TS 01S (S Indian) - Observations, Interpretations, Analyses

[wxmann_91]

Very, very, very early for a TS in the Southern Hemisphere, but it's a TC nonetheless.

Probably going to be a non-event.



Doesn't look to great right now, and JTWC forecasts it to die




EDIT: Link to Invest that preceded this: Invest 91S

[senorpepr]

Ahh... thanks for posting on this wxmann. Very interesting to see a tropical cyclone in this part of the world in late July. Of course, it's not unheard of... just "interesting."

[Chacor]

Meteo-France carried this as 01R but never issued any warnings...

Based on the JTWC's position it's now into Perth's AOR.

[HURAKAN]

Almost 10 years since the last July cyclone in the South Indian Ocean.

[HURAKAN]

A picture of the storm.

[HURAKAN]

Very, very, very early for a TS in the Southern Hemisphere, but it's a TC nonetheless.

Probably going to be a non-event.

I could argue it's a very late season storm.

The season ended on April-May. It will start in November, therefore, this storm should be a late season storm, not an early season storm.

Like in the Atlantic, was the storm that formed in February in 1952, a late season storm or an early season storm?

Since in the Atlantic the hurricane season always falls in a year and not two, then a storm forming after December but before June, it's considered an early season storm.

In the Southern Hemisphere is different because the season falls between two years.

[Chacor]

Not exactly. The TC year ends June 30 and starts July 1.

[HURAKAN]

Not exactly. The TC year ends June 30 and starts July 1.

http://en.wikipedia.org/wiki/2007-08_Au ... one_season

"The 2007-08 Australian region cyclone season will be an event in the ongoing cycle of tropical cyclone formation. It will run from November 1, 2007 to April 30, 2008. The regional tropical cyclone operational plan also defines a tropical cyclone year separately from a tropical cyclone season; the "tropical cyclone year" began on July 1, 2007 and will end on June 30, 2008."

[RL3AO]

Not exactly. The TC year ends June 30 and starts July 1.

http://en.wikipedia.org/wiki/2007-08_Au ... one_season

"The 2007-08 Australian region cyclone season will be an event in the ongoing cycle of tropical cyclone formation. It will run from November 1, 2007 to April 30, 2008. The regional tropical cyclone operational plan also defines a tropical cyclone year separately from a tropical cyclone season; the "tropical cyclone year" began on July 1, 2007 and will end on June 30, 2008."

So you agree with him?

[HURAKAN]

There is a difference between "tropical cyclone year" and "tropical cyclone season." A season is defined as that part of the year where most of the cyclonic activity is concentrated. In the Southern Hemisphere is usually between Nov. and May.

[Chacor]

Yes. And since the TC year runs July 1 - June 30 (v.s. Atlantic Jan 1 - Dec 31) anything after July 1 goes in the new season

[Chacor]

WOAU06 APRF 300208
40:3:1:24:11S091E999:11:00
IDW21200
SECURITE

HIGH SEAS WEATHER WARNING FOR METAREA 10
ISSUED BY THE AUSTRALIAN BUREAU OF METEOROLOGY, PERTH
AT 0205UTC 30 JULY 2007

Gale Warning FOR THE WESTERN AREA

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 2300UTC
Tropical low 1002hPa near 11S091E moving south southeast at 10 knots.


AREA AFFECTED
Within 240nm of low in southern semicircle.


FORECAST
E/SE winds 25/35 knots. Rough to very rough seas, moderate swell.


WEATHER PERTH

———————————————————————————————————————————
FQAU23 APRF 300205
IDW11900

UPDATED
SECURITE

HIGH SEAS FORECAST FOR METAREA 10
WESTERN AREA 12/30S 90/125E, 30/50S 80/129E
ISSUED BY THE AUSTRALIAN BUREAU OF METEOROLOGY, PERTH

FOR 24 HOURS COMMENCING 2300UTC 30 JULY 2007

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.

PART 1 WARNINGS
1. Gale Warning south of a line 50S085E 30S095E 28S105E 30S115E 40S125E 50S125E
becoming south of a line 50S093E 40S093E 28S110E 28S115E 38S129E at 300600UTC
and south of a line 50S098E 40S098E 32S110E 32S115E 37S129E at 301800UTC.
2. Gale Warning within 240nm of tropical low 1002hPa near 11S091E moving south
southeast at 10 knots.

PART 2 SITUATION AT at 2300UTC
Refer to warnings.
Ridge 30S080E 22S105E 25S129E.

PART 3 FORECAST
Within 150nm of ridge:
Variable winds 5/15 knots. Slight to moderate seas. Moderate swell.
Remainder north of ridge:
S/SE winds 10/20 knots, increasing to 15/25 knots west of 95E and north of 20S.
Moderate seas tending moderate to rough west of 95E, moderate swell.
Remainder south of ridge, outside first warning area:
NW/SW winds 15/25 knots, increasing to 25/33 knots within 180nm of first warning
area. Moderate to rough seas. Moderate to heavy swell.

WEATHER PERTH

[Chacor]

Perth is now issuing warnings.

