SEASONAL CLIMATE OUTLOOK
JULY - DECEMBER 2017
El Nino Southern Oscillation (ENSO)-neutral condition is present in the tropical Pacific. Sea surface temperatures (SSTs) have increased since May but remained within the neutral state. Latest analyses and most climate models suggest that this warm ENSO-neutral condition will likely continue during the remainder of the year.
July- September 2017
Warm ENSO-neutral condition is likely to prevail during the season.
The normal climate pattern during these months are characterized by widespread and heavy rainfall affecting the western sections of Luzon and Visayas since this is the peak of the Southwest (SW) monsoon season or "Habagat". Likewise, tropical cyclones are more active during this period with average tracks mostly located over the northern part of the country which could enhance the SW monsoon. Rain-causing weather systems such as thunderstorms, inter-tropical convergence zone (ITCZ), low pressure areas (LPAs), SW monsoon and six (6) to nine (9) tropical cyclones will dominate the season. However, breaks in the monsoon events are also expected to occur as the ridge of the North Pacific high pressure area (HPA) extends towards the country, giving warm and sunny weather in some affected areas.
Rainfall condition is predicted to be above normal in the Cordillera Administrative Region (CAR), Region I and Batanes. The rest of Luzon, Visayas and Mindanao will likely receive near normal rainfall during the season. In general, surface air temperatures are expected to be slightly warmer than average in most parts of Luzon and Mindanao but slightly cooler than average in the Visayas.
Gradual recession of rains associated with the SW monsoon is expected during the later part of September and the start of the transition period from the SW monsoon to the Northeast (NE) monsoon season is expected.
October - December 2017
ENSO-neutral conditions are still expected to continue as predicted by majority of climate models.
The period covers the first half of the NE monsoon season. The weather systems likely to influence the country are the easterlies, ITCZ, easterly wave, LPA, ridge of HPA, tail end of the cold front, NE monsoon and three (3) to five (5) tropical cyclone occurrences. Tropical cyclones originating from the northwestern Pacific Ocean tend to move in a westerly direction, with average tracks across central and southern Luzon and secondary tracks over Visayas and Northern Mindanao.
For October-November-December season, generally near normal rainfall conditions are expected over the entire country. However, monthly rainfall distribution suggests that in October, western Luzon will likely receive below normal rainfall while the rest of the country may experience near normal rainfall condition. For November and December, near to above normal rainfall condition is expected in most areas of the country. Furthermore, surface air temperatures are predicted to be slightly warmer than average during the season.
PAGASA will continue to closely monitor these climate conditions and regular updates and advisories shall be issued as appropriate. Concerned agencies are advised to take precautionary measures to mitigate the potential adverse impacts of the "Habagat" season which may cause flood and landslides over vulnerable areas of the country. For further information, please contact the Climatology and Agrometeorology Division (CAD) at telephone numbers 434-0955 or 435-1675.
VICENTE B. MALANO, Ph.D.