Tropical Cyclone Alenga – December 2011

Tropical Cyclone Alenga has now moved into the Australian region after forming west of Cocos Island 36 hours ago.

It's the first TC of the season though another unnamed TC is further west in the South Indian Ocean - it formed about 24 hours ago.

The season has been slow to start with typically a couple of TCs in Spring.

About Michael Bath

http://www.facebook.com/michaeljohnbath http://www.lightningphotography.com/ http://australiasevereweather.com/ http://www.extremestorms.com.au/ http://www.ewn.com.au/

3 thoughts on “Tropical Cyclone Alenga – December 2011

  1. Michael Bath Post author

    It’s a cat 3 at present though expected to quickly weaken tomorrow.

    TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA – WESTERN REGION
    Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
    at: 0149 UTC 08/12/2011
    Name: Severe Tropical Cyclone Alenga
    Identifier: 01U
    Data At: 0000 UTC
    Latitude: 16.2S
    Longitude: 94.9E
    Location Accuracy: within 20 nm [35 km]
    Movement Towards: east southeast [115 deg]
    Speed of Movement: 19 knots [34 km/h]
    Maximum 10-Minute Wind: 70 knots [130 km/h]
    Maximum 3-Second Wind Gust: 100 knots [185 km/h]
    Central Pressure: 976 hPa
    Radius of 34-knot winds NE quadrant: 80 nm [150 km]
    Radius of 34-knot winds SE quadrant: 80 nm [150 km]
    Radius of 34-knot winds SW quadrant: 80 nm [150 km]
    Radius of 34-knot winds NW quadrant: 80 nm [150 km]
    Radius of 48-knot winds NE quadrant: 40 nm [75 km]
    Radius of 48-knot winds SE quadrant: 40 nm [75 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: 25 nm [45 km]
    Radius of Maximum Winds: 20 nm [35 km]
    Dvorak Intensity Code: T4.5/4.5/D1.5/24HRS STT:D1.0/12HRS
    Pressure of outermost isobar: 1004 hPa
    Radius of outermost closed isobar: 300 nm [555 km]
    Storm Depth: Deep
    FORECAST DATA
    Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
    [UTC] : degrees : nm [km]: knots[km/h]: hPa
    +12: 08/1200: 17.8S 97.7E: 045 [085]: 065 [120]: 979
    +24: 09/0000: 19.3S 99.9E: 065 [120]: 055 [100]: 983
    +36: 09/1200: 20.2S 101.5E: 095 [180]: 045 [085]: 989
    +48: 10/0000: 21.0S 102.3E: 130 [240]: 040 [075]: 991
    +60: 10/1200: 21.6S 102.6E: 175 [325]: 030 [055]: 997
    +72: 11/0000: 22.2S 102.6E: 225 [415]: 025 [045]: 1000
    REMARKS:
    Tropical Cyclone Alenga was located by microwave and infra-red satellite imagery
    over the past 6 hours. DT has averaged 5.0 over the last 3 images based on an
    EIR pattern. MET is consistently 4.0 [based on D trend] and PAT 4.5. FT and CI
    set to 4.5. This is generally consistent with ADT though ADT has an increasing
    trend towards 5.0 in recent images. No AMSU/SATCON available since 14Z. No
    recent ascat pass.Vmax is set at 70 knots 10-min.

    Recent microwave imagery shows development of the system around a reasonably
    well defined eye.

    The system has been in a low shear environment and CIMSS shear at 00 UTC was
    about 8 knots from the westnorthwest. Shear is forecast to increase in the next
    24 to 48 hours as an upper low and trough approach from the west.

    NWP guidance is quite consistent with general southeast motion likely over the
    next 48 hours due to the upper trough. In the longer term the weakening system
    may be steered towards the west southwest by a developing ridge well to the
    south. Gales may persist to the south of the system in the tight easterly
    pressure gradient.

    Alenga is now near its maximum forecast intensity and should begin to weaken
    beyond the next 12 hours as the system moves southeast into a high shear
    environment with cooler SST’s. The mid-level trough has also brought dry air in
    close proximity which may also weaken the system if it is entrained into the
    core.

  2. Michael Bath Post author

    It’s a cat 3 at present but expected to weaken tomorrow.

    TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA – WESTERN REGION
    Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
    at: 0149 UTC 08/12/2011
    Name: Severe Tropical Cyclone Alenga
    Identifier: 01U
    Data At: 0000 UTC
    Latitude: 16.2S
    Longitude: 94.9E
    Location Accuracy: within 20 nm [35 km]
    Movement Towards: east southeast [115 deg]
    Speed of Movement: 19 knots [34 km/h]
    Maximum 10-Minute Wind: 70 knots [130 km/h]
    Maximum 3-Second Wind Gust: 100 knots [185 km/h]
    Central Pressure: 976 hPa
    Radius of 34-knot winds NE quadrant: 80 nm [150 km]
    Radius of 34-knot winds SE quadrant: 80 nm [150 km]
    Radius of 34-knot winds SW quadrant: 80 nm [150 km]
    Radius of 34-knot winds NW quadrant: 80 nm [150 km]
    Radius of 48-knot winds NE quadrant: 40 nm [75 km]
    Radius of 48-knot winds SE quadrant: 40 nm [75 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: 25 nm [45 km]
    Radius of Maximum Winds: 20 nm [35 km]
    Dvorak Intensity Code: T4.5/4.5/D1.5/24HRS STT:D1.0/12HRS
    Pressure of outermost isobar: 1004 hPa
    Radius of outermost closed isobar: 300 nm [555 km]
    Storm Depth: Deep
    FORECAST DATA
    Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
    [UTC] : degrees : nm [km]: knots[km/h]: hPa
    +12: 08/1200: 17.8S 97.7E: 045 [085]: 065 [120]: 979
    +24: 09/0000: 19.3S 99.9E: 065 [120]: 055 [100]: 983
    +36: 09/1200: 20.2S 101.5E: 095 [180]: 045 [085]: 989
    +48: 10/0000: 21.0S 102.3E: 130 [240]: 040 [075]: 991
    +60: 10/1200: 21.6S 102.6E: 175 [325]: 030 [055]: 997
    +72: 11/0000: 22.2S 102.6E: 225 [415]: 025 [045]: 1000
    REMARKS:
    Tropical Cyclone Alenga was located by microwave and infra-red satellite imagery
    over the past 6 hours. DT has averaged 5.0 over the last 3 images based on an
    EIR pattern. MET is consistently 4.0 [based on D trend] and PAT 4.5. FT and CI
    set to 4.5. This is generally consistent with ADT though ADT has an increasing
    trend towards 5.0 in recent images. No AMSU/SATCON available since 14Z. No
    recent ascat pass.Vmax is set at 70 knots 10-min.

    Recent microwave imagery shows development of the system around a reasonably
    well defined eye.

    The system has been in a low shear environment and CIMSS shear at 00 UTC was
    about 8 knots from the westnorthwest. Shear is forecast to increase in the next
    24 to 48 hours as an upper low and trough approach from the west.

    NWP guidance is quite consistent with general southeast motion likely over the
    next 48 hours due to the upper trough. In the longer term the weakening system
    may be steered towards the west southwest by a developing ridge well to the
    south. Gales may persist to the south of the system in the tight easterly
    pressure gradient.

    Alenga is now near its maximum forecast intensity and should begin to weaken
    beyond the next 12 hours as the system moves southeast into a high shear
    environment with cooler SST’s. The mid-level trough has also brought dry air in
    close proximity which may also weaken the system if it is entrained into the
    core.

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