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Tropical Cyclone Dumile (07S) Near Madagascar – January 3rd, 2013

11.1S 51.5E

January 3rd, 2013 Category: Image of the day, Tropical Storms

Tropical Storm 07S – January 1st, 2013

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Track of Tropical Storm 07S - January 2nd, 2013 © Univ. of Wisconsin

Track of TS 07S

Tropical Cyclone Dumile (07S), located approximately 85 nm northwest of La Reunion, has tracked southward at 13 knots over the past six hours. Here the system can be seen northeast of Madagascar. Maximum significant wave height is 34 feet.

Animated multispectral and enhanced infrared satellite imagery shows convective organization has continued to weaken and that the system has lost its eye. An AMSU-B 89 ghz microwave image continues to show a microwave eye feature but weak convection over the northern eyewall and the bulk of the deep convection is now confined to the southwestern quadrant.

The initial intensity is maintained at 65 knots, based upon congruent Dvorak intensity estimates of the same intensity from PGTW and KNES, which is consistent with the current storm structure. There is high confidence in the initial position based on the eye feature in the microwave imagery and radar imagery from FMEE.

Upper-level analysis reveals TC 07S has strong poleward outflow into the westerlies to the south but moderate (10-20 knots) vertical wind shear (VWS). Dumile is tracking southward along the western periphery of the deep subtropical ridge (STR) positioned to the east. The system is forecast to recurve around the STR and accelerate southeastward after TAU 24 and begin extra-tropical transition (ETT) near TAU 48 and complete ETT by TAU 72.

TC 07S is forecast to maintain 65 knots for the next 12 hours due to the upper-level conditions and warm sea surface temperatures (SST) (26-28 degrees Celsius) and then subsequently weaken through the forecast period due to increasing VWS and cooler SST (less than 25ºC). Dynamic model guidance as well as ensemble guidance remains in tight agreement supporting the JTWC forecast track with high confidence.

Tropical Cyclone Dumile (07S) Tracking Southward at 13 Knots

13.2S 56.4E

January 3rd, 2013 Category: Tropical Storms

Tropical Storm 07S – January 1st, 2013

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Track of Tropical Storm 07S - January 2nd, 2013 © Univ. of Wisconsin

Track of TS 07S

Tropical Cyclone Dumile (07S), located approximately 200 nm north of La Reunion, has tracked southward at 13 knots over the past six hours.

Animated infrared satellite imagery shows that a 16-nm ragged eye has developed over the past six hours; however, with the exception of the eyewall convection, deep convective banding has diminished. An SSMIS 37 ghz image depicts a microwave eye feature (broken ring over the north quadrant), fragmented deep convective banding north wrapping into the east quadrant and tightly-curved shallow banding elsewhere.

Based on the improved eyewall convection, the Dvorak intensity estimates have increased to 65 knots from all agencies, therefore, the initial intensity is assessed at 65 knots. This is consistent with the recent SATCON estimates of about 70 knots. There is high confidence in the initial position based on the eye feature.

TC 07S is tracking just west of southward along the western periphery of the deep subtropical ridge (STR) positioned to the east. The system is forecast to recurve around the STR and accelerate southeastward after TAU 36. Dynamic model guidance as well as ensemble guidance is in tight agreement supporting the JTWC forecast track with high confidence.

The recent FMEE upper-air sounding also bolsters the dynamic guidance showing northeast flow at 25 to 35 knots, indicative of the strong STR and further supporting the westward bias to the forecast track. TC 07S is forecast to peak near 75 knots by TAU 12 to 24 due to the favorable upper-level conditions. By TAU 36, the system should begin to weaken due to increasing vertical wind shear (VWS) and cooler SST (less than 25C).

Dumile should begin extra-tropical transition (ETT) near TAU 48 and should complete ETT by TAU 72. Concurrently, significant weakening is forecast due to cold SST (less than 20C) and strong VWS associated with strong midlatitude westerly flow impinging on the system. Maximum significant wave height is 28 feet.

Tropical Cyclone Dumile (07S) Tracking South-southeastward

15.9S 54.1E

January 2nd, 2013 Category: Tropical Storms

Tropical Storm 07S – December 31st, 2012

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Track of Tropical Storm 07S - January 1st, 2013 © Univ. of Wisconsin

Track of TS 07S

Tropical Cyclone Dumile (07S), located approximately 370 nm north of La Reunion, has tracked south-southeastward at 14 knots over the past six hours. Maximum significant wave height is 24 feet.

