MEDIUM - 西澳西北热带低压21U(99S) - 13.4S 120.7E

pocketbox

ABIO10 PGTW 200200
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE INDIAN OCEAN
REISSUED/200200Z-201800ZFEB2025//
RMKS/
1. NORTH INDIAN OCEAN AREA (MALAY PENINSULA WEST TO COAST OF AFRICA):
   A. TROPICAL CYCLONE SUMMARY: NONE.
   B. TROPICAL DISTURBANCE SUMMARY: NONE.
   C. SUBTROPICAL SYSTEM SUMMARY: NONE.
2. SOUTH INDIAN OCEAN AREA (135E WEST TO COAST OF AFRICA):
   A. TROPICAL CYCLONE SUMMARY: NONE.
   B. TROPICAL DISTURBANCE SUMMARY:
      (1) THE AREA OF CONVECTION (INVEST 99S) PREVIOUSLY LOCATED NEAR
11.4S 127.4E IS NOW LOCATED NEAR 13.3S 121.2E, APPROXIMATELY 285 NM
NORTH-NORTHEAST OF ROWLEY SHOALS ATOLL. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) DEPICTS A SLOWLY CONSOLIDATING LOW-LEVEL CIRCULATION
(LLC) AS LOW-LEVEL CLOUD LINES HAVE STARTED TO WRAP BENEATH A
SUPPORTIVE CONVECTIVE STRUCTURE NEAR THE ASSESSED CENTER. THE
ENVIRONMENT IS FAVORABLE FOR DEVELOPMENT WITH LOW VERTICAL WIND SHEAR
(VWS) OF 10-15 KNOTS, MODERATE EQUATORWARD UPPER-LEVEL OUTFLOW, AND
WARM SEA SURFACE TEMPERATURES (SST) OF 29-30 C. DETERMINISTIC AND
ENSEMBLES ARE IN AGREEMENT THAT INVEST 99S WILL CONTINUE TO TRACK
SOUTHWESTWARD TOWARD ROWLEY SHOALS ATOLL AS IT SLOWLY INTENSIFIES OVER
THE NEXT 24 TO 48 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT
23 TO 28 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005
MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS UPGRADED TO MEDIUM.
      (2) NO OTHER SUSPECT AREAS.
   C. SUBTROPICAL SYSTEM SUMMARY: NONE.
3. JUSTIFICATION FOR REISSUE: UPGRADED AREA IN PARA 2.B.(1) TO
MEDIUM.//
NNNN

Leonardo

TPXS10 PGTW 200926

A. TROPICAL DISTURBANCE 99S (W OF BROWSE ISLAND)

B. 20/0830Z

C. 13.54S

D. 120.37E

E. FIVE/GK2A

F. T1.0/2.0/S0.0/21HRS  STT: W0.5/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 63A/PBO PRLY ORGNZD LLCC/ANMTN. LOOSELY DEFINED CLOUD
LINES WITH OVERCAST LESS THAN 90NM ACROSS YIELD A DT OF 1.0. MET
AND PT AGREE. DBO DT.

I. ADDITIONAL POSITIONS: NONE


   HUYNH

Leonardo

TXXS24 KNES 200613
TCSSIO

A.  TROPICAL DISTURBANCE (99S)

B.  20/0530Z

C.  14.7S

D.  119.8E

E.  FIVE/HIMAWARI-9

F.  T1.5/1.5

G.  IR/EIR/VIS

H.  REMARKS...3.5/10 BANDING RESULTS IN A DT OF 2.0. OVERALL CIRCULATION
ENVELOPE QUITE LARGE WITH MULTIPLE WEAK LLCC EVIDENT ALTHO MORE FOCUSED
LLCC APPARENT ASSOC WITH AREA OF PERSISTENT STRONG CONVECTION. CENTER
RELOCATED FM VIS IMAGERY. MET AND PT=1.5. FT BASED ON MET DUE TO BANDING
NOT CLR-CUT.


I.  ADDL POSITIONS

    NIL


...KONON

=

Leonardo

ygsj24

WTAU05 APRF 201256
IDW23100

40:2:2:24:14S120E400:11:00
SECURITE

OCEAN WIND WARNING FOR METAREA 10
Issued by the Australian Bureau of Meteorology
Tropical Cyclone Warning Centre
at 1256 UTC 20 FEBRUARY 2025

GALE WARNING

Please be aware, wind gusts can be a further 40 percent stronger than the
averages given here, and maximum waves may be up to twice the height.

