IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0147 UTC 25/02/2021
Name: Tropical Low
Identifier: 15U
Data At: 0000 UTC
Latitude: 12.4S
Longitude: 107.0E
Location Accuracy: within 60 nm [110 km]
Movement Towards: west southwest [258 deg]
Speed of Movement: 11 knots [20 km/h]
Maximum 10-Minute Wind: 30 knots [55 km/h]
Maximum 3-Second Wind Gust: 45 knots [85 km/h]
Central Pressure: 997 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: T2.0/2.0/D1.0/24HRS STT:S0.0/06HRS
Pressure of outermost isobar: 1002 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: 25/0600: 12.8S 105.9E: 075 [135]: 030 [055]: 997
+12: 25/1200: 13.3S 104.5E: 080 [145]: 030 [055]: 997
+18: 25/1800: 13.6S 102.8E: 085 [155]: 035 [065]: 995
+24: 26/0000: 13.9S 101.1E: 075 [135]: 035 [065]: 995
+36: 26/1200: 14.2S 98.1E: 070 [125]: 040 [075]: 992
+48: 27/0000: 14.6S 95.8E: 085 [160]: 050 [095]: 985
+60: 27/1200: 15.3S 94.3E: 110 [205]: 055 [100]: 981
+72: 28/0000: 16.1S 93.3E: 130 [235]: 060 [110]: 976
+96: 01/0000: 17.4S 91.8E: 165 [305]: 060 [110]: 977
+120: 02/0000: 18.1S 91.3E: 220 [410]: 060 [110]: 974
REMARKS:
The tropical low 15U has been impacted by easterly wind shear in the past few
days but a slight easing of upper level easterlies combined with enhanced low
level monsoonal flow is resulting in convection extending to the eastern side of
the circulation.
Dvorak analysis of 2.0 based upon slight curvature in deep convection supported
by MET [D1.0/24h]. Intensity of 30kn is higher than Dvorak based upon synoptic
forcing both north and south of the centre as indicated by overnight SCATSAT at
1246UTC.
Gales are forecast to begin in the ESE flow on the southern side within 24h with
gales likely to extend to northern quadrants in the 24-36 time frame.
The combined synoptic influences of the monsoonal flow and the sub-tropical
ridge to the south will assist in developing a larger circulation than is
typical for this region. Being a large system it may also take a little longer
than normal to intensify further and at this stage it is not forecast to reach
category 3 intensity in the next 72 hours.
The mid-level ridge to the south is expected to dominate the steering for a
steady WSW motion through into Saturday [+48]. From then a developing
mid-latitude trough is expected to erode the ridge and slow the system. The
prevailing monsoonal NW flow will assist in a more southerly track. In the
longer term there is higher uncertainty - a slow drift south over cooler waters
contrasts with a potential recurvature to the southeast as the mid-latitude
trough amplifies off the western Australian coast. Even in this scenario the
track should remain west of the Australian mainland.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 25/0730 UTC.
WTXS21 PGTW 250330
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 98S)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
140 NM EITHER SIDE OF A LINE FROM 12.5S 107.8E TO 14.3S 98.7E
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT
IMAGERY AT 250230Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 12.7S 106.9E. THE SYSTEM IS MOVING WESTWARD AT 19 KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 98S) PREVIOUSLY LOCATED
NEAR 14.3S 110.3E IS NOW LOCATED NEAR 12.7S 106.9E, APPROXIMATELY
712 NM NORTHWEST OF LEARMONTH, AUSTRALIA. ANIMATED ENHANCED INFRARED
IMAGERY (EIR) AND A 242118Z SSMIS 91GHZ MICROWAVE IMAGE DEPICT A
CONSOLIDATING LOW LEVEL CIRCULATION WITH PERSISTENT DEEP CONVECTION.