Animated multispectral satellite imagery shows the central convection has deepened as feeder bands wrapped tighter into the low level circulation center. The initial position was based on the above animation and from a microwave pass. Upper level analysis indicates the system has maintained a mesoscale anticyclone that is enhancing radial outflow. This is readily evident on animated water vapor imagery.

The cyclone is tracking along the western periphery of a subtropical ridge to the east that has weakened from the approach of a mid-latitude trough from the southwest. The system is expected to steadily intensify over the next 48 hours as the good radial outflow persists.

After TAU 48, the steering ridge will weaken further causing the cyclone to accelerate southeastward into the baroclinic zone. Increasing vertical wind shear and cooling sea surface temperatures will cause the system to steadily decay. TC 07S will commence extra-tropical transition by TAU 96 and become a cold-core low by TAU 120. The available numerical guidance is in excellent agreement, lending high confidence to this track forecast.

Tropical Storm Dumile (07S) Tracking Southwestward Towards Madagascar

11.1S 53.6E

January 1st, 2013 Category: Tropical Storms

Tropical Storm 07S – December 30th, 2012

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Track of Tropical Storm 07S - January 1st, 2013 © Univ. of Wisconsin

Track of TS 07S

On December 28 a low pressure area continued to organize, with a significant increase in convection, located just to the west of an anticyclone. Tropical Cyclone Dumile (07S), located approximately 525 nm north of La Reunion, has tracked southwestward at 03 knots over the past six hours. Maximum significant wave height is 21 feet.

Animated multispectral satellite imagery shows a well defined low level circulation center (LLCC) with a primary band of deep convection wrapping from the southern periphery into the northern half of the LLCC. The convection remains strongest near the center and in the northern half of the system.

The organization remains well defined but has struggled over the last 24 hours to intensify. Upper level analysis indicates the mesoscale anticyclone continues to provide good equatorward outflow, but has been weak on the poleward side of the system. This lack of strong dual outflow channels appears to be the main factor limiting stronger development.

The current intensity is estimated at 45 knots. Animated water vapor imagery shows the poleward outflow channel has started to improve in the past six hours and should help to intensify the system as it tracks south- southwestward along the northwestern extension of a deep layered subtropical ridge (STR) located to the southeast.

A mid-latitude trough, to the south of Madagascar, will track eastward weakening the western extent of the STR over the next 24 hours. As the trough tracks to the south of the STR, the STR itself will shift, bringing the track for TC 07S more southward.

In the extended forecast, a second mid-latitude trough will cross over southern Africa into the Indian Ocean and again weaken the STR, allowing the track for TC 07S to shift to the southeast. By TAU 96 the system is expected to begin weakening due to increasing vertical wind shear, decreasing sea surface temperatures and interaction with the second mid-latitude trough. Extra-tropical transition is expected to begin by TAU 120. Model guidance is in good agreement through TAU 48 but begins to differ in the timing of the recurvature to the southeast.

Tropical Storm Earl (07S) Racing Over Gulf of Saint Lawrence – September 5th, 2010

47.3N 59.8W

September 5th, 2010 Category: Image of the day, Tropical Storms

Tropical Storm Earl (07L) - September 4th, 2010

Track of TS 07L - September 4th, 2010 © Univ. of Wisconsin

Track of TS 07L

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At 8:00 PM EDT (00:00 UTC), the center of Tropical Storm Earl (07L) was located near latitude 49.4 North, longitude 60.4 West. Part of the system is visible in the main image, north of New York’s Long Island and Cape Cod, Massachusetts. In the full image, much more of the storm is visible, obscuring most of the Canadian terrain below, while the eastern seaboard of the USA can be observed to the south.

Earl is moving toward the north-northeast near 45 mph (75 km/hr). This motion will bring Earl across extreme southeastern Quebec and Newfoundland tonight.

Maximum sustained winds are near 65 mph (100 km/hr) with higher gusts. Earl is forecast to become post-tropical tonight.
Tropical storm force winds extend outward up to 250 miles (400 km) from the center. Estimated minimum central pressure is 966 mb (28.53 inches).

Hazards affecting land include winds and rainfall. Tropical storm conditions are still occurring over extreme eastern Nova Scotia and Prince Edward Island. These conditions will spread over western Newfoundland tonight. Rains associated with Earl should decrease tonight over the region.