Philippines extreme precipitation patterns from observations and two-way coupled modeling

During December 2007-February 2008 the Philippines experienced the greatest rainfall in 40 winters. We use a combination of observations (including 48 meteorological stations distributed throughout the islands, TRMM satellite-sensed precipitation, and shipboard measurements) along with a high-resolution two-way coupled ocean/atmosphere model (3 km COAMPS) to examine this anomalous season. As expected from climatology, rainfall was greatest on the eastern side of the archipelago, with seasonal totals exceeding 4000 mm in some locations. Discrete precipitation events delivered the bulk of the rain to the region. General patterns and magnitudes of rainfall produced by the two-way coupled model agreed with observations from land and from space, with the 3-km COAMPS nest more aligned with observations than the coarser 9 km resolution grid. In addition, shipboard measurements from January 2008 (collected by the PhilEx program) reveal a fresh lens of water to the southwest of the island of Mindoro, which likely originated from river run-off. The 3-km COAMPS produced precipitation in the mountainous areas of the Philippines that supports this hypothesis, although observations were limited in this region. The roles of MJO and La Nina in the dynamics of this anomalously rainy season are also assessed.