Tropical Cyclone Anja

[Cookie]

its looking good

[Somerset Squall]

Agreed Cookie, the LLC of 93S has really tightened today and thus the storm has now been declared Tropical Cyclone Anja, the first cyclone of the south indian tropical cyclone season 2009/10, located just south of Diego Garcia. Deep convection is persisting healthily over the LLC, and and an eye like feature is emerging. Therefore, I don't think it will be long before Anja becomes a cat 1 on the SS scale- this cyclone looks really impressive currently, especially for a storm that is only around 12 hours old.

Anja is currently being steered westwards along the northern periphery of a subtropical ridge to the south. A trough is forecast to break down the ridge which will allow Anja to move southwards. Anja has a good 72hrs to strengthen before the southward motion takes the cyclone over cooler waters, initiating extratropical transition. Shear is low, waters are warm and outflow is good, so Anja has the potential to become intense, just how intense I really wouldn't like to say currently until I've seen what the storm does over the next 12hrs.

Anja is thankfully no threat to land.

[Somerset Squall]

Anja's intensity has been adjusted to 45kts. However, I think this is conservative. An eye is becoming clearly discernable, and I think the intensity is nearer 55kts. Based on the satellite run below, Anja seems to be rapidly intensifying:

[Cookie]

yeah this has really gotten up fast

[Somerset Squall]

It's nice to see a tropical cyclone spinning the other way, lol. Here's hoping for an active south indian ocean season. I reckon JTWC will upgrade to cat 1 come next advisory.

[Cookie]

It's nice to see a tropical cyclone spinning the other way, lol. Here's hoping for an active south indian ocean season. I reckon JTWC will upgrade to cat 1 come next advisory.

I sware you say that every year, and every year I go oh yeah it is :lol:

[Somerset Squall]

LOL Cookie. This is even more true now!

Anja has bombed overnight! JTWC have risen the intensity to 90kts (cat 2), but latest satellite imagery estimates now put Anja at 100kts, making the storm a cat 3 on the SS scale. Pressure has fallen to 948mb. This is an amazing rate of intensification. Anja has another 72hrs to intensify, and cat 4 is not out of the equation.

Anja is sat in an environment of low shear, warm sea surface temperatures and high ocean heat content, and excellent outflow, particularly in a poleward direction. Anja has a well defined eye with excellent spiral banding. Anja will continue to move westwards then will veer southwards as the ridge to the south breaks down.

[Cookie]

wow, talk about flying out the traps

[Somerset Squall]

Anja continues to intensify, and intensity is now at 105kts. JTWC peak Anja at 120kts which seems reasonable as Anja is now moving southwestwards which will eventually take the cyclone over cooler waters initiating weakening then extratropical transition. The ridge to the south will continue to break down allowing a southward turn in about 24hrs time. Anja will then accelerate southeastwards into the westerlies whilst completing ET.

[Cookie]

recently we've had some epic hurricanes lately! in both the west east pacfic as well as the SIO

[Somerset Squall]

And this is early too! Nov and Dec aren't usually known for strong cyclones in the Southern Hemisphere, usually that's Jan and Feb.

[Cookie]

what has caused the sudden surge?

[Somerset Squall]

Not sure really. We've seen a fair few invests in the South Indian Ocean, though shear heavily disrupted development in each. Anja just managed to find a lull in the shear. Shear should continue to ease down in the basin as a whole over the next month as the weather settles into the Summer pattern.

[Cookie]

for the life of me, I cant find the dam link I read it on.

but I read a link that suggest the strength of Anja and the massive surge from invest to cyclone was helped in some way by the moon.

now I know that moon has a lot affect on the sea but was not aware of its affects on hurricanes?

[Somerset Squall]

Anja's structure has changed significantly today, but winds around the centre remain at 105kts. Much of the banding has dissapeared and the storm respresents a midget cyclone. Anja consists of a small, well defined eye surrounded by a solid, circular ring of convection. This satellite appearance suggests that Anja has become annular- not a common occurance for TC's as a whole. Anja will move over cooler waters overnight, but it still expected to strengthen as poleward outflow increases towards a passing trough, and because of the annular properties which will allow Anja to survive longer over colder waters. Eventually though, Anja will become extratropical.

