SEIO Tropical Low

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Digital-TC-Chaser

SEIO Tropical Low

#1 Postby Digital-TC-Chaser » Sat Apr 29, 2017 10:45 pm

IDW27700
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
at: 0309 UTC 30/04/2017
Name: Tropical Low
Identifier: 30U
Data At: 0000 UTC
Latitude: 10.0S
Longitude: 101.8E
Location Accuracy: within 30 nm [55 km]
Movement Towards: south southwest [206 deg]
Speed of Movement: 2 knots [4 km/h]
Maximum 10-Minute Wind: 30 knots [55 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:
Radius of Maximum Winds:
Dvorak Intensity Code: T2.5/2.5/D1.5/24HRS STT:D0.5/06HRS
Pressure of outermost isobar: 1010 hPa
Radius of outermost closed isobar: 90 nm [165 km]
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 30/0600: 10.2S 101.6E: 040 [080]: 035 [065]: 1002
+12: 30/1200: 10.3S 101.0E: 055 [100]: 040 [075]: 1002
+18: 30/1800: 10.4S 100.3E: 065 [125]: 045 [085]: 1000
+24: 01/0000: 10.4S 99.5E: 080 [145]: 045 [085]: 997
+36: 01/1200: 10.1S 97.6E: 100 [185]: 040 [075]: 1000
+48: 02/0000: 10.2S 95.5E: 120 [220]: 030 [055]: 1006
+60: 02/1200: 10.1S 93.7E: 140 [255]: 030 [055]: 1005
+72: 03/0000: 10.4S 92.0E: 155 [290]: 025 [045]: 1008
+96: 04/0000: 10.7S 88.4E: 200 [370]: 025 [045]: 1008
+120: 05/0000: 12.4S 85.6E: 290 [535]: 025 [045]: 1008
REMARKS:
The tropical low was located using microwave imagery and animated visible and
infrared imagery with some confidence.

Microwave imagery overnight showed a small tight circulation in the low levels
and upper levels [1806UTC and 2119UTC passes]. Dvorak is problematic due to the
small size and rapid development of the system. Initial classification could be
re-analysed to 00Z Saturday. Based on this and a D+ development, FT and CI are
2.5 at 00Z. Soon to arrive ASCAT should provide more information as to the
surface circulation.

Current intensity is set to 30 knots based on a CI of 2.5.

Shear is currentkly 5 to 10 knots [low] and forecast to remain that way until
mid Monday when it starts to increase. Thus, a strengthening trend is forecast
for the short term. Due to the small size, the system may reach category 2
tonight. A weakening trend is forecast for late Monday. The track has the system
moving over cooler SST's which should further weaken the system



Image





WTXS21 PGTW 300200
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
300 NM EITHER SIDE OF A LINE FROM 10.1S 101.8E TO 12.8S 95.8E
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 290000Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 10.3S 101.7E. THE SYSTEM IS MOVING SOUTH-SOUTHWESTWARD AT 04
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 98S) PREVIOUSLY LOCATED
NEAR 9.9S 101.6E, IS NOW LOCATED NEAR 10.3S 101.7E, APPROXIMATELY
300 NM NORTH-NORTHEAST OF COCOS ISLAND. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY SHOWS A COMPACT BUT WELL DEFINED CIRCULATION WITH
PERSISTENT CONVECTION OVER AND WRAPPING INTO THE CENTER. A 292331Z
SSMIS 91GHZ MICROWAVE IMAGE SHOWS DEEP CONVECTION OVER THE CENTER OF
A LOW LEVEL CIRCULATION WITH DEFINED BANDING. THE DISTURBANCE IS
CURRENTLY LOCATED IN AN AREA OF GOOD DIVERGENCE ALOFT WITH A
POLEWARD OUTFLOW CHANNEL AND WARM SEA SURFACE TEMPERATURES (29-30
CELSIUS). THE SYSTEM IS ALSO POSITIONED IN AN AREA OF LOW (5-10
KNOTS) VERTICAL WIND SHEAR, BUT THE UPPER-LEVEL JET JUST TO THE
SOUTH IS CREATING A STEEP SHEAR GRADIENT AND POTENTIALLY HOSTILE
ENVIRONMENT. GLOBAL MODELS ARE IN AGREEMENT THAT THE SYSTEM WILL
CONTINUE TO TRACK TO THE WEST OVER THE NEXT SEVERAL DAYS, HOWEVER,
THEY ARE MIXED AS TO WHAT DEGREE THE SYSTEM WILL DEVELOP. MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 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.








