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Tropical Cyclone Sandra (19P) Tracking Southward at 12 Knots

March 14th, 2013 Category: Tropical Cyclones

Tropical Cyclone Sandra (19P) – March 13th, 2013

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Track of Tropical Cyclone Sandra (19P) - March 10th, 2013 © Univ. of Wisconsin

Track of TC 19P

Tropical Cyclone Sandra (19P), located approximately 325 nm southwest of Noumea, New Caledonia, has tracked southward at 12 knots over the past six hours.

Animated enhanced infrared satellite imagery shows the low level circulation center (LLCC) has been fully exposed for the past 18 hours but remains well organized. A recent ASCAT pass indicated 35 to 40 knot winds along the eastern periphery. The current intensity has been maintained above the Dvorak estimates from PGTW, PHFO, and NFFN, which indicate a much weaker system than the ASCAT pass suggests.

Total precipitable water imagery indicates dry air wrapping into the LLCC from the western periphery and has nearly separated the central core of tropical moisture from the larger source of tropical moisture to the northeast. Upper level analysis indicates a trough to the southwest and ridging to the northeast are creating high levels (30 to 40 knots) of vertical wind shear (VWS).

Continued inflow of dry air and high VWS will start the extra-tropical transition process within the next 12 hours, and will be fully extra-tropical by TAU 36. Based on good agreement in the model guidance, there is high confidence in the forecast track. Maximum significant wave height is 20 feet

Tropical Cyclone Sandra (19P) Expected to Weaken

20.4S 151.8E

March 13th, 2013 Category: Tropical Cyclones

Tropical Cyclone Sandra (19P) – March 12th, 2013

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Track of Tropical Cyclone Sandra (19P) - March 10th, 2013 © Univ. of Wisconsin

Track of TC 19P

Tropical Cyclone Sandra (19P) will gradually weaken as strong vertical wind shear (VWS) persists and sea surface temperatures (SSTs) drop to below 25 Celsius after TAU 24.

There is a distinct possibility that Sandra will dissipate before end of forecast due to the high VWS and low SSTs. The JTWC forecast is laid with high confidence close to model consensus despite the moderate spread in the available numeric guidance. Maximum significant wave height is 23 feet.

Tropical Cyclone Sandra Tracking South-southwestward at 8 Knots

21.2S 152.5E

March 13th, 2013 Category: Tropical Cyclones

Tropical Cyclone Sandra (19P) – March 11th, 2013

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Track of Tropical Cyclone Sandra (19P) - March 10th, 2013 © Univ. of Wisconsin

Track of TC 19P

Tropical Cyclone Sandra (19P), located approximately 270 nm west-southwest of Noumea, New Caledonia, has tracked south-southwestward at 08 knots over the past six hours.

Animated multispectral satellite imagery shows the low level circulation center has become almost fully exposed as the convection has significantly weakened and sheared southward. The initial position is based on the above animation with high confidence.

The initial intensity is based on the high end of Dvorak estimates from PGTW, PHFO, and NFFN. Upper level analysis indicates the system has moved well south of the ridge axis and into an area of strong (30-40) knot northerly vertical wind shear (VWS).

The cyclone is tracking along the western periphery of a deep subtropical ridge and is expected to continue along this track until it becomes embedded in the baroclinic zone and becomes a cold core low by TAU 48.

Tropical Cyclone Sandra (19P) Forecast to Continue Tracking Southward

17.5S 153.9E

March 12th, 2013 Category: Tropical Cyclones

Tropical Cyclone Sandra (19P) – March 11th, 2013

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Track of Tropical Cyclone Sandra (19P) - March 10th, 2013 © Univ. of Wisconsin

Track of TC 19P

Tropical Cyclone Sandra (19P) is tracking slowly along the western periphery of the deep subtropical ridge (STR) positioned to the east. Since the STR is expected to remain north-south oriented, TC 19P is forecast to continue tracking southward through TAU 72.

The system is forecast to begin extra-tropical transition (ETT) by TAU 48 and should complete ETT by TAU 72. Dynamic model guidance is in good agreement with the bulk of the models supporting the current JTWC forecast track. TC 19P is to weaken significantly after TAU 24 as the system encounters strong vertical wind shear and tracks over cooler SSTs. A sharper weakening trend is expected after TAU 36 as TC 19P tracks over very cold SSTs (less than 23C). Overall, there is high confidence in the JTWC forecast track.

Tropical Cyclone Sandra (19P) Weakens Over Past 12 Hours

20.4S 151.1E

March 12th, 2013 Category: Tropical Cyclones

Tropical Cyclone Sandra (19P) – March 11th, 2013

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Track of Tropical Cyclone Sandra (19P) - March 10th, 2013 © Univ. of Wisconsin

Track of TC 19P

Tropical Cyclone Sandra (19P), located approximately 350 nm northwest of Noumea, New Caledonia, has tracked south-southeastward at 05 knots over the past six hours.

Animated infrared (IR) satellite imagery indicates that the system has weakened over the past 12 hours with deep convection decreasing in areal extent. A METOP-A image depicts a well-defined center with a microwave eye feature; however, deep convective banding has become more fragmented. There is good confidence in the initial position based on this image.

The initial intensity is assessed at 90 knots based on the lower end of Dvorak intensity estimates ranging from 90 to 102 knots. Maximum significant wave height is 30 feet.