SITUATION
At 1200 UTC a Tropical Low was centred within 50 nautical miles of
latitude thirteen decimal nine south (13.9S)
longitude one hundred and nineteen decimal five east (119.5E)
Recent movement : west southwest at 10 knots
Maximum winds   : 25 knots
Central pressure: 1005 hPa
The low is expected to develop into a tropical cyclone in the next 36 to 48
hours.

AREA AFFECTED
Within 60 nautical miles in SW quadrant
  and within 50 nautical miles in NW quadrant.

FORECAST
Maximum winds to 25 knots near the centre increasing to 35 knots by 1200 UTC 21
February.


From 1200 UTC 21 February winds above 34 knots within 60 nautical miles in SW
quadrant
  and within 50 nautical miles in NW quadrant with very rough seas and moderate
swell.


Forecast positions
At 0000 UTC 21 February: Within 30 nautical miles of 13.9 south 117.7 east
                        Central pressure 1003 hPa.
                        Winds to 30 knots near centre.
At 1200 UTC 21 February: Within 50 nautical miles of 14.5 south 115.2 east
                        Central pressure 1001 hPa.
                        Winds to 35 knots near centre.

REMARKS
All ships in the area please send weather reports every three hours.
Regular weather observing ships use normal channels.
Other ships please use email to [email protected].

Next warning will be issued by 1900 UTC 20 February 2025.

AUSTRALIAN BUREAU OF METEOROLOGY
TROPICAL CYCLONE WARNING CENTRE



Headline:
Tropical Low 21U to develop into a tropical cyclone in the Indian Ocean over the weekend.


Areas affected:
Warning zone: None.

Watch zone: None.

Cancelled zones: None.


Details of Tropical Low 21U at 8:00 pm AWST:
Intensity: tropical low, sustained winds near the centre of 45 kilometres per hour with wind gusts to 85 kilometres per hour.
Location: within 95 kilometres of 13.9 degrees South, 119.5 degrees East , 535 kilometres north northwest of Broome and 720 kilometres north of Port Hedland .
Movement: west southwest at 19 kilometres per hour .

Tropical Low 21U is located in the Indian Ocean well to the north northwest of the Kimberly and is moving to the west south west. It is expected to develop into a tropical cyclone on Saturday, over open waters. It is expected to continue to move to the southwest over open waters with no direct impacts at any Austrlian mainland or Island communities.


Hazards:
No direct impacts are expected at any Australian mainland or Island communities.

Details:

	Time (AWST)	Intensity Category	Latitude (decimal deg.)	Longitude (decimal deg.)	Estimated Position Accuracy (km)
0hr	8 pm February 20	tropical low	13.9S	119.5E	95
+6hr	2 am February 21	tropical low	13.8S	118.6E	50
+12hr	8 am February 21	tropical low	13.9S	117.7E	50
+18hr	2 pm February 21	tropical low	14.3S	116.5E	70
+24hr	8 pm February 21	tropical low	14.5S	115.2E	95
+36hr	8 am February 22	tropical low	14.9S	112.6E	110
+48hr	8 pm February 22	2	15.3S	110.4E	145
+60hr	8 am February 23	2	15.8S	108.1E	160
+72hr	8 pm February 23	2	16.8S	106.1E	185

pocketbox

Tropical Low 21U
Tropical low (21U) developing to the northwest of the Kimberley will remain well off the WA coast.

• Tropical low (21U) is expected to continue moving westwards into the weekend, while remaining well to the north of the Pilbara coast.
• The risk of 21U developing into a tropical cyclone increases to Moderate on Friday and High on the weekend.
• 21U does not pose a direct threat to Western Australian mainland or island communities.
• During next week, 21U is expected to curve towards the south and the southeast, while remaining well off the Western Australian coast.
  

Last updated
30 minutes ago, 01:01 pm UTC

Tropical lows

Tomorrow 12:00 am

Tomorrow 12:00 pm

Sat 22  Feb 12:00 am

Sat 22  Feb 12:00 pm

Sun 23  Feb 12:00 am

Sun 23  Feb 12:00 pm

Mon 24  Feb 12:00 am

Mon 24  Feb 12:00 pm

Tue 25  Feb 12:00 am

Tue 25  Feb 12:00 pm

Wed 26  Feb 12:00 am

Wed 26  Feb 12:00 pm

Thu 27  Feb 12:00 am

Thu 27  Feb 12:00 pm

Tropical Low 21U

10 (Low)

25 (Moderate)

45 (Moderate)

55 (High)

60 (High)

60 (High)

