(2) AN AREA OF CONVECTION (INVEST 99S) HAS PERSISTED NEAR
10.7S 114.5E, APPROXIMATELY 560 NM EAST-SOUTHEAST OF JAKARTA.
ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND A 080106Z GMI 89GHZ
MICROWAVE IMAGE SHOW A PERSISTENT BALL OF DEEP CONVECTION OVER AND
OBSCURING THE LLC. 99S IS CURRENTLY IN A VERY FAVORABLE ENVIRONMENT
WITH EXCELLENT POLEWARD OUTFLOW, VERY LOW (5 TO 10 KNOTS) VWS, AND
VERY WARM (29 TO 30 CELSIUS) SST. GLOBAL MODELS ARE IN GOOD
AGREEMENT THAT 99S WILL CONTINUE TO TRACK WESTWARD BEFORE BEGINNING
TO RECURVE SOUTHWEST, ALL THE WHILE INTENSIFYING. MAXIMUM SUSTAINED
SURFACE WINDS ARE ESTIMATED AT 10 TO 15 KNOTS. MINIMUM SEA LEVEL
PRESSURE IS ESTIMATED TO BE NEAR 1008 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS LOW.
A tropical low (17U) was located near 11.6S 114.1E at 11am WST Friday, about 350km SSW of Denpasar (Bali). It is expected to track in a west to southwesterly direction and gradually develop, and may pass close to Christmas Island late Sunday or during Monday, and close to the Cocos (Keeling) Islands during Tuesday or Wednesday. There is a Low (less than 20%) chance of this system developing into a tropical cyclone on Saturday and Sunday, increasing to a Moderate chance on Monday.
Likelihood of this system being a tropical cyclone in the Western Region on:
Saturday:Low
Sunday:Low
Monday:Moderate
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
at: 0739 UTC 13/03/2019
Name: Tropical Low
Identifier: 17U
Data At: 0600 UTC
Latitude: 9.7S
Longitude: 97.6E
Location Accuracy: within 30 nm [55 km]
Movement Towards: southwest [219 deg]
Speed of Movement: 8 knots [14 km/h]
Maximum 10-Minute Wind: 30 knots [55 km/h]
Maximum 3-Second Wind Gust: 45 knots [85 km/h]
Central Pressure: 1000 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant:
Radius of 34-knot winds SW quadrant:
Radius of 34-knot winds NW quadrant:
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:
Radius of Maximum Winds:
Dvorak Intensity Code: T2.5/2.5/D1.0/24HRS STT:S0.0/06HRS
Pressure of outermost isobar: 1008 hPa
Radius of outermost closed isobar: 60 nm [110 km]
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 13/1200: 10.5S 97.4E: 040 [080]: 030 [055]: 1003
+12: 13/1800: 11.4S 97.3E: 055 [100]: 035 [065]: 1001
+18: 14/0000: 12.3S 97.2E: 065 [125]: 040 [075]: 998
+24: 14/0600: 13.3S 96.9E: 080 [145]: 040 [075]: 998
+36: 14/1800: 14.8S 96.9E: 100 [180]: 040 [075]: 998
+48: 15/0600: 16.1S 96.8E: 120 [220]: 045 [085]: 994
+60: 15/1800: 17.1S 96.3E: 140 [255]: 045 [085]: 994
+72: 16/0600: 17.6S 95.4E: 155 [290]: 045 [085]: 994
+96: 17/0600: 17.9S 93.0E: 200 [370]: 045 [085]: 994
+120: 18/0600: 17.9S 90.9E: 290 [535]: 040 [075]: 997
REMARKS:
Tropical Low 17U was located using visible imagery and an ASCAT pass.
The low has developed over the past 12 to 24 hours. The ASCAT pass around 03 UTC
showed 25 to 30 knot winds to the south of the centre.
Dvorak: Shear pattern with centre <0.75 degree from edge. DT was 2.5. Trend was
D. MET/PAT was 2.5. FT/CI set to 2.5. Final intensity was 30 knots [10 minute
mean winds].
