IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
at: 1917 UTC 24/01/2019
Name: Tropical Cyclone Riley
Identifier: 12U
Data At: 1800 UTC
Latitude: 16.6S
Longitude: 119.0E
Location Accuracy: within 30 nm [55 km]
Movement Towards: west northwest [285 deg]
Speed of Movement: 4 knots [7 km/h]
Maximum 10-Minute Wind: 50 knots [95 km/h]
Maximum 3-Second Wind Gust: 70 knots [130 km/h]
Central Pressure: 985 hPa
Radius of 34-knot winds NE quadrant: 90 nm [165 km]
Radius of 34-knot winds SE quadrant: 60 nm [110 km]
Radius of 34-knot winds SW quadrant: 60 nm [110 km]
Radius of 34-knot winds NW quadrant: 90 nm [165 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: 20 nm [35 km]
Dvorak Intensity Code: T3.5/3.5/D1.0/24HRS STT:D0.5/06HRS
Pressure of outermost isobar: 1002 hPa
Radius of outermost closed isobar: 110 nm [205 km]
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 25/0000: 16.6S 118.6E: 035 [070]: 055 [100]: 979
+12: 25/0600: 16.7S 118.1E: 045 [080]: 060 [110]: 976
+18: 25/1200: 16.8S 117.7E: 055 [105]: 065 [120]: 972
+24: 25/1800: 17.0S 117.2E: 070 [130]: 070 [130]: 969
+36: 26/0600: 17.3S 116.0E: 090 [165]: 070 [130]: 969
+48: 26/1800: 17.6S 114.4E: 110 [200]: 065 [120]: 972
+60: 27/0600: 17.8S 112.5E: 130 [235]: 055 [100]: 979
+72: 27/1800: 18.0S 110.3E: 145 [270]: 045 [085]: 987
+96: 28/1800: 19.1S 106.6E: 190 [355]: 040 [075]: 989
+120: 29/1800: 20.0S 102.9E: 280 [515]: 030 [055]: 995
REMARKS:
Riley's latest position is based on overnight IR imagery along with observations
from Rowley Shoals. Deep convection has consolidated near the centre and covers
the low level centre.
Moderate easterly shear provides a clear shear pattern with the centre 1/3 into
the strong T gradient yielding a DT 0f 3.5. MET is 3.0 based on a D- trend and
PAT is 3.5. FT based on DT/PAT. ADT gives a 1-minute wind speed of 51 knots.
SATCON estimate of 53 knots 1-minute mean wind speed. Current Intensity is 50
knots [10-min mean winds].
Recent movement has been towards the west northwest, however the longer term
trend is to the west southwest, away from the west Kimberley coast. The main
steering influence is the subtropical ridge over SE Australia. The forecast
track remains generally west southwest parallel to the Pilbara coast during
Friday and Saturday. NWP is in good agreement with this movement. A more
southerly track which may take the system closer to the WA Pilbara coast on
Saturday remains a slight chance.
Riley is positioned near the upper level ridge with diffluent outflow
equatorward and poleward. CIMMS analysis shows 20 knots of easterly shear over
the system. The system is surrounded by deep moisture and SSTs are around
29/30C. Conditions are favourable for further development.
A monsoonal surge combined with dual outflow pattern suggests that rapid
intensification is also possible in the next 24 to 36 hours. Peak intensity of
70 knots is forecast during Saturday. Increasing vertical wind shear resulting
from the upper ridge moving south away from the system combined with dry air
around the western and northern sectors is forecast to prevent further
intensification from late Saturday or early Sunday. A mid-level ridge to the
southwest of WA later in the weekend and early next week is expected to maintain
a west southwest track in the longer term.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 25/0130 UTC by Perth TCWC.
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
at: 1253 UTC 25/01/2019
Name: Tropical Cyclone Riley
Identifier: 12U
Data At: 1200 UTC
Latitude: 16.9S
Longitude: 117.8E
Location Accuracy: within 30 nm [55 km]
Movement Towards: west southwest [258 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: 981 hPa
Radius of 34-knot winds NE quadrant: 100 nm [185 km]
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: 100 nm [185 km]
Radius of 48-knot winds NE quadrant: 40 nm [75 km]
Radius of 48-knot winds SE quadrant: 40 nm [75 km]
Radius of 48-knot winds SW quadrant: 40 nm [75 km]
Radius of 48-knot winds NW quadrant: 40 nm [75 km]
Radius of 64-knot winds:
Radius of Maximum Winds: 30 nm [55 km]
Dvorak Intensity Code: T3.0/3.5/S0.0/24HRS STT:W0.5/06HRS
Pressure of outermost isobar: 998 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: 25/1800: 17.0S 117.3E: 040 [080]: 060 [110]: 974
+12: 26/0000: 17.2S 116.8E: 055 [100]: 060 [110]: 974
+18: 26/0600: 17.5S 116.1E: 065 [125]: 055 [100]: 978
+24: 26/1200: 17.8S 115.3E: 080 [145]: 050 [095]: 982
+36: 27/0000: 18.0S 113.3E: 100 [180]: 045 [085]: 985
+48: 27/1200: 18.3S 111.2E: 120 [220]: 035 [065]: 991
+60: 28/0000: 18.3S 109.0E: 140 [255]: 035 [065]: 991
+72: 28/1200: 18.6S 107.2E: 155 [290]: 030 [055]: 994
+96: 29/1200: 19.4S 103.7E: 200 [370]: 030 [055]: 994
+120: 30/1200: 19.4S 100.5E: 290 [535]: 030 [055]: 993
REMARKS:
Riley's position is based on recent microwave passes and is consistent with
available surface observations.
The tropical cyclone has shown signs of weakening over the last few hours.
Microwave imagery showed an exposed low level centre with deep convection
located to the northwest of the centre. EIR imagery shows grately reduced cold
cloud however a new burst of deep convection has appeared to the north of the
centre in the last hour.
The system is still embedded in ample moisture and SSTs are around 29C. It is
under 25-30 knots of easterly shear and satellite imagery would support this.
Shear analysis over the last three hours yields a DT of 3.0. MET is 2.5 based on
W- trend, PAT agrees and FT is set to 3.0 with CI held at 3.5. Scatterometer
passes around 01Z indicated 50 knot winds in northern quadrants, not extending
into southern quadrants. CIMSS ADT is at T3.9 while NESDIS is at T3.8. SATCON
has fluctuated during the day ranging from 66 to 60 to currently 67 knots
[1-minute winds]. Final intensity estimate is set at 50 knots 10-minute mean
wind speed.
Recent movement is towards the west southwest, consistent with model guidance.
The main steering influence is the subtropical ridge over SE Australia. The
forecast track remains generally west southwest during Friday and Saturday. NWP
is in good agreement with this movement. A more southerly track which may take
the system closer to the WA Pilbara coast on Saturday remains a slight chance.
Shear is above 25 knots and may increase further, making rapid intensification
unlikely. While it is possible it may still intensify to Category 3 during the
early hours of Saturday, this is looking unlikely. Increasing vertical wind
shear resulting from the upper ridge moving south away from the system combined
with dry air around the western and northern sectors is forecast to cause
weakening during Saturday and Sunday. A mid-level ridge to the southwest of WA
later in the weekend and early next week is expected to maintain a west
southwest track in the longer term.
Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 25/1930 UTC by Perth TCWC.
