TO CENTREOUTLOOK :AT 36 HRS VALID AT 131800 UTC 24.8S 174.4E MOV SSE AT 12 KT WITH 70 KT CLOSE TO CENTREAT 48 HRS VALID AT 140600 UTC 27.4S 174.1E MOV S AT 12 KT WITH 60 KT CLOSE TO CENTRETHE NEXT TROPICAL DISTURBANCE ADVISORY ON TROPICAL CYCLONE LUSI WILL BE ISSUED AROUND 121400 UTC 

[Chris W]

After last week's deep low that brought severe flooding to Christchurch (from 150mm of rain over 24 hours) we need this like a hole in the head.  It is a very interesting system though, and only the second ex-tropical cyclone I will have seen striking NZ since I moved here.  The latest estimate I heard is for 80mm of rain on Sunday for Christchurch, and impacts all over the North Island and upper South Island.  I'm not sure how strong the easterly gales will be, but we had a lot of tree damage last week from up to 100kph winds in the city (up to 160kph on the Port Hills) and trees will have been weakened whilst still in full leaf.

 

5-day Metvuw rain, MSLP and wind speed forecasts for NZ here with the t+84 chart below:

http://metvuw.com/forecast/forecast.php?type=rain&region=nz&noofdays=5

 

 

N.B. This should surely be tagged SW Pacific, not South Indian Ocean - unless we have been moved!

Edited March 12, 2014 by Chris W

[Somerset Squall]

Lusi peaked at 75kts according to JTWC, but is now weakening as shear is rising as Lusi moves southwards towards New Zealand. Winds are now down to 65kts. As sea temps decline along track, Lusi will begin extratropical transition.

[tropicbreeze]

Wasn't it Sandra last year that reached NZ? Negligible rain in that one despite a lot of people hoping for more.

[Chris W]

Metservice 3-day rainfall forecast with wind direction:

http://www.metservice.com/maps-radar/rain-forecast/rain-forecast-3-day

 

Looking a bit worse for the South Island at present due to the eastward recurve.  I'd be pretty surprised if there is not a large amount of rain from this on Sunday, though at least it will be warmer than last week's southerly.  The North Island, however, really does need rain.

Edited March 13, 2014 by Chris W

[Vorticity0123]

N.B. This should surely be tagged SW Pacific, not South Indian Ocean - unless we have been moved!

 

Your topic tag says the southern Indian ocean not Pacific lol.

 

Well noted, I made that mistake while starting the thread. Sorry for that! I am unable to change it for now, as far as I know. Next time I'll check it twice, in order to do it right next time.

 

Current state of Lusi

 

When looking at satellite images, the first thing that shows up is that Lusi is a mess. There is only one intense area of convection located to the east of the system. In fact, the system looks already quite extratropical. The current Dvorak satellite image of Lusi can be seen below:

 

Dvorak satellite image of Lusi.

 

Of note is that Lusi still had some pretty vigorous convection over its centre about 6 hours ago (as of 18 UTC). The extratropical transition seems to have progressed rather rapid. The process itself can be seen in the visible satellite loop below:

 

Visible satellite loop of Lusi.

 

For further analysis on the extratropical transition process, check the phase diagram of Lusi below:

 

GFS phase diagram of Lusi (as of 12Z). The A indicates the starting position, while the C indicates the current position. The Z stands for the end position (this may be the end of a forecast period but also dissipation).

 

What can be seen is that Lusi at the time of initialization had a strong (though asymmetric) warm core. This means the cyclone was most likely still fully tropical by then. Even in a few days, the system is still forecast to be a tropical system (warm core) by the GFS. This does seem a little suspicious to me. 

A reason for the current extratropical transition is that Lusi is crossing the 26*C isotherm at the moment. This is (usually) the minimum sea surface temperature needed to sustain a tropical cyclone. The 26*C isotherm can be seen on the top-right end of the image above.

 

Despite the current extratropical transition and disorganized satellite appearance, Lusi remains a vigorous cyclone. Recent CIMSS ADT estimates (16:30 Z) still yielded a maximum intensity of 74.6 kt, coupled with a minimum pressure of 967.1 hPa. The satellite intensity estimates have come down sharply, though, during the past few hours. This can be seen in the image below:

 

CIMSS ADT satellite intensity trend.

 

Note the very sharp drop in intensity during the past few hours.

 

Forecasts

 

The JTWC forecasts the system to weaken significantly toward a borderline gale storm (35 kt) while curving more and more toward the south-southwest. This means that New Zealand will most likely be hit by the eastern flank of the system. The forecast from JTWC can be seen below:

 

JTWC forecast of Lusi.

 

Because of the forecasted weakening of the wind strength around Lusi, it appears that rain will be the most significant threat.

 

 

Looking a bit worse for the South Island at present due to the eastward recurve.  I'd be pretty surprised if there is not a large amount of rain from this on Sunday, though at least it will be warmer than last week's southerly.  The North Island, however, really does need rain.

 

For now, the meteorological centre of New Zeeland forecasts both islands to receive high amounts of rain during the next few days. It seems that the southern island will be hit the hardest, mainly because the center of the low pressure system will move initially to the west of New Zealand, and then make landfall near Greymouth. The landfalling location forecast can be seen below:

 

 

Note that the most intense rain is to the west of the system, leaving New Zealand mostly unaffected. Of a side note: the GFS also agrees on the landfalling location (check the phase diagram given above). 

