Tropical depression in Philippine Sea remains poorly organized, rainfall threat for Philippines

Happy New Year!  We hope 2018 is good to you and your family.

JMA continues to list the area in the southern Philippine Sea as a tropical depression.  PAGASA and JTWC maintain 99W as a low pressure area, with the latter giving it a medium chance at developing into a tropical cyclone within 24 hours.

20171231 2100 99W METSAT.jpg

As the sun rises on 99W, we see convection remains widely scattered, lacking consolidation over the center of circulation.  Latest microwave pass indicates the low-level circulation remains broad and elongated with a few pockets of winds at 45 km/h.  Given the close proximity to the Philippines, little change in strength is expected over the next couple days.  I wouldn’t be surprised to see PAGASA and JTWC upgrade prior to landfall to a tropical depression–matching JMA’s analysis, but tropical storm status does not seem likely before landfall.  With it now being 2018, a tropical depression declared by PAGASA would name the system as Agaton.

Forecast track continues to move the cyclone across northern Mindanao before emerging in the Sulu Sea on Tuesday.  In the meantime, heavy rain will threaten Mindanao and the Visayas, with 24-hour rainfalls of 50-150 mm.  Flooding and landslides will be possible as 99W passes through.  Once it reaches the Sulu Sea, Palawan and interests across the Spratly Islands will have to monitor the storm as is should being developing at that point.  The consensus forecast has it developing into a tropical storm by mid-week in the South China Sea before threatening coastal Vietnam (likely staying off-shore) toward Thursday and Friday as the storm weakens.

Mike Adcock
Meteorologist, Western Pacific Weather

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