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Severe Tropical Cyclone Robyn


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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

Invest 94S has become sufficiently organised to be classified as a tropical cyclone, with intensity at 35kts. Deep convection continues to persist over the LLC, and some fairly impressive banding is evident on the western and southern sides of the storm. 23S is in a moderately sheared environment, though this is expected to ease over the next 24hrs promoting strengthening of the cyclone over warm water. 23S is expected to move southeastwards along the southwestern periphery of an steering ridge to the northeast. This will eventually take 23S over cooler waters in around 72hrs. Also at this time, shear is expected to increase dramatically as the system moves into the mid-lattitiude westerlies. Though the cyclone is to the west of the Cocos Islands and is not far away at present, the easterly shear will probably keep most of the convection away from the islands as 23S passes to the southwest. Other than this, 23S is not expected to significantly affect land.

post-1820-12702286207955_thumb.jpg

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

23S has become Tropical Cyclone Robyn, with intensity rising to 55kts. Curved banding surrounds a solid central dense overcast feature. JTWC are expecting a peak of 70kts before waters cool and shear increases, which will initiate weakening. The track forwecast has also changed. The subtropical ridge formerly steering Robyn southeastwards has now re-orientated to lie to the east of the cyclone deflecting the track southwards. Once Robyn weakens, she will be steered by the low level easterly flow towards the west as the shear rips the system apart.

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

Several of the cyclones have been names of people I know too. The names seem far more usual in the Australian region wheras the idea in other regions is that the name is to be fairly uncommon as to not offend.

Robyn has weakened slightly this morning. The moderate shear from which she initially suffered appears to have re-developed again, and is elongating the cyclone northeast-southwest. Intensity has been reduced to 50kts, and it seems that Robyn will no longer make cat 1 status on the SS scale. Even stronger shear lies to the south which will enforce weakening proper in 36hrs time.

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Posted
  • Location: Tiree
  • Location: Tiree

20100404.1700.meteo7.x.ir1km.23SROBYN.60kts-978mb-149S-918E.100pc.jpg

UW - CIMSS

ADVANCED DVORAK TECHNIQUE

ADT-Version 8.1.1

Tropical Cyclone Intensity Algorithm

----- Current Analysis -----

Date : 04 APR 2010 Time : 163000 UTC

Lat : 15:12:26 S Lon : 91:39:39 E

CI# /Pressure/ Vmax

4.3 / 972.7mb/ 72.2kt

Final T# Adj T# Raw T#

4.3 4.3 3.2

Latitude bias adjustment to MSLP : +2.7mb

Center Temp : -64.7C Cloud Region Temp : -66.1C

Scene Type : UNIFORM CDO CLOUD REGION

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : INDIAN

Dvorak CI > MSLP Conversion Used : PACIFIC

Tno/CI Rules : Constraint Limits : MW HOLD

Weakening Flag : OFF

Rapid Dissipation Flag : OFF

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

Robyn has strengthened despite the shear. Intensity has risen to 60kts. Moderate northeasterly shear is still impinging on Robyn, but excellent poleward outflow has allowed the cyclone to intensify despite this. Deep convection has been persistant, and well defined banding features have become evident again after they all but dissipated this morning. Based on the strengthening in the face of the shear, JTWC are once again expecting Robyn to become a cat 1 on the SS scale- with forecast peak of 70kts.

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

Robyn has strengthened a little more this morning to 65kts, and has been upgraded to a severe tropical cyclone by BOM. An ill defined eye appeared a little earlier in the central dense overcast feature but this has since dissapeared. Moderate to high shear continues to buffer Robyn, but strong poleward outflow continues, for now, to prevent weakening. However, with the continued southeasterly motion, Robyn will be moving into even higher shear and once the trough to the south moves away, poleward outflow will wane also. This will cause weakening to begin in around 24hrs time.

As Robyn weakens, it will feel the effects of the low level easterly flow which will accelerate the declining tropical cyclone westwards. It is interesting to note that Robyn is forecast to still be at tropical storm intensity as it crosses 90E, if this does indeed occur it will move into MeteoFrance's area of responsibility and acquire a second name.

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Posted
  • Location: Taunton, Somerset
  • Weather Preferences: Snow, thunder, strong winds
  • Location: Taunton, Somerset

Robyn has weakened faster and sooner than expected. Shear has risen to 40kts which has stripped the majority of convection away from Robyn's centre. Intensity has decreased to 45kts. Robyn should turn towards the west tomorrow and further weaken in high shear and restricted outflow.

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