Warnings in the Australian Region are issued by three separate TCWCs
at Brisbane (Queensland), Perth (Western Australia), and Darwin
(Northern Territory) with Darwin being the RSMC for the region. In
addition to these, a TCWC at Port Moresby, Papua New Guinea (formerly
an Australian territory) issues warnings for a small portion of the
region near and east of the island of New Guinea, and a TCWC at Jakarta,
Indonesia, issues warnings for the region west of 125E and north of
10S. The Papua New Guinea and Indonesian regions have an extremely low
incidence of tropical cyclone occurrences.

The Australian centres avoid use of the term "tropical depression" in
public advices primarily to reduce possible confusion with the use of
the term "depression" in association with extratropical systems; and
also possibly because until recently (early 1990's), in the Southwest
Indian Ocean Basin, a "tropical depression" meant any system with winds
up to 63 kts (hurricane force). The Australian TCWCs utilize a
conversion factor of 0.88 or 0.90 to modify the 1-minute Dvorak scale to
an equivalent 10-minute average scale.

In the Australian Region to qualify as a tropical cyclone a tropical
LOW must be accompanied by gales surrounding more than 50% of the center
of circulation for a period of at least six hours. In order to insure
that adequate warnings are provided, it is not at all unusual for a
system to be named as a tropical cyclone, but later reduced to tropical
LOW status after a careful post-storm analysis reveals that this spatial
distribution of gales criterion was not met, e.g., Isobel and Odette,
2007, and Gabrielle, 2009.
http://australiasevereweather.com/cyclo ... nology.htm
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Digital-TC-Chaser

Re: SEIO Tropical Cyclone Greg

#2 Postby Digital-TC-Chaser » Sun Apr 30, 2017 4:38 am

IDW27700
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
at: 0714 UTC 30/04/2017
Name: Tropical Cyclone Greg
Identifier: 30U
Data At: 0600 UTC
Latitude: 10.4S
Longitude: 101.3E
Location Accuracy: within 20 nm [35 km]
Movement Towards: southwest [231 deg]
Speed of Movement: 6 knots [12 km/h]
Maximum 10-Minute Wind: 35 knots [65 km/h]
Maximum 3-Second Wind Gust: 50 knots [95 km/h]
Central Pressure: 1002 hPa
Radius of 34-knot winds NE quadrant: 50 nm [95 km]
Radius of 34-knot winds SE quadrant: 50 nm [95 km]
Radius of 34-knot winds SW quadrant: 50 nm [95 km]
Radius of 34-knot winds NW quadrant: 50 nm [95 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: 15 nm [30 km]
Dvorak Intensity Code: T3.0/3.0/D1.5/24HRS STT:D0.5/06HRS
Pressure of outermost isobar: 1010 hPa
Radius of outermost closed isobar: 80 nm [150 km]
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 30/1200: 10.6S 101.0E: 035 [065]: 040 [075]: 999
+12: 30/1800: 10.7S 100.3E: 040 [075]: 050 [095]: 993
+18: 01/0000: 10.7S 99.6E: 050 [095]: 050 [095]: 994
+24: 01/0600: 10.5S 98.6E: 060 [110]: 050 [095]: 994
+36: 01/1800: 10.4S 96.5E: 090 [165]: 040 [075]: 1000
+48: 02/0600: 10.4S 94.6E: 115 [215]: 030 [055]: 1005
+60: 02/1800: 10.5S 92.8E: 150 [280]: 030 [055]: 1005
+72: 03/0600: 10.7S 91.0E: 180 [335]: 030 [055]: 1005
+96: 04/0600: 11.1S 87.6E: 235 [435]: 030 [055]: 1005
+120: 05/0600: 12.3S 84.5E: 300 [555]: 030 [055]: 1005
REMARKS:
The tropical low was located using animated visible and infrared imagery with
some confidence.

Dvorak is based on visible imagery and a curved band of 0.7 for the last 2 hours
and 0.5 before that, giving an average DT of 2.8 and an FT/CI of 3.0. PAT
adjusted MET agrees. NESDIS ADT has a CI of 2.8 of 0530UTC.


There has been no recent ASCAT or microwave. Intensity of 35 knots and tropical
cyclone intensity based on Dvorak analysis.

Low to upper level shear is currentkly 5 to 10 knots [low] and forecast to
remain that way in gthe short term. However, low to mid level shear is forecast
to increase Monday, which will also help the entrainment of dry air. Thus, a
strengthening trend is forecast for the short term. Due to the small size, the
system may reach category 2 tonight. A weakening trend is forecast to start
during Monday. However, with light upper winds forecast along the track of the
system for the next 5 or so days, after the forecast weakening on Tuesday, there
remains a moderate chance of the system being a tropical cyclone.

Track is based on a concensus of global models [ECMWF, UK, US-GFS and ACCESS-G]
with steering being dominated by a high pressure ridge to the south.

Image
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