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Posts tagged Madagascar

Tropical Cyclone Imelda East of Madagascar – April 15th, 2013

19.3S 52.0E

April 15th, 2013 Category: Image of the day, Tropical Cyclones

Tropical Storm Twenty One (21S) – April 14th, 2013

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Track of Tropical Storm Twenty One (21S) - April 14th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S) is tracking along the southwest periphery of a near-equatorial ridge and is expected to recurve westward after TAU 36 as a building subtropical ridge to the south assumes steering.

As the system continues to move poleward, the vertical wind shear (VWS) will steadily increase causing its gradual erosion and, finally, dissipation by TAU 72. The available numeric guidance is in overall good agreement with WBAR as the sole outlier extending the track southeastward beyond 72 hours. The remainder of the models recurve the vortex westward, albeit at varying increments. The JTWC track forecast is laid closely to model consensus with high confidence.

Tropical Cyclone Imelda (21S) Tracking Southeastward at 14 Knots

20.1S 52.0E

April 15th, 2013 Category: Tropical Cyclones

Tropical Storm Twenty One (21S) – April 14th, 2013

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Track of Tropical Storm Twenty One (21S) - April 14th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S), located approximately 340 nm east-northeast of La Reunion, has tracked southeastward at 14 knots over the past six hours. Maximum significant wave height is 32 feet.

Animated infrared satellite imagery indicates the system has significantly deepened. Additionally, an eye has opened then closed in the past 12 hours. The initial intensity is based on closely-grouped agency fixes and lined up well with a central warm spot on an SSMI-S microwave pass.

The initial intensity is based on a consensus of subjective Dvorak estimates from PGTW, KNES, and FIMP. Upper level analysis indicates the system is south of a ridge axis in an area of moderate (15-20 knot) northwesterly vertical wind shear (VWS); however, poleward outflow, which is enhancing the convection, remains robust, as evidenced on animated water vapor imagery.

Tropical Cyclone Imelda (21S) Expected to Turn Back to Southward Trajectory

20.6S 52.7E

April 14th, 2013 Category: Tropical Cyclones

Tropical Storm Twenty One (21S) – April 13th, 2013

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Track of Tropical Storm Twenty One (21S) - April 12th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S) should revert to a generally poleward trajectory by TAU 12 after it rounds the southern edge of the steering ridge. After TAU 48, a building subtropical ridge to the south will begin to deflect the cyclone westward.

The system will peak intensity over the next 12 hours as good outflow persists; afterwards, increasing vertical wind shear (VWS) will gradually weaken and eventually dissipate the system by TAU 72. The available numeric guidance is widely spread and lends low confidence to the track forecast. Maximum significant wave height is 25 feet.

Tropical Cyclone Imelda (21S) Restrengthens, Continues Towards Madagascar – April 14th, 2013

10.7S 53.4E

April 14th, 2013 Category: Image of the day, Tropical Cyclones

Tropical Storm Twenty One (21S) – April 13th, 2013

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Track of Tropical Storm Twenty One (21S) - April 12th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S), located approximately 315 nm northeast of La Reunion, has tracked west-southwestward at 03 knots over the past six hours.

Animated infrared satellite imagery shows a deepened central dense overcast feature over a well-defined low-level circulation center. This is also evident on an SSMI-S microwave pass. The initial position is based on closely grouped agency fixes and on the above microwave image with high confidence. The initial intensity is an average of subjective Dvorak estimates from PGTW, KNES, and FIMP.

Upper level analysis (ULA) indicates the system is between two ridge axes – one to the north and another to south in an area of low (05-10 knot) vertical wind shear (VWS). TC 21S has unpredictably tracked west-southwestward over the past 12 hours. From the same ULA, the steering ridge to the east was not significantly weakened by a passing mid-latitude trough as previously forecast. Instead, the ridge was deformed into a kidney-shaped anticyclone along a meridional axis. In response to this transformation to the steering ridge, 21S jogged westward. This recent development necessitated a slight change in the JTWC track forecast philosophy.

Tropical Cyclone Imelda (21S) Dissipating

12S 54.8E

April 13th, 2013 Category: Tropical Cyclones

Tropical Storm Twenty One (21S) – April 12th, 2013

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Track of Tropical Storm Twenty One (21S) - April 12th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S) is expected to struggle in maintaining its structure but will continue to track along the southwestern periphery of a near-equatorial ridge to the northeast.

Vertical wind shear (VWS) values are expected to increase as the system tracks poleward, contributing to the gradual dissipation by TAU 36. There is a distinct possibility that the cyclone will dissipate sooner. As the system weakens, the steering flow will begin to shift to lower levels. Available numerical model shows a large spread in the tracks, therefore, there is low confidence in the current track forecast. Maximum significant wave height is 18 feet.