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
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.
At 2pm WST 24 February a weak tropical low (15U) was located near 13.0S 112.8E, about 960 kilometres north northwest of Karratha. It is expected to track to the west and gradually develop, and by Friday there is a high chance of it reach tropical cyclone intensity.
It will move to the south of Christmas Island during Thursday, and although it is unlikely to produce gales at the Island, it will result in an freshening of the northwesterly monsoonal flow, and an increase in shower and thunderstorm activity.
On Saturday it should pass to the south of the Cocos (Keeling) Islands. A period of gale force winds are possible on Saturday if it passes close enough to the Islands.
Likelihood of this system being a tropical cyclone in the Western Region on:
Thursday:
Low
Friday:
High
Saturday:
High
H. REMARKS...THIS INTENSITY ESTIMATE WAS DERIVED USING 4 KM IR DATA. 5/10
BANDING RESULTS IN A DT OF 2.5. MET AND PT ARE 1.5. FT IS BASED ON MET DUE
TO UNCERTAINTY IN LLCC LOCATION AND BECAUSE THE BANDING WAS NOT CLEAR CUT.
(1) AN AREA OF CONVECTION (INVEST 98S) HAS PERSISTED NEAR
13.7S 116.3E, APPROXIMATELY 526 NM NORTH-NORTHEAST OF LEARMONTH,
AUSTRALIA. ANIMATED ENHANCED INFRARED IMAGERY AND A 231900Z GMI
89GHZ MICROWAVE IMAGE DEPICT A CONSOLIDATING LOW LEVEL CIRCULATION
CENTER WITH PERSISTENT DEEP CONVECTION. RADIAL OUTFLOW, LOW VERTICAL
WIND SHEAR (10-15KTS) AND WARM SEA SURFACE TEMPERATURES (29-30C)
CREATE FAVORABLE CONDITIONS FOR FURTHER DEVELOPMENT. GLOBAL MODELS
INDICATE INVEST 98S WILL TRACK WESTWARD AND INTENSIFY QUICKLY OVER
THE NEXT 36-48 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED
AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE
NEAR 1002 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT
TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS MEDIUM.
