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Tropical Cyclone Emang (09S) Expected to Dissipate

6.7S 74.5E

January 17th, 2013 Category: Tropical Storms

Tropical Storm 09S – January 17th, 2013

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Track of Tropical Storm 09S - January 17th, 2013 © Univ. of Wisconsin

Track of TS 09S

Recent scatterometer data on Tropical Cyclone Emang (09S), supports a 30 to 35 knot system with the strongest winds over the southern semi-circle, enhanced by the subtropical high. Due to the lack of convective structure, Dvorak intensity estimates have decreased to 25 to 30 knots; however, the initial intensity is assessed slightly higher at 35 knots.

TC 09S is located within a marginal environment, under convergent upper-level flow, which is inhibiting convective development, and is embedded along the northern periphery of the subtropical high. Emang is forecast to continue weakening and should dissipate by TAU 12. The system will be closely monitored for signs of regeneration.

Tropical Cyclone Emang (09S) Tracking West-Southwestward

10.7S 74.5E

January 17th, 2013 Category: Tropical Storms

Tropical Storm 09S – January 16th, 2013

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Track of Tropical Storm 09S - January 17th, 2013 © Univ. of Wisconsin

Track of TS 09S

Tropical Cyclone Emang (09S),

located approximately 490 nm south-southeast of Diego Garcia, has tracked west-southwestward at 07 knots over the past six hours. Maximum significant wave height is 14 feet.

Animated multispectral satellite imagery (MSI) indicates an exposed low-level circulation center (LLCC) with isolated deep convection over the southeast quadrant. MSI also shows that the LLCC has begun to elongate and unravel over the past six hours. This weakening trend is clearly depicted in a 170607z TRMM 37ghz image, which shows a broad LLCC with shallow banding over the southeast quadrant.

Tropical Cyclone Emang (09S) Tracking Southwestward

12.5S 75.9E

January 15th, 2013 Category: Tropical Storms

Tropical Storm 09S – January 14th, 2013

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Track of Tropical Storm 09S - January 14th, 2013 © Univ. of Wisconsin

Track of TS 09S

Tropical Cyclone Emang (09S), located approximately 515 nm southeast of Diego Garcia, has tracked southwestward at 06 knots over the past six hours. Maximum significant wave height is 15 feet.

Animated enhanced infrared satellite imagery shows the system has maintained overall convective banding even as the low level circulation center has moved under the central convection. The initial intensity is based on congruent Dvorak estimates from PGTW, KNES and FMEE. The initial position is based on the above animation with poor confidence.

Upper level analysis indicates the system is 07 degrees north of the ridge axis in an area of light to moderate 10-20 knot vertical wind shear (VWS). The cyclone is tracking along the northern periphery of a deep-layered subtropical ridge to the south. This ridge is expected to build over the next 12-24 hours causing Emang to track on a more westward trajectory. As the system gets closer the the ridge axis, the VWS will weaken and promote gradual intensification. The limited available numerical guidance is in tight agreement. Given the solid steering pattern and the tight grouping in the numeric guidance, there is high confidence in the JTWC track forecast.

Tropical Cyclone Emang (09S) Picks Up Speed

11.1S 77.3E

January 14th, 2013 Category: Tropical Storms

Tropical Storm 09S – January 13th, 2013

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Track of Tropical Storm 09S - January 13th, 2013 © Univ. of Wisconsin

Track of TS 09S

Tropical Cyclone Emang (09S), located approximately 525 nm east- southeast of Diego Garcia, has tracked westward at 05 knots over the past six hours. Maximum significant wave height is 13 feet.

Animated infrared (IR) satellite imagery depicts a partially-exposed low-level circulation center (LLCC) with a recent flare of convection over the northwest quadrant of the LLCC. The initial position based on the IR imagery and extrapolation from an ASCAT pass with fair confidence.

The initial intensity remains assessed at 35 knots based on Dvorak intensity estimates of 35 knots and is consistent with storm structure as organization has not improved over the past 12 hours. Upper level analysis reveals TC 09S is located within a marginal environment with poor outflow and moderate (10-20 knots) vertical wind shear. The system remains within a weak steering environment but has picked up speed over the last six hours tracking westward under the influence of a building subtropical ridge (STR) to the south.

TC 09S is expected to slowly track southwestward by TAU 12 along the northern periphery of this building STR. After TAU 48, the system should track more west- southwestward as the steering STR responds to deep mid-latitude trough. Emang is expected to intensify slowly to a peak intensity of 65 knots by TAU 120 under the moderately favorable environmental conditions throughout the forecast period. Dynamic model guidance is in fair agreement with continued differences in track speed, as the European models are showing a slower track westward. Low confidence remains in the JTWC forecast track due to the differences in track speeds in the models and the past erratic motion, but is improving based on the recent increase in motion.

Tropical Cyclone 09S Remaining Stationary

13.2S 75.4E

January 13th, 2013 Category: Tropical Storms

Tropical Storm 09S – January 12th, 2013

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Track of Tropical Storm 09S - January 12th, 2013 © Univ. of Wisconsin

Track of TS 09S

Tropical Cyclone 09S, located approximately 545 nm east-southeast of Diego Garcia has tracked westward at 1 knot, exhibiting quasistationary movement. Maximum significant wave height is 12 feet.

Animated infrared satellite imagery depicts a consolidating system with improved deep convective banding wrapping into a well-defined low-level circulation center (LLCC). An SSMIS microwave image wind product shows 30 to 35 knot winds located in the formative banding to the south. Based on this, and overall improved storm structure, the intensity is assessed at 35 knots.

Upper level analysis reveals TC 09S is located slightly equatorward of the subtropical ridge axis and vertical wind shear has decreased to moderate (10-20 knot) levels allowing for the recent improvement. The system is currently located in a weak steering environment between the steering influences of the low to mid-level near equatorial ridge and subtropical ridge (STR).

TC 09S is forecast to remain nearly quasistationary for the next 24 hours as it slowly intensifies. After TAU 24, the system will slowly track more southwest as the mid to deep level subtropical ridge to the southeast becomes the more dominant steering influence and cause a more westward track through TAU 120. It will struggle to intensify through the forecast as VWS will remain at moderate levels and increase to strong levels in the later TAUs. Dynamic model guidance is widely spread but generally agrees on slow track to the south to southwest and slow intensification. Due to this poor agreement among the models, forecast confidence is low.

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