"UPDATED THRU THE LA NINA ADVISORY"

 

Weather Situation in the Philippines
September  2011

 

 

The cooling trend in the central and eastern equatorial Pacific (CEEP) persisted during the month as negative sea surface temperature anomalies increased, with consistent positive values of the southern oscillation index (SOI), an indication of a developing La Niña.

The weather systems that affected the country during the month were the southwest (SW) monsoon, the intertropical convergence zone (ITCZ), low pressure areas (LPAs), and four (4) tropical cyclones (TCs) namely: Tropical Storm (TS) "Nonoy" (Sept. 8), Tropical Depression (TD) "Onyok" (Sept. 12-13) and re-entered as TS "Onyok" (Sept. 17-18), Typhoon (TY) "Pedring" (Sept. 24-28) and TY "Quiel" (Sept. 29 - Oct. 2).       (View:  TC Rainfall Charts)  

The two TCs that entered the Philippine Area of Responsibility (PAR) during the first half of September did not have much impact to the country. The latter two typhoons were stronger and rain effective due to enhanced southwest monsoon. Both made landfall over Isabela-Aurora area and traversed northern Luzon. These caused massive flooding, flashfloods, and landslides in many areas of northern and central Luzon including the National Capital Region (NCR). TY "Pedring" also generated storm surge along Manila Bay which damaged its seawall and brought floodwaters in nearby areas. To date, more than 70 casualties and about 30 missing were reported. For TY "Pedring" alone, the estimated damage to agriculture and infrastructure was almost 9-billion pesos, based on the National Disaster Risk Reduction and Management Council (NDRRMC) report.

Assessment of rainfall for the month showed that most parts of Luzon received above normal rainfall, including Central Mindanao, Davao del Norte and Davao Oriental, while Western Mindanao, Masbate and northern Samar experienced below normal rainfall condition. The rest of Mindanao and most areas of Visayas recorded near normal rainfall.  (View Rainfall Charts)

On the average, minimum air temperatures observed over most parts of the country were slightly warmer than normal. However, maximum temperatures in most parts of Luzon were slightly cooler than normal while in Visayas and Mindanao, slightly warmer than normal temperature was observed. The actual temperature ranges recorded were as follows: 21°C - 33°C in Luzon while 15°C - 22°C over its mountainous areas; 24°C - 33°C in Visayas; 23°C - 33°C in Mindanao, and 18°C - 30°C over its mountainous areas.

 

Weather Outlook for October  2011

The recent La Niña-like conditions in the tropical Pacific is predicted to strengthen in the coming months and may continue until the last quarter of 2011, based on majority of the leading statistical and dynamical climate models.

 The weather systems that are likely to affect the country during the period are the easterlies, ITCZ, LPAs, ridge of high pressure areas and two (2) or three (3) tropical cyclones to enter the PAR.  Transition of the seasonal winds from the southwest to the northeast is expected during the month and signals the start of the colder months of the year.  Most parts of the country will likely receive near normal rainfall except for some areas in western Luzon that may experience below normal conditions.

 Slightly warmer than normal air temperatures will likely be felt in most parts of the country. Predicted ranges will be as follows:  23°C – 33°C over Luzon, 16°C – 24°C over mountainous areas of Luzon, 23°C – 32°C over Visayas, 22°C – 33°C over Mindanao, and 19°C – 29°C over mountainous areas of Mindanao.

PAGASA will continue to monitor the day-to-day rainfall/weather conditions and the large-scale climatic patterns that will affect the country especially on the possible impacts of the developing La Niña. Meanwhile, the public is advised to take precautionary measures against floods and rain-induced landslides in hazard prone areas.

Climate Information, Monitoring and Prediction Section (CLIMPS)
 Climatology and Agrometeorology Division (CAD)
Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA)