The possibility of a typhoon forming in mid-December has sparked interest among weather enthusiasts and residents of the Western Pacific. Meteorologists are keeping a close eye on an area southeast of Guam, where conditions might support tropical cyclone development. Here’s a breakdown of the latest forecasts and what they mean for regions like the Philippines, Vietnam, and Malaysia.
The Current Weather Picture: Shear Line Brings Heavy Rain
Right now, the dominant weather feature in the region is a shear line—a boundary where cooler, drier air from the Northeast Monsoon meets warm, moist tropical air. This shear line has been responsible for flooding rains across parts of the Philippines, including northeastern Luzon and the northern Visayas.
Northeastern Luzon has already received over 300 mm of rainfall, with areas like Santa Ana and parts of the Cagayan Valley experiencing significant precipitation. Meanwhile, locations further south, such as Isabela, have seen comparatively lighter rains. This interaction between the monsoon and tropical air will continue to influence the near-term forecast.
Monitoring Potential Development Southeast of Guam
Looking beyond the immediate effects of the shear line, meteorologists are closely analyzing a developing area of low pressure southeast of Guam. By this weekend, models suggest a weak low-pressure system could form.
However, the more intriguing development may come from a second area behind this initial system. This secondary disturbance is expected to develop south of Guam and may approach the Philippines around December 10.
What Do the Models Show?
- European ECMWF Model:
The ECMWF shows limited development for the first disturbance but hints at a weak low-pressure area by early next week. While it does not suggest a fully developed tropical cyclone, it indicates increased rainfall over the Philippines. - American GFS Model:
The GFS paints a slightly different picture, showing a 990-millibar low forming near Mindanao by December 10–11. A system with this intensity would likely be categorized as a tropical storm, potentially bringing significant rainfall and gusty winds.
Challenges to Typhoon Formation
While the sea surface temperatures in the region are warm enough to support tropical cyclone development, there are factors working against a full-fledged typhoon:
- Increased Wind Shear:
The ongoing shear line disrupts organized convection, limiting the ability of a tropical system to strengthen. - Uncertainty in Model Guidance:
Long-range forecasts are inherently uncertain. While both the ECMWF and GFS show potential development, they differ on timing, intensity, and impact.
Rainfall Outlook for the Philippines
Regardless of whether a typhoon forms, mid-December is likely to bring another round of heavy rains to parts of the Philippines. The interaction of tropical disturbances with the shear line could create a setup similar to recent days, where southeastern Luzon and areas like Samar and Catanduanes experienced flooding rains.
Rainfall totals could exceed 200–300 mm in some areas, particularly if tropical systems enhance the monsoon.
The Broader Picture: December’s Tropical Cyclone Risk
The Climate Prediction Center has indicated an above-average chance of tropical cyclone development in the Philippine Sea between December 11 and 17. While this does not guarantee a typhoon, it underscores the importance of monitoring weather patterns closely.
Waves and Temperature Updates
In addition to rain, the region will experience significant wave activity, with swells increasing toward the weekend. Coastal areas should be cautious of rough seas, especially as winds strengthen with the arrival of these systems.
Temperature-wise, the Northeast Monsoon is bringing cooler conditions to East Asia. Highs will range from 30°C in Manila to 24°C in Hong Kong and a chilly 2°C in Seoul by Thursday.
What’s Next?
As meteorologists continue to analyze data, the key message remains clear: stay informed and prepared. The potential for tropical development, combined with ongoing shear line activity, makes mid-December a critical period for weather monitoring in the Western Pacific.
For now, northeastern Luzon remains the wettest area in the Philippines, but all eyes will be on the tropics as we approach next week.
Stay tuned for updates, and always prioritize safety during this active weather period.
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