CIMSS shear at 06 UTC was E'ly between 15 and 20 knots and there was some
equatorward outflow. SSTs are between 28 and 30C.
17U has started to move generally towards the south due to a mid level ridge to
the east. Shear is forecast to decrease during Thursday as an upper trough
passes to the south. The system is expected to develop into a tropical cyclone
during Thursday morning as it passes close to the Cocos [Keeling] Islands with a
period of gales and heavy rainfall possible.
Over the weekend, the system is forecast to move towards the west as a mid level
ridge builds to the south. It may reach category 2 intensity on Sunday or Monday
as shear is forecast to remain low. There is evidence of dry air in the vicinity
of 17U over the weekend and into next week which may inhibit develop.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 13/1330 UTC by Perth TCWC.
(1) THE AREA OF CONVECTION (INVEST 99S) PREVIOUSLY LOCATED
NEAR 8.9S 99.1E, IS NOW LOCATED NEAR 10.4S 96.8E, APPROXIMATELY 87
NM NORTH OF COCO ISLANDS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS PERSISTENT CONVECTION OVER THE LOW LEVEL CIRCULATION
CENTER (LLCC). A 131433Z MHS METOP-A 89GHZ MICROWAVE IMAGE DEPICTS A
CONSOLIDATING LLCC WITH FORMATIVE BANDING AND EXPANSIVE CENTRAL
DENSE OVERCAST BUILDING OVER THE CENTER. A RECENT ASCAT PASS SHOWS A
DEFINED CIRCULATION WITH 30 KNOT WINDS WRAPPING AROUND THE SYSTEM.
UPPER LEVEL ANALYSIS SHOWS THAT 99S IS BORDERING AN AREA OF LOW TO
MODERATE (10-25 KNOT) VERTICAL WIND SHEAR WITH WESTWARD DIFFLUENCE
ALOFT. SEA SURFACE TEMPERATURES (28-30 CELSIUS) IN THE SURROUNDING
WATERS SUPPORT FUTURE DEVELOPMENT. GLOBAL MODELS ARE IN GOOD
AGREEMENT THAT 99S WILL TRACK SOUTH-SOUTHWESTWARD AND INTENSIFY
WITHIN THE NEXT 36-48 HOURS. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO
HIGH.
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
at: 0130 UTC 14/03/2019
Name: Tropical Cyclone Savannah
Identifier: 17U
Data At: 0000 UTC
Latitude: 11.6S
Longitude: 96.5E
Location Accuracy: within 30 nm [55 km]
Movement Towards: south southwest [206 deg]
Speed of Movement: 7 knots [12 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: 45 nm [85 km]
Radius of 34-knot winds NW quadrant: 45 nm [85 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:
Radius of Maximum Winds: 20 nm [35 km]
Dvorak Intensity Code: T3.0/3.0/D0.5/24HRS STT: D0.5/06HRS
Pressure of outermost isobar: 1008 hPa
Radius of outermost closed isobar: 130 nm [240 km]
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 14/0600: 12.3S 96.3E: 040 [080]: 040 [075]: 998
+12: 14/1200: 12.9S 96.3E: 055 [100]: 040 [075]: 998
+18: 14/1800: 13.6S 96.3E: 065 [125]: 045 [085]: 994
+24: 15/0000: 14.1S 96.2E: 080 [145]: 045 [085]: 994
+36: 15/1200: 15.1S 96.0E: 100 [180]: 045 [085]: 994
+48: 16/0000: 15.7S 95.4E: 120 [220]: 050 [095]: 991
+60: 16/1200: 16.2S 94.6E: 140 [255]: 055 [100]: 987
+72: 17/0000: 16.4S 93.6E: 155 [290]: 060 [110]: 984
+96: 18/0000: 16.8S 91.8E: 200 [370]: 060 [110]: 983
+120: 19/0000: 17.2S 90.0E: 290 [535]: 050 [095]: 991
REMARKS:
Tropical Cyclone Savannah was named at 21UTC and was located using EIR and
microwave imagery [SSMIS 13/2257UTC].
Deep convection continues to persist on the western flank. Partial scatterometry
passes around 1430 UTC showed 30 to 40 knot winds to the west of the centre.
