Tropical Cyclone Vaianu

Discussion of weather and climate outside of NZ's waters. Australian weather, tropical cyclones and USA storm chasing feature here.
Manukau heads obs
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Unread post by Manukau heads obs »

the water must always be alot warmer to the NE of NZ than to the NNW of NZ, as TC's maintain their intensity alot longer as they move south when to the NE of NE
(i.e the ITCZ is on a tilt, and extends further south to the NE of NZ)
is that because of the cold SSW blasts that come up through the tasman?

i thought it was just that the ITCZ bends up and over australia becuase thats a dry land mass...and then that bend/tilt carrys on to the east....but there also must be warmer water further south to the NE of NZ than to our NNE, even though there is a warm current coming down the east coast of AUS, but that does cool down alot by the time it swings over to NZ, and then NZ must deflect that cooler current (mixed in with southern ocean temperatures around tasmania?) to the waters to the NNE and N of NZ, but then that current bends around NZ and moves south again, leaving wamer tropic al waters to move further south to the NE NZ
(actualy the west coast here i think is warmer than the east coast, and the sallow manukau harbour at times must get to 30oC water temperature as the tide comes in across sun warmed mud flats (i.e when you hope in its not cold at all)
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Achten
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Unread post by Achten »

The general trend seems to be that they south east, although TC Jim did a loop the other week. The steering mechanics are quite fascinating. The building ridge east of us is one of those factors in this case. Did Bola at the time come in fronm the NE?
Manukau heads obs
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Unread post by Manukau heads obs »

i was in the USA when bola hit, but i think it came in from the same place as this one....but started a bit further west...it moved south, to lie east of east cape, bu then slowly drifted WNW and passed to the north of north cape eventualy...
is that correct, others?

ps, a the moment, its still miving S to SSW by the looks:
http://www.metservice.co.nz/default/ind ... liteseries
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Unread post by Willoughby »

I believe the two most important factors in the steering of tropical cyclones are jetstream behavior and just how deep that warm water lies. (NOAA use the isotherm layer in metres of 26ºC for their TC Heat Potential products)

This doesn't apply at all for the waters around NZ.. so the jetstream takes over a little bit more in our latitudes.

http://www.aoml.noaa.gov/phod/cyclone/data/method.html

Here's Sunday's 'upper ocean heat content index', derived from isotherm level @ 26c and SST data.
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Gary Roberts
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Unread post by Gary Roberts »

Foggy Hamilton wrote:I believe the two most important factors in the steering of tropical cyclones are jetstream behavior and just how deep that warm water lies. (NOAA use the isotherm layer in metres of 26ºC for their TC Heat Potential products)

This doesn't apply at all for the waters around NZ.. so the jetstream takes over a little bit more in our latitudes.

http://www.aoml.noaa.gov/phod/cyclone/data/method.html

Here's Sunday's 'upper ocean heat content index', derived from isotherm level @ 26c and SST data.
Cheers Foggy.
Manukau heads obs
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Unread post by Manukau heads obs »

cool image, shame it does not go a bit further east

it does seem that tc's stay stronger for longer to the east of us than for same lat to the north or NNW of us
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An update...

Unread post by gllitz »

From those weather-guessers at the Joint Typhoon Warning Center :-) :

REMARKS:
132100Z POSITION NEAR 22.6S 176.8W.
TROPICAL CYCLONE (TC) 11P (VAIANU), LOCATED APPROXIMATELY 365 NM SOUTHEAST OF SUVA, FIJI, HAS TRACKED SOUTHWARD AT 06 KNOTS
OVER THE PAST SIX HOURS. TC 11P WILL CONTINUE TO TRACK POLEWARD ALONG THE SOUTHWESTERN PERIPHERY OF A HIGH AMPLITUDE STEERING RIDGE CENTERED NORTHEAST OF THE SYSTEM. UPPER LEVEL ANALYSIS AND WATER VAPOR IMAGERY REVEALS CONTINUED SUPPRESSION OF STORM OUTFLOW IN THE WESTERN QUADRANTS DUE TO AN IMPINGING UPPER LEVEL TROUGH. THE STORM
HAS MAINTAINED INTENSITY HOWEVER DUE TO DIURNAL INFLUENCE AND GOOD DIVERGENCE ALOFT CREATED BY AN UPPER LEVEL ANTICYCLONE CENTERED NORTHWEST OF TC 11P. THE STORM WILL BEGIN TO WEAKEN NEAR TAU 24 DUE TO INCREASING VERTICAL WIND SHEAR, AND DECREASING SEA SURFACE TEMPERATURES. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 131800Z IS 32 FEET.
NEXT WARNINGS AT 140900Z AND 142100Z.//

