SPO: INVEST 94P

[cycloneye]

A new invest in the Southern Pacific Ocean. This looks very well organized.

[HURAKAN]

Clearly a tropical cyclone, nothing yet from Fiji or the JTWC

[P.K.]

Yes I was looking at this yesterday before it appeared on the NRL. It does look very much like a TC even if the SSTs are rather low. This is a rather unusual case as Fiji wouldn't be able to name this anyway as it has formed in Wellington's AOR. They currently have warnings out for it but don't have it as tropical.

GALE WARNING 310
This affects ocean area(s): SUBTROPIC
AT 6:00pm Monday 10 May 2010

GALE WARNING 310
This affects ocean area: SUBTROPIC
AT 100600UTC
Low 992hPa near 31S 170E, slow moving.
1. Within 240 miles of low in sector from east through south to southwest: Clockwise 40kt.
2. Within 240 miles of low in western quadrant: Clockwise 40kt easing next 6-12 hours.
3. Within 180 miles of low in northern quadrant: Clockwise 35kt easing next 6 hours.
Gale areas moving with low.
This warning cancels and replaces warning 303.

Issued at 7:25pm Monday 10 May 2010

[HURAKAN]

Less convection

[KWT]

That looked like a classic NE Atlantic shallow late autumn system, not a lot of convection and thats only weakening but no doubt that was a TC os somen sorts at one point IMO.

[HURAKAN]

Latest

[theavocado]

I took a good look at this last night, and it appears that we didn't see all of the history here. This appears to have developed from an upper level low, and it remains stacked (one would expect an upper level anti-cyclone in a tropical system). Additionally, it's poleward of a finger of the subtropical jet, and in-fact seems to be getting upper-level support from the jet. Finally, the AMSU-A cross section shows that there is little to no warm core in the mid-levels, where you would expect the large amount of latent heat release, which is not surprising given the limited deep convection associated with this system.

Last night it looked like KNES was giving it tropical designation while JTWC left it unclass, and Wellington called it sub-tropical. Clearly challenging, and possibly political forecasting.

AMSU-A temperature anomaly cross-section below, note the weak warm core near the surface associated with the shallow convection (1 km) and the warm core in the upper-levels (16km) associated with stratospheric air intrusion from the upper-level low, but nothing near 8-10km where you would expect it for a system at this latitude:




(Edit) And here is an image showing 50-70kt upper-level winds on the equator-side of the system (near the northern tip of New Zealand) indicating that there is a jet maximum supporting this system in the upper-levels, and this is most likely a subtropical low or a cut-off extratropical low:

[KWT]

Very good post, from those analysis I'd agree it was probably at best a subtropical system, or perhaps some sort of hybrid development that may not be quite subtropical.

[HURAKAN]

Sometimes it looks like a tropical cyclone, acts like a tropical cyclone, but it's not a tropical cyclone. Nothing is easy in this world!!

[HURAKAN]

Code: Select all

South Pacific Ocean Basin:
   DATE/TIME     LAT      LON      CLASSIFICATION       STORM
  12/1430 UTC   41.3S    170.5E     EXTRATROPICAL      94P 
  12/0830 UTC   38.0S    170.2E       T1.0/1.0         94P 
  12/0230 UTC   35.8S    170.0E       T1.0/1.5         94P 
  11/2030 UTC   34.1S    170.3E       T1.0/2.0         94P 
  11/1430 UTC   32.9S    170.7E       T1.5/2.5         94P 
  11/0830 UTC   32.1S    170.8E       T2.0/2.5         94P 
  11/0230 UTC   31.2S    170.9E       T2.5/2.5         94P 
  10/2030 UTC   30.6S    171.4E       T2.5/2.5         94P 
  10/1430 UTC   30.1S    171.1E       T2.5/2.5         94P 
  10/0830 UTC   30.0S    170.9E       T2.5/2.5         94P 
  10/0230 UTC   30.5S    170.5E        ST2.5           94P