Saturday, July 9, 2011

Tropical Update

Invest 94W continues to spin east of Taiwan. The exposed low level circulation was last spotted drifting near Miyakojima or about 310km east southeast of Taipei, Taiwan or 440km northeast of Basco, Batanes. Based on recent ASCAT pass, IR and VIS satellite images, as well as AMSRE 37Ghz microwave image, 94W and its low-level structure has improved a bit over the past 24 hours. Recent wind reports in Miyakojima indicate winds of 20-35kph. Furthermore, reports in Taiwan indicate around 1000mb of pressure. Radar from JMA shows bands of light to moderate rain just south of the Miyako islands and just east of Taiwan.

Image from NLRMRY showing the low-level circulation center and the convection associated with the LPA. Blue-arrows indicate wind reports around the area.

The JMA has gone ahead and is now classifying this system as a tropical depression. JTWC is still holding on to its "Medium" rating. The system remains in a moderate to high northerly wind shear environment of about 20-30kts, displacing the convection south of the LLCC. Fewer computer models are forecasting a storm out of this but we'll continue to watch.

Moving now to Invest 90W. This LPA continues to slowly move westward across the Pacific. ASCAT pass shows southwesterly winds of abour 20-30kph wrapping into what seems to be a low-level circulation. A recent 37Ghz SSMIS image shows improved low level activity. Computer models continue to show a storm forming in this area in about 3 days. Invest 90W is in an area of low to moderate wind shear of 10-20kts. Sea surface temps in the region is also high (around 30C). JTWC is still not rating this storm though.

The Philippines continue to be affected by the SW Monsoon bringing scattered light to moderate rain showers. Best chances for precipitation are in Luzon particularly to the north and western sections (including Metro Manila). Visayas will have partly cloudy skies with occasional showers. Eastern sections of Mindanao, meanwhile, will have unsettled weather due to the southerly flow and a weak disturbance, not expected to develop, between the Mindanao and Palau. The rest of the country will have cloudy skies with increased chance of rain, especially in the afternoon.

Issued (0830 UTC) 430pm PhT 070911

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