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Tropical Storm Sanvu (03W) Expected to Become Typhoon by Thursday

16.1N 140.8E

May 23rd, 2012 Category: Tropical Storms

Tropical Storm Sanvu (03W) - May 23rd, 2012

Enhanced image

Track of Tropical Storm Sanvu (03W) - May 23rd, 2012 © Univ. of Wisconsin

Track of TS 03W

On May 17, a disturbance associated with a low presure area, and the ITCZ formed southeast of Guam. Late on May 20, the JTWC issued a TCFA on the system because of improving equator-ward outflow. Early on May 21, the JMA upgraded the low-pressure area to a tropical depression, and the JTWC also upgraded the system to a tropical depression later.

Early on May 22, the JMA upgraded the system to a tropical storm and named it Sanvu, as the tropical depression intensified even as it moved northwestward away from coastal waters of the Marianas.

As of 5pm yesterday, Tropical Storm Sanvu was still churning northwestward at 12 miles per hour with maximum sustained winds near 85 km/hr (45 knots) with higher gusts. At that time, Sanvu’s center was 130 miles west-northwest of Guam, 155 miles west of Rota, 190 miles west-southwest of Tinian, and 200 miles southwest of Saipan. Tropical Storm Force Winds (62-117 km/hr) extend outward up to 185 kilometers (100 nautical miles) from the center. Sanvu is an average-sized tropical cyclone with a diameter of 480 kilometers (260 nautical miles).

A tropical storm warning at that time was still in effect for Guam and Rota, while a tropical storm watch was also still in effect for Tinian and Saipan. The storm brought numerous showers and isolated thunderstorms in the morning until last night, Tuesday. NWS said that scattered showers and isolated thunderstorms will linger into Wednesday night in the region.

Sanvu is expected to continue moving NW for the next 12 to 24 hours, before turning more northerly on Friday and recurving NNE to NE-ward on Saturday. On the forecast track, the core of Sanvu will pass very close to Iwo To by early Saturday morning. The system is forecast to continue intensifying and will likely become a Typhoon on Thursday.

Typhoon Vamco (11W)

18.7N 157.1E

August 20th, 2009 Category: Tropical Cyclones

Typhoon Vamco - August 20th, 2009

Typhoon Vamco - August 20th, 2009

Enhanced image of Vamco

Enhanced image of Vamco

Track of Typhoon Vamco - August 20th, 2009 © Univ. of Wisconsin

Track of Typhoon Vamco

Typhoon 11W (Vamco), located approximately 970 nm east-southeast of iwo to, has tracked north-northwestward at 02 knots over the past six hours.

The steering environment remains weak as the mid-level subtropical ridge (str) located to the east-northeast of Vamco has been interrupted by an upper level tropical tropospheric trough (TUTT) cell that has developed from the upper level into the mid-level. Upper level analysis indicates the poleward outflow from Vamco into another TUTT cell located to the north remains well defined and in association with the equatorward outflow channel has helped to increase the maximum intensity over the past 06 hours.

The vertical wind shear (VWS) has remained low over the past 12 hours and the sea surface temperatures (SST) have helped to fuel the recent increase in intensity. The current position and intensity are based on animated multispectral satellite imagery, and on dvorak estimates from PGTW, KNES, and RJTD.

Vamco is expected to remain in a weak steering environment through the next 48 hours as the tutt cell to the east-northeast begins to move northward towards the mid-latitude flow and get absorbed. This will allow the mid-level str to build westward increasing track speed for Vamco beyond tau 48.

An approaching mid-latitude trough will track north of the STR axis, creating a weakness around tau 72 allowing a turn northward. The VWS and SST will remain favorable for continued development through tau 72. The upper level environment will maintain in a dual outflow pattern through the early portion of the forecast helping to enhance and sustain the intensity of Vamco through tau 72.

An approaching mid-latitude trough is forecast to track along the northern axis of the STR, creating a weakness in the STR around tau 72 allowing for a more northward track. As the trough digs southward increased upper level outflow will be captured in the mid-latitude flow, helping to slow the weakening of Vamco through tau 120. Additionally, the digging trough will enhance to break in the str allowing Vamco to recurve along the orthwestern periphery of the str. Increased VWS, decreased SST values, and less favorable ocean heat content will be the primary factors causing the system to begin weakening beyond tau 96.