AXAU01 APRF 300702
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0702 UTC 30/03/2023
Name: Tropical Cyclone Herman
Identifier: 21U
Data At: 0600 UTC
Latitude: 15.2S
Longitude: 104.7E
Location Accuracy: within 20nm (35 km)
Movement Towards: east southeast (123 deg)
Speed of Movement: 9 knots (17 km/h)
Maximum 10-Minute Wind: 55 knots (100 km/h)
Maximum 3-Second Wind Gust: 75 knots (140 km/h)
Central Pressure: 986 hPa
Radius of 34-knot winds NE quadrant: 40 nm (75 km)
Radius of 34-knot winds SE quadrant: 40 nm (75 km)
Radius of 34-knot winds SW quadrant: 50 nm (95 km)
Radius of 34-knot winds NW quadrant: 50 nm (95 km)
Radius of 48-knot winds NE quadrant: 20 nm (35 km)
Radius of 48-knot winds SE quadrant: 20 nm (35 km)
Radius of 48-knot winds SW quadrant: 20 nm (35 km)
Radius of 48-knot winds NW quadrant: 20 nm (35 km)
Radius of 64-knot winds:  nm ( km)
Radius of Maximum Winds: 15 nm (30 km)
Dvorak Intensity Code: T4.0/4.0/D1.5/24HRS STT:S0.0/06HRS
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:  30/1200: 15.6S 105.5E:     040 (070):  055  (100):  986
+12:  30/1800: 15.9S 106.0E:     050 (090):  050  (095):  989
+18:  31/0000: 16.3S 106.5E:     055 (105):  050  (095):  989
+24:  31/0600: 16.6S 106.9E:     065 (125):  045  (085):  992
+36:  31/1800: 16.9S 107.2E:     090 (165):  040  (075):  994
+48:  01/0600: 17.3S 107.0E:     115 (215):  035  (065):  997
+60:  01/1800: 17.3S 106.4E:     145 (275):  030  (055): 1000
+72:  02/0600: 17.4S 105.4E:     175 (325):  030  (055): 1001
+96:  03/0600: 17.1S 102.7E:     205 (375):  030  (055): 1001
+120: 04/0600: 16.2S  99.9E:     225 (420):  025  (045): 1003
REMARKS:
Tropical Cyclone Herman likely at or near its peak intensity. 

The system was located using VIS imagery and earlier scatterometer passes and
there is high confidence in the position. A curved band pattern with wrap of
0.9, indicates a DT of 3.5. MET is 3.5 based on a D trend with PAT adjusted to
4.0. FT/CI is set to 4.0. 

Objective guidance (all 1-minute mean): CIMSS ADT 55kt at 0600Z, NESDIS ADT
61kt at 0610Z, AiDT 43 knots at 0600Z, CIMMS OPEN-AIR 60kt at 0600Z. CIMSS DMN
has been unavailable since before 00Z. An eye has been evident on microwave
imagery during the morning. 

Intensity set at 55 knots (10-minute mean) based on Dvorak analysis,
development trends and objective guidance. 

Model guidance is reasonably consistent both in development and movement,
though global deterministic models are struggling to capture the current
intensity of the system. 

Dry air wrapping around the north of Herman is evidenced by a lack of
convection, however there is still reasonable moist inflow within the
northerlies wrapping around the eastern side of the system. 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
the dry air wrapping around the north of the system is expected to be ingested
into the centre by moderate mid-level northerly winds on the eastern periphery
of the centre.

Herman is currently being steered to the southeast by the mid-level trough
located to the south of the system. 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: 30/1330 UTC.