AXAU01 APRF 291908
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 1908 UTC 29/03/2023
Name: Tropical Cyclone Herman
Identifier: 21U
Data At: 1800 UTC
Latitude: 14.4S
Longitude: 103.0E
Location Accuracy: within 20nm (35 km)
Movement Towards: east southeast (117 deg)
Speed of Movement: 9 knots (16 km/h)
Maximum 10-Minute Wind: 50 knots (95 km/h)
Maximum 3-Second Wind Gust: 70 knots (130 km/h)
Central Pressure: 990 hPa
Radius of 34-knot winds NE quadrant: 70 nm (130 km)
Radius of 34-knot winds SE quadrant: 80 nm (150 km)
Radius of 34-knot winds SW quadrant: 90 nm (165 km)
Radius of 34-knot winds NW quadrant: 70 nm (130 km)
Radius of 48-knot winds NE quadrant: 30 nm (55 km)
Radius of 48-knot winds SE quadrant: 30 nm (55 km)
Radius of 48-knot winds SW quadrant: 40 nm (75 km)
Radius of 48-knot winds NW quadrant: 40 nm (75 km)
Radius of 64-knot winds:  nm ( km)
Radius of Maximum Winds: 25 nm (45 km)
Dvorak Intensity Code: T3.5/3.5/D2.0/24HRS STT:D0.5/06HRS
Pressure of outermost isobar: 1006 hPa
Radius of outermost closed isobar: 160 nm (295 km)
FORECAST DATA
Date/Time    : Location    : Loc. Accuracy: Max Wind   : Central Pressure
(UTC)        : degrees     :      nm  (km): knots(km/h): hPa
+06:  30/0000: 14.7S 103.8E:     040 (070):  055  (100):  986
+12:  30/0600: 15.1S 104.5E:     050 (095):  055  (100):  986
+18:  30/1200: 15.4S 105.3E:     060 (115):  055  (100):  986
+24:  30/1800: 15.7S 105.8E:     070 (130):  050  (095):  989
+36:  31/0600: 16.3S 106.5E:     090 (165):  040  (075):  995
+48:  31/1800: 16.7S 106.7E:     115 (215):  030  (055): 1000
+60:  01/0600: 17.0S 106.4E:     150 (275):  030  (055): 1000
+72:  01/1800: 17.1S 105.6E:     175 (325):  025  (045): 1003
+96:  02/1800: 17.1S 103.2E:     225 (420):  025  (045): 1003
+120: 03/1800: 16.5S 100.4E:     260 (480):  025  (045): 1004
REMARKS:
Tropical Cyclone Herman continues to develop over open waters in the Indian
Ocean. 

The system was located using EIR imagery and earlier microwave passes and there
is moderate confidence in the position. On recent imagery there has been a
curved band becoming apparent, with wrap of around 0.8 averaged over the last
few hours, yielding a DT of 3.5. MET and PAT are 3.5 based on a D+ trend, and
FT/CI is set to 3.5. 

Objective guidance (all 1-minute mean): CIMSS ADT 57kt at 1800Z, NESDIS ADT
57kt at 1810Z, AiDT 43 knots at 1800Z, CIMMS OPEN-AIR 52kt at 18Z. CIMMS DMN
has not updated since 12Z. 

Intensity set at 50 knots (10-minute mean) based on Dvorak analysis,
development trends and objective guidance. 

Model guidance is reasonably consistent both in development and movement. 

Herman is expected to intensify further over the next 12-24 hours in a
favourable environment. It is currently located under a shear ridge in a moist
environment. An upper trough located to the south is providing good upper
divergence and a good outflow channel to the south. During Friday the
environment will become unfavourable as dry air is forecast to wrap around the
north of the system and be ingested into the centre by moderate mid-level
northerly winds on the eastern periphery of the centre. As Herman weakens due
to the effect of this dry air, the upper circulation should become removed from
the centre under the influence of an upper trough. 

Herman is currently being steered to the southeast by the mid-level trough
located to the south of the system and this steering regime is expected to
persist through Thursday. During Friday the trough will assist in removing the
upper circulation and the steering influence is likely to be lower down in the
atmosphere. Guidance suggests Herman will move steadily to the west from
Saturday under the influence of the 700 hPa ridge. 

Copyright Commonwealth of Australia
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The next bulletin for this system will be issued by: 30/0130 UTC.