65 (High)

65 (High)

60 (High)

55 (High)

55 (High)

25 (Moderate)

15 (Low)

5 (Low)

ygsj24

AXAU01 APRF 201858
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
ISSUED BY AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
AT: 1858 UTC 20/02/2025
NAME: TROPICAL LOW
IDENTIFIER: 21U
DATA AT: 1800 UTC
LATITUDE: 13.7S
LONGITUDE: 118.5E
LOCATION ACCURACY: WITHIN 40NM (75 KM)
MOVEMENT TOWARDS: WEST (273 DEG)
SPEED OF MOVEMENT: 9 KNOTS (17 KM/H)
MAXIMUM 10-MINUTE WIND: 30 KNOTS (55 KM/H)
MAXIMUM 3-SECOND WIND GUST: 45 KNOTS (85 KM/H)
CENTRAL PRESSURE: 1004 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:   NM (  KM)
RADIUS OF MAXIMUM WINDS:   NM (  KM)
DVORAK INTENSITY CODE: T2.0/2.0/D0.5/24HRS STT:D0.5/06HRS
PRESSURE OF OUTERMOST ISOBAR: 1007 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:  21/0000: 14.0S 117.1E:     055 (100):  030  (055): 1003
+12:  21/0600: 14.3S 115.9E:     065 (115):  030  (055): 1003
+18:  21/1200: 14.7S 114.8E:     065 (120):  035  (065): 1000
+24:  21/1800: 14.8S 113.6E:     070 (125):  035  (065): 1000
+36:  22/0600: 15.1S 111.3E:     075 (145):  045  (085):  995
+48:  22/1800: 15.6S 109.2E:     080 (145):  050  (095):  991
+60:  23/0600: 16.4S 106.9E:     090 (165):  060  (110):  985
+72:  23/1800: 17.4S 105.2E:     100 (185):  065  (120):  981
+96:  24/1800: 19.9S 102.7E:     140 (260):  070  (130):  973
+120: 25/1800: 22.8S 101.2E:     195 (365):  055  (100):  983
REMARKS:
TROPICAL LOW 21U HAS DEVELOPED DURING THE LAST 6-12 HOURS, WITH THE SURFACE
CIRCULATION BECOMING MORE ESTABLISHED AND CONVECTION DEVELOPING JUST TO ITS
WEST.

LOCATING THE LOW LEVEL CENTRE HAS BEEN DIFFICULT, WITH THE SURFACE CIRCULATION
DISPLACED TO THE EAST OF THE MID-LEVEL CIRCULATION LINKED TO THE DEEP
CONVECTION. AN ASCAT-B PASS AT 1343 UTC SHOWED THAT WHILE STILL ELONGATED, THE
SURFACE CIRCULATION IS NOW CLOSER TO THE CONVECTION, AND WINDS NOW REACH UP TO
30 KNOTS IN THE SW QUADRANT.

DVORAK ANALYSIS: DT HAS AVERAGED 3.0 OVER THE PAST 3 HOURS BASED ON A SHEAR
PATTERN, HOWEVER AS THE LOW LEVEL CENTRE IS STILL POORLY DEFINED THIS MAY NOT
BE RELIABLE. MET IS 2.0 BASED ON A D- TREND, WITH NO ADJUSTMENT FOR PAT.
FT/CI=2.0. OBJECTIVE GUIDANCE IS NOT YET AVAILABLE. INTENSITY IS SET TO 30
KNOTS.

THE ENVIRONMENTAL CONDITIONS FOR 21U APPEAR FINELY BALANCED IN THE NEXT 24-48
HOURS. SHEAR MAY BE MODERATE TO HIGH AT TIMES AS 21U SITS ON THE WESTERN EDGE
OF AN UPPER RIDGE. UPPER SUPPORT IS GOOD, BUT GUIDANCE SUGGESTS THAT THE
POLEWARD OUTFLOW TO THE SOUTHWEST MAY BE LOST OVER THE WEEKEND. WHILE DRY
MID-LEVEL AIR TO THE WEST IS UNLIKELY TO IMPACT THE SYSTEM IN THE SHORT TERM,
THE CURRENT MOIST INFEED FROM THE NORTH MAY BE LOST BY SATURDAY. FROM SUNDAY,
THE DEVELOPMENT OF 21U MAY BE AIDED BY INTERACTION WITH AN UPPER TROUGH TO THE
SOUTHWEST.

THERE IS HIGH CONFIDENCE THAT 21U WILL BE STEERED TO THE WEST SOUTHWEST IN THE
NEXT FEW DAYS DUE TO A MID-LEVEL RIDGE TO THE SOUTH. THE RIDGE WILL SHIFT EAST
BY MONDAY AS A MID-LEVEL TROUGH APPROACHES FROM THE SOUTHWEST, AND 21U SHOULD
BEGIN MOVING TOWARDS THE SOUTH. AS IT WEAKENS MID NEXT WEEK, IT MAY BE STEERED
TOWARDS THE SOUTHEAST BY THE MID-LEVEL TROUGH, HOWEVER IT IS EXPECTED TO
DISSIPATE WHILE STILL WELL TO THE WEST OF THE AUSTRALIAN MAINLAND.

COPYRIGHT COMMONWEALTH OF AUSTRALIA
==
THE NEXT BULLETIN FOR THIS SYSTEM WILL BE ISSUED BY: 21/0130 UTC.=



Headline:
Tropical Low 21U forecast to develop into a tropical cyclone in the Indian Ocean over the weekend.

Areas affected:
Warning zone: None.

Watch zone: None.

Cancelled zones: None.

Details of Tropical Low 21U at 2:00 am AWST:
Intensity: tropical low, sustained winds near the centre of 55 kilometres per hour with wind gusts to 85 kilometres per hour.
Location: within 75 kilometres of 13.7 degrees South, 118.5 degrees East , 620 kilometres northwest of Broome and 740 kilometres north of Port Hedland .
Movement: west at 17 kilometres per hour .

Tropical Low 21U is located in the Indian Ocean well to the west northwest of the Kimberley, and is moving towards the west. It is forecast to develop into a tropical cyclone on Saturday, well to the northwest of the WA coast. It is then expected to continue to move to the southwest over open waters with no direct impacts at any Australian mainland or Island communities.

Hazards:
No direct impacts are expected at any Australian mainland or Island communities.

Details:

	Time (AWST)	Intensity Category	Latitude (decimal deg.)	Longitude (decimal deg.)	Estimated Position Accuracy (km)
0hr	2 am February 21	tropical low	13.7S	118.5E	75
+6hr	8 am February 21	tropical low	14.0S	117.1E	100
+12hr	2 pm February 21	tropical low	14.3S	115.9E	115
+18hr	8 pm February 21	tropical low	14.7S	114.8E	120
+24hr	2 am February 22	tropical low	14.8S	113.6E	125
+36hr	2 pm February 22	1	15.1S	111.3E	145
+48hr	2 am February 23	2	15.6S	109.2E	145
+60hr	2 pm February 23	2	16.4S	106.9E	165
+72hr	2 am February 24	3	17.4S	105.2E	185

pocketbox

IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0101 UTC 21/02/2025
Name: Tropical Low  
Identifier: 21U
Data At: 0000 UTC
Latitude: 14.1S
Longitude: 116.9E
Location Accuracy: within 50nm (95 km)
Movement Towards: west (265 deg)
Speed of Movement: 13 knots (23 km/h)
Maximum 10-Minute Wind: 30 knots (55 km/h)
Maximum 3-Second Wind Gust: 45 knots (85 km/h)
Central Pressure: 1004 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:   nm (  km)
Radius of Maximum Winds:   nm (  km)
Dvorak Intensity Code: T2.0/2.0/D0.5/24HRS SST:S0.0/06HRS
Pressure of outermost isobar: 1008 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:  21/0600: 14.7S 115.4E:     055 (105):  030  (055): 1004
+12:  21/1200: 14.9S 114.3E:     050 (090):  030  (055): 1004
+18:  21/1800: 15.0S 113.2E:     060 (110):  035  (065): 1001
+24:  22/0000: 15.1S 112.1E:     055 (105):  035  (065): 1001
+36:  22/1200: 15.4S 110.0E:     065 (125):  040  (075):  998
+48:  23/0000: 16.0S 107.9E:     075 (140):  050  (095):  992
+60:  23/1200: 17.0S 106.1E:     090 (165):  055  (100):  989
+72:  24/0000: 18.1S 104.5E:     100 (190):  060  (110):  983
+96:  25/0000: 20.9S 102.5E:     155 (285):  070  (130):  973
+120: 26/0000: 24.1S 101.7E:     205 (375):  055  (100):  984
REMARKS:
Tropical Low 21U remains sheared with the low level centre to the northeast of
persistent convection.

Locating the low level centre continues to be difficult with cirrus blocking
the low level centre in the first few visible images of the day. The
circulation is likely still displaced about 50nm to the northeast of the
mid-level circulation linked to the deep convection. No recent scatterometry
passes to verify the location.