As for the above Cookie, don't really know, lol.

[Cookie]

its ok

very small

[Somerset Squall]

Anja became a cat 4 this morning, with intensity peaking at 115kts. The tiny cyclone had a pinhole eye at the time. Since then, Anja has remained small, but lost it's annular properties and has now rapidly weakened under heavy shear and decreasing sea temps. Intensity has been reduced to 75kts. Because Anja is small, more rapid weakening is expected before transition to a weak extratropical cyclone in 36hrs time.

[Cookie]

going down very fast

[Cookie]

all but gone now

ZCZC 011

WTIO30 FMEE 180634

RSMC / TROPICAL CYCLONE CENTRE / LA REUNION

TROPICAL CYCLONE TECHNICAL BULLETIN (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER : 17/4/20092010

1.A TROPICAL DEPRESSION 4 (EX-ANJA)

2.A POSITION 2009/11/18 AT 0600 UTC :

WITHIN 20 NM RADIUS OF POINT 21.6S / 66.3E

(TWENTY ONE DECIMAL SIX DEGREES SOUTH AND SIXTY SIX DECIMAL THREE

DEGREES

EAST)

MOVEMENT : SOUTH 5 KT

3.A DVORAK ANALYSIS : 2.0/2.5 /W 0.5/6 H

4.A CENTRAL PRESSURE : 999 HPA

5.A MAX AVERAGE WIND SPEED (10 MN) : 30 KT

RADIUS OF MAXIMUM WINDS (RMW) : NIL

6.A EXTENSION OF WINDS BY QUADRANTS (KM):

30 KT NE: SE: 070 SO: NO:

7.A FIRST CLOSED ISOBARE (PRESSURE / AVERAGE DIAM): 1010 HPA / 600 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: SHALLOW

1.B FORECASTS:

12H: 2009/11/18 18 UTC: 25.1S/67.5E, MAX WIND=030KT, FILLING UP.

24H: 2009/11/19 06 UTC: 29.0S/71.7E DISSIPATING.

36H: 2009/11/19 18 UTC: 34.4S/78.1E DISSIPATED.

2.B OTHER INFORMATIONS:

T=2.0 AND CI=2.5

FIRST VISIBLE IMAGERY OF THIS MORNING HAS BEEN HELPFUL TO RELOCALISE

THE

CENTER MORE EASTWARDS THAN PREVIOUSLY ESTIMATED.

THE LOW LEVEL VORTEX IS NOW FULL EXPOSED WESTNORTHWEST OF THE

RESIDUAL

CONVECTION.

EARLY FIX SUGGEST THAT THE SYSTEM HAS SLOW DOWN ITS SOUTHWARDS TRACK

OVER

TH EPAST 6 HOURS.

QUICKSCAT OF 02:10Z SUGGEST THAT WINDS HAVE STRONGLY WEAKEN WITHIN

THE

SMALL CIRCULATION (NEAR GALE FORCE WINDS ONLY OVER THE SOUTHEASTERN

QUADRANT). IT'S ON THIS BASIS THAT THE SYSTEM IS DOWGRADED TO THE

SIMPLE

TROPICAL DEPRESSION STATUS.

EX-ANJA CONFIRMS ITS EVACUATION TOWARDS THE MID-LAT. IN FACT, IT

SHOULD

MERGE WITHIN THE COLD FRONT LOCATED TO THE SOUTHWEST OVER THE NEXT 36

HOURS.

AN INTERESTING POINT TO NOTE IS THAT THIS KIND OF TRACK OF ANJA

(PARABOLIC TRACK AND CYCLOLYSIS WITHIN THE EXTRATROPICAL AREA) IS

VERY

UNUSUAL FOR A NOVEMBER TC IN THE SWIO ...=

NNNN