1100Z – 24 July 2012

TY 09W underwent an impressive RI event today, which far surpassed all previous forecasts! At 23/00Z, max sustained winds were estimated at 55 kts. By 23/18Z, the intensity had increased rapidly to 115kts! The greatest 6hr intensity change occurred from 23/12Z to 23/18Z, where the intensity increased from 70 to 115kts! Naturally, this explosive deepening has already spurred discussion within both research and operational communities.

In conversation with JTWC forecasters today, we identified the possible effects of a mini-TUTTc over southeast China to the west of 09W that may have partly contributed to this RI. Although the near-mesoscale circulation of this possible TUTTc was difficult to identify in animated WV satellite imagery, a broader, synoptic scale inverted upper-level trough could be seen amplifying immediately to the west of 09W just prior to its RI phase.

This upper-level trough amplification might have lead to an increase in radial outflow aloft. However, it is not immediately clear whether this was a significant effect, given the pre-existing, excellent outflow channels to the east and south.

From animated WV satellite imagery (click on image below to animate), it appeared that a burst of convection wrapped quickly around the center of circulation during RI, with little change in the outer circulation envelope of 09W. No asymmetric, upper-level deformation zones were evident. Thus, this could have been be a case where inner core dynamics played a greater role than the large-scale flow with regard to initiating RI at this particular time. The background, synoptic conditions were favorable, but other smaller-scale factors may have played a role in this burst of eyewall convection. A more comprehensive case study would be necessary to identify the dynamics involved with this RI episode.

Highly meridional pattern persists in the WPAC, due to the presence of two large TUTTcs, C22 and C23.

By TAU 72, C22 is forecast to enter southeast China, with C30 and C31 become a pair of twin TUTTcs in the CPAC located along 30N.

All is quiet in the EPAC, once C29 opens into a trough and ejects toward California.

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