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Tropical Cyclone Irina Expected to Move Towards Mozambique

27.6S 29.5E

March 4th, 2012 Category: Tropical Storms

Tropical Cyclone Irina (14S) - March 3rd, 2012

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Track of TS 14S - March 4th, 2012 © Univ. of Wisconsin

Track of TS 14S

Tropical Cyclone Irina (14S), located approximately 90 nm east-southeast of Maputo, Mozambique, has tracked southwestward at 06 knots over the past six hours. Maximum significant wave height is 18 feet. Animated infrared satellite imagery shows that TC 14S is regenerating deep convection and turning back into the Mozambique Channel.

Despite the recent movement away from land, rainbands in the outer periphery are generating downpours along the coast, especially between Maputo and Inhambane, Mozambique. The other concentration of heavy convection associated with the storm is displaced to the distant southwest, a product of convergence within the belt of easterlies feeding into the system.

An ASCAT image depicts an expansive area of persistent gales over the southeastern quadrant. An SSMIS image shows the improved organization in the convective banding, and the 37 ghz image reveals a developing microwave eye. PGTW upper level streamline analysis depicts a cyclone just north of Inhambane, and its associated subsidence is stifling convection over the northeastern quadrant of the storm.

The cyclone has been retrograding slowly southwest and neither filling nor deepening. Total precipitable water loops confirm a general lack of deep moisture over the northern semicircle. Sscatterometry data also confirm the lop-sided nature of the system, with expansive areas of gale force winds over the poleward semicircle and a very narrow area of gales on the equatorial side. Animated water vapor imagery indicates that the system has lost the superb equatorial outflow channel that existed 24 hours ago, but vigorous poleward outflow persists, and there is adequate outflow over the western quadrant.

The upper level cyclone is severely impinging on outflow over the northern semicircle. Water vapor animation also shows a deep mid-latitude trough tracking over South Africa that will exert an increasing steering influence on the storm during the next 24 hours, along with a boost to poleward outflow. The upper levels of the storm and the northwesterlies ahead of the trough are going to begin linkage during the next 12 hours.

Currently, Irina is being kept over the western Mozambique Channel by a low- to mid-level anticyclone directly south of Madagascar, which is part of the subtropical ridge. The anticyclone is beginning to give way and reorient eastward, allowing the system to drift back towards the center of the channel. The retreating anticyclone coupled with the southeastward draw from the approaching trough will cause a net southward movement of the storm over the next 24 hours. The majority of model guidance indicates the trough will be a near miss and not couple with the storm, passing over the system between TAU 24 and 48. Following the passage of the trough, the subtropical ridge will rebuild south of Madagascar and Irina will resume movement towards southern Mozambique, where it will maintain intensity at low tropical storm strength in the moderately favorable environment of the Mozambique Channel. Thus, the forecast continues to call for a slow reversal back towards landfall over southern Mozambique after TAU 24 and a relatively flat intensity trend through landfall.

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