Sunday, August 21, 2011

Tropical Update

Invests 95W and 96W continue to develop while a new low pressure has popped up: Invest 97W.

Given the latest data, there is a potential for a tropical cyclone development within the next two days. Among the three systems we're watching, 96W has the highest chance of becoming a significant tropical cyclone in a few days.

But we begin first with Invest 95W. This LPA is still struggling and its low-level center has become fully exposed due to the wind shear that has increased this past 24 hours. Westerly shear of 20 to 30kts is displacing the main convection east and southeast of the center making it hard for 95W to really consolidate and intensify.
Nevertheless, JMA is still classifying 95W as a weak Tropical Depression while the JTWC is keeping its "MEDIUM" rating for the said system. Computer models, on the other hand, don't really forecast 95W to get stronger anymore, with the exception of the CMC. With that said, 95W could still develop into an organized tropical depression if wind shear relaxes in the area so we will still continue watching this.

Now onto Invest 96W. It was last located approximately 460km east southeast of Borongan, Eastern Samar. Visual satellite image shows improving mid-level presentation with clouds spinning around the center. There is also healthy convective activity, especially on the northern quadrant. An ASCAT pass earlier this morning suggests the possibility of a closed circulation with winds ranging from 20 to 35kph.

JTWC is still rating 96W as "MEDIUM". Computer models also in good agreement with the development of 96W. The general consensus is for 96W to move northward, avoiding a direct landfall in the Philippines. Potential targets right now would be the area from Northern Taiwan all the way to Southern Japan (Kyushu).

As we have mentioned at the top of this post, a new Invest has popped up along the monsoon trough. Invest 97W is still largely disorganized although a couple of computer models show this system developing next week, alongside 96W. The ECMWF, in particular, is showing the possibility of two typhoons next weekend, that are interacting with each other via the Fujiwhara effect. Confidence in this solution is still low due to it being far out.

The Philippines, meanwhile, will continue experiencing scattered thunderstorms and rainshowers. Highest chances of seeing rain will be in Visayas and Mindanao due to the ITCZ as well as rainbands caused by the developing LPA-96W.
Issued (0930 UTC) 530pm PhT 082111

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