....lots of fancy words for what we all know what will happen :)....goes over cool waters and fizzles out... ;)
Manukau heads obs
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Unread post by Manukau heads obs »

and it still has not started to move SE yet, even though it was supposed to be now...yes/no?
they do tend to have a bit of a mind of their own sometimes,,,like a spinning top

the models in the US with the hurricanes there seem to have done well lately with picking where they will go next

if this TC was moving faster then it would get further south and closer to nz before the next high moves in

anyway, next one looks to be a coral sea one
according to metvuw models
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Michael
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Re: From the JTWC....

Unread post by Michael »

Of coarse we need cyclones, Auckland and Northland really needs the rain ;)


The only way we will get real rain is if an upper trough forms in the easterly allowing a new low to form away from the cyclone and it has to be to targeted at the NW of Cape Reianga and then move SE
Manukau heads obs
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Unread post by Manukau heads obs »

some parts of northland got good rains with that last tropical low we got at the end of jan
but north auckland through to north waikato has missed out on alot of rain :)
starting to try out again after the last lot.....follow up rain right now will be great for farmers (which are not expecting a very good payout this year at all)
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Unread post by Razor »

The DOC crew up on Raoul Island will be the first to let us know if theres any unepxected shift in this storm. My bet is it'll die out to the NE and maybe the next one will give us a look.

I remember Bola did weird things, even shimmied down the west coast of Auckland at one point, and hung around as a fairly major event for a good week or so in the Queen City.
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Unread post by spwill »

When the Tropical lows come out of the tropics they move SE unless there's a fat slow moving High in the way.
Manukau heads obs
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Unread post by Manukau heads obs »

i remember one that slid (moved WSW) right across the north tasman and hit between brisbane and sydney once!
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Unread post by squid »

it is starting to move to the SE now looks liek a no go for NZ but models have a coral sea cyclone spinning up within the next week around vanuatu area something to keep an eye on
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Unread post by squid »

Tropical Disturbance Advisory Number A16 issued from RSMC NADI
Feb 14/0157 UTC 2006 UTC.

Tropical Cyclone VAIANU [965hPa] centre was located near 22.7 South
176.3 West at 140000 UTC. Position fair based on MTSAT EIR/VIS
imagery with animation and peripheral surface reports. Cyclone now
moving southeast about 08 knots. Expect sustained winds of 70 knots
close to the centre possibly increasing to 75 knots in the next 12
hours. Expect winds over 63 knots within 20 miles of centre, over 47
knots within 40 miles of centre and over 33 knots within 120 miles of
centre in sectors from north through east to southwest and within 80
miles elsewhere.

Overall organisation remains good, despite brief entrainment of dry
air. Convective bands continue to wrap tightly around llcc. Cyclone
struggling to form a banding eye under diurnal influence. Outflow
good to south but restricted elsewhere. Shear remains minimal. SST
about 28C. Further intensification possible if shear to south remains
weak. Dvorak analysis based on centre embedded in LG yielding DT=4.5.
PT=MET=4.5, thus T4.5/4.5/D0.5/24hrs. Cyclone is being steered
southeast by a deep northwest steering flow. Global models generally
agree on this with possible further intensification.

FORECAST:
12hrs valid at 141200 UTC near 23.9S 175.2W mov SE at 08kt with 75 kt
close to the centre.
24hrs valid at 150000 UTC near 25.1S 174.1W mov SE at 08kt with 75 kt
close to the centre.