Dvorak analysis: DT has averaged 2.5 over the past 3 hours based on a shear
pattern, however as the low level centre is still poorly defined this may not
be reliable. MET is 1.5 based on a S trend, and PAT adjusted to 2.0. FT/CI=2.0
based on PAT. Objective guidance is not yet available. Intensity is set to 30
knots.  

The environmental conditions for 21U appear finely balanced in the next 24-48
hours. Shear may be moderate to high at times as 21U sits on the western edge
of an upper ridge. Upper support is good, but guidance suggests that the
poleward outflow to the southwest may be lost over the weekend. While dry
mid-level air to the west is unlikely to impact the system in the short term,
the current moist infeed from the north may be lost by Saturday. From Sunday,
the development of 21U may be aided by interaction with an upper trough to the
southwest. If the low level centre does move into the lower shear environment
over the next 24 hours, being a small system it may react quickly and develop
into a tropical cyclone overnight tonight or tomorrow  

There is high confidence that 21U will be steered to the west southwest in the
next few days due to a mid-level ridge to the south. The ridge will shift east
by Monday as a mid-level trough approaches from the southwest, and 21U should
begin moving towards the south. As it weakens mid next week, it may be steered
towards the southeast by the mid-level trough, however it is expected to
dissipate while still well to the west of the Australian mainland.

Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 21/0730 UTC.


Headline:
Tropical Low 21U forecast to develop into a tropical cyclone in the Indian Ocean over the weekend.


Areas affected:
Warning zone: None.

Watch zone: None.

Cancelled zones: None.


Details of Tropical Low 21U at 8:00 am AWST:
Intensity: tropical low, sustained winds near the centre of 55 kilometres per hour with wind gusts to 85 kilometres per hour.
Location: within 95 kilometres of 14.1 degrees South, 116.9 degrees East , 710 kilometres north northwest of Port Hedland and 710 kilometres northwest of Broome .
Movement: west at 23 kilometres per hour .

Tropical Low 21U is located in the Indian Ocean well to the north of the Pilbara and is moving towards the west. It is forecast to develop into a tropical cyclone later Saturday, well to the northwest of the WA coast. It is then expected to continue to move to the southwest over open waters with no direct impacts at any Australian mainland or Island communities.


Hazards:
No direct impacts are expected at any Australian mainland or Island communities.


Details:

	Time (AWST)	Intensity Category	Latitude (decimal deg.)	Longitude (decimal deg.)	Estimated Position Accuracy (km)
0hr	8 am February 21	tropical low	14.1S	116.9E	95
+6hr	2 pm February 21	tropical low	14.7S	115.4E	105
+12hr	8 pm February 21	tropical low	14.9S	114.3E	90
+18hr	2 am February 22	tropical low	15.0S	113.2E	110
+24hr	8 am February 22	tropical low	15.1S	112.1E	105
+36hr	8 pm February 22	1	15.4S	110.0E	125
+48hr	8 am February 23	2	16.0S	107.9E	140
+60hr	8 pm February 23	2	17.0S	106.1E	165
+72hr	8 am February 24	2	18.1S	104.5E	190

Next Issue
The next Forecast Track Map will be issued by 3:00 pm AWST Friday

pocketbox

IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0720 UTC 21/02/2025
Name: Tropical Low  
Identifier: 21U
Data At: 0600 UTC
Latitude: 14.6S
Longitude: 116.9E
Location Accuracy: within 50nm (95 km)
Movement Towards: west southwest (240 deg)
Speed of Movement: 9 knots (17 km/h)
Maximum 10-Minute Wind: 20 knots (35 km/h)
Maximum 3-Second Wind Gust: 45 knots (85 km/h)
Central Pressure: 1006 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:   nm (  km)
Radius of Maximum Winds:   nm (  km)
Dvorak Intensity Code: T1.5/2.0/S0.0/24HRS SST:W0.5/06HRS
Pressure of outermost isobar: 1008 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:  21/1200: 14.8S 115.6E:     065 (125):  025  (045): 1007
+12:  21/1800: 14.9S 114.4E:     070 (130):  025  (045): 1006
+18:  22/0000: 15.1S 112.9E:     065 (125):  025  (045): 1006
+24:  22/0600: 15.2S 111.6E:     065 (120):  025  (045): 1006
+36:  22/1800: 15.6S 109.0E:     065 (125):  030  (055): 1004
+48:  23/0600: 16.5S 107.0E:     080 (145):  035  (065): 1001
+60:  23/1800: 17.6S 105.4E:     095 (180):  040  (075):  998
+72:  24/0600: 19.0S 104.0E:     110 (205):  045  (085):  994
+96:  25/0600: 21.8S 102.5E:     160 (295):  060  (110):  981
+120: 26/0600: 24.5S 102.1E:     205 (375):  045  (085):  990
REMARKS:
Tropical Low 21U continues to be affected by high shear, limiting any
development today.  