STRONG OUTFLOW, LOW VERTICAL WIND SHEAR (<15KTS) AND WARM (29-30C)
SEA SURFACE TEMPERATURES (SST) CREATE FAVORABLE CONDITIONS FOR
FURTHER DEVELOPMENT. GLOBAL MODELS INDICATE INVEST 98S WILL TRACK
WESTWARD AND CONTINUE TO INTENSIFY. MAXIMUM SUSTAINED SURFACE WINDS
ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS
ESTIMATED TO BE NEAR 1004 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
260330Z.//
NNNN
A developing tropical low (15U) may cause a period of gales and heavy rain on Cocos (Keeling) Islands overnight Friday into Saturday.
Areas affected:
Warning zone: None.
Watch zone: the Cocos Islands.
Cancelled zones: None.
Details of Tropical Low at 12:30 pm CCT:
Intensity: tropical low, sustained winds near the centre of 55 kilometres per hour with wind gusts to 85 kilometres per hour.
Location: within 45 kilometres of 13.1 degrees South, 105.8 degrees East , 980 kilometres east of Cocos Island and 295 kilometres south of Christmas Island .
Movement: west southwest at 22 kilometres per hour .
Tropical low (15U) is moving steadily to the west southwest and is expected to gradually strengthen. It is forecast to develop into a tropical cyclone on Friday and pass south of Cocos (Keeling) Islands overnight Friday night. The risk of gales and heavy rain increases if the system moves closer to the islands further north than the forecast track indicates.
During Saturday it is likely to be moving away from the islands.
Hazards:
GALES may develop over Cocos (Keeling) Islands for a period from Friday night into Saturday. Strong northwesterly winds are expected to result in choppy seas in the lagoon overnight Friday night and on Saturday.
A period of heavy rainfall is possible over the Cocos (Keeling) Islands from late Friday and on Saturday.
Recommended Action:
The Australian Federal Police advise that there are no community alerts at present.
Communities on Home and West Islands should listen for the next advice.
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0728 UTC 25/02/2021
Name: Tropical Low
Identifier: 15U
Data At: 0600 UTC
Latitude: 13.1S
Longitude: 105.8E
Location Accuracy: within 25 nm [45 km]
Movement Towards: west southwest [247 deg]
Speed of Movement: 12 knots [22 km/h]
Maximum 10-Minute Wind: 30 knots [55 km/h]
Maximum 3-Second Wind Gust: 45 knots [85 km/h]
Central Pressure: 997 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: T2.0/2.0/D0.5/24HRS STT:S0.0/6HRS
Pressure of outermost isobar: 1002 hPa
Radius of outermost closed isobar: 180 nm [335 km]
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 25/1200: 13.6S 104.4E: 040 [075]: 030 [055]: 998
+12: 25/1800: 14.0S 102.8E: 060 [110]: 035 [065]: 994
+18: 26/0000: 14.5S 101.2E: 065 [120]: 035 [065]: 995
+24: 26/0600: 14.6S 99.4E: 070 [135]: 040 [075]: 993
+36: 26/1800: 14.8S 96.6E: 090 [165]: 045 [085]: 989
+48: 27/0600: 15.5S 94.7E: 100 [185]: 050 [095]: 985
+60: 27/1800: 16.2S 93.4E: 120 [220]: 055 [100]: 981
+72: 28/0600: 16.9S 92.6E: 130 [245]: 065 [120]: 973 +96: 01/0600: 17.9S 91.3E: 185 [340]: 070 [130]: 969
+120: 02/0600: 18.6S 91.1E: 245 [450]: 060 [110]: 974
REMARKS:
Tropical low 15U is gradually consolidating although still somewhat constrained
by ongoing easterly wind shear. Visible imagery shows a better defined
circulation with a more definitive convective banding to the west.
Dvorak analysis of 2.0 based upon curved band pattern 0.3-0.4 - DT of 2.0-2.5
,and a slight 24h development to indicate a MET of 2.0. Intensity of 30kn is
higher than Dvorak based upon synoptic forcing in convective bands both
northeast and southwest of the centre as indicated by SCATSAT at 0118UTC.
Gales are forecast to begin in the ESE flow on the southern side within 12-24h
with gales likely to extend to northern quadrants in the 24-36 time frame.