AXAU01 APRF 300553
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
at: 0553 UTC 30/07/2007
Tropical Cyclone: Tropical Low
Data At: 0400 UTC
Latitude: 11.3S
Longitude: 91.6E
Location Accuracy: within 20 nm [37 km]
Movement Towards: east southeast [104 deg]
Speed of Movement: 7 knots [13 km/h]
Maximum 10-Minute Wind: 30 knots [55 km/h]
Maximum 3-Second Wind Gust: 45 knots [85 km/h]
Central Pressure: 998 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant: 200 nm [370 km]
Radius of 34-knot winds SW quadrant: 200 nm [370 km]
Radius of 34-knot winds NW quadrant:
Radius of Maximum Winds: 30 nm [55 km]
Dvorak Intensity Code: 2.5/2.5/D1.0/24HRS
Pressure of outermost isobar: 1010 hPa
Radius of outermost closed isobar: 90 nm [165 km]
Storm Depth: Medium
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+12: 30/1600: 12.6S 92.3E: 060 [110]: 035 [065]: 994
+24: 31/0400: 13.9S 93.2E: 110 [205]: 040 [075]: 996
+36: 31/1600: 14.4S 92.2E: 150 [280]: 030 [055]: 998
+48: 01/0400: 14.3S 90.9E: 250 [465]: 030 [055]: 1000
+60: 01/1600: 14.2S 89.5E: 300 [555]: 025 [045]: 1002
+72: 02/0400: 14.0S 88.2E: 350 [650]: 025 [045]: 1004
REMARKS:
The low level circulation is well defined with gales particularly likely in
southern quadrants. A strong mid-latitude trough is providing strong upper
outflow to the south of the system. The latest quickscat shows potential gales
near the centre. However convection is likely to struggle to the north of the
system with ongoing shear and also through the diurnal minumum in the
short-term. Cooler ocean waters to the south are also likely be a hindrance to
further development.

The system is expect to continue its southeastward track but the low level
centre may take a more westward track in the longer term should it become more
sheared and be influenced by the strengthening low level ridge.
==
The next bulletin for this system will be issued by: 30/1300 UTC by Perth TCWC.

[Chacor]

IDW23100
40:3:1:24:11S091E999:11:00
SECURITE

HIGH SEAS WEATHER WARNING FOR METAREA 10 ISSUED BY THE
AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING
CENTRE PERTH AT 0447UTC 30 JULY 2007

Gale Warning FOR THE WESTERN AREA

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 0400UTC a tropical low was located within 20 nautical miles of
Latitude eleven decimal three degrees South [11.3 S]
Longitude ninety one decimal six degrees East [91.6 E]
Recent movement southeast at 8 knots.
Maximum winds 30 knots.
Central pressure 998 hPa.

AREA AFFECTED
Within 90 nautical miles of the centre extending to 200 nautical miles
in southern quadrants.

FORECAST
Sustained clockwise winds 30/40 knots in southern quadrants possibly extending
to northern quadrants should the low develop into a tropical cyclone in the next
12 to 24 hours. Rough to very rough seas and moderate swell.


At 1600 UTC 30 July: Within 60 nautical miles of 12.6 South 92.3 East
Central pressure 994 hPa.
Winds to 40 knots near centre.
At 0400 UTC 31 July: Within 110 nautical miles of 13.9 South 93.2 East
Central pressure 996 hPa.
Winds to 35 knots near centre.

Next warning issued by 0700 UTC 30 July 2007.

WEATHER PERTH

[P.K.]

If the tropical low does form into a TC today it will be only the second TC to form in July since the 1969-1970 season (As far back as my spreadsheet goes at the moment from the BT file).

[Aslkahuna]

Latest satellite shows a strongly sheared system now with the convection south of an exposed LLCC.

Steve

[Chacor]

Dead from JTWC.

No longer expected to become a TC according to Perth due to the shear, so they've tentatively stopped bulletins. Here's the last one from 12Z...

AXAU01 APRF 301239
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by PERTH TROPICAL CYCLONE WARNING CENTRE
at: 1239 UTC 30/07/2007
Tropical Cyclone: Tropical Low
Data At: 1200 UTC
Latitude: 12.1S
Longitude: 91.6E
Location Accuracy: within 20 nm [37 km]
Movement Towards: south [180 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: 998 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant: 200 nm [370 km]
Radius of 34-knot winds SW quadrant: 200 nm [370 km]
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: 40 nm [75 km]
Dvorak Intensity Code: T2.0/2.5/W0.5/12HRS
Pressure of outermost isobar: 1010 hPa
Radius of outermost closed isobar: 90 nm [165 km]
Storm Depth: Medium
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+12: 31/0000: 12.9S 91.0E: 060 [110]: 030 [055]: 1000
+24: 31/1200: 13.1S 90.0E: 100 [185]: 025 [045]: 1002
+36: 01/0000: : : :
+48: 01/1200: : : :
+60: 02/0000: : : :
+72: 02/1200: : : :
REMARKS:
The low continues to be hampered by N'ly shear and seems unlikely to reintensify
particularly as it moves over cooler water. Also the strong mid-latitude trough
that has provided strong upper outflow to the south is contracting to the east.


The system may revert to a more westerly track as the low-level centre is
influenced by the strengthening low level ridge.

==
No further technical bulletins are likely to be issued for this system.

[CrazyC83]

This would be like a February or March storm in the Atlantic?

[P.K.]

Well the season doesn't start until November in this region which would compare with late Feb in the N Atl. Systems have been known to form in most months of the year though (Except June but if I go back in the BT far enough I'm sure I'll find one).

We'll have to wait a little longer for 200701 then, no surprise really given the time of year.

[RL3AO]

If comparing to the Atlantic, I would compare it to more like a late April storm.