(2) AN AREA OF CONVECTION (INVEST 90S) HAS PERSISTED NEAR
11.8S 98.7E, APPROXIMATELY 111 NM EAST-NORTHEAST OF THE COCOS
ISLANDS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 130730Z
AMSR2 89GHZ MICROWAVE IMAGE REVEAL FRAGMENTED FORMATIVE BANDING
WRAPPING INTO A BROAD LOW LEVEL CIRCULATION CENTER. A 130309Z ASCAT-
B IMAGE REVEALS AN ELONGATED CIRCULATION OF MAINLY 15-20KT WINDS IN
THE NORTHERN AND SOUTHERN SEMICIRCLES WITH A SMALL SWATH OF 25KT
WINDS TO THE SOUTH. INVEST 90S IS IN A FAVORABLE ENVIRONMENT FOR
DEVELOPMENT WITH GOOD OUTFLOW ALOFT, LOW TO MODERATE (15-20KTS)
VERTICAL WIND SHEAR, AND WARM (28-30C) SEA SURFACE TEMPERATURES.
GLOBAL MODELS ARE IN GENERAL AGREEMENT THAT INVEST 90S WILL CONTINUE
TO CONSOLIDATE AND TRACK SOUTHWESTWARD OVER THE NEXT 24-36 HOURS.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1003 MB. THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS LOW.
(2) THE AREA OF CONVECTION (INVEST 90S) PREVIOUSLY LOCATED
NEAR 11.8S 98.7E IS NOW LOCATED NEAR 11.7S 97.8E, APPROXIMATELY 59
NM NORTHEAST OF THE COCOS ISLANDS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY AND A 131115Z SSMIS 91GHZ MICROWAVE IMAGE REVEAL A
CONSOLIDATING SYSTEM WITH IMPROVING CONVECTIVE BANDING OVER THE
WESTERN SEMICIRCLE WRAPPING INTO A BROAD CENTER. SURFACE
OBSERVATIONS FROM THE COCOS ISLANDS (YPCC) INDICATE SOUTHERLY WINDS
AT 27KTS WITH SLP 1004MB (3MB 24HR PRESSURE DECREASE). INVEST 90S IS
IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH GOOD OUTFLOW ALOFT,
LOW TO MODERATE (15-20KTS) VERTICAL WIND SHEAR, AND WARM (28-30C)
SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE IN GENERAL AGREEMENT
THAT INVEST 90S WILL CONTINUE TO CONSOLIDATE AND TRACK SOUTHWESTWARD
OVER THE NEXT 24-36 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE
ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED
TO BE NEAR 1001 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO
MEDIUM.
(3) NO OTHER SUSPECT AREAS.
C. SUBTROPICAL SYSTEM SUMMARY: NONE.
3. JUSTIFICATION FOR REISSUE: UPGRADED AREA IN PARA 2.B.(2) TO
MEDIUM.//
BoM編號07U，48小時發展展望中等
At 1100 WST Wednesday 13 January, a tropical low (07U) was located near 11.6S 98.6E, approximately 200 kilometres east-northeast of the Cocos Islands. The low is forecast to move southwest over the next several days. From Thursday evening, conditions become more favourable for development of 07U, and there is a Moderate risk of it developing to tropical cyclone intensity from Friday. It is highly likely for 07U to move west of 90E (the border of the Western Region) during Sunday, though it may be as late as Monday.
Although there isn't any direct impact expected for the Cocos Islands, there is likely to be increased rainfall particularly over the next 24 to 36 hours whilst 07U lies in close proximity.
Likelihood of this system being a tropical cyclone in the Western Region on:
Thursday:Very Low
Friday:Moderate
Saturday:Moderate
WTXS21 PGTW 132200
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 90S)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
120 NM EITHER SIDE OF A LINE FROM 11.8S 97.4E TO 14.3S 95.2E
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 25 TO 30 KNOTS. METSAT
IMAGERY AT 131800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 12.1S 97.2E. THE SYSTEM IS MOVING WEST-SOUTHWESTWARD AT 07
KNOTS.
2. REMARKS:
THE AREA OF CONVECTION (INVEST 90S) PREVIOUSLY LOCATED NEAR 11.8S
97.3E IS NOW LOCATED NEAR 12.1S 97.2E, APPROXIMATELY 15 NM EAST OF
COCOS ISLAND. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A
131541Z MHS 89GHZ MICROWAVE IMAGE REVEAL A CONSOLIDATING SYSTEM WITH
BUILDING DEEP CONVECTION OVERHEAD AND IMPROVING CONVECTIVE BANDING
OVER THE WESTERN SEMICIRCLE WRAPPING INTO A TIGHTENING CENTER.
SURFACE OBSERVATIONS FROM THE COCOS ISLANDS (YPCC) INDICATE
SOUTHERLY WINDS AT 27KTS WITH SLP 1004MB (3MB 24HR PRESSURE
DECREASE). A 131425Z METOP-A ASCAT PASS SHOWS A TIGHT LLCC WITH 20-
25 KNOT WRAPPING WINDS AND SMALL AREA OF 30-35 KNOT WINDS TO THE
SOUTHWEST. INVEST 90S IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT
WITH GOOD POLEWARD OUTFLOW ALOFT, MODERATE (20-25KTS) VERTICAL WIND
SHEAR, AND WARM (28-30C) SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE
IN GOOD AGREEMENT THAT INVEST 90S WILL TRACK SOUTHWESTWARD,
INTENSIFYING TO WARNING THRESHOLD WITHIN THE NEXT 24-36 HOURS.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000 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
142200Z.//
NNNN
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 1848 UTC 14/01/2021
Name: Tropical Low
Identifier: 07U
Data At: 1800 UTC
Latitude: 14.3S
Longitude: 96.1E
Location Accuracy: within 30 nm [55 km]
Movement Towards: southwest [216 deg]
Speed of Movement: 5 knots [9 km/h]
Maximum 10-Minute Wind: 30 knots [55 km/h]
Maximum 3-Second Wind Gust: 45 knots [85 km/h]
Central Pressure: 1001 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:S0.0/6HRS
Pressure of outermost isobar: 1006 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: 15/0000: 14.7S 95.7E: 045 [085]: 030 [055]: 1001
+12: 15/0600: 15.0S 95.3E: 060 [105]: 030 [055]: 1000
+18: 15/1200: 15.4S 94.9E: 065 [120]: 035 [065]: 999
+24: 15/1800: 15.7S 94.4E: 075 [135]: 035 [065]: 998
+36: 16/0600: 16.2S 93.2E: 085 [160]: 040 [075]: 996
+48: 16/1800: 16.7S 92.0E: 105 [195]: 045 [085]: 992
+60: 17/0600: 17.3S 90.8E: 120 [220]: 045 [085]: 993
+72: 17/1800: 17.9S 89.5E: 130 [245]: 045 [085]: 992
+96: 18/1800: 18.5S 87.3E: 165 [310]: 045 [085]: 992
+120: 19/1800: 18.9S 83.6E: 195 [355]: 045 [085]: 992
REMARKS:
An exposed LLCC during the day has slowly moved closer to deep convection by
1800UTC, but remains about 30nm to the northeast of the strong gradient. Dvorak
based on shear pattern, yielding a DT of 3.0. MT and PT suggest a 2.5. FT based
on PT and CI held at 2.5 also based on constraints with initial classification
at 1700UTC 13 January. Intensity set at 30 knots as confirmed by an OSCAT pass
at 1330UTC.
Tropical Low 07U has seen increased persistent deep convection during the
overnight period [during the diurnally favourable time] to the southwest of an
exposed LLCC. It currently lies in a moderate to high [20 to 30 knots CIMSS
12UTC] northeasterly sheared environment with warm SST. There is moderate upper
divergence to the southwest and northwest.
The system will track steadily to the southwest over the coming days under the
influence of a mid level ridge. It will slowly develop over the next 24 for 48
hours as the NE'ly shear eases, possibly reaching tropical cyclone strength
during Saturday morning.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 15/0130 UTC.
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 1909 UTC 16/01/2021
Name: Tropical Cyclone Joshua
Identifier: 07U
Data At: 1800 UTC
Latitude: 17.3S
Longitude: 91.4E
Location Accuracy: within 25 nm [45 km]
Movement Towards: west southwest [242 deg]
Speed of Movement: 6 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: 992 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant: 70 nm [130 km]
Radius of 34-knot winds SW quadrant: 70 nm [130 km]
Radius of 34-knot winds NW quadrant: 40 nm [75 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: 25 nm [45 km]
Dvorak Intensity Code: T2.5/3.0/D0.5/24HRS STT:W0.5/06HRS
Pressure of outermost isobar: 1002 hPa
Radius of outermost closed isobar: 100 nm [185 km]
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 17/0000: 17.6S 90.7E: 040 [080]: 040 [075]: 992
+12: 17/0600: 18.0S 90.0E: 055 [100]: 040 [075]: 992
+18: 17/1200: 18.3S 89.4E: 060 [115]: 040 [075]: 991
+24: 17/1800: 18.6S 88.7E: 070 [130]: 040 [075]: 991
+36: 18/0600: 19.1S 87.4E: 080 [150]: 035 [065]: 991
+48: 18/1800: 19.2S 85.8E: 100 [185]: 035 [065]: 994
+60: 19/0600: 19.4S 84.0E: 115 [210]: 030 [055]: 998
+72: 19/1800: 19.8S 81.7E: 125 [235]: 030 [055]: 998
+96: 20/1800: : : :
+120: 21/1800: : : :
REMARKS:
Following a day-time period of vigorous convection over the centre, since 11UTC
convection has dramatically weakened exposing the centre on IR imagery. The most
recent IR imagery is showing some renewed convection in southern quadrants with
curvature evident. Whilst the cloud structure is quite symmetrical under low
wind shear, without renewed convection the circulation may struggle as a TC and
intensity forecasts have been eased back somewhat.
None of the ascending scat passes [ASCAT/SCATSAT/HY2B] provided coverage over
the circulation, so intensity of 40kn based on Dvorak with some influence from
ADT/SATCON [-45kn]. Dvorak FT estimated at 2.5 [3h curved band 0.5 wrap] but CI
held at 3.0.
The environment remains moderately favourable for the circulation, shear is low
easterly, with upper level outflow assisted by an upper trough to the south,
with deep moisture connected to the tropics. However SSTs are only marginal at
around 27C and there is limited low-level inflow from the north - factors that
may ultimately account for the lack of development.
Latest model guidance have eased back on intensification, and restrict the area
of gales largely to southern quadrants before weakening after about +48h.
A general west southwest track is expected to persist associated with a weak
mid-level ridge to the south.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 17/0130 UTC.
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