SIO: IGGY - Post-Tropical

[Subtrop]

90S INVEST 251229 0600 8.0S 101.5E SHEM 15 0

[Subtrop]

IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0440 UTC 01/01/2026
Name: Tropical Cyclone Iggy
Identifier: 10U
Data At: 0300 UTC
Latitude: 12.5S
Longitude: 107.9E
Location Accuracy: within 20nm (35 km)
Movement Towards: south southeast (148 deg)
Speed of Movement: 8 knots (15 km/h)
Maximum 10-Minute Wind: 40 knots (75 km/h)
Maximum 3-Second Wind Gust: 55 knots (100 km/h)
Central Pressure: 998 hPa
Radius of 34-knot winds NE quadrant: 30 nm (55 km)
Radius of 34-knot winds SE quadrant: 30 nm (55 km)
Radius of 34-knot winds SW quadrant: 35 nm (65 km)
Radius of 34-knot winds NW quadrant: 40 nm (75 km)
Radius of 48-knot winds NE quadrant:
Radius of 48-knot winds SE quadrant:
Radius of 48-knot winds SW quadrant:
Radius of 48-knot winds NW quadrant:
Radius of 64-knot winds: nm ( km)
Radius of Maximum Winds: nm ( km)
Dvorak Intensity Code: T2.0/2.0/D1.0/12HRS STT:D0.5/06HRS
Pressure of outermost isobar: 1008 hPa
Radius of outermost closed isobar: 120 nm (220 km)
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
(UTC) : degrees : nm (km): knots(km/h): hPa
+06: 01/0900: 12.9S 108.5E: 030 (060): 045 (085): 995
+12: 01/1500: 13.5S 109.2E: 040 (080): 050 (095): 992
+18: 01/2100: 14.0S 109.8E: 050 (090): 050 (095): 992
+24: 02/0300: 14.4S 110.3E: 055 (100): 055 (100): 988
+36: 02/1500: 14.8S 110.8E: 070 (135): 060 (110): 983
+48: 03/0300: 15.0S 110.7E: 085 (155): 060 (110): 983
+60: 03/1500: 15.4S 110.0E: 095 (180): 050 (095): 991
+72: 04/0300: 15.9S 108.8E: 115 (215): 035 (065): 1000
+96: 05/0300: 16.0S 105.8E: 170 (315): 030 (055): 1003
+120: 06/0300: 15.6S 103.2E: 245 (455): 025 (045): 1006
REMARKS:
Tropical Cyclone Iggy (10U), located to the southeast of Christmas Island has
developed faster than forecast.

Tropical Cyclone Iggy (10U) has developed gales in all quadrants, shown in
ASCAT at 0107 UTC. The centre of Iggy is under the deep convection and has
continued to develop through the day.

Dvorak analysis: initial T1.0 classification occurred at 12 UTC 31 Dec, and
have seen improvement in curvature since. At 03UTC a curved band with wrap of
0.5 gives a DT of 2.5. FT/CI limited to 2.0 by constraints. At 03UTC intensity
analysed at 40kn consistent with the ASCAT at 0107 UTC. Objective guidance
(1-min mean) at 0340 UTC is ADT 43kn and AiDT 31kn.

There is some small displacement with the deepest convection to the south
southwest of the centre, consistent with some north northeasterly winds over
the system and the CIMSS upper wind analysis depicting low to moderate deep
layer wind shear.

The environment in the short term is favourable for further development. Sea
surface temperatures are 30 degrees C. An upper trough to the south is
enhancing poleward outflow and is likely to continue to aid development for the
rest of today and during Friday. Development is forecast until Saturday
morning, when the upper trough slides to the east and 10U moves south into a
region with higher shear and increasing dry air. As well as the less favourable
upper support, 10U is likely to be located south of about 15S, with decreasing
sea surface temperatures and weakening is expected to commence.

10U is currently being steered to the southeast by the upper trough to the
south. Once this trough moves to the east during Saturday, a upper anticyclone
than becomes the dominant steering influence and takes 10U to the west.

Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 01/0730 UTC.

[Ulf]

First named storm of the year. Has 24 hours in favorable condition but none of the models are bullish on it taking advantage of this.

[cycloneye]

Intensity
category 1, sustained winds near the centre of 75 kilometres per hour with wind gusts to 100 kilometres per hour

Location
within 35 kilometres of 15.2 degrees South, 109.5 degrees East, 890 kilometres north northwest of Exmouth and 670 kilometres southeast of Christmas Island

Movement
south southeast at 13 kilometres per hour

Tropical Cyclone Iggy (10U) lies over open waters well to the northwest of the WA mainland and well to the south southeast of Christmas Island.

Iggy is expected to slow today then turn to the west and remain over open waters. Iggy should weaken below tropical cyclone intensity by Saturday.