Tropical Storm Dianmu

[Cookie]

[Somerset Squall]

Indeed Cookie, invest 96W has finally become a tropical depression, with intensity at 25kts. 05W is still quite a broad system, and as a result, despite favourable conditions, any intensification is expected to be modest and slow. This system has more of the look of a monsoon depression which I think may struggle to intensify. Low shear, warm sea temps and strong equatorward outflow should at least allow 05W to become a moderate tropical storm over the next day or two.

05W is moving northwards east of Taiwan towards South Korea along the western side of a subtropical steering ridge to the east. This motion is expected to continue over the next few days though exact landfall in still uncertain. What is likely to happen after 72hrs is the onset of extratropical transition and the waters are much colder around the Korean and Japanese waters.

There pressure is already a rather low 1000mb, indicating that this system is very broad to have such a weak intensity.

[Somerset Squall]

05W has strengthened a little quicker than expected, with a stronger LLC now being evident. Intensity has increased to 35kts, and 05W is upgraded to Tropical Storm Dianmu. Dianmu is still a large monsoonal type system, so further strengthening is still expected to be modest and slow.

[Somerset Squall]

Dianmu's very large but well defined LLC is clear to see on satellite imagery, but the convective canopy is very lopsided. Deep swathes of convection stretch out to the south of the circulation centre, but the northern quadrant is practically convection free. This is due to an upper level low to the north of Dianmu (the same creatures that plagued Bonnie and Colin in the Atlantic), but this feature should move away over the next day or so which should add some moisture for Dianmu to track into. This should allow for the progged intensification (favourable conditions should last about 48hrs), but I still can't see this system getting intense as it is too large to intensify rapidly.

[Cookie]

Plenty to track at the moment eh?

[CardiffStorm]

Latest IR image of Dianmu (in the correct thread this time lol)

[Somerset Squall]

As Jamo's image shows, Dianmu has much more centralised convection now and the storm has accordingly strengthened to 50kts, a little stronger than anticipated. Based on the changed structure of Dianmu, I think this one does have a shot at becoming a typhoon now, though may well just fall short. A lot of rainfall is attached to this system so south Korea and western Japan need to closely watch Dianmu.

[Somerset Squall]

Intetresting to note that the 2010 west pacific typhoon season has had it's 4th slowest start on record. The average number of storms to occur by now is ten. Dianmu is only the fourth storm of the season.

[Somerset Squall]

Dianmu has strengthened to 55kts just south of South Korea. Dianmu should make landfall in later on thsi evening then weaken as it heads north of Japan. Extratropical transition will occur in the cooler waters here and Dianmu should be extratropical in about 48hrs time.

[Somerset Squall]

Dianmu made landfall last night in South Korea and has since accelerated east-northeastwards into the Sea Of Japan. Much cooler waters have greeted the storm here, and extratropical transition is well underway. It should be complete in around 12hrs time.