Tropical Storm Jangmi 12Z September 29th, 2008

At 12Z, September 29th JTWC analyzed Jangmi at  27.2N 122.1E, moving 09 kts at 065 degrees with an intensity of 055 kt, and gusts of 070 kts.

Attached is the IR, upper-level AMV, and analyzed divergence animation valid at 14Z:

Jangmi has been hit hard by shear from the upper-level westerlies off of China. These westerlies  have enhanced the outflow and divergence to Jangmi’s northeast, but the associated shear has helped weaken the storm significantly as well.

As of 13Z the ADT analyzed an intensity of 39 kts, and the 08Z AMSU and SATCON had an intensity of 45 kts. The 12Z TMI image shows some convection to the northeast as well, but no organized eyewall.

Looking at the phase diagrams, the GFS diagram shows ET is underway, loosing its symmetric representation already, and then becoming cold-core by the 2nd of October. The Met Office diagram has similar timing. The NOGAPS analysis is similar early on, but then becomes more symmetric before becoming cold core.

The models are moving the system eastward, well south of Japan, and shearing it out quickly. They vary a bit in their frontal development and placement, however. By 00Z on the 3rd, all of the models except the NOGAPS analyze the system around 30N, 140E. The NOGAPS, the most symmetric of the analyzed systems, is also the slowest; bringing it to 30N 130E by that same time. The ECMWF seems the most sheared.

Model forecasts: ECMWF,Met Office,GFS, NOGAPS.

Either way, in the shorter term, this system is likely to weaken in the near time. The recurvature is interesting, because it was only recently predicted by the models. Looking back, the model consensus forecast on the 26th still shows Jangmi heading into China. By the 27th, the 12Z run began forecasting recurvature. This may be a good potential case to look at the effect of observations to see if the track prediction can be improved.

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