Tropical Cyclone Innis

[Somerset Squall]

Invest 93P has continued to get better organised and has now been upgraded to Tropical Cyclone 15P, with an initial intensity of 35kts. 15P is very near New Caledonia at the moment, where it's providing some very heavy rains, potential exists for some severe flooding and perhaps mudslides, so the situation needs to be watched. Land interaction with New Caledonia will probably hinder development in the near term. Conditions are otherwise favourable with decreasing shear, high sea temps and improving poleward outflow, which may allow strengthening after 15P clears New Caledonia. However, a great deal of uncertainty exists on just where 15P will go after New Caledonia, and that obviously has a big bearing on how much more 15P will develop. If it continues southwestwards, it will soon hit colder waters and mid-lattitude westerlies which would most likely initiate quick extratropical transistion. If 15P manages to head more west it will stay in the warmer waters thus allowing some proper intensification. 15P is currently heading along the northwestern periphery of a subtropical steering ridge to the southeast, and the southward turn is perhaps more likely as 15P rounds the periphery of the ridge. However, if the ridge manages to build south of the storm, it would essentially block southwards motion, enforcing a westerly heading. A lot of uncertainty, so will be interesting to see what happens.

[Cookie]

thanks for the update

its a bit old but

Storm Alert issued at 17 Feb, 2009 0:00 GMT

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

Yellow Alert Country(s) or Province(s)

New Caledonia

probability for TS is 70% currently

Yellow Alert City(s) and Town(s)

Kone (21.0 S, 164.8 E)

probability for TS is 70% currently

Koumac (20.5 S, 164.3 E)

probability for TS is 55% currently

Green Alert City(s) and Town(s)

Bourail (21.6 S, 165.5 E)

probability for TS is 50% within 12 hours

Note that

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

Green Alert (Low) is TS to between 31% and 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.

[Somerset Squall]

Thanks for the update Cookie.

Tropical Cyclone 15P has been upgraded to Tropical Cyclone Innis by Fiji Meteorological department, and intensity remains at 35kts. Innis has crossed New Caledonia as convection has decreased a little due to land interaction. However, the LLC remains well defined and therefore Innis is forecast to intensify over the next 36hrs. Innis is currently in a low shear environment with warm sea temperatures and good poleward outflow, which is also improving in other quadrants now Innis is moving away from land. These factors will promote the forecast intensification, and JTWC expect a peak of 50kts before the storm reaches cooler waters on the southwest, then southeast track. The 1st scenario I mentioned above still seems most likely in terms of steering, Innis will follow the boundaries of the steering ridge currently located to the southeast, which will cause a motion clearly shown by Cookie's track map above (thanks for posting that Cookie). Innis is not expected to threaten land again after New Caledonia, however it may affect New Zealand as an extratropical storm later in the week.

[kold weather]

Still got a good shape to it with pretty strong circulation seemingly evident on that Sat.imagery there SS, though as you note convection is a little on the weak side and also a touch lop-sided on the southern side of the circulation, possibly this is to do with the time the system spent overland I suspect. Once the circulation clears land a little more convection should spread out across the systems center a little better and we should see some steady strengthening between the 12-36hr time period.

[Somerset Squall]

Once the circulation clears land a little more convection should spread out across the systems center a little better and we should see some steady strengthening between the 12-36hr time period.

Indeed KW, and that seems to be happening now. Convective coverage has improved this evening, and Innis has strengthened slightly to 40kts. Innis has another 24hrs for any more intensification before conditions rapidly deteriorate.

[Cookie]

thanks for the updates guys

[Somerset Squall]

Well, we may be saying goodbye to Innis sooner than originally anticipated. The subtropical ridge to the east has got stronger, and there is a trough approaching Innis rapidly from the west. The combination of these factors has caused Innis to accelerate southwards very rapidly (now moving at 21kts as opposed to 10kt!), meaning the system is moving over colder waters already. Also, the trough is now buffeting Innis with some strong shear, which has weakened the storm back to 35kts. Convection is well removed from the LLC now and Innis is likely to dissipate within the next 12 hours as the very hostile conditions take hold.

The latest satellite image shows the trouble Innis is in:

[J07]

It officially no longer exists as a Tropical Cyclone:

GALE WARNING 349

This affects ocean area: SUBTROPIC

AT 180000UTC

Over waters east of 160E and south of 25S.

Low 996hPa, former Cyclone INNIS, near 26S 161E moving south 20kt.

1. Within 180 miles of low in southeast semicircle: Clockwise 35kt.

2. Within 60 miles of low in northwest semicircle: Clockwise 35kt.

Gale areas moving with low.

This warning cancels and replaces warning 344.

Issued at 00:35:32Z on 18-Feb-2009

It fell into NZ RSMC waters and was downgraded.

The expectation is for it to merge with a low off the eastern coast of Australia and then enjoy close relations with New Zealand over the end of the week/into the weekend. By the time it hits us, it will still have a warm core, and associated cold advection will be lagging some way behind where you would expect it to be. i.e. it will no longer be a tropical cyclone, but it won't be a standard mid latitude cyclone either.

Interestingly, there was a forecast track from the Fiji office earlier today which had it forecast to make 30S whilst remaining as a Cat 1 TC. That did seem a little optimistic.

[Cookie]

thanks for the updates guys, that happened fast!

[J07]

This is what happened to it post ET transition and after merging with a low off the Queensland coast.

You can see it acquired mid latitude type structure, with a very clear warm sector there, but the air on the western flank is notably "not cold".

[Somerset Squall]

This is what happened to it post ET transition and after merging with a low off the Queensland coast.

You can see it acquired mid latitude type structure, with a very clear warm sector there, but the air on the western flank is notably "not cold".

Yes, was looking as satellite imagery of Innis yesterday, looked to be providing some quite heavy rains to NZ. Have you had much rain?

[J07]

Yes, was looking as satellite imagery of Innis yesterday, looked to be providing some quite heavy rains to NZ. Have you had much rain?

Some places did. 300mm + on the northern slopes of Mt Taranaki. We had about 50-60mm around the Wellington area.

The attached image shows the situation now. It's unusual to see this in mid February. Despite the rather bleak appearance we're actually having a lovely day in Wellington with 22c and blue skies.

There is a lack of open cell cumulus on the western flank, but gradually it will work it's way in (colder air). Somewhat notable was having a cold front pass over the country and yet still retain dewpoints of 20C over the north, and 17C here.