 

The complete rain forecast during the next 5 days for New Zealand can be found in the link below:

 

http://www.metservice.com/maps-radar/rain-forecast/rain-forecast-5-day

 

I hope damage in New Zealand from Lusi will not become too severe!

 

Sources:

http://www.ssd.noaa.gov/PS/TROP/floaters/18P/18P_floater.html

http://www.usno.navy.mil/JTWC/

http://tropic.ssec.wisc.edu/#

http://moe.met.fsu.edu/cyclonephase/gfs/fcst/index.html

http://www.metservice.com/maps-radar/rain-forecast/rain-forecast-5-day

Edited March 13, 2014 by Vorticity0123

[tropicbreeze]

From NZ MetserviceSTORM WARNING 242This affects ocean area: SUBTROPICAT 140000UTCOver waters south of 25S.Low 977hPa, former Cyclone LUSI, near 28S 173E moving southsouthwest 15kt.1. Within 60 nautical miles of low: Clockwise 50kt.2. Outside area 1 and in a belt 300 nautical miles wide centred on a line 29S 179E 30S 174E 29S 171E: Easterly 35kt.3. Outside areas 1 and 2 and within 180 nautical miles of low in sector from southwest through northwest to east: Clockwise 35kt.Storm and gale areas moving with low.This warning cancels and replaces warning 240.Issued at 1:31pm Friday 14 Mar 2014

[Chris W]

Lusi has arrived at Kaitaia and Kerikeri in the far reaches of Northland tonight.  She looks to have downgraded slightly for Christchurch by taking a more westward track, but I will still not underestimate how wet it could be here on Sunday.  Metservice are forecasting the worst rain for Northland, Bay of Plenty, East Cape, Hawke's Bay and Nelson/Marlborough as well as easterly gales for the North Island.  It will get windy down here too, with strong easterlies/north-easterlies but perhaps not as strong as the North island.  The west coast will get some significant rain as well as North Otago.

 

http://www.metservice.com/warnings/severe-weather-outlook

http://www.metservice.com/warnings/severe-weather-warnings

 

Following Lusi's departure a quite vigorous cold front will move up the South Island and to the North Island, bringing the usual hot Nor'wester for Canterbury, heavy rain for Westland and gales for Wellington.

 

A satellite loop showing the rapid extratropical transition that Lusi underwent today is below:

http://www.metservice.com/maps-radar/satellite/tasman-sea-nz-infrared

[tropicbreeze]

With a blocking ridge east of NZ ex-Lusi will produce very strong winds. Ex-Oswald did the same on the south coast of Queensland last year. Although it had long gone extratropical, once pushed up against the ridge in the Tasman it started to produce cyclonic winds, and of course torrential rain. Might be good to batten down the hatches and keep your head down in NZ.

[tropicbreeze]

The remnants are just off the tip of North Island.

 

Analysis for 7:00pm Saturday 15 Mar 2014Issued at: 7:51pm Saturday 15 Mar 2014

[Chris W]

Morning Lusi.  Waking up to heavy rain and a gusty easterly - the heaviest rain for us seems to be due up to and around lunchtime (late evening GMT).  Little idea of North Island totals, but I hear Te Aroha in Waikato got 100mm+.

[tropicbreeze]

This gives a good indication of the winds.

 

http://earth.nullschool.net/#current/wind/surface/level/orthographic=-184.92,-34.12,1689

[Chris W]

Wet and windy this morning, then calmer on the rain front and a fresh to strong wind all day.  One last burst of heavy rain coming down towards Christchurch this afternoon/evening:

 

 

Nelson looks set to be hammered by rain later.

[knocker]

Hand-drawn analysis of Post-Tropical Cyclone Lusi west of New Zealand today. https://www.facebook.com/photo.php?fbid=672041296191265&set=a.154197624642304.35091.136819026380164&type=1&theater 

[Chris W]

I loved that chart.  The radar now shows Lusi crossing Marlborough after pasting Nelson, and heading to her demise over the Pacific. 

 

http://www.metservice.com/maps-radar/rain-radar/all-new-zealand

 

Certainly a very cyclonic day here, pretty wet and windy at times with rain persisting between light and heavy all day, and some tasty gusts - in my estimation up to around 60kph here but much higher further north.  Possibly around 30-50mm of rain here.  No significant flooding to my knowledge, but some power outages.

 

27C for Christchurch tomorrow due to the warm air dragged down and the coming nor'wester.

Edited March 16, 2014 by Chris W

[Vorticity0123]

I loved that chart.  The radar now shows Lusi crossing Marlborough after pasting Nelson, and heading to her demise over the Pacific. 

 

It definitely is a beautiful radar loop! The center of Lusi is very clearly discernible, along with the well-defined rainbands spiralling into the system.

 

A nice satellite image of ex-Lusi as of Saturday 16 March can be seen below:

 

Satellite image of Ex-Lusi (source: MetService)

 

A full blog about TC Lusi by MetService New Zealand can be found in the link below:

 

http://blog.metservice.com/wp-content/uploads/2014/03/polar-sat-16-march.jpg

 

EDIT: The topic tag has been changed to match the basin it is located.

Edited March 17, 2014 by Vorticity0123