The combined synoptic influences of the monsoonal flow and the sub-tropical
ridge to the south will assist in developing a larger circulation than is
typical for this region. Being a large system it may also take a little longer
than normal to intensify further reducing the chance of rapid intensification
within the next 72 hours. Model guidance does sustain the system through 5 to 7
days in a marginally favourable environment until eventually it moves over
cooler waters.
The mid-level ridge to the south is expected to dominate the steering for a
steady WSW motion through into Saturday [+48]. From then a developing
mid-latitude trough is expected to erode the ridge and slow the system. The
prevailing monsoonal NW flow will assist in a more southerly track. In the
longer term there is higher uncertainty - a slow drift south or southwest over
cooler waters contrasts with a potential recurvature to the southeast as the
mid-latitude trough amplifies off the western Australian coast. Even in this
scenario the track should remain west of the Australian mainland.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 25/1330 UTC.
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0138 UTC 26/02/2021
Name: Tropical Low
Identifier: 15U
Data At: 0000 UTC
Latitude: 14.2S
Longitude: 100.5E
Location Accuracy: within 30 nm [55 km]
Movement Towards: west southwest [255 deg]
Speed of Movement: 18 knots [33 km/h]
Maximum 10-Minute Wind: 35 knots [65 km/h]
Maximum 3-Second Wind Gust: 50 knots [95 km/h]
Central Pressure: 995 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant: 150 nm [280 km]
Radius of 34-knot winds SW quadrant: 150 nm [280 km]
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: T3.0/3.0/D1.0/24HRS STT: D0.5/06HRS
Pressure of outermost isobar: 1002 hPa
Radius of outermost closed isobar: 200 nm [370 km]
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 26/0600: 14.4S 98.7E: 035 [065]: 040 [075]: 993
+12: 26/1200: 14.6S 97.2E: 040 [075]: 040 [075]: 992
+18: 26/1800: 14.7S 96.0E: 050 [090]: 045 [085]: 989
+24: 27/0000: 14.9S 94.9E: 050 [095]: 050 [095]: 986
+36: 27/1200: 15.7S 93.4E: 065 [125]: 055 [100]: 981
+48: 28/0000: 16.3S 92.2E: 085 [160]: 060 [110]: 977
+60: 28/1200: 16.9S 91.4E: 095 [175]: 065 [120]: 973
+72: 01/0000: 17.4S 90.6E: 110 [205]: 070 [130]: 969
+96: 02/0000: 18.1S 90.0E: 145 [265]: 065 [120]: 970
+120: 03/0000: 18.9S 91.7E: 195 [360]: 055 [100]: 979
REMARKS:
Tropical low 15U continues to develop and is near TC intensity. Deep convection
has developed near the centre overnight with improved convective banding since
22UTC.
Dvorak analysis of 3.0 based upon curved band pattern [0.7 wrap] supported by
MET of 3.0 [D1.0 over 24h]. This is higher than objective NOAA ADT values of
2.4.
The Dvorak rating would normally equate to tropical cyclone intensity and while
the maximum winds are 35 kn, gales are currently estimated only in southern
quadrants and so not extending more than halfway around. This estimation is
based on the 18kn translation speed to the WSW, however if the satellite
signature continues, TC intensity is likely imminent and upcoming scatterometry
should assist in that assessment.
The analysed high shear is being offset by the split flow in the upper levels
from the recent convective burst northeast of the centre so it is expected that
the vortex tilt will reduce permitting further intensification. However the
chance for rapid intensification in the next 24-36h is reduced as the system is
larger than normal owing to the synoptic forcing especially south of the system.
Peak intensity is forecast at 70kn within 72h and maybe sustained for a period
in a marginally favourable environment. Indeed model guidance maintains the
system at TC intensity through the next 5-7 days.
The mid-level ridge to the south continues to dominate the steering with a WSW
motion forecast although on Saturday the motion will slow as the system deepens
and the ridge weakens in response to a developing mid-latitude trough to the
southeast off southern Western Australia. By Tuesday the slow moving system
should track to the southeast and accelerate somewhat owing to an approaching
mid-latitude trough. At this range there is a considerable spread in model
guidance.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 26/0730 UTC.
