Tag Archives: Chuuk

Tropical Storm Dolphin Moving West and Organizing Slowly

Tropical Storm Dolphin turned toward the west on Monday and showed signs of more organization.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Dolphin was located at latitude 10.3°N and longitude 158.0°E which put it about 490 miles east-northeast of Chuuk and about 950 miles east-southeast of Guam.  Dolphin was moving toward the west at 8 m.p.h.  The maximum sustained wind speed was 50 m.p.h. and there were gusts to 65 m.p.h.  The minimum surface pressure was 989 mb.

Dolphin is moving over water where the Sea Surface Temperature (SST) is near 29°C.  Satellite imagery suggests that the circulation became more symmetrical although many of the stronger thunderstorms are west of the center of circulation.  A strong upper level ridge is located northwest of Dolphin and it is generating easterly winds winds over the top of the circulation.  The vertical wind shear may be the reason why the stronger thunderstorms are west of the center.  The upper level ridge is also contributing to an outflow channel to the southwest of Dolphin which cold pump out more mass.  The vertical wind shear is inhibiting the intensification of Dolphin.  However, as the tropical storm moves farther west, it could move into an area where the upper level winds are lighter.  Given the warm SSTs, a decrease in shear would lead to more intensification.

A subtropical ridge is expected to steer Dolphin toward the west during the next two or three days.  A turn toward the west-northwest will be possible later in the week if a weakness develops in the ridge.  On the anticipated track Dolphin could approach Guam in 48 to 60 hours and it could be a typhoon by that time.

Tropical Depression 07W Forms South of Pohnpei

The active period over the tropical Western North Pacific Ocean continues with the development of another tropical cyclone south of Pohnpei.  At 8:00 p.m. EDT on Wednesday the center of Tropical Depression 07W was located at latitude 4.4°N and longitude 156.8°E which put it about 160 miles south-southeast of Pohnpei.  The tropical depression was stationary.  The maximum sustained wind speed was 35 m.p.h. and there were gusts to 50 m.p.h.  The minimum surface pressure was 1004 mb.

A low level circulation center formed within a broad area of thunderstorms and the system was classified as Tropical Depression 07W.  The strongest thunderstorms are mainly located in the northwestern part of the circulation.  An upper level ridge located east of the depression is generating southeasterly winds over the top of it which is producing modest vertical wind shear.  The wind shear is the probably reason why most of the thunderstorms are northwest of the center of circulation.  The wind shear will also limit the rate of intensification during the next day or two.  Eventually the depression is expected to move farther west into an area with less wind shear and it could intensify more quickly.

Tropical Depression 07W is located near the western end of a subtropical ridge and the steering currents are relatively weak.  It may not move much for the next 12 to 24 hours.  Later this week the ridge is expected to strengthen and steer the depression toward the west-northwest.  On its projected track the depression could approach Pohnpei in two or three days.