OUTLOOK:
36hrs valid at 151200 UTC near 26.2S 172.9W mov SE at 08kt with 60kt
close to the centre.
48hrs valid at 160000 UTC near 27.6S 171.9W mov SE at 08kt with 50kt
close to the centre.

The next Tropical Disturbance Advisory on Tropical Cyclone VAIANU
will be issued around 140800 UTC.
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Unread post by squid »

Tropical Disturbance Advisory Number A17 issued from RSMC NADI
Feb 14/0803 UTC 2006 UTC.

Tropical Cyclone VAIANU [965hPa] centre was located near 23.6 South
175.5 West at 140600 UTC. Position fair based on MTSAT EIR/VIS
imagery with animation and peripheral surface reports. Cyclone moving
southeast about 10 knots. Expect sustained winds of 70 knots close to
the centre. Expect winds over 63 knots within 20 miles of centre,
over 47 knots within 40 miles of centre and over 33 knots within 150
miles of centre in sectors from north through east to southwest and
within 100 miles elsewhere.

Overall organisation remains good. Convective bands continue to wrap
tightly around llcc but system still struggling to form a banding
eye. Outflow remains good to south and east but restricted elsewhere.
Shear remains minimal. SST about 28C. Further intensification
possible as shear to south remains weak but system is expected to
beyound 25S due to cooler SSTs. Dvorak analysis based on centre
embedded in MG yielding DT=4.0. PT=MET=4.5, thus T4.5/4.5/D0.5/24hrs.
Cyclone is being steered southeast by a deep northwest steering flow.
Global models generally agree on this with possible further
intensification.

FORECAST:
12hrs valid at 141800 UTC near 24.6S 174.3W mov SE at 08kt with 70 kt
close to the centre.
24hrs valid at 150600 UTC near 26.0S 172.9W mov SE at 08kt with 60 kt
close to the centre.

OUTLOOK:
36hrs valid at 151800 UTC near 27.3S 171.3W mov SE at 08kt with 50kt
close to the centre.
48hrs valid at 160600 UTC near 28.7S 169.8W mov SE at 08kt with 40kt
close to the centre.

The next Tropical Disturbance Advisory on Tropical Cyclone VAIANU
will be issued around 141400 UTC.
Manukau heads obs
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Unread post by Manukau heads obs »

yes, moving SE now as predicted
nice spiral bands showing!
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Unread post by squid »

weakening now

Tropical Disturbance Advisory Number A19 issued from RSMC NADI
Feb 14/2023 UTC 2006 UTC.

Tropical Cyclone VAIANU [975hPa] centre was located near 24.6 South
173.6 West at 141800 UTC. Position poor based on MTSAT EIR imagery
with animation. Cyclone moving southeast about 10 knots. Cyclone
weakening. Expect sustained winds of 60 knots close to the centre
decreasing to 50 knots in the next 12 to 18 hours. Expect winds over
47 knots within 40 miles of centre, over 33 knots within 150 miles of
centre in sectors from north through east to southwest and within 100
miles elsewhere.

Vaianu is moving into increased shear and cooler SSTs. The cyclone
remains in a diffluent region close to the 250 hPa subtropical ridge
and has maintained central convection sofar. Outlow remains fair from
southwest to east but is restricted elsewhere. Dvorak analysis based
on a 0.85 log10 spiral gives DT=PT=MET=3.5, yielding
T3.5/4.0/W1.0/24hrs. Cyclone is being steered southeast by a mid
level ridge to the northeast and by a broad 250 hPa trough to the
west. Global models agree on a southeast track with gradual
weakening.

FORECAST:
12hrs valid at 150600 UTC near 25.9S 171.5W mov SE at 12kt with 55 kt
close to the centre.
24hrs valid at 151800 UTC near 27.2S 169.6W mov SE at 10kt with 45 kt
close to the centre.

OUTLOOK:
36hrs valid at 160600 UTC near 28.5S 168.8W mov SE at 10kt with 40kt
close to the centre.
48hrs valid at 161800 UTC near 29.8S 16.1W mov SE at 10kt with 40kt
close to the centre.

This is the final Tropical Disturbance Advisory on Tropical Cyclone
Vaianu unless the cyclone recurves into Nadi's warning area.
Locked