A elongated weak low level centre is evident in visible satellite imagery about
80 nm to the northeast of the mid-level circulation linked to the deep
convection. ASCAT imagery at 0050 UTC verified that there was no low level
centre underneath the convection with maximum winds near the centre at 15 to 20
kn. There has been 25 kn observed under the convection to the southwest.

Dvorak analysis: DT has averaged 1.5-2.0 over the past 3 hours based on a shear
pattern. The low level centre is still poorly defined this may not be reliable.
MET/PAT is 1.5 based on a S trend. FT=1.5 based on MET/PAT. CI held at 2.0 due
to restraints of initial weakening. Objective guidance is not yet available.
Intensity is set to 20 knots.   

The system today has been affected by high shear and with a weak low level
circulation it is now not expected to reach tropical cyclone strength until
Monday.  The environmental conditions for 21U appear finely balanced in the
next 24-48 hours. Shear may continue to be moderate to high at times as 21U
sits on the western edge of an upper ridge. Upper support is good, but guidance
suggests that the poleward outflow to the southwest may be lost over the
weekend. While dry mid-level air to the west is unlikely to impact the system
in the short term, The current moist infeed from the north may be lost by
Saturday. From Sunday, the development of 21U may be aided by interaction with
an upper trough to the southwest. If the system continues to be affected by
high shear over the next 48 hours, it may fail to develop into a tropical
cyclone at all.  

There is high confidence that 21U will be steered to the west southwest in the
next few days due to a mid-level ridge to the south. The ridge will shift east
by Monday as a mid-level trough approaches from the southwest, and 21U should
begin moving towards the south. As it weakens mid next week, it may be steered
towards the southeast by the mid-level trough, however it is expected to
dissipate while still well to the west of the Australian mainland.  

Guidance from 12UTC Thursday 20 February has the system about 60nm further west
in a lower shear environment this morning. They were indicating development
over the weekend. However the 00UTC guidance improved on the initial position
and most delayed any development into a tropical cyclone until at least Monday,
if at all. This is more consistent with the forecast track issued.  

Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 21/1330 UTC.


Headline:
Tropical Low 21U struggling to intensify, now forecast to develop into a tropical cyclone in the Indian Ocean from Monday.


Areas affected:
Warning zone: None.

Watch zone: None.

Cancelled zones: None.


Details of Tropical Low 21U at 2:00 pm AWST:
Intensity: tropical low, sustained winds near the centre of 35 kilometres per hour with wind gusts to 85 kilometres per hour.
Location: within 95 kilometres of 14.6 degrees South, 116.9 degrees East , 660 kilometres north northwest of Port Hedland and 870 kilometres north northeast of Exmouth .
Movement: west southwest at 17 kilometres per hour .

Tropical Low 21U is located in the Indian Ocean well to the north of the Pilbara and is moving towards the west. It is forecast to develop into a tropical cyclone during Monday, well to the northwest of the WA coast. It is then expected to continue to move to the southwest over open waters with no direct impacts at any Australian mainland or Island communities.


Hazards:
No direct impacts are expected at any Australian mainland or Island communities.


Details:

	Time (AWST)	Intensity Category	Latitude (decimal deg.)	Longitude (decimal deg.)	Estimated Position Accuracy (km)
0hr	2 pm February 21	tropical low	14.6S	116.9E	95
+6hr	8 pm February 21	tropical low	14.8S	115.6E	125
+12hr	2 am February 22	tropical low	14.9S	114.4E	130
+18hr	8 am February 22	tropical low	15.1S	112.9E	125
+24hr	2 pm February 22	tropical low	15.2S	111.6E	120
+36hr	2 am February 23	tropical low	15.6S	109.0E	125
+48hr	2 pm February 23	tropical low	16.5S	107.0E	145
+60hr	2 am February 24	tropical low	17.6S	105.4E	180
+72hr	2 pm February 24	1	19.0S	104.0E	205

Next Issue
The next Forecast Track Map will be issued by 9:00 pm AWST Friday