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Tropical Cyclone Felleng (13S) East of Madagascar – February 2nd, 2013

21S 51.3E

February 2nd, 2013 Category: Image of the day, Tropical Cyclones

Tropical Cyclone Felleng (13S) – February 1st, 2013

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Track of Tropical Cyclone Felleng (13S) - February 1st, 2013 © Univ. of Wisconsin

Track of TC 13S

Tropical Cyclone Felleng (13S), located approximately 275 nm west-southwest of La Reunion, has tracked south-southeastward at 14 knots over the past six hours. Here, the system can be seen east of Madagascar. Maximum significant wave height at 31 feet.

The current position is based on recent position fixes from multiple reporting agencies and an SSMIS pass. The current intensity of 70 knots is consistent with a consensus of subjective Dvorak estimates and recent automated intensity estimates from CIMSS and CIRA.

Recent animated water vapor satellite imagery shows deep convection persisting over a tightly- wrapped low level circulation center (LLCC) and strong equatorward and eastward outflow driven by an upper-level ridge over the cyclone.

Tropical Cyclone Felleng (13S) Still Tracking Southward

16.4S 52.7E

February 1st, 2013 Category: Tropical Cyclones

Tropical Cyclone Felleng (13S) – January 31st, 2013

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Track of Tropical Cyclone Felleng (13S) - January 31st, 2013 © Univ. of Wisconsin

Track of TC 13S

Tropical Cyclone Felleng (13S), continues to track southward along the western periphery of a north-south oriented subtropical steering ridge (STR). The system should continue to track southward through TAU 36 then will begin to turn south-southeastward as it rounds the southern periphery of the STR.

Here, it can be seen encroaching upon the Madagascar shoreline thanks to the use of the Chelys Satellite Rapid Response System (SRRS) “borders” feature (best observed in full image), which allows the  coastline to be seen through the convection that partially covers it.

Dynamic model guidance is in tight agreement (135 nm spread in model solutions at TAU 96) through TAU 96, therefore, the JTWC forecast is positioned close to the multi-model consensus. There is high confidence in the forecast track. Felleng is expected to weaken rapidly after TAU 24 as it encounters increasing, strong vws associated with an approaching shortwave trough and also tracks over cool SSTs, which range from 25ºC to as low as 20ºC. The system is also forecast to begin extra- tropical transition (ETT) near TAU 48 and should complete ETT by TAU 96 as it becomes embedded in the midlatitude westerlies and begins to accelerate southeastward.

Tropical Cyclone Felleng (13S) Off Coast of Madagascar – February 1st, 2013

16.6S 53.4E

February 1st, 2013 Category: Image of the day, Tropical Cyclones

Tropical Cyclone Felleng (13S) – January 31st, 2013

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Track of Tropical Cyclone Felleng (13S) - January 31st, 2013 © Univ. of Wisconsin

Track of TC 13S

Tropical Cyclone Felleng (13S), located approximately 295 nm west-northwest of La Reunion, has tracked south-southwestward at 10 knots over the past six hours. Here, it can be seen off the coast of Madagascar. Thanks to the use of the Chelys Satellite Rapid Response System (SRRS) “borders” feature (best observed in full image), the country’s coastline is clearly visible despite the convection covering parts of it.

Animated infrared satellite imagery indicates that TC 13S has continued to weaken over the past six hours due to moderate to strong (20 to 30 knots), westerly vertical wind shear (VWS). An SSMIS image indicates that the system has become tilted with the low-level circulation center positioned on the western edge of the deep convection, which is sheared primarily over the eastern semi-circle.

The initial position is based, with good confidence, on the SSMIS 37 ghz image, which shows a microwave eye feature. The initial intensity is assessed at 70 knots based on an average of Dvorak current intensity estimates ranging from 65 to 77 knots. Maximum significant wave height is 30 feet.

Tropical Cyclone Felleng (13S) Now Expected to Weaken Rapidly – January 31st, 2013

13.9S 51.3E

January 31st, 2013 Category: Image of the day, Tropical Cyclones

Tropical Cyclone Felleng (13S) – January 30th, 2013

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Track of Tropical Cyclone Felleng (13S) - January 30th, 2013 © Univ. of Wisconsin

Track of TC 13S

Tropical Cyclone Felleng (13S), located approximately 310 nm northwest of La Reunion (and visible here off the coast of Madagascar), has tracked south-southwestward at 11 knots over the past six hours. Maximum significant wave height is 35 feet.

Animated infrared (IR) satellite imagery indicates that TC 13S has weakened over the past six hours due to moderate (15 to 20 knots) southwesterly vertical wind shear (VWS). IR imagery shows that deep convection is decreasing in areal extent with warming cloud top temperatures.

Despite the cloud-filled eye, a TRMM 37ghz image depicts a small microwave eye feature with the bulk of the deep convection located over the eastern semi- circle. There is high confidence in the initial position based on the TRMM image. The initial intensity is assessed at 105 knots based on Dvorak current intensity estimates ranging from 102 to 115 knots.

Felleng continues to track southward along the western periphery of a north-south oriented subtropical steering ridge (STR). The system should continue to track southward through TAU 48 then will begin to turn south-southeastward to southeastward as it rounds the southern periphery of the STR.

Dynamic model guidance is in tight agreement through TAU 72 but diverges in the extended TAUs due to minor differences in how each model depicts the orientation and strength of the STR. Additionally, GFS indicates a sharp turn south- southwestward, which is likely due to erroneous interaction with a midlatitude shortwave trough. The JTWC forecast is consistent with the previous track forecast and is positioned close to, but slightly faster than, the multi-model consensus. There is high confidence in the forecast track.

In the extended period, there are significant changes to the JTWC intensity forecast. TC 13S is now expected to weaken rapidly after TAU 48 as it encounters strong VWS associated with an approaching shortwave trough and also tracks over cool SST, which range from 25ºC to as low as 20ºC. The system is also forecast to begin extra-tropical transition (ETT) near TAU 96 and should complete ETT by TAU 120 as it becomes embedded in the midlatitude westerlies and begins to accelerate southeastward.

Tropical Cyclone Felleng (13S) North of La Reunion

12S 53.4E

January 30th, 2013 Category: Tropical Cyclones

Tropical Cyclone Felleng (13S) – January 29th, 2013

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Track of Tropical Cyclone Felleng (13S) - January 29th, 2013 © Univ. of Wisconsin

Track of TC 13S

Tropical Cyclone Felleng (13S), located approximately 420 nm north of La Reunion, has tracked west-southwestward at 08 knots over the past six hours. Maximum significant wave height is 30 feet.

Animated enhanced infrared satellite imagery shows the system has significantly deepened with convective bands wrapping tighter into a symmetrical, albeit cloud-filled 22-nm eye. The initial position is fixed with high confidence based on the eye feature in the above animation.

Upper level analysis indicates the system is in the vicinity of a ridge axis in an area of light to moderate (10-15 knot) vertical wind shear (VWS). Furthermore, animated water vapor imagery shows a strong poleward outflow. The cyclone is tracking along the northwest extension of a deep-layered subtropical ridge (STR) to the southeast.

After TAU 24, a mid-latitude trough approaching from the southwest is expected to weaken the str and cause TC 13S to track more poleward. The system is forecast to further intensify due to the continued favorable upper level environment, enhanced by an opening of a poleward outflow channel with the approach of the aforementioned mid-latitude trough.

However, after TAU 72, Felleng will gradually weaken as VWS increases and sea surface temperatures begin to cool. The available numeric guidance is in tight agreement with the sole exception of WBAR that continues to deflect the vortex to the right of the model envelope. There is high confidence in the JTWC track forecast which is laid just to the left of consensus to offset WBAR.