Dvorak analysis: Shear pattern, <0.5 degree from strong T gradient yields a DT
of 3.0. Trend is D-, MET/PAT is 3.0. FT/CI set to 3.0 with intensity of 40 knots
[10 minute mean wind].
CIMSS wind shear at 21 UTC was E'ly between 20 and 25 knots, and upper winds
showed moderate outflow equatorward. SSTs are between 28 and 30C.
Savannah is continuing to move generally towards the south-southwest due to a
mid level ridge to the east. Shear is forecast to decrease during Thursday as an
upper trough passes to the south. The system will pass to the west of the Cocos
[Keeling] Islands during Thursday with a period of gales possible. Peak gust
recorded to date was 43 knots at 2135 UTC.
Over the weekend, the system is forecast to move towards the west southwest as a
mid level ridge builds to the southwest and an upper level trough passes to the
south. Savannah is forecast to reach category 2 intensity on Saturday as shear
is forecast to remain low, though this could occur as early as Friday evening.
There is potential for Savannah to reach category 3 intensity on Sunday or
Monday with improved poleward outflow. There is potential for dry air to wrap
around the periphery over the weekend and into next week. It is unclear whether
this will impact the intensity as there is uncertainty surrounding the
likelihood of this dry air being ingested into the system.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 14/0730 UTC by Perth TCWC.
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
at: 0115 UTC 15/03/2019
Name: Tropical Cyclone Savannah
Identifier: 17U
Data At: 0000 UTC
Latitude: 13.5S
Longitude: 95.2E
Location Accuracy: within 30 nm [55 km]
Movement Towards: south southwest [203 deg]
Speed of Movement: 5 knots [9 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: 60 nm [110 km]
Radius of 34-knot winds SE quadrant: 90 nm [165 km]
Radius of 34-knot winds SW quadrant: 90 nm [165 km]
Radius of 34-knot winds NW quadrant: 75 nm [140 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:
Radius of Maximum Winds: 15 nm [30 km]
Dvorak Intensity Code: T3.5/3.5/D0.5/24HRS STT:D0.5/06HRS
Pressure of outermost isobar: 1008 hPa
Radius of outermost closed isobar: 150 nm [280 km]
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 15/0600: 14.0S 95.1E: 040 [080]: 050 [095]: 990
+12: 15/1200: 14.5S 94.9E: 055 [100]: 055 [100]: 988
+18: 15/1800: 14.9S 94.5E: 065 [125]: 055 [100]: 988
+24: 16/0000: 15.1S 94.0E: 080 [145]: 060 [110]: 984
+36: 16/1200: 15.4S 93.0E: 100 [180]: 060 [110]: 984
+48: 17/0000: 15.7S 91.8E: 120 [220]: 065 [120]: 980
+60: 17/1200: 15.8S 90.6E: 140 [255]: 065 [120]: 980
+72: 18/0000: 15.9S 89.7E: 155 [290]: 065 [120]: 980
+96: 19/0000: 16.2S 88.1E: 200 [370]: 050 [095]: 991
+120: 20/0000: 16.6S 86.7E: 290 [535]: 045 [085]: 994
REMARKS:
Tropical Cyclone Savannah was located using EIR imagery and recent microwave
imagery [AMSR2 1903 UTC, SSMI 2027 UTC, TC_SSMIS 2246 UTC].
Deep convection has started to wrap around the centre. Microwave imagery showed
a pin hole eye with deep convection to the north and east of the centre.
Dvorak analysis: Curved band wrap of 0.8 on EIR imagery yielded a DT of 3.5.
Trend is D with PAT of 3.5. FT/CI set to 3.5 with intensity of 50 knots [10 min
mean wind]. CIMMS ADT was 3.5 and NESDIS ADT was 3.7 around 00 UTC. SATCON at
1927 UTC was 48 knots [1 min mean wind].
CIMMS wind shear at 21 UTC was E'ly around 5 to 10 knots. Upper winds showed
moderate outflow equatorward. SSTs are between 28 and 30C.
Savannah is continuing to move generally towards the southwest due to a mid
level ridge to the east and an upper trough to the south and will continue to
move away from the Cocos [Keeling] Islands.Over the weekend, the system is
forecast to move towards the west southwest as a mid level ridge builds to the
southwest and an upper level trough passes to the south. ECMWF has more of a
southwest track with the majority of other guidance favouring a more westerly
track. This is likely due to the influence of the upper level trough.
Savannah is intensifying and with shear expected to remain low, is forecast to
reach category 3 intensity on Sunday or as early as Saturday. There is potential
for dry air to wrap around the periphery over the weekend and into next week.
Shear is also forecast to increase and with cooler SSTs, Savannah is expected to
weaken early next week.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 15/0730 UTC by Perth TCWC.
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
at: 1834 UTC 15/03/2019
Name: Severe Tropical Cyclone Savannah
Identifier: 17U
Data At: 1800 UTC
Latitude: 14.8S
Longitude: 94.2E
Location Accuracy: within 25 nm [45 km]
Movement Towards: southwest [216 deg]
Speed of Movement: 5 knots [10 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: 70 nm [130 km]
Radius of 34-knot winds SE quadrant: 90 nm [165 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: 30 nm [55 km]
Radius of 48-knot winds NW quadrant: 30 nm [55 km]
Radius of 64-knot winds:
Radius of Maximum Winds: 15 nm [30 km]
Dvorak Intensity Code: T4.5/4.5/D1.5/24HRS STT:D0.5/06HRS
Pressure of outermost isobar: 1008 hPa
Radius of outermost closed isobar: 130 nm [240 km]
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 16/0000: 15.2S 93.7E: 030 [060]: 075 [140]: 972
+12: 16/0600: 15.4S 93.3E: 045 [080]: 085 [155]: 968
+18: 16/1200: 15.6S 92.8E: 055 [105]: 085 [155]: 963
+24: 16/1800: 15.9S 92.2E: 070 [130]: 085 [155]: 963
+36: 17/0600: 16.1S 91.1E: 090 [165]: 085 [155]: 963
+48: 17/1800: 16.4S 90.1E: 110 [200]: 085 [155]: 963
+60: 18/0600: 16.6S 89.1E: 130 [235]: 085 [155]: 963
+72: 18/1800: 16.9S 88.1E: 145 [270]: 080 [150]: 968
+96: 19/1800: 17.5S 86.6E: 190 [355]: 055 [100]: 987
+120: 20/1800: 17.9S 85.2E: 280 [515]: 045 [085]: 994
REMARKS:
Severe Tropical Cyclone Savannah was located using microwave imagery. Deep
convection continues to consolidate about the centre responding to the low wind
shear environment.
Dvorak analysis: FT/CI=4.5. Intensity of 70 knots [10 min mean wind], ADT agrees
[CI=4.5].
The prevailing environmental influences are favourable for further
intensification: low wind shear; upper level outflow both equatorward and
particularly poleward in response to a mid-latitude trough to the south; and
SSTs around 28C. Further development is possible right through the weekend.
While dry air lurks on the periphery of the circulation, the fact that wind
shear should continue to be low for several days means the circulation could be
pouched in a moist environment and hence maintain intensity for several days.
The forecast intensity exceeds the range of model guidance possibly because of
the small circulation, but an even more intense system can't be ruled out at
this stage. Rapid intensity Index does not indicate RI is likely but this may be
unduly influenced by dry air on the periphery.
Savannah is continuing to move generally towards the southwest due to a mid
level ridge to the east and an upper trough to the south and will continue to
move away from the Cocos [Keeling] Islands.Over the weekend, the system is
forecast to move towards the west southwest as a mid level ridge builds to the
southwest and the upper level trough passes to the south.
Weakening may be rapid next week once the shear increases and dry air is
ingested however gales may persist long on the southern side owing to motion and
synoptic assistance from the ridge.
Based on the current official forecast track, Savannah is forecast to cross 90E
[into La Reunion's Area of Responsibility] early on Monday 18 March.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 16/0130 UTC by